explain xkcd - User contributions [en]

Talk:207: What xkcd Means

2024-03-10T18:37:02Z

108.162.237.88:

I'm pretty sure that the first panel isn't talking about the legality of U-turns; I think it's actually talking about the legality of bypassing traffic signals:
https://www.drivinglaws.org/resources/is-it-illegal-to-cut-through-a-parking-lot-to-avoid-a-red-light.html

I do the last panel ALL THE FRIGGIN' TIME. [[User:Alpha|Alpha]] ([[User talk:Alpha|talk]]) 20:07, 8 March 2013 (UTC)
:Graham's Number has not had that title for several years now.... See here: http://googology.wikia.com/wiki/Graham's_number XKCD also means getting addicted to webcomics because they are too funny --[[Special:Contributions/108.162.237.175|108.162.237.175]] 21:57, 22 June 2015 (UTC)

A question, what is meant with "(In fact, A(g64, g64) is less than g65)"? Is g65 more than g64? Is it much more? Is A(g64, g64 "insanely large" compared to what you would expect or not? [[User:Maplestrip|Maplestrip]] ([[User talk:Maplestrip|talk]]) 13:05, 24 June 2015 (UTC)

:It means that mathematicians who read XKCD are not horrified by the idea, but calmly compute the result. (g65 is obviously more than g64 ; both Graham's number and Ackermann functions are methods to make ludicrously high numbers, and the "only slightly more" means that they growing in roughly same ludicrous speed) -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 02:04, 2 June 2016 (UTC)

You know, if everyone did the traffic thing at intersections, it would basically be the same as a roundabout. --[[Special:Contributions/162.158.102.150|162.158.102.150]] 16:19, 26 November 2015 (UTC)

[https://dps.mn.gov/divisions/dvs/forms-documents/Documents/Minnesota_Drivers_Manual.pdf Apparently (page 28)] some intersections where I live are designed ''for'' the maneuver in panel 1.--[[User:Troy0|Troy0]] ([[User talk:Troy0|talk]]) 17:30, 29 July 2016 (UTC)

Yo mama ≡ 1 modulo A(g64, g64) [[User:Int|unsigned int]] ([[User talk:Int|talk]]) 22:13, 22 March 2017 (UTC)

"Using ketchup to cover up stigmata wouldn't be a very good idea, as from afar people would think that you actually are bleeding from your (supposed) stigmata." ...Is the joke not that the ketchup itself is supposed to resemble the bleeding? Why is that not even mentioned as a possibility? [[Special:Contributions/108.162.237.88|108.162.237.88]] 18:37, 10 March 2024 (UTC)

I ran into a situation yesterday where the first panel saved me five minutes in traffic. The road I was driving on had two lanes on each side. The left lane was backed up a quarter mile and the right lane was empty, as across the next road, construction trucks blocked the right lane. I drove all the way down the right lane, took a right turn, and then proceeded to execute the maneuver depicted in the comic. Half a dozen other cars caught on and followed. [[Special:Contributions/173.245.52.169|173.245.52.169]] 21:16, 23 February 2018 (UTC)

Maybe it's about his ex Casey D.

Xylophone kicking contest delayed, x-rays knitting crumbles Denmark, xenon kangaroos can't derive, xylocarp kiwi creates dimension, xebec krypton concedes durian [[User:Certified_nqh|Me]][[[285: Wikipedian Protester|''citation needed'']]][[Category:Pages using the "citation needed" template]] 05:53, 2 October 2023 (UTC)

Left turn on red is also legal. But the basic rule is that the turn can't require crossing any traffic lanes, so you can only do it when turning from one one-way road to another. So it's not useful for the maneuver in the comic, because you can't make a U-turn on the second road. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 15:38, 29 February 2024 (UTC)

"how could he get someone outside the house to call it" Some of us still have land lines (and far more did when the comic was written). You can also use email or online messaging. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 15:44, 29 February 2024 (UTC)
:Generally, if you have a landline to talk to someone outside your house, you can do the "call your own (mobile/cell) phone from your (landline) one" without even needing anybody else. (As long as you can remember/look up your own number! That'd might be a necessity, 'cos I can still remember other peoples' phone numbers ''from decades ago'', that no longer apply, but still struggle to remember my own without always initially self-doubting if it starts "0754... or "0745...".)
:That said, post-landline I've also had to go out without my mobile (because I couldn't work out which cushion/whatever it had clearly hidden itself beneath) and then as I was about to leave the venue, where I'd prearranged a meet with someone, have asked the person concerned to "wait half an hour for me to get home, then try to give me a ring... and if I don't call back within five minutes, try once more as I instead specifically listen out upstairs...". Which worked, incidentally, but can't remember offhand if it actually needed that second attempt.
:And I always interpreted the comic as being someone not ''in the same room'', or at least outside the immediate frame of view, to add yet another reason to be drawn that way. But who knows what exact kind of situation Randall was imagining. (Well, Randall might...) [[Special:Contributions/172.71.178.76|172.71.178.76]] 16:30, 29 February 2024 (UTC)

1732: Earth Temperature Timeline

2018-03-13T16:14:37Z

108.162.237.88: /* Jokes in the comic */

{{comic
| number = 1732
| date = September 12, 2016
| title = Earth Temperature Timeline
| before = [[#Explanation|↓ Skip to explanation ↓]]
| image = earth_temperature_timeline.png
| titletext = [After setting your car on fire] Listen, your car's temperature has changed before.
}}

==Explanation==
{{TOC}}
This comic is a [[:Category:Timelines|timeline]] on how the temperature has changed from 20,000 BCE (Before {{w|Common Era}}) to the present day (2016), with three predictions for the rest of the 21st century depending on what actions are taken (or not taken) to stop CO₂ emission. This comic is a direct, but much more thorough, follow up on the previous global warming comic: [[1379: 4.5 Degrees]]. By having readers scroll through millennia of slow-paced natural changes, Randall uses the comic to confront the the rapid temperature rise in the recent years.

Over the past 100 years, human action has produced a large amount of {{w|CO₂ emissions}}, which have caused a rise in average global temperature through the {{w|greenhouse effect}}. This is called {{w|global warming}} and is part of a {{w|climate change}}, a subject that has become a [[:Category:Climate change|recurrent subject]] on xkcd. There are still many people who claim that this is not happening, or at least that it is not caused by any human actions, called {{w|Climate change denial|climate change deniers}}. One argument of theirs is that global warming is happening for natural causes, summarized with the phrase "temperature has changed before".

This comic shows that while temperature changes have indeed occurred before, the speed of the current temperature rise is much, much faster than those measured for many previous thousands of years. The comic became so popular that [[Randall]] [[#Popularity_of_comic|postponed the release]] of his next comic to keep this one on the front page one day longer.

The temperature curve is a dotted line most of the time, but from about 1850 to 2016 the measurement data is good enough to let the curve become a solid line indicating that this is not an estimate. Before 1850 the temperature is an estimate based on the [[#Sources|sources]] given. And likewise into the future the three possible curves are also dotted to show that they are predictions, based on how seriously the population of Earth takes knowledge (and comics) like this.

Although this is a topic Randall obviously takes very seriously, and by far most of the facts fit with known history, he still includes several [[#Jokes in the comic|jokes in the comic]]. See also the [[#Table of all elements|table]] explaining each item in the comic. So after the election of a climate change denier later in the year of this comic's release, [[1756:_I'm_With_Her#Sad_comics|several sad comics]] has been posted. Some of the reason could be that Randall no longer believes that even his worst fears (as expressed by the current path at the bottom) will hold up, when USA gets a president, who will on purpose act in a way that scientist claims will make the temperature rise even more. [[1756:_I'm_With_Her#Sad_comics|See more here]].

The title text compares the saying that "the temperature has changed before" comparing temperature changes over thousands of years to the rapid global warming over the last century with saying that the "small" changes to the temperature a car experiences over the years of normal usage should not make you worried over the rapid temperature increase that happens when someone sets your car on fire. A related joke was used recently in [[1693: Oxidation]].

===Jokes in the comic===
* By placing the invention of the internet at 1980 in the chart, just where the temperature curve starts its most rapid increase, Randall humorously implies that the internet caused the rise in temperature.
* At 13600 BCE a glacier is shown retreating from New York because of the warm up. It is disgusted by the new changes and proclaims: ''That’s it! I’m moving to Canada!'' A joke on the typical saying by US citizens that are unhappy with changes in their country, as a kind of protest. According to the chart the glacier first retreated over the Canadian border around 8400 BCE more than 5000 years later.
* At 13400 BCE it is mentioned that {{w|origin of the domestic dog|humans domesticate dogs}}. [[Megan]] talks to a wolf about to be tamed making a deal with it, that it can eat and sleep with the humans as long as they can yell at it for pooping indoor. This sounds like a sweet deal for the wolf until [[Cueball]] mentions that they will {{w|Dog breeding|breed}} it to be {{w|Chihuahua (dog)|very small}} and then dress it up in small {{w|Dog's fashion|costumes}}. The wolf says wait, but it is already too late...
* The {{w|Pokémon}} reference at 9000 BCE about them going extinct in North America (although Megan does proclaim that this is not a real fact). As the writing stated that ''Pokémon go extinct'' this can also be seen as a reference to a popular video game called {{w|Pokémon Go}} and hence also the recent comic [[1705: Pokémon Go]].
* At 4500 BCE, next to "{{w|Proto-Indo-European language}} develops", [[Ponytail]] gets the idea to develop the language heavily inflected to make it difficult to remember all the verb endings for future students. A direct reference to the recent comic [[1709: Inflection]].
* The reference to the 1984 {{w|mockumentary}} about the fake rock band {{w|This Is Spinal Tap}} in conjunction with {{w|Stonehenge}} at 2200 BCE. In the movie the band ordered a giant 18 feet Stonehenge megalith but a writing mistake gives them one that is only 18 inches high.
**Another real band {{w|Nine Inch Nails}} is referenced 16000 BCE where Megan writes the bands stylized name NIИ on the wall next to [[Hairy]] who is in the process of painting the {{w|cave painting}} at {{w|Lascaux}} in France.
* Around the setting of the {{w|Iliad}} and the {{w|Odyssey}} (1200 BCE) a drawing of the {{w|Trojan Horse}} has writing on it that states: ''Not a trap''.
* Just below the previous entry also at 1200 BCE is the mentioning of the invasion of the {{w|Sea Peoples}}. This sounds so much like a reference to {{w|Mermaid|mermaids}}, often called {{w|Mermaid#One_Thousand_and_One_Nights|sea people}} that Randall feels the need to note that this invasion and these sea people is ''a real thing'' in a footnote. This is opposed to the Pokémon reference above where he notes that it is ''not a real fact''. The sea people was a seafaring confederation of groups known to have attacked ancient Egypt and other Bronze age civilizations around this time. It is widely regarded to be one of the major causes of the {{w|Late_Bronze_Age_Collapse|Bronze Age Collapse}}.
* At 450 BCE a reference to the {{w|Battle of Thermopylae}} (also known as 300 Spartans) he references this by comparing the event with the 2007 movie ''{{w|300 (film)|300}}'' about this battle. But notes that in the real world the fighting of course occurred at regular speed and that they probably had more clothing on in the real world than in the fictionalized action movie.
*There are other minor jokes but this list mentions all the major jokes.

===Table of all elements===
*Here is table including all elements in the chart with explanations including reading off temperature and year for each event from the curve.
**The year group is just an easy way to find the section.
**Element is a description mainly taken from the transcript.
**The actual year of an event has been read off more precisely on the chart.
***The central part of the element has mainly been used.
***Only rarely has ranges below 100 years been used but if a location is clearly midway between two hundred years intervals 50 year range has been used.
***Only when there are several posts close to each other has smaller range been used a few times.
**T (°C) is the number of degrees Celsius above or below the 1961-1990 average, which on this graph is set to zero, (i.e. not the number of physical degrees above or below this 0°C).
***These have been read of to 0.1°C rounding up or down. Lines have been inserted over the chart, 10 for each degree, to make this as accurate as possible.
***In a few cases where a maximum is reached 0.05°C has been used
**Explanation of each element.
{| class="wikitable"
!Year group
!Element
!Year
!T (°C)
!Explanation
|-
| rowspan="2"| 20000 BCE
| [An arrow goes from the dotted line to the central line at 0°C (representing the 1961-1990 average). In the middle of the line there is a temperature label:] 4.3°C At the start of our timeline, 22,000 years ago, Earth is 4°C colder than during the late 20th century. || 20000 BCE || -4.3 || The scale here is relative, showing the magnitude of change rather than an absolute temperature reading. As a rule, {{w|climate}} changes are compared with a 30 year interval, and {{w|Climate#Definition|recently}} the 1961-1990 average was chosen for convenience as the "normal" to compare temperature changes with, but any other choice of baseline would show the exact same changes. The {{w|Last glacial period}} (aka ice age) reached its {{w|Last Glacial Maximum|maximum extent}} approximately 22 to 24 thousand years ago.
|-

| {{w|Boston}} is buried under almost a mile of ice, and the {{w|glaciers}} reach as far south as {{w|New York City}}. [The Statue of Liberty is shown in front of a glacier front. A guy with a white {{w|knit cap}} is seen walking in a snowy landscape. The skyline of Boston is shown under a half a mile of ice.] || 19700 BCE || -4.3 || This shows what a difference 4 degree in global temperature means (massive effect), as opposed to four degrees on a daily weather wise scale (trivial). The Boston image is directly taken from [[1225: Ice Sheets]] about the ice age glacier coverage; it was also shown buried in ice in [[1379: 4.5 Degrees]]. The guy with the white knit cap could be the guy from [[1321: Cold]] also about global warming. Knit caps have only been used a few times in xkcd, most prominently on [[1350:_Lorenz#Knit_Cap_Girl|Knit Cap Girl]] in [[1350: Lorenz]].

|-
| rowspan="3"| 19500 BCE
| But the world is about to warm up. || 19500 BCE|| -4.3 || The warming process actually takes thousands of years, which this comic will portray down thousands of pixels to come. This is not a fast warm up, especially not compared to the one we are currently experiencing (at the bottom of the chart).
|-
| By this time, humans have already spread across {{w|Africa}}, {{w|Eurasia}}, and {{w|Australia}}. || 19300 BCE || -4.3 || {{w|Homo Sapiens}} successfully {{w|Recent_African_origin_of_modern_humans#Movement_out_of_Africa|migrated out of Africa}} somewhere between {{w|Recent_African_origin_of_modern_humans#Dating:_pre-or_post-Toba|130,000}} and {{w|Recent_African_origin_of_modern_humans#Coastal_route|70,000}} BCE.
|-
| They’ve created {{w|painting}}, {{w|pottery}}, {{w|rope}}, and {{w|Bow and arrow|bows and arrows}}, but haven’t developed {{w|writing}} or {{w|farming}}. || 19100 BCE || -4.3 || The {{w|History of painting#Pre-history|oldest known paintings}} date back to about 38,000 BCE. The {{w|Ceramic_art#History|oldest known pottery}} date back to about 20,000 BCE. The {{w|Rope#History|oldest known rope}} date back to about 26,000 BCE. The {{w|History_of_archery#Stone_Age_and_Bronze_Age_archery|oldest known arrows}} date back to about 70,000 BCE, but Randall seems to be mistaken about the bows which seems to be {{w|History_of_archery#Stone_Age_and_Bronze_Age_archery|at most 10,000 years old}}. Writing is mentioned again at 3500 BCE and farming at 10,000 BCE.

|-
| rowspan="2"| 19000 BCE
| Changes in the Earth’s orbit mean that more sunlight reaches the polar ice… || 18600 BCE || -4.2 ||{{w|Milankovitch cycles}} are repeated climate variations on a timescale of tens of millennia caused by cyclic variations in {{w|Orbital eccentricity|eccentricity}}, {{w|axial tilt}}, and {{w|precession}} of the {{w|Earth's orbit}}, which thus then determined climatic patterns on Earth. The Milankovitch cycles are referenced again around 4700 BCE.

|-
| [A line chart with a labeled Y-axis "Summer sun W/m2 at 60°N" with three labeled ticks ranging from 450-550. The curve starts up and then goes down five times and up four times ending down. There is one plateau towards the end compared to the rest of the curve where the ups and downs are quite alike.] || 18600 BCE || -4.2 || The chart shows the input of sun during summer time in the {{w|Northern hemisphere}} (at {{w|60° northern latitude}}) as the effect (W) per square meter (m2) which fluctuated in the range from 450-550 during the time shown in the chart. There is, however, no scale for the time between the peaks. This chart relates to the text about increasing sun to the polar ice in the entry above.

|-
| rowspan="1"| 18500 BCE
| [A map of the world. At the top is a light gray area covering {{w|North America}}, {{w|Greenland}} and northern {{w|Europe}} and most of the northern part of {{w|Russia}}. A similar gray area covers {{w|Antarctica}}. The gray areas are labeled as ice.] || 18300 BCE || -4.2 || This [[:Category:Maps|map]] shows where the ice covered the {{w|northern hemisphere}} (and Antarctica) during the {{w|Last Glacial Maximum}}. The continents have not moved much since then, but the lower water level caused by the amount of water bound up in the ice, can clearly be seen in several locations. For instance, the {{w|British islands}}, Greenland, and {{w|Papua New Guinea}} are connected to their respective neighboring continents. Also {{w|Alaska}} and Russia are connected through the ice sheets covering the northern part of the Earth.
|-
| rowspan="1"| 18000 BCE
| …And the ice sheets start to melt. || 17900 BCE || -4.1 || This was a slow process that takes 10,000 years. The ice is mentioned again at 13,600 and 8400 BCE.

|-
| rowspan="1"| 17500 BCE
| Temperatures have been creeping upward, but around this point, CO2 levels start to climb…|| 17300 BCE || -4.1 || Due to the release of gasses from various sources (dissolved in the ocean, trapped in {{w|permafrost}}, etc), {{w|Carbon dioxide in Earth's_atmosphere#Measuring ancient-Earth carbon dioxide concentration|atmospheric CO2 levels}} increased by 100 parts per million over a span of thousands of years. Modern civilization has added the same amount in a single century.

|-
| rowspan="1"| 17000 BCE
| …And then the warming speeds up. || 16700 BCE || -4.1 || It took 3000 years for the temperature to increase with one degree. So this sentence can be seen as sarcasm about the rate of natural climate change compared to modern {{w|anthropogenic}} (human caused) warming.

|-
| rowspan="1"| 16500 BCE
| [Cueball is standing with a spear just the right of the graph talking to a rabbit.] Cueball: Still pretty cold. || 16200 BCE || -4.0 || True, because although the temperature has risen with 0.3°C over the last 4000 years, it's still 4°C below the 1961-1990 average.

|-
| rowspan="2"| 16000 BCE
| [Megan touches the dotted line to the right of her, with Ponytail standing on the other side. The graph has finally passed the -4°C line below the 1961-1990 average.] || 15600 BCE || -3.9 || Megan is the first drawing on the left side of the curve. She seems to be pushing the temperature up.
|-
| [In the right part of the chart is an explanation of the data. Below the first two lines there are four drawings each showing possible temperature swings in reality compared to the smoothed data that represents the dotted curve of the entire chart. The dotted curve is shown in all four drawings and a thin line is shown running along it but with much more fluctuation left and right on the first two, a large spike right on the third and a large bump way right on the fourth. Above these there are two labels. The first labels is inside a bracket that covers the first three, and the last label is for the last drawing. Below is a list of sources.] Limits of this data: Short warming or cooling spikes might be “smoothed out” by these reconstructions but only if they’re small or brief enough. Possible Unlikely Reconstructions are from Shakun (2012) and Marcott (2013), scaled to Annan + Hargreaves (2013) estimate for the last glacial period. || 15600 BCE || -3.9 || This is Randall's pre-emptive response to skepticism about the accuracy of prehistoric data. {{w|Ice cores}} and similar records might miss individual year-to-year variation, but should catch sustained changes lasting many decades, which is the time scale that matters for climate. See links to the [[#Sources|sources below]].

|-
| rowspan="1"| 15500 BCE
| In what is now {{w|France}}, humans paint murals on the walls of the {{w|Lascaux}} caves [Hairy paints three animals, two with horns, and two humans, Cueball holding hand with Hairy who has a spear. On the other side of the central line Megan writes three letters, the last of which is reversed:] NIИ || 15200 BCE || -3.8 || A reference to the industrial techno band {{w|Nine Inch Nails}} as Megan writes the bands stylized name NIИ on the wall next to Hairy who is in the process of painting part of the {{w|cave paintings}} at Lascaux in France.

|-
| rowspan="1"| 15000 BCE
| Ice sheets around {{w|Alaska}} shrink, exposing a land bridge between Asia and North America [From around the bottom if this section and down to 11500 BCE the dotted curve moved steadily to the right towards warmed temperature peaking close to 1.5°C below the 1961-1990 average. Before this the temperature had not moved much away from that at the start.] || 14600 BCE || -3.5 || This land bridge is known as {{w|Beringia}}. It is mentioned again at 8300 when it disappears due to the rising seas.
|-
| rowspan="1"| 14500 BCE
| [Cueball walks right looking back at the graph behind him. Megan walks in front of him pointing further right.] Cueball: Cool. Humans reach {{w|North America}}. || 14200 BCE || -3.3 || This is approximately when the humans from {{w|Asia}} crossed the land bridge mentioned in the previous entry, from what is now {{w|Siberia}} to what is now {{w|Alaska}}. {{w|Settlement of the Americas}} occurred around the time shown in the chart, although {{w|Settlement_of_the_Americas#Chronology|it's possible}} that earlier humans did so by boat prior to the formation of the land bridge. Cueball's comment is a double entendre; it was figuratively "cool" that early people migrated this far, and the climate was literally cool compared to modern times.

|-
| rowspan="2"| 14000 BCE
| The edge of the ice withdraws from {{w|New York City}} and retreats north. || 13700 BCE || -3.1 || Even though the ice began to melt 4000 years before (at 18,000 BCE in the chart) it is first now that New York City is free of ice.
|-
| [A large glacier front speaks in a speech bubble with an arrow pointing at it. Behind is there are four peaks in the horizon and in front of it three small melting pools and some rocks on the ground.] Glacier: ''That’s it! I’m moving to Canada!'' || 13600 BCE || -3.0 || When US citizens are unhappy with changes in their country, they sometimes say they will move to Canada in protest. Here it is the glacier that is anthropomorphically unhappy with the climate changes. However this is a slow process; it crosses the Canadian border more than 5000 years later.

|-
| rowspan="2"| 13500 BCE
| Humans domesticate dogs (Date uncertain, may be much earlier) || 13400 BCE || -3.0 || See {{w|Origin of the domestic dog}}. This timeline event is not quite accurate. The first dogs differentiated from {{w|Gray wolf|wolves}} about {{w|Origin_of_the_domestic_dog#Time_of_domestication|23,500 years ago}}, but there was an event around 13500 BCE that increased the population size and may be attributable to domestication events.
|-
|| [Megan and Cueball is watching a wolf looking at them.] Megan: Okay, you can live in our homes and we’ll feed you, but we’ll still get mad if you poop on the floor. Wolf: Deal. Cueball: And we get to breed you to be tiny and dress you in little costumes. Wolf: …Wait. || 13100 BCE || -2.8 || Megan is making a deal with the wolf that it can eat and sleep with the humans as long as they can yell at it for pooping indoor. This sounds like a sweet deal for the wolf until Cueball mentions that they will {{w|Dog breeding|breed}} it to be {{w|Chihuahua (dog)|very small}} and then dress it up in small {{w|Dog's fashion|costumes}}. The wolf says wait, but it is already too late...

|-
| rowspan="2"| 13000 BCE
| {{w|Woolly Rhino}} goes extinct || 12900 BCE || -2.7 || Mainland woolly rhinos died in the {{w|Quaternary extinction event}}, but a small island population survived until {{w|Woolly_rhinoceros#Extinction|around 8000 BCE}}. Woolly rhinos likely became extinct in part due to {{w|Holocene extinction|over-hunting}}. Randall's choice of species on this chart seems to focus on animals that were greatly affected by humans, for good or ill.
|-
| {{w|Oregon}} is scoured by huge floods as glacial dams burst and lakes of meltwater flow to the sea || 12600 BCE || -2.2 || This is a reference to the {{w|Missoula Floods}} several cataclysmic floods that swept periodically across eastern {{w|Washington}} and down the {{w|Columbia River Gorge}} flooding much of eastern Washington and the {{w|Willamette Valley}} in western Oregon at the end of the last ice age. During the last {{w|deglaciation}} ice dams formed then burst several times between 13,000 and 11,000 BCE.

|-
| rowspan="1"| 12500 BCE
| Ice sheets withdraw from Chicago || 12200 BCE || -1.8 || The next step towards the Canadian border, after they left New York at 13,600 BCE.

|-
| rowspan="1"| 12000 BCE
| Humans settle {{w|Abu Hureyra}} in {{w|Syria}} || 11550 BCE || -1.6 || A well-preserved prehistoric village that existed from 11,000 to 7000 BCE (a little later than noted in the chart), allowing archaeologists to study how their culture developed.

|-
| rowspan="1"| 11500 BCE
| [An arrow on the left side of the dotted curve is pointing down along the dotted curve and to the left indicate temperature is declining again, meaning the dotted curve now moves left to colder temperatures. This only continues until 10500 BCE. It is only the second time something is noted on the left side after Megan at 16000 BCE] Temperatures start to decline, mainly in the Northern hemisphere This may be caused by changes in ocean circulation due to the floods of cold fresh meltwater flowing into the Atlantic as the North American ice sheet melts. This cooler period is called the {{w|Younger Dryas}} || 11300 BCE || -1.6 || In the Younger Dryas, the Earth cooled by almost one degree over 1000 years. There were {{w|Outburst flood#Glacial_floods_in_North_America_.288.2C000_to_15.2C000_years_ago.29|several floods}} during the end of the ice age but the most famous is the one from {{w|Lake Agassiz}}. A similar but less global effect could occur if the ice on {{w|Greenland}} melts too quickly and causes a {{w|shutdown of thermohaline circulation}}. Without the {{w|Gulf Stream}}, hot water would remain in the Gulf of Mexico and the Caribbean instead of warming the {{w|North Atlantic}} and Europe. The movie {{w|The Day After Tomorrow}} dramatized a worse-than-worst-case version of this, happening in days instead of centuries.

|-
| rowspan="1"| 11000 BCE
| [This is the first text to the left of the dotted curve:] Humans reach {{w|Argentina}} || 10900 BCE || -1.8 || The earliest evidence of {{w|Indigenous_peoples_in_Argentina#Prehistory|humans in Argentina}}. Finally the temperature graph has risen enough that there is space to write text on the left side of the curve.

|-
| rowspan="2"| 10500 BCE
| [An arrow pointing down along the right side of the dotted curve and to the right indicate temperature is increasing again, meaning the dotted curve now moves right to hotter temperatures. This continues until 8000 BCE where it levels out just above the 1961-1990 average.] Warming resumes || 10500 BCE || -1.8 || After 1000 years of slightly decreasing temperatures the warm up of Earth resumes. Over the next 3000 years the temperature increases 2.5°C, reaching a long plateau about 0.5°C above the 1961-1990 average around 7500 BCE.
|-
| Human settlements at {{w|Jericho}} ||10050 BCE || -1.4 || The {{w|Jericho#Pre-Pottery_Neolithic.2C_c._9500_BCE|first permanent settlement}} on the site of Jericho occurred around 9500 BCE, but there is evidence of {{w|Jericho#Natufian_hunter-gatherers.2C_c._10.2C000_BCE|non permanent settlement}} during this period, when cold and drought made permanent habitation in that region difficult.

|-
| rowspan="1"| 10000 BCE
| First development of {{w|farming}} || 9750 BCE || -1.1 || This is now called the {{w|Neolithic Revolution}}, i.e. the wide-scale transition of many human cultures from a lifestyle of {{w|Hunter-gatherer|hunting and gathering}} to one of {{w|agriculture}} and settlement. The {{w|history of agriculture}} began independently in several locations with both {{w|domestication}} of animals and the farming of different {{w|cereals}}. One of the first regions to develop farming was the {{w|Fertile Crescent}}. This is also around this time that the last ice age is said to have ended.

|-
| rowspan="2"| 9500 BCE
| {{w|Saber-toothed cat}} goes extinct || 9200 BCE || -0.3 || Although one of these (Smilodon) was known as the {{w|saber-toothed tiger}}, most saber-toothed "cats" are not related to tigers, or any modern {{w|cats}} at all, but can be viewed as examples of convergent evolution. {{w|Smilodon}} became extinct around 8000 BCE, and the last Saber-toothed cat first became extinct around 7000 BCE, which does not fit very well with Randall's range. Indirectly humans may have caused the extinction of the Saber-toothed cat by over-hunting their {{w|megafauna}} prey, depriving the cats of food sources.

|-
| {{w|Horses}} disappear from {{w|North America}} || 9100 BCE || -0.2 || The {{w|evolution of the horse}} began millions of years ago in North America; early species {{w|https://en.wikipedia.org/wiki/Evolution_of_the_horse#Miocene_and_Pliocene:_true_equines|migrated across Beringia into Eurasia}} before their predecessors {{w|https://en.wikipedia.org/wiki/Evolution_of_the_horse#Pleistocene_extinctions|died out}}.

|-
| rowspan="4"| 9000 BCE
| | Last North American {{w|Pokémon}} go extinct [Cueball with a spear and Megan is looking up at this last “fact”.] Megan: That is not a real fact. || 8900 BCE || -0.1 || Pokemon are not real. This faux-extinction is likely a reference to the recent {{w|Pokémon Go}} game, which Randall spoofed in [[1705: Pokémon Go]]. Virtual Pokémon now thrive throughout the entire world, and are most commonly found near [http://time.com/4443225/pokemon-go-affluent-white-neighborhoods-report/ affluent first world neighborhoods].

|-
| Temperatures reach modern levels || 8800 BCE || 0.0 || It took 11,200 years for the temperature to increase 4.3°C. It's possible that human-created effects will produce an equal change in a few hundred years.
|-
| Rising seas cut off the {{w|land bridge}} between North America and Asia || 8700 BCE || 0.1 || {{w|Beringia}} was freed of ice in 15,000 BCE. This is an example of what happens when the temperature rises and glaciers melt. Sea levels are rising again as ice on {{w|Greenland}} and {{w|Antarctica}} continues to melt.

|-
| {{w|Cattle}} domesticated || 8500 BCE || 0.2 || Cattle feature prominently in the comic [[1338: Land Mammals]].

|-
| rowspan="2"| 8500 BCE
| Ice sheets retreat across the Canadian border || 8400 BCE || 0.3 || Finally the glacier that began retreating from New York around 13,600 BCE succeeded in moving to Canada as it had threatened to do...
|-
| Temperatures start to level out slightly above 1961-1990 levels || 8050 BCE || 0.4 || The next 3000 years the temperature stays within 0.2°C degree of a temperature 0.5°C above the 1961-1990 average. A very long and stable period.

|-
| rowspan="1"| 8000 BCE
| [The above sentence breaks over the 8000 BCE line. From here a maximum in temperature on the chart is reached at 0.5°C above the 1961-1990 average, which will not be overtaken until 2000 CE. It stays almost constant here until 5000 BCE where a slight cooling begins.] || 8000 BCE || 0.4 || This is the only five hundred year span with no events listed fully inside. Maybe because nothing happens with the temperature.

|-
| rowspan="2"| 7500 BCE
| This warm, stable period is called the {{w|Holocene Climate Optimum}} || 7400 BCE || 0.5 || Some skeptics like to say "[http://www.skepticalscience.com/10000-years-warmer.htm it was warmer in the Holocene]." This is no longer true. Global temperature began encroaching Holocene levels in 1998, and has equaled or possibly exceeded them since 2014.
|-
| {{w|Jiahu}} settled in China || 7050 BCE || 0.5 || Jiahu is another prehistoric settlement, similar to Abu Hureyra (12000 BCE), that was extensively studied by archaeologists.

|-
| rowspan="2"| 7000 BCE
| Final collapse of the North American ice sheet leads to rapid 2-4m sea level rise… || 6800 BCE || 0.55 || The temperature almost reached 0.6°C above the 1961-1990 average before this happened and caused the slight decrease in temperature mentioned below.
|-
| [A small arrow points down and left to the right of the dotted curve. There is a small decrease in temperature but it is very small and would have been missed without the arrow and label.] …And a period of cooling in the Northern hemisphere || 6550 BCE || 0.5 || A 0.05 degree decrease in 200 years again refers to the theme of slow natural climate change.

|-
| rowspan="1"| 6500 BCE
| As seas rise to near their modern levels, Britain is cut off from mainland Europe || 6300 BCE || 0.45 || This is a reference to the flooding of {{w|Doggerland}}.

|-
| rowspan="1"| 6000 BCE
| Humans develop copper metalworking || 5600 BCE || 0.5 || The {{w|copper age}} was relatively brief before humans discovered how to make {{w|bronze}}.

|-
| rowspan="2"| 5500 BCE
| Massive volcanic eruption in {{w|Oregon}} creates crater lake || 5300 BCE || 0.55 || {{w|Crater Lake}} is the caldera at the top of Mount Mazama, a collapsed stratovolcano. If it erupted again, it could become a Somma volcano (see [[1714: Volcano Types]]).
|-
| {{w|Gold}} metalworking || 5050 BCE || 0.6 || The temperature peaks here at just a bit more than 0.6°C above the 1961-1990 average. It will not rise above this level until the global warming sets in in the 1900s.

|-
| rowspan="2"| 5000 BCE
| {{w|Invention of the wheel}} || 4900 BCE || 0.6 || Wheels are one of the most important inventions of humanity. They feature in many xkcd comics, such as [[1075: Warning]].
|-
| [To the right of the dotted curve is an arrow pointing down and slightly left. From here temperature decreases very slowly but steadily from 0.5°C above the 1961-1990 average until 1000 BCE where a stable plateau is reached around the 1961-1990 average.] Earth begins to cool slowly mainly due to regular cycles in its orbit || 4800 BCE || 0.5 || Again a reference to the {{w|Milankovitch cycles}} mentioned in detail at 18,600 BCE. Here they cause a cooling rather than a heating as they did back then.

|-
| rowspan="3"| 4500 BCE
| {{w|Proto-Indo-European language}} develops || 4400 BCE || 0.5 || Most of the languages in Europe, the Middle East, and India share a surprising number of common roots. PIE is the theoretical ancestor from which they descend. Randall mentions this language family in many comics, such as [[890: Etymology]].
|-
| [To the right of the curve Ponytail holds up a hand towards Cueball.] Ponytail: Let’s make out language heavily inflected, so future students have to memorize a zillion verb endings! Cueball: Okay! || 4400 BCE || 0.5 || Ponytail gets the idea to develop the language heavily inflected to make it difficult to remember all the verb endings for future students and Cueball is okay with that. This is a direct reference to the recent comic [[1709: Inflection]].
|-
| Permanent settlements in the {{w|fertile crescent}} || 4200 BCE || 0.5 || The Fertile Crescent is one of those things you're supposed to remember from grade school. A lot of historic milestones happened there, such as the pyramids of Giza, the code of Hammurabi, and the Abrahamic religions.

|-
| rowspan="2"| 4000 BCE
| Horses domesticated || 3950 BCE || 0.5 || Horse riding was the greatest advance in land travel until the invention of engines. Horses appear in many xkcd comics, such as [[936: Password Strength]].
|-
| {{w|Minoan culture}} arises on Crete || 3700 BCE || 0.5 || Minoan culture invented many strange and wonderful things, such as the Labyrinth at Knossos and {{w|Bull-leaping}}.

|-
| rowspan="4"| 3500 BCE
| {{w|Egyptian mummification}} || 3500 BCE || 0.5 || xkcd has discussed mummification in {{what if|134|What If? 134: Space Burial}}.
|-
| Rise of the {{w|Indus Valley civilization}} || 3300 BCE || 0.5 || The largest bronze-age civilization.
|-
| Invention of {{w|writing}} in {{w|Sumer}} “{{w|prehistory}}” ends, “{{w|history}}” begins || 3200 BCE || 0.5 || Our knowledge of prehistoric events must rely on digging up artifacts and making inferences. After this time, it became possible to find descriptions of past people and events, which is the definition of history. (Old guy in Sumer: Kids these days with their new-fangled stone tablets, instead of using their memory...)
|-
| Earliest human whose name we know (Pharaoh {{w|Iry-Hor}} in Egypt) || 3100 BCE || 0.5 || The first named person we know of today! This was also mentioned as a "cool fact" in the title text of [[1355: Airplane Message]].
|-
| rowspan="5"| 3000 BCE
| {{w|Three Sovereigns and Five Emperors}} period in China || 2800 BCE || 0.4 || The temperature has finally dropped below 0.5°C above the 1961-1990 average after almost 2000 years of cooling from 0.6°C above the 1961-1990 average.
|-
| {{w|Gilgamesh}} || 2700 BCE || 0.4 || Gilgamesh was probably a Sumerian king whose tales were exaggerated into mythology.
|-
| {{w|Imhotep}} || 2600 BCE || 0.4 || Imhotep was not a pharaoh, but a wise commoner who was elevated to chancellor, high priest, and post-mortem divinity.
|-
| {{w|Maya civilization|Mayan}} culture emerges || 2600 BCE || 0.4 || Like the ancient Egyptians, Mayans are remembered for pyramids and {{w|logograph}}s.
|-
| {{w|Great Pyramid}} constructed || 2650 BCE || 0.4 || xkcd has discussed pyramids in [[1717: Pyramid Honey]] and {{what if|95|What If? 95: Pryamid Energy}}.

|-
| rowspan="3"| 2500 BCE
| {{w|Corded Ware culture}} in Europe || 2500 BCE || 0.3 || The term Corded Ware was invented by an archaeologist; no civilization actually called themselves that.
|-
| [To the left of the curve two rock musicians with long hair and electrical guitars are standing on either side of a small gate made of three slabs of stone, one on top of the other two standing stones.] {{w|Stonehenge}} completed || 2200 || 0.3 || This is a reference to the 1984 {{w|mockumentary}} about the fake rock band {{w|This Is Spinal Tap}}. In the movie the band wanted a giant Stonehenge prop 18 feet high, but a writing mistake gives them one that is only 18 inches.
|-
| {{w|Chariots}} developed || 2000 BCE || 0.3 || But {{w|Chariots of Fire}} came much later.

|-
| rowspan="3"| 2000 BCE
| {{w|Alphabetic writing}} developed in Egypt || 1750 BCE || 0.2 || Obligatory reference to xkcd [[1069: Alphabet]].
|-
| Last {{w|mammoth}}s on a tiny Siberian island go extinct || 1650 BCE || 0.2 || Many of the {{w|Pleistocene megafauna}} died in the {{w|Quaternary extinction event}}. Like the {{w|woolly rhino}} (see 12900 BCE) these animals likely became extinct in part due to {{w|Holocene extinction|humans hunting them}}, which may be why Randall included them in the chart. Most of the mammoths died out before 8000 BCE but {{w|Woolly_mammoth#Extinction|some survived in remote areas}} and the last known population died on {{w|Wrangel Island}} in the {{w|Arctic Ocean}} around 2000 BCE, slightly earlier than Randall shows here.
|-
| {{w|Minoan eruption}} || 1600 BCE || 0.2 || This volcano may have led to the downfall of Minoan civilization.

|-
| rowspan="5"| 1500 BCE
| {{w|Iron smelting}} || 1400 BCE || 0.1 || The beginning of the {{w|Iron Age}}.
|-
| {{w|Olmec}} civilization develops in Central America || 1350 BCE || 0.1 || No, Maggie, not Aztec, [http://vimeo.com/34002760 Olmec].
|-
| [A Trojan horse with two Cueball-like guys in front and a third standing on its back. Its back is at three Cueball’s height and its head rises to the level of the Cueball on its back. It stands on a platform with four wheel on the visible side. There is text on the horse] Setting of the ''{{w|Iliad}}'' and the ''{{w|Odyssey}}'' Text on horse: Not a trap || 1250 BCE || 0.1 || A reference to the {{w|Trojan War}} qua the drawing of the {{w|Trojan Horse}}. The horse was a big trap letting the soldiers hidden inside it into {{w|Troy}}. This explains why it has ''Not a trap'' written on it. Else they would not have taken the giant wooden horse present from their sworn enemies into their city just like that... Note that the Trojan horse isn't mentioned in the Iliad, and only recalled in passing by the characters in the Odyssey.
|-
| Invasion of the {{w|Sea peoples}}* * A real thing || 1200 BCE || 0.1 || {{w|Mermaid#One_Thousand_and_One_Nights|Sea people}} might sound like a reference to mythical {{w|mermaid}}s, so Randall feels the need to footnote that this event was ''a real thing'' (as opposed to his Pokémon reference, which he notes is ''not a real fact''). The sea peoples were a seafaring confederation of groups known to have attacked ancient Egypt around this time.
|-
| {{w|Polynesians}} explore the Pacific Ocean || 1000 BCE || 0.1 || {{w|Polynesian navigation}} was surprisingly widespread.

|-
| rowspan="8"| 1000 BCE
| [From 1000 BBC to 1000 CE the temperature is stable and very close to the 1961-1990 average.] || 1000 BCE || 0.1 || The temperature has fallen from the Holocene Optimum by half a degree to just a bit above the the 1961-1990 average. It will stay in this range for the next 2000 years.
|-
| {{w|Solomon}} || 1000 BCE || 0.1 || Solomon may have been a real historical king, but he probably did not threaten to chop a baby in half.
|-
| {{w|Iliad}} and {{w|Odyssey}} composed || 900 BCE || 0.1 || These classic myths were written more than 300 years after their supposed events. Archaeologists believe the city of {{w|Troy}} existed (and was destroyed by war around the right time period), but characters like Helen, Odysseus, and Achilles did not.
|-
| Rise of {{w|Greek city-states}} || 800 BCE || 0.1 || This is ''Sparta'', along with Athens and several others.
|-
| {{w|Neo-Assyrian Empire}} || 800 BCE || 0.1 || Hi, you may remember us from such kings as Adad-nirari and Sennacherib.
|-
| {{w|Ancient Olympic Games|First Olympics}} || 750 BCE || 0.1 || The first of the ancient Olympic Games is traditionally dated to 776 BC.
|-
| {{w|Zapotec civilization|Zapotec}} writing in modern Mexico || 600 BCE || 0.0 || Another Central American culture that fell to the Spanish invasion.
|-
| {{w|Confucius}} || 550 BCE || 0.0 || "He who knows all the answers has not been asked all the questions."

|-
| rowspan="10"| 500 BCE
| The stuff in the {{w|300 (film)|movie ''300''}}, but regular speed and with more clothing || 450 BCE || 0.0 || A reference to the {{w|Battle of Thermopylae}} by comparison with the 2007 movie ''300'' about this battle. The real Spartans wore armor, and real humans don't [http://www.google.com/search?q=300+slow-motion fly through the air in slow motion when struck].
|-
| {{w|Buddha}} || 450 BCE || 0.0 || Randall also mentions other religious figures like {{w|Jesus}} and {{w|Muhammad}}.
|-
| {{w|Nazca Lines}} || 350 BCE || 0.0 || These huge ancient drawings are difficult to see from ground level, leading some people to believe that they were intended for aliens.
|-
| {{w|Alexander the Great}} || 350 BCE || 0.0 || One of the most successful conquerors of the iron age, known for supposedly cutting the {{w|Gordian Knot}}.
|-
| {{w|Mayan hieroglyphics}} || 250 BCE || 0.0 || The {{w|Maya Calendar}} was probably created hundreds of years later.
|-
| {{w|Ashoka the Great}} || 250 BCE || 0.0 || The {{w|Edicts of Ashoka}} proselytized Buddhism across the continent.
|-
| {{w|Paper}} invented || 200 BCE || 0.0 || A significant step up from stone tablets or even papyrus.
|-
| {{w|Asterix}} || 100 BCE || 0.0 || Fictional main character in ''The Adventures of Asterix'', a comic series set around 50 BCE when {{w|Julius Caesar}} conquered {{w|Gaul}}.
|-
| {{w| Teotihuacan|Teotihuacán}} metropolis || 100 BCE || 0.0 || Another ancient city much beloved by archaeologists, even though they don't know who built it.
|-
| {{w|Julius Caesar}} || 50 BCE || 0.0 || Aside from being a conqueror, dictator, and deity, Julius had a big impact on {{w|Julian Calendar|calendars}}. The month of Quintilis was renamed July to honor him, and he was famously assassinated on the ides (middle day) of March.
|-

|-
| rowspan="8"|1 BCE 1 CE
| [Instead of a zero, there are two numbers for each of the two scales before (1 BCE) and after Christ (1 CE)] || 0 CE || -0.1 || Originally the year range went directly from 1 BC to 1 AD. The year zero has since been added for ease of mathematical and astronomical calculations.
|-
| {{w|Roman Empire}} || 1 CE || -0.1 || Julius never held the title "Emperor"; his adoptive son Augustus was the first to do so.
|-
| {{w|Jesus}} || 1 CE || -0.1 || Randall also mentions other religious figures like {{w|Buddha}} and {{w|Muhammad}}.
|-
| [To the left and erupting volcano.] {{w|Pompeii}} || 100 CE || -0.1 || The volcano is {{w|Mount Vesuvius}} which exploded in 79 CE and is famous for burying everyone in the close by city Pompeii preserving peoples bodies inside the huge amount of ash that swallowed the city very rapidly. Today it has given the archeologist lots of knowledge about the culture of that time.
|-
| {{w|Three Kingdoms}} period || 250 CE || -0.1 || Not just a series of movies and video games, but an actual thing that happened in China.
|-
| {{w|Gupta empire}} || 700 CE || -0.1 || Not as great as Ashoka, but still a pretty important time in the history of India.
|-
| Various groups take turns sacking {{w|Rome}} || 550 CE || -0.1 || 500 years is a pretty successful span for an empire.
|-
| {{w|Attila the Hun}} || 550 CE || -0.1 || He probably would not mind being remembered as one of the most infamous barbarians in history.

|-
| rowspan="4"| 500 CE
| {{w|Muhammad}} || 600 CE || 0.0 || Randall also mentions other religious figures like {{w|Buddha}} and {{w|Jesus}}
|-
| {{w|Tang Dynasty}} || 750 CE || 0.0 || A golden age in China, responsible for the development of printing, gunpowder, and many other advances.
|-
| [An arrow to the right of the dotted curve pointing down, takes a swing far out from the curve and then bends back again. The text label next to it breaks into the next 500 period. The dotted curve stays stable at the 1961-1990 average along this arrow.] {{w|Medieval warm period}} in Europe and some northern regions (too regional to affect the global average much) || 900 CE || 0.0 || Changes in ocean currents caused various regions to warm up while others cooled.
|-
| {{w|Leif Eriksson}} || 950 CE || 0.0 || Probably the first European explorer to reach North America.

|-
| rowspan="7"| 1000 CE
| [To the left a drawing of a compass with needle pointing the black end towards north east. There are labels for the four main directions (N, S, W, E) and a label next to it:] {{w|Magnetic compass}} navigation || 1050 CE || 0.0 || It's much easier to sail to the Orient when you can orient yourself.
|-
| [The dotted curve moves to the left towards lower temperature reaching a minimum around 1650 CE of about 0.6°C below the 1961-1990 average at the {{w|Little Ice Age}}.] || 1150 CE || -0.1 || This less than half a degree drop in temperature over 500 years was enough to cause the "Little Ice Age" which resulted in extended ice coverage in the winters in instance Europe. See more below at the entry for the Little Ice Age.
|-
| {{w|Ghengis Khan}} || 1200 CE || -0.2 || Mongol emperor. {{w|Gengar}} is not named after him, but [http://bulbapedia.bulbagarden.net/wiki/Kangaskhan_(Pokémon) Kangaskhan] and [http://awoiaf.westeros.org/index.php/Khal the Khals] are.
|-
| {{w|Zheng He}}’s fleet explores Asia and Africa || 1400 CE || -0.3 || He explored farther than European contemporaries like Dias or de Gama.
|-
| {{w|Aztec Empire|Aztec Alliance}} || 1400 CE || -0.3 || Aztec dominance only lasted a century until Cortes arrived, but their cultural legacy is indisputable.
|-
| {{w|Printing press}} || 1450 CE || -0.3 || {{w|Johannes Gutenburg}} ushered in the {{w|Age of Enlightenment}}.
|-
| {{w|Christopher Columbus|Columbus}} || 1490 CE || -0.3 || The time given here references when Christopher Columbus reached the {{w|Americas|New World}} in 1492. The five events around 1500 CE lies very close together but it fits with Columbus fitted in just before 1500.

|-
| rowspan="2"| 1500 CE
| {{w|European Renaissance}} || 1500 CE || -0.3 || From here on, the chart has labels for each 100 year increment instead of 500, but the scale stays the same. Important events happens so much faster in these last five hundred years, there isn't enough space to write all of them, so Randall has had to be selective. He includes {{w|Isaac Newton}} but leaves out {{w|Albert Einstein}}, includes {{w|airplane}}s but leaves out {{w|car}}s, etc.
|-
| {{w|Shakespeare}} || 1600 CE || -0.4 || xkcd references Shakespeare many times, such as [[79: Iambic Pentameter]] and [[1026: Compare and Contrast]].

|-
| rowspan="2"| 1600
| {{w|Isaac Newton|Newton}} || 1650 CE || -0.4 || Isaac Newton appears in various xkcd comics, such as [[626: Newton and Leibniz]].
|-
| [To the right of the dotted curve there is an arrow pointing down that makes a swing in towards the curve and then back out again. This is the coldest it has been since 9500 BCE. It is labeled:] ”{{w|Little Ice Age}}” || 1650 CE || -0.4 || This was not a true geologic Ice Age, just a slightly chilly period when the temperature fell a fraction of a degree, but still colder than it had been through 11,000 years of human civilization. In Europe the winters were so cold that the river {{w|Thames}} {{w|Little_Ice_Age#Europe|froze over}} hard enough to hold {{w|River Thames frost fairs}} between 1607 and 1814. And in 1658 {{w|Sweden}} crossed the {{w|Danish Straits}} on foot to invade {{w|Copenhagen}} in the {{w|March Across the Belts}}. It was only possible due to the harsh winters of the Little Ice Age, demonstrating how much half a degree of climate change can mean.

|-
| rowspan="2"| 1700
| {{w|Steam engines}} || 1750 CE || -0.4 || The {{w|Age of Steam}} heralded the upsurge of human CO2 emissions.
|-
| {{w|United States Declaration of Independence|Unites States Independence}} || 1770 CE || -0.3 || On July 4, 1776.

|-
| rowspan="3"| 1800
| {{w|Industrial Revolution}} || 1825 CE || -0.3 || Not to be confused with {{w|Industrial music}} such as Nine Inch Nails.
|-
| {{w|Electrical telegraph|Telegraphs}} || 1830 CE || -0.3 || [https://youtu.be/gEGQUgWBQL4?t=56s -. --- .-- --..-- / - .... . / -- --- - .... . .-. / --- ..-. / ... .- -- ..- . .-.. / -- --- .-. ... . / .- .-.. .-- .- -.-- ... / ... . -. - / - .... . / .-.. .- -.. / --- ..- - / --- -. / .- / .... --- .-. ... .]
|-
| [After this the dotted curve becomes solid.] || 1850 CE || -0.3 || From 1850 weather records became sufficiently accurate and widespread to greatly improve the precision of climate measurements. Hence the curve stops being an estimate and thus also stops being a dotted curve and becomes solid.

|-
| rowspan="6"| 1900
| {{w|Airplane}}s || 1900 CE || -0.3 || xkcd discusses airplanes many times, such as [[726: Seat Selection]] and {{what if|30|30: Interplanetary Cessna}}.
|-
| {{w|World Wars}} || 1930 CE || -0.2 || Likewise, there are many xkcds on this topic, such as [[261: Regarding Mussolini]] and {{what if|100|100: WWII Films}}.
|-
| [The solid line takes a step to the right close to the 1961-1990 average. Over the rest of the 1900s it moves closer to the 1961-1990 average, crossing it before 2000 where it almost reaches the maximum temperature of 0.5 °C above the 1961-1990 average from earlier in 8000 BCE.] || 1940 CE || -0.2 || This is what the previous 14000 pixels of comic has been leading up to. After a laborious 20 millennia of gradual and meandering climate change, it should be clear that a full degree of warming in a single century is unprecedented in human history, and very unlikely to be natural variation.
|-
| {{w|Fossil fuel}} CO2 emissions start rapidly increasing || 1950 CE || -0.1 || The infamous [http://www.skepticalscience.com/Hockey-stick-or-hockey-league.html "hockey stick"] starts around here.
|-
| {{w|Nuclear weapons}} || 1950 CE || -0.1 || The Working Group on the 'Anthropocene' suggests dating the {{w|Anthropocene}} epoch from ~1950. The week after this comic [[1736: Manhattan Project]] with a mushroom cloud was released.
|-
| {{w|Internet}} || 1980 CE || 0.1 || The origin of the internet dates back to 1960 but it began growing rapidly in 1980. By placing the invention of the {{w|internet}} at 1980 in the chart, just where the temperature curve starts its most rapid increase, Randall uses this [[552: Correlation|correlation]] to humorously imply that the internet caused the rise in temperature. This is also where the temperature crosses the 1961-1990 average, which has to happen somewhere due to the {{w|Intermediate Value Theorem}}.

|-
| rowspan="2"| 2000
| {{w|Northwest Passage}} opens || 2000 CE || 0.4 || This was dramatic evidence that the climate had changed. When global warming removes enough sea ice to create shipping routes that never existed before, then it is clear to people that ''something'' is changing, even if they disregard who/what is responsible for the change.
|-
|[From here to present day the solid line increases rapidly and in 2016, present day, is almost reaches 1°C above the 1961-1990 average, with about 0.8°C above the 1961-1990 average.] || 2016 CE || 0.8 || '''Notice''': [http://www.skepticalscience.com/argument.php?a=11&p=2 Warming did not stop] in 1998.

|-
| rowspan="3"| 2016
| | Present day || 2016 CE || 0.8 || Today, just after the two hottest months ever measured since 1850 had ended (July and August 2016), this comic was released with the message displayed very clearly here below. Act now or fry...
|-
| [From here the curve once again becomes dotted as this is the future. After one dot it splits in two and after the first two dots another split between them occurs forming three possible future dotted curves.] || 2016 CE || 0.8 || Here stops the data and the projection into the future begins so the curve again becomes dotted. Three different scenarios are depicted.
|-
|The first curve bending down before the others, and thus to the right of the other two reaches about 1.2°C above the 1961-1990 average and then goes straight down and stops at the 2100 line. An arrow points to it from the left and a label is written partly before and the rest after the 2100 line to the left of the curve:] Best-case scenario assuming immediate massive action to limit emissions || 2100 CE || 1.2 || If humanity does all in its power to stop global warming we might be able to halt the global warming already before 2050 keeping the maximum temperature to just 1.2°C above the 1961-1990 average. Only 0.4°C above today's temperature. (Note that this is not, in fact, the absolute best-case scenario, as it assumes that no new greenhouse gasses are either added to or removed from the atmosphere in the future; the temperature rise could be kept to an even lower level if some or all of the already-emitted greenhouse gasses were removed from the atmosphere.)

|-
| rowspan="2"| 2100
| [The middle curve bends a little down after reaching 1.3°C above the 1961-1990 average, and then continues this path reaching 2°C above the 1961-1990 average in 2100. An arrow point from below to it and a label is written below the curve and below 2100 line:] Optimistic scenario|| 2100 CE || 2.0 || If all the current realistic preventions are implemented, which might not be so realistic, then we may not even stop the warming but slow it down so we "only" reach 2°C above the 1961-1990 average in 2100 CE but it would not stop there. This is half the temperature change experienced since the ice age, but the other way. This was directly referenced in the title text of [[1379: 4.5 Degrees]]: ''That's only HALF an ice age unit (IAU), which is probably no big deal.''
|-
| [The last line continues along the path from the last 16 years of the solid line reaching 4.2°C above the 1961-1990 average at 2100, almost as far on the other side of the 1961-1990 average in 150 years as it took 14,000 years to move from the other side from the start of the chart. Another arrow point to this from below with a label below the curve and below 2100 line:] Current Path || 2100 CE || 4.2 || In this last scary scenario Randall assumes the temperature keeps rising steadily by extrapolating along the slope of the last two to three years. Randall has warned about the hazards of [[Extrapolating]], but this line is in fact [http://www.skepticalscience.com/climate-best-to-worst-case-scenarios.html below the worst case predictions]. If this comes true we will reach a temperature increase taking us from the 1961-1990 average and in just 125 years to 4.2°C above this average. That is just as far above this average in that short time span as the ice age temperature was below. And it took more than 11,000 years for nature to reach such an increase. Randall already contemplated what this would be like in the +1 ice age unit (IAU) panel of [[1379: 4.5 Degrees]] two years ago, as well as in [[164: Playing Devil's Advocate to Win]] almost 10 years ago. He may get to ''enjoy quite a ride'' as he "wished" for back then.

There is no reason to assume the temperature will not keep rising past 2100 CE, so the {{w|Cretaceous Thermal Maximum|"Hothouse Earth"}} of the early {{w|Cretaceous period}} mentioned in the 4.5 degree comics +2 IAU panel might come to pass in future centuries if we continue on our current path. On the bright side, modern civilization might collapse if this trend keeps up, which would drastically cut our releases of carbon dioxide and other greenhouse gasses into the atmosphere. But then again, positive feedback from methane in melting {{w|permafrost}} might take over... Good luck Earth.
|}

===Sources===
The image attributes climate data sources as "Shakun et al. (2012), Marcott et al. (2013), Annan and Hargreaves (2013), HadCRUT4, IPCC":
* Shakun et al. (2012) - [http://www.nature.com/nature/journal/v484/n7392/full/nature10915.html Nature], [http://www.atm.damtp.cam.ac.uk/mcintyre/shakun-co2-temp-lag-nat12.pdf (pdf)]
* Marcott et al. (2013) - [http://science.sciencemag.org/content/339/6124/1198 Science], [http://content.csbs.utah.edu/~mli/Economics%207004/Marcott_Global%20Temperature%20Reconstructed.pdf (pdf)]
* Annan and Hargreaves (2013) - [http://www.clim-past.net/9/367/2013/cp-9-367-2013.html Climate of the Past] [http://www.jamstec.go.jp/frsgc/research/d5/jdannan/LGM_temp.pdf (pdf)]
* {{w|HadCRUT#HadCRUT4 wikipedia|HadCRUT4}} - [http://www.metoffice.gov.uk/hadobs/hadcrut4/ Official site]
* {{w|Intergovernmental_Panel_on_Climate_Change|IPCC}} -[http://www.ipcc.ch/ Official site]

==Transcript==
'''Note''' there are several spelling errors in the comic, so please do only correct spelling errors that are not part of the comic! See more in the [[#Trivia|trivia section]].
:[A large heading, followed by a sub-caption. Below that two lines with a statement in between:]
:<big>A timeline of Earth’s average temperature</big>
:since the last ice age glaciation
:When people say “The climate has changed before,” these are the kinds of changes they’re talking about.

:[A very long chart below the headings above is headed with a label for the scale of the X-axis above the chart. Below that a sub-caption. To the left an arrow down to the top of the chart pointing to the dotted curves starting point (at -4.3°C below the 1961-1990 average) with a label above the arrow. And arrow pointing left to the left of the center and another pointing right to the right of the center has labels. Below these is the temperature scale of the X-axis, with 9 ticks between the borders each with a label ranging from -4 to +4°C compared to the 1961-1990 average, but with another step in each direction not labeled towards to axis so the chart covers -5 to +5°C compared to the 1961-1990 average.]
:'''Temperature'''
: Compared to the 1961-1990 average
:Start
:Colder
:Warmer
:-4°C -3°C -2°C -1°C 0°C +1°C +2°C +3°C +4°C

:[To the right of the chart is a gray text standing on the side down along the outer boarder of the chart with the sources for the chart:]
: Source: Shakun et. al. (2012) , Marcott et. al. (2013), Annan and Hargreaves (2013) , HadCRUT4, IPCC 

:[The chart is split in 10 columns by the temperature scale and the borders. The two central columns are white, and then from there to the left the background becomes a faded color that changes from light blue to blue at the edge in four steps. Similarly to the right the color changes from light red to red. To the left there is a time scale taking 500 years leaps from 20,000 BCE all the way to year 1, where there are two years, one for BBC and one for CE. The 500 year leaps continue until 1500 CE and from there the steps are down to 100 years until 2100 with also present day 2016 labeled. After 1500 the CE is omitted. The labels stop there, but there is space below covering down to 2200 CE. There is clearly visible division line across the chart on the level of each of the 500 step, and fainter lines for each of the 100 steps all the way even though only the last 5 of these 100 steps are labeled. There is a similar clear line at 2016. Below each step on the Y-axis is noted, and then any text starting before the next step is noted below indented. If there are extra image belonging to text this is indented once more. The graph that the whole chart is about is a dotted line that begins at the “start” point mentioned above at -4.3°C and then begins to go straight down. It will change left and right all the way down. To being with all text and most drawings are to right of the dotted curve. Whenever something is to the left it will be noted. When it says to the left above something, and then nothing over the next, then the next will be to the right. Only at the very bottom are there more entries to the left than right. ]
:20000 BCE
::[An arrow goes from the dotted line to the central line at 0°C. In the middle of the line there is a temperature label:]
::4.3°C
::At the start of our timeline, 22,000 years ago, Earth is 4°C colder than during the late 20th century.
::Boston is buried under almost a mile of ice, and the glaciers reach as far south as New York City.
:::[The Statue of Liberty is shown in front of a glacier front. A very tiny Cueball is on top of the glacier. The drawing is labeled and so is also the glacier.]
:::New York
:::Ice
:::[A guy with a white knit cap is seen walking in a snowy landscape leaving black footprints behind him. He walks through the white central part of the chart.]
:::[The skyline of Boston is shown with two clear buildings among all the other. Above it is a line and in between this area has been filled with thin lines. The drawing is labeled and so is this area. Also the skyline has an arrow pointing at it with a label:]
:::Boston
:::Ice
:::Modern skyline

:19500 BCE
::But the world is about to warm up.
::By this time, humans have already spread across Africa, Eurasia, and Australia.
::They’ve created painting, pottery, rope, and bows and arrows, but haven’t developed writing or farming.

:19000 BCE
::Changes in the Earth’s orbit mean that more sunlight reaches the polar ice…
:::[A line chart with a labeled Y-axis with three labeled ticks. The curve starts up and then goes down five times and up four times ending down. There is one plateau towards the end compared to the rest of the curve where the ups and downs are quite alike.]
:::Summer sun W/m2 at 60°N
:::550
:::500
:::450

:18500 BCE
::[A map of the world. At the top is a light gray area covering North America, Greenland and northern Europe and most of the northern part of Russia. A similar gray area covers Antarctica. There are two labels in the gray area above and one in the gray area below:]
::Ice Ice
::Ice

:18000 BCE
::…And the ice sheets start to melt.

:17500 BCE
::Temperatures have been creeping upward, but around this point, CO2 levels start to climb…

:17000 BCE
::…And then the warming speeds up.

:16500 BCE
::[Cueball is standing with a spear just the right of the graph talking to a rabbit.]
::Cueball: Still pretty cold.

:16000 BCE
::[Megan points to the graph to the right of her and between her and Ponytail standing on the other side. Mean is the first drawing on the left side of the dotted curve, which has hardly moved since the beginning, only to just on the other side of 4°C.]
::[In the right part of the chart is an explanation of the data. Below the first two lines there are four drawings each showing possible temperature swings in reality compared to the smoothed data that represents the dotted curve of the entire chart. The dotted curve is shown in all four drawings and a thin line is shown running along it but with much more fluctuation left and right on the first two, a large spike right on the third and a large bump way right on the fourth. Above these there are two labels. The first labels is inside a bracket that covers the first three, and the last label is for the last drawing. Below is a list of sources.]
::Limits of this data:
::Short warming or cooling spikes might be “smoothed out” by these reconstructions but only if they’re small or brief enough.
:::Possible Unlikely
::Reconstructions are from Shakun (2012) and Marcott (2013), scaled to Annan + Hargreaves (2013) estimate for the last glacial period.

:15500 BCE
::In what is now France, humans paint murals on the walls of the Lascaux caves
::[Hairy paints three animals, two with horns, and two humans, Cueball holding hand with Hairy who has a spear. On the other side of the central line Megan writes three letters, the last of which is reversed.]
:::NIИ

:15000 BCE
::Ice sheets around Alaska shrink, exposing a land bridge between Asia and North America
::[From around the bottom if this section and down to 11500 BCE the dotted curve moved steadily to the right towards warmed temperature peaking close to -1.5°C. Before this the temperature had not moved much away from that at the start.]

:14500 BCE
::[Cueball walks right looking back at the graph behind him. Megan walks in front of him pointing further right.]
::Cueball: Cool.
::Humans reach North America.

:14000 BCE
::The edge of the ice withdraws from New York City and retreats North.
::[A large glacier front speaks in a speech bubble with an arrow pointing at it. Behind is there are four peaks in the horizon and in front of it three small melting pools and some rocks on the ground.]
::Glacier: ''That’s it! I’m moving to Canada!''

:13500 BCE
::Humans domesticate dogs
::(Date uncertain, may be much earlier)
::[Megan and Cueball is watching a wolf looking at them.]
::Megan: Okay, you can live in our homes and we’ll feed you, but we’ll still get mad f you poop on the floor.
::Wolf: Deal.
::Cueball: And we get to breed you to be tiny and dress you in little costumes.
::Wolf: …Wait.

:13000 BCE
::[Randall did not use the normal spelling for Woolly Rhino, but this is an accepted alternative spelling:]
::Wooly Rhino goes extinct
::Oregon is scoured by huge floods as glacial dams burst and lakes of meltwater flow to the sea

:12500 BCE
::Ice sheets withdraw from Chicago

:12000 BCE
::Humans settle Abu Hureyra in Syria

:11500 BCE
::[An arrow on the left side of the dotted curve is pointing down along the dotted curve and to the left indicate temperature is declining again, meaning the dotted curve now moves left to colder temperatures. This only continues until 10500 BCE. It is only the second time something is noted on the left side after Megan at 16000 BCE]
::Temperatures start to decline, mainly in the Northern hemisphere
::This may be caused by changes in ocean circulation due to the floods of cold fresh meltwater flowing into the Atlantic as the North American ice sheet melts.
::This cooler period is called the Younger Dryas

:11000 BCE
::[This is the first text to the left of the dotted curve:]
::Humans reach Argentina

:10500 BCE
::[An arrow pointing down along the right side of the dotted curve and to the right indicate temperature is increasing again, meaning the dotted curve now moves right to hotter temperatures. This continues until 8000 BCE where it levels out just above 0°C.]
::Warming resumes
::Human settlements at Jericho

:10000 BCE
::First development of farming

:9500 BCE
::Saber-toothed cat goes extinct
::[To the left:]
::Horses disappear from North America

:9000 BCE
::[To the left, Randall spelled Pokémon wrong:]
:::Last North American Pokemon go extinct
:::[Cueball with a speak and Megan is looking up at this last “fact”.]
:::Megan: That is not a real fact.
::Temperatures reach modern levels
::Rising seas cut off the land bridge between North America and Asia
::Cattle domesticated

:8500 BCE
::Ice sheets retreat across the Canadian border
::Temperatures start to level out slightly above 1961-1990 levels

:8000 BCE
::[The above sentence breaks over the 8000 BCE line. From here a maximum in temperature on the chart is reached at 0.5°C which will not be overtaken until 2000 CE. It stays almost constant here until 5000 BCE where a slight cooling begins.]

:7500 BCE
::[To the left:]
::This warm, stable period is called the Holocene Climate Optimum
::[To the left:]
::Jiahu settled in China

:7000 BCE
::Final collapse of the North American ice sheet leads to rapid 2-4m sea level rise…
::[A small arrow points down and left to the right of the dotted curve. There is a small decrease in temperature but it is very small and would have been missed without the arrow and label.]
::…And a period of cooling in the Northern hemisphere

:6500 BCE
::[To the left:]
::As seas rise to near their modern levels, Britain is cut off from mainland Europe

:6000 BCE
::Humans develop copper metalworking

:5500 BCE
::[To the left:]
::Massive volcanic eruption in Oregon creates crater lake
::Gold metalworking

:5000 BCE
::[To the left:]
::Invention of the wheel
::[To the left. To the right of the dotted curve is an arrow pointing down and slightly left. From here temperature decreases very slowly but steadily from 0.5°C until 1000 BCE where a stable plateau is reached around 0°C.]
::Earth begins to cool slowly mainly due to regular cycles in its orbit

:4500 BCE
::[To the left:]
:: Proto-Indo-European language develops
:::[To the right of the curve Ponytail holds up a hand towards Cueball.]
:::Ponytail: Let’s make out language heavily inflected, so future students have to memorize a zillion verb endings!
:::Cueball: Okay!
::[To the left:]
::Permanent settlements in the fertile crescent

:4000 BCE
::Horses domesticated
::[To the left:]
::Minoan culture arises on Crete

:3500 BCE
::Egyptian mummification
::Rise of the Indus Valley civilization
::[To the left:]
::Invention of writing in Sumer “prehistory” ends, “history” begins
::Earliest human whose name we know
::(Pharaoh Iry-Hor in Egypt)

:3000 BCE
::''Three Sovereigns and five emperors'' period in China
::Gilgamesh
::[To the left:]
::Imhotep
::Mayan culture emerges
::[To the left:]
::Great Pyramid constructed

:2500 BCE
::Corded Ware culture in Europe
::[To the left of the curve two rock musicians with long hair and electrical guitars are standing on either side of a small gate made of three slabs of stone, one on top of the other two standing stones.]
::Stonehenge completed
::Chariots developed

:2000 BCE
::[To the left:]
::Alphabetic writing developed in Egypt
::Last mammoths on a tiny Siberian island go extinct
::[To the left:]
::Minoan eruption

:1500 BCE
::[To the left:]
::Iron smelting
::Olmec civilization develops in Central America
::[A Trojan horse with two Cueball-like guys in front and a third standing on its back. Its back is at three Cueball’s height and its head rises to the level of the Cueball on its back. It stands on a platform with four wheel on the visible side. There is text on the horse]
:::Setting of the ''Iliad'' and the ''Odyssey''
:::Text on horse: Not a trap
::[To the left:]
::Invasion of the Sea peoples*
::* A real thing
::Polynesians explore the Pacific Ocean

:1000 BCE
::[From 1000 BBC to 1000 CE the temperature is stable and very close to 0°C.]
::[To the left:]
::Solomon
::[Randall spelled Iliad wrongly this time:]
::Illiad and Odyssey composed
::[To the left:]
::Rise of Greek city-states
::Neo-Assyrian empire
::[To the left:]
::First Olympics
::Zapotec writing in modern Mexico
::[To the left:]
::Confucius

:500 BCE
::[To the left:]
::The stuff in the 300 (film)|movie ''300'', but regular speed and with more clothing
::Buddha
::Nazca Lines
::[To the left:]
::Alexander the Great
::[To the left:]
::Mayan hieroglyphics
::Ashoka the Great
::[To the left:]
::Paper invented
::[To the left:]
::Asterix
::Teotihuacán metropolis
::[To the left:]
::Julius Caesar

:[At the year 0, there is instead two numbers for each of the two scales before and after Christ:]
:1 BCE
:1 CE
::[To the left:]
::Roman Empire
::Jesus
::[To the left and erupting volcano.]
::Pompeii
::Three Kingdoms period
::[To the left:]
::Gupta empire
::[To the left:]
::Various groups take turns sacking Rome
::[Randall spelled Attila wrong:]
::Atilla the Hun

:500 CE
::Muhammad
::[To the left:]
::Tang Dynasty
::[An arrow to the right of the dotted curve pointing down, takes a swing far out from the curve and then bends back again. The text label next to it breaks into the next 500 period. The dotted curve stays stable at 0°C along this arrow.]
::Medieval warm period in Europe and some northern regions (too regional to affect the global average much)
::[To the left:]
::Leif Eriksson

:1000 CE
::[The dotted curve moves to the left towards lower temperature reaching a minimum around 1650 of about -0.6°C at the Little Ice Age.]
::[To the left a drawing of a compass with needle pointing the black end towards north east. There are labels for the four main directions and a label next to it:]
:::N
:::W E
:::S
:::Magnetic compass navigation
::[To the left:]
::Ghengis Khan
::Zheng He’s fleet explores Asia and Africa
::[To the left:]
::Aztec Alliance
::[To the left:]
::Printing press
::[To the left:]
::Columbus

:1500 CE
::European Renaissance
::[To the left:]
::Shakespeare

:1600
::[To the left:]
::Newton
::[To the right of the dotted curve there is an arrow pointing down that makes a swing in towards the curve and then back out again. At -0.6°C this is the coldest it has been since 9500 BCE. It is labeled:]
::”Little Ice Age”

:1700
::Steam engines
::[To the left:]
::Unites States Independence

:1800
::Industrial Revolution
::[To the left:]
::Telegraphs
::[After this the dotted curve becomes solid.]

:1900
::[To the left, and on the line for 1900:]
::Airplanes
::[To the left:]
::World Wars
::[The solid line takes a step to the right close to 0°C. Over the rest of the 1900s it moves closer to 0°C crossing it before 2000 where it almost reaches the maximum temperature of 0.5 °C from earlier in 8000 BCE.]
::Fossil fuel CO2 emissions start rapidly increasing
::[To the left:]
::Nuclear weapons
::[To the left:]
::Internet

:2000
::Northwest Passage opens
::[From here to present day the solid line increases rapidly and in 2016 present day is almost reaches 1°C, with about 0.8°C.]

:2016
::[To the left on the line for 2016:]
::Present day
::[From here the curve once again becomes dotted as this is the future. After one dot it splits in two and after the first two dots another split between them occurs forming three possible future dotted curves. The first curve bending down before the others, and thus to the right of the other two reaches about 1.2°C and then goes straight down and stops at the 2100 line. An arrow points to it from the left and a label is written patly before and the rest after the 2100 line to the left of the curve:]
::Best-case scenario assuming immediate massive action to limit emissions

:2100
::[The middle curve bends a little down after reaching 1.3°C and then continues this path reaching 2°C in 2100. An arrow point from below to it and a label is written below the curve and below 2100 line:]
::Optimistic scenario
::[The last line continues along the path from the last 16 years of the solid line reaching 4.2°C at 2100, almost as far on the other side of 0°C in 150 years as it took 14000 years to move from the other side from the start of the chart. Another arrow point to this from below with a label below the curve and below 2100 line:]
::Current Path

==Trivia==
*There have been several ''[[:Category:Large drawings|large drawings]]'' in the history of xkcd, and also some that are bigger than this one (for instance [[1110: Click and Drag]]).
**But among those that can be viewed in one go, without downloading a larger file or moving around, this is by far the longest.
**The next longest is probably [[482: Height]].
*The timeline starts at 20,000 BCE (22,000 years ago) and ends at 2100 CE, thus covering 22,100 years.
*There are several spelling mistakes.
**Most obvious is the second time Randall wrote the word "Iliad," because he just spelled it correctly at 1500 BCE and then spelled it ''Illiad'' at 1000 BCE with two "L"s.
**Attila the Hun becomes ''Atilla the Hun'' with ''one'' T and ''two'' L's.
**Pokémon is spelled ''Pokemon'', but then again that is not so strange for Randall (see [[1647: Diacritics]]). But he usually spells it correctly as in the recent comic [[1705: Pokémon Go]].
**Note that the fact that Woolly rhinoceros becomes ''Wooly rhino'' with only one l is not a spelling mistake but an alternative spelling of the word.
*Notably absent are the following facts
**1850: methodical temperature record begins. Although this fact is indirectly indicated when the temperature curve becomes solid around 1850 and until present day.
**The entire swing period between 20 and 200 thousand years prior to now, which would depict temperature swings with increasing frequency and amplitude (ref geological record). But of course this could not be included in a comic that only goes back to 20,000 BCE. And as is clear from the curve the temperature has been very stable these last 10,000 years which may explain why human civilization has peace from rapid changes in the environment to develop in the first place. And now it seems that we are causing this stable plateau to come to an end, and that was the point of the comic.
**The 300 million years prior to that, during much of which the Earth was significantly warmer than now. However, the data's temporal precision decreases with age; seemingly abrupt changes millions of years ago might have happened over centuries or millennia. Hence, the older data is not usable to compare rates of change.

===Popularity of comic===
*This comic became popular with a much broader audience than most xkcd comics. It was discussed admiringly by news sites such as [http://www.popsci.com/xkcd-earth-average-temperature-timeline Popular Science], [http://reason.com/blog/2016/09/14/send-around-this-xkcd-climate-change-web Reason], [http://www.slate.com/blogs/bad_astronomy/2016/09/13/xkcd_takes_on_global_warming.html Slate], [http://www.smithsonianmag.com/smart-news/new-comic-masterfully-shows-how-climate-has-changed-through-time-180960451/ Smithsonian], and [http://www.forbes.com/sites/ericmack/2016/09/13/heres-22000-years-of-climate-changes-in-a-single-comic/ Forbes]. It was promoted by famous individuals such as [[Elon Musk]] and [http://www.ecowatch.com/xkcd-climate-change-2003991855.html John Green], and of course criticized by climate skeptics such as [http://wattsupwiththat.com/2016/09/20/josh-takes-on-xkcds-climate-timeline/ Anthony Watts] and [http://joannenova.com.au/2016/09/how-to-make-climate-graphs-look-scary-a-reply-to-xkcd/ Joanne Nova].
*Due to increased interest, Randall decided to push the release of the next comic [[1733: Solar Spectrum]] one day back for a rare [[:Category:Thursday comics|Thursday release]] instead of the scheduled [[:Category:Wednesday comics|Wednesday release]].
**He [http://web.archive.org/web/20160915101125/http://xkcd.com/ noted this] above [http://www.explainxkcd.com/wiki/images/a/a6/1732_Earth_Temperature_Timeline_header_text_changed_for_all_comics.png all the comics] in the [http://www.explainxkcd.com/wiki/images/6/6d/1732_Earth_Temperature_Timeline_header_text_changed.png header text on xkcd]:
::Note: Since a lot of new people are here looking for this chart today,
::I'll be posting Wednesday's comic on Thursday instead.
*Before that the [http://web.archive.org/web/20160912181546/https://xkcd.com/ normal heading] with the release day of xkcd was shown.
**This was (of course) still there Tuesday the [http://web.archive.org/web/20160913231501/http://xkcd.com/ day after] the release, because it was first on Wednesday there were reason to note the delay.
**It stayed in place even [http://www.explainxkcd.com/wiki/images/6/62/1732_Earth_Temperature_Timeline_header_text_changed_also_when_next_comic_was_released.png for some time after] the "Wednesday" comic was released on Thursday, but was [http://web.archive.org/web/20160915154605/http://xkcd.com/ then removed] before [http://www.explainxkcd.com/wiki/images/e/ee/1732_Earth_Temperature_Timeline_header_text_back_to_normal_shortly_after_next_comic_was_released.png noon (EST)] on Thursday.
***Randall did thus not post a link to this comic in the header text for new visitors to use, only giving them that one extra day.
*Even though the next comic was released on a Thursday, the scheduled Friday comic [[1734: Reductionism]] was still released as planned.
**This was also the first time this occurred on xkcd - see [[1734:_Reductionism#Trivia|this trivia item]] from the Friday comic.
==== Removal of warning and footnote ====
*Maybe it was because of this popularity that both the more than 10 year old [[xkcd warning]] as well as the [[footnote#Original_footnote|original footnote]] was [[footnote#Removal_of_original_footnote|removed]] on the day of this comic's release?
**The next footnote was added 22 days later.

{{comic discussion}}

[[Category:Comics with color]]
[[Category:Large drawings]]
[[Category:Charts]]
[[Category:Timelines]]
[[Category:Line graphs]]
[[Category:Maps]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Hairy]]
[[Category:Comics featuring real people]] 
[[Category:Multiple Cueballs]]
[[Category:Climate change]]
[[Category:Science]]
[[Category:Animals]]
[[Category:Music]] 
[[Category:Fiction]] 
[[Category:Sport]] 
[[Category:Religion]] 
[[Category:Internet]]
[[Category:Pokémon]]

1760: TV Problems

2017-01-07T02:57:45Z

108.162.237.88: /* Explanation */

{{comic
| number = 1760
| date = November 16, 2016
| title = TV Problems
| image = tv_problems.png
| titletext = Certified skydiving instructors know way more about safely falling from planes than I do, and are way more likely to die that way.
}}

==Explanation==
In this comic, [[Cueball]] has broken his computer's software so much that he is unable to "turn on the news" as requested by [[White Hat]]. Since his computer is not working at all, he is using the next best thing to download a fix: his smartphone, via a {{w|CD}}. This is probably one of two things:

# Cueball has broken his computer enough that the operating system no longer works, in which case he would probably be downloading an {{w|ISO file}}(which is the type of image on a CD) to his phone. This would enable him to connect his phone as a USB device to his computer and boot from it. After booting from his phone, he could repair or reinstall his computer's operating system.
# Cueball is trying to connect his computer to his TV, but needs a driver or other software to make the connection. He is unable to connect to the Internet from his computer (Maybe he is using a network dongle that also requires drivers/software to function, or maybe the internet from his ISP is down, so he is using cellular data), so he is using his phone to download the files. Perhaps the computer has internal {{w|Bluetooth}} or he can transfer files from his phone to his computer via a wired connection.

He later states that even that first step of mending won't be enough to display the news, as his computer's state is so bad that being able to send information to the TV screen is just the first step of debugging. In the last panel, he tells White Hat that his computer science degree just helps him understand ''how'' he ended up with such a terrible situation, but did not give him enough foresight to prevent the most unexpected issues. The title text clarifies this statement with a similar problem- when things start to go horribly wrong while falling from a plane, certified skydiving instructors will be able to better understand why and how bad the situation is, but won't be able to do anything if their usual tools have failed them. Besides, while they are less likely to make a fatal mistake on a given flight and fall, they are more likely to make one in their life, because of the far greater number of attempts. This is especially true considering most people ''never'' attempt a jump in their lives, giving them absolutely ''zero'' probability of dying in a skydiving accident. This also resembles [[795: Conditional Risk]]: the more informed a person is, the more likely this person is to suffer from the issue they know about.

Computers breaking in unexpected ways, and somewhat weird solutions to computer problems seems to be a thing with Cueball - and probably Randall as well. At that point, you might assume he probably enjoys it. In [[1586: Keyboard Problems]], he also had a problem involving both software and hardware. [[1739: Fixing Problems]] could very well apply to this comic; Cueball may have ended with this situation while trying to correct a simple problem (eg: channels in the wrong order), and just made the situation worse every step of the way. In [[456: Cautionary]], he teaches his cousin about <s>break</s>fixing a computer.

<ref>Martin_Samuelson, [https://www.reddit.com/r/apple/comments/3w32by/eddy_cue_says_were_working_on_a_new_apple_tv/cxt0noy/ "Physical buttons are great"]</ref> In this instance Cueball has his single tasking phone busy while he downloads to it and cannot interrupt what he's doing just to use the phone as a remote for the TV, although it appears more that the TV is one of the things he is trying to fix.

==Transcript==
:[Cueball is sitting by his TV, holding his phone, when White Hat walks in.]
:White Hat: Hey, turn on the news.
:Cueball (Sitting on the floor in front of a computer holding a cell phone): Can't. Downloading a CD onto my phone.

:White Hat (off-screen): Why?
:Cueball: So I can use it to fix my computer's operating system enough that I can teach it to talk to my TV screen.

:White Hat: But then you'll be able to watch the news?
:Cueball: (off-screen): No.

:White Hat: Don't you have a computer science degree?
:Cueball: That just means I ''understand'' how everything went so wrong.

==References==
<references />

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring White Hat]]
[[Category:Computers]]

Talk:1767: US State Names

2016-12-02T21:14:29Z

108.162.237.88:

I'm wondering whether this could be a joke about autocorrect/suggested completion as found in smartphone texting apps.
[[User:Dromaeosaur|Dromaeosaur]] ([[User talk:Dromaeosaur|talk]]) 08:06, 2 December 2016 (UTC)
:But would autocorrect replace Texas with Hexxus?--[[User:Blaisorblade|Blaisorblade]] ([[User talk:Blaisorblade|talk]]) 09:02, 2 December 2016 (UTC)

According to Wikipedia Will Wheaton is not from Washington [[Special:Contributions/162.158.133.150|162.158.133.150]] 08:56, 2 December 2016 (UTC)

I think the starting point is the ambiguity of the standard "Name all 50 states" challenge. I'm no native speaker but "Name" means both "invent a new name" and "give the correct name for", and Randall is misunderstanding this on purpose. Maybe that's obvious to some, but it seems the sort of thing worth explaining here?--[[User:Blaisorblade|Blaisorblade]] ([[User talk:Blaisorblade|talk]]) 09:02, 2 December 2016 (UTC)

"Colocated" is technically misspelled (it's either "co-located" or "collocated"), though that could be for the sake of matching it to "Colorado." However, the word is used in many situations other than "co-location center" (e.g. workers being collocated in the same office), so unless Colorado is particularly notable for its co-location centers, I don't think it makes sense to claim that that's what it's specifically referring to. –[[User:PhantomLimbic|PhantomLimbic]] ([[User talk:PhantomLimbic|talk]]) 09:36, 2 December 2016 (UTC)
:Hmm, it looks like "colocated" is a spelling used specifically within the industry, so perhaps the claim is warranted after all. –[[User:PhantomLimbic|PhantomLimbic]] ([[User talk:PhantomLimbic|talk]]) 09:50, 2 December 2016 (UTC)

Isn't it a challenge to correctly name all the states with clues given as to the proper name?[[Special:Contributions/162.158.91.95|162.158.91.95]] 10:27, 2 December 2016 (UTC)

I think the challenge is supposed to be a blank map that someone has filled out in red pen. The joke is that whoever filled it out does pretty much know all of the states but isn't really clear on their actual names.[[Special:Contributions/108.162.238.50|108.162.238.50]] 10:34, 2 December 2016 (UTC)
Right, I get you. Something a bored Geography teacher may or may not find amusing when it comes to giving out detentions for the week :)[[Special:Contributions/162.158.91.95|162.158.91.95]] 10:40, 2 December 2016 (UTC)

Is Georgia / George a reference to the kings of georgia (of which 9 were named george)? (https://en.wikipedia.org/wiki/List_of_Georgian_monarchs) [[Special:Contributions/141.101.98.253|141.101.98.253]] 10:49, 2 December 2016 (UTC)

About "OH HI", I've understood it as a reference to the cult movie "The Room" (2003) (http://www.imdb.com/title/tt0368226), where the main character Johnny greets the other ones with a "Oh hi!". But that's maybe only my view. [[Special:Contributions/108.162.226.112|108.162.226.112]] 12:12, 2 December 2016 (UTC)

As a Hoosier, I think that the name given to Indiana is on point. [[Special:Contributions/108.162.238.45|108.162.238.45]] 14:06, 2 December 2016 (UTC)

Shouldn't the table be alphabetical and the transcript be in geographical order (rather than the other way around as it is now)?[[Special:Contributions/108.162.219.83|108.162.219.83]] 15:12, 2 December 2016 (UTC)

I'm fairly confident that "Mossouri" is not a typo, but rather a reference to Katie Mossouris, the Microsoft security researcher who created the bug bounty program. see https://en.wikipedia.org/wiki/Katie_Moussouris. [[Special:Contributions/108.162.245.54|108.162.245.54]] 18:06, 2 December 2016 (UTC)

Dear, it's old to complain of xkcd's various quality drops, but I think this is my turn. A good number of recent comics have just been variously exaggerated text lists of stuff. Randall might just as well switch to a written format; pictorial context is becoming less and less necessary for his comics by the week. <nowiki>~~~~</nowiki> {{unsigned ip|162.158.203.149}}

I'm thinking that at least in part, it's a commentary on what the average American middle-schooler knows about their country's geography. [[Special:Contributions/173.245.52.98|173.245.52.98]] 10:56, 2 December 2016 (UTC)

I'm pretty sure there is no 'ee' sound in Michigan, also of note the Carolina's are named for one the British King Charles's although I'm not sure which, and Wysiwyg has been used in xkcd before... Somewhere[[Special:Contributions/108.162.237.88|108.162.237.88]] 21:14, 2 December 2016 (UTC)

Talk:1755: Old Days

2016-11-04T19:56:58Z

108.162.237.88: sense

[https://www.ece.cmu.edu/~ganger/712.fall02/papers/p761-thompson.pdf Reflections on Trusting Trust] (pdf), Ken Thompson's acceptance speech for the 1984 Turing Award, in which he discusses creating a backdoor in the C compiler (yes, there was only 1 when he invented the language) that itself creates a second backdoor in the login program when it is compiled. Additionally, it reproduces itself when compiling the C compiler from un-tampered-with source code, so that anyone using the binary (compiled) compiler would be unable to avoid reproducing the backdoor in all its forms. This is the sort of thing that gives security programmers nightmares. [[Special:Contributions/108.162.221.168|108.162.221.168]] 04:52, 4 November 2016 (UTC) (bonsaiviking)

The "4-6 weeks" thing might be a reference to high-performance computing, in particular scientific calculations, a few decades back. From what I've heard from older people in my scientific field (I'm too young to have experienced it myself), you'd prepare your program on punch cards, mail these to an institution owning a fast computer (because your group or university didn't have one), and they'd run the program and mail the result back to you. This, I've been told, took a few weeks. Maybe someone with first-hand experience can give more information. [[Special:Contributions/141.101.104.98|141.101.104.98]] 10:34, 4 November 2016 (UTC)

Source Code on Punched Cards: As an undergrad at Durham Uni I remember punching PL1 source code onto cards to be inserted into a batch queue to be compiled and run on an IBM360 at the nearby city of Newcastle, overnight.
[[Special:Contributions/141.101.98.160|141.101.98.160]] 11:57, 4 November 2016 (UTC)

At the risk of emulating Dilbert's "Topper", I remember at school writing programs on coding sheets (effectively squared paper; one character in each box), which would get sent to the local university, where they would be punched onto cards and run on the mainframe. The following week, you'd get your coding sheets back, plus the cards and the printout from your batch job. Then you'd make your corrections, also on coding sheets... [[Special:Contributions/141.101.98.143|141.101.98.143]] 13:35, 4 November 2016 (UTC)

I'm reminded of Frank Hayes' song, "When I Was a Boy": "And we programmed in ones and in zeroes / And sometimes we ran out of ones!" On a more serious note, C came out in the late seventies, and I was using punch cards as late as 1975. That's not "long" before, and I wouldn't be too surprised if there were C compilers that accepted punched card input. [[User:Gmcgath|Gmcgath]] ([[User talk:Gmcgath|talk]]) 12:27, 4 November 2016 (UTC)

: Punch cards 79-80 in the U.S. for C programming. We did have text editors too for other languages, but we'd punch up and submit decks to a queue for batch processing. Usually only waited minutes (though the when big projects were due, it could take an hour - the bad part was there wasn't any way to stop an infinite loop until the job limit ran out. We were given so much in "computer dollars" for the class (because the machines were also used for outside work for real money) and you'd have to ask for extra if you used it up. I miss the green bar paper though. [[User:Afbach|Afbach]] ([[User talk:Afbach|talk]]) 18:25, 4 November 2016 (UTC)

I think the punched cards explanation is missing the point that C (or any language, that I know) didn't _require_ that it be on punched cards. I.e. there was nothing in the language specification that prohibited the program from being on paper tape, mag tape, disk, etc. [[Special:Contributions/162.158.74.70|162.158.74.70]] 14:22, 4 November 2016 (UTC)Pat

: I strongly echo 141.101's recollections. The second panel of 1755 is not far from the truth.

: I wrote my first program in FORTRAN IV in 1972 in an "enrichment" class at my school in Worthing - in the south of England (it calculated the average of 10 numbers). We wrote the programs out by hand on 80 column "coding forms" which were then snail-mailed to the regional computing center. When their keypunch operators had time, they'd punch our programs onto cards. On the following night, after the payroll software had been run, they'd stick our cards into the batch queue of their over-worked IBM 360. If they compiled, the programs would auto-run and would be allowed to produce at most 6 sheets of line-printer paper of output. If they didn't compile, then the first six pages of source code and error messages would go to the printer instead. The following morning, someone would collect our printouts and snail-mail them back to the school.

: If you had a compile error, you'd have to copy everything out onto fresh coding forms and re-submit it.

: When the "unofficial" project to teach programming to 14/15 year-olds ran low on cash, they switched to 2nd class mail in each direction. We did two programming classes a week but we'd be VERY lucky to get a turnaround time of less than a week. So the line on panel two: "To compile your code, you had to mail it to IBM, took 4-6 weeks"...isn't *that* much of an exaggeration! We mailed it to the regional computing center - and it rarely took more than 2 weeks...but what she says isn't very far from the truth!

: In practice, things never went smoothly. The keypunch operators didn't routinely type FORTRAN code - they mostly entered stuff like names and addresses, that are somewhat tolerant of typo's. If you were struck by a typo, you'd have to just resubmit the exact same coding forms and hope you didn't get a typo on the following week! Since it was only a 10 week course, you got VERY good at writing your coding forms up clearly, to NEVER forgetting to slash your zeroes and put serifs on your I's...making 100% sure your code would compile first time around was essential to getting anything to run. We quickly learned that using "I" as a loop variable was worse than (say) "COUNT" because it was more likely to get mis-typed as a '1'.

: I begged and pleaded to be allowed to do the same course for two years running but on the second year, the keypunch operators finally rebelled at the extra work we were giving them as our programs grew larger and more ambitious. So we were instructed to punch our own cards using a "hand punch" machine where you manually held down a "chord" of keys to punch raw binary into the cards. Get just one bit wrong, and you had to toss out the entire card and start again. It would take multiple hours to punch in even a very short program! Gone was the idea of using "COUNT" for a loop variable! The idea of commenting your code became simply ludicrous - so the teacher told us to write comments onto blank cards and stick them into the deck where needed!

: Because of that horrendous problem, the concept of "code-reuse" was important! If you could re-use some of the cards from a previous program, or '''''borrow''''' a subroutine from a friend (they'd want it back afterwards!), you'd save yourself a mountain of time! Decks of handy subroutines had value...you could exchange them for all sorts of playground "items-of-value" with the other geeks who did the class.

: I'm tempted to say that this taught me a lot about the art of programming and the importance of checking your code and writing for re-use...but I rather doubt it. When I finally got to my second year in college, I had access to a PDP-11/20 with DecTapes and a DecWriter terminal, that's about when I started to learn something useful...and in my final year, 1977 - I was finally granted access to the PDP-11/70, UNIX and a ADM 3a "glass teletype". I could really get to learning the craft that's still paying my mortgage 40 years later. [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 14:25, 4 November 2016 (UTC)

Is it just me, or is there a parallel between sending you code off to be compiled and sending your code off to an app store. In both cases a required part of the build is sending your code off to a private company for approval. [[User:Olleicua|Olleicua]] ([[User talk:Olleicua|talk]]) 15:28, 4 November 2016 (UTC)

Can someone please verify that it is "actually very difficult" to punch holes in floppy disks? Probably it should be attempted on at least 1000 different disks of different kinds to make sure. {{unsigned ip|162.158.75.64}}

Interesting: there exist two versions of this comic with different size https://imgs.xkcd.com/comics/old_days.png and https://imgs.xkcd.com/comics/old_days_2x.png The latter is used when zooming in on the comic's page --[[Special:Contributions/172.68.51.70|172.68.51.70]] 19:48, 4 November 2016 (UTC)

You didn't have to ship the punch cards to a company, but you did have to put them into a queue to be processed, and if you did have a typo or other simple mistake, you'd have to wait to get the output before knowing (which could take days). Most of what she says actually makes sense, it's just not fully accurate. You use to have to manually collect your garbage (making sure you unallocated your memory). You often did have to mix code and assembly (thought not for comments, and would that be // or /* */ or # or...). She also follows computer storage history. So again, not accurate, but it makes sense. [[Special:Contributions/108.162.237.88|108.162.237.88]] 19:56, 4 November 2016 (UTC)

Talk:1747: Spider Paleontology

2016-10-17T16:08:13Z

108.162.237.88:

I think it the first XKCD I don't get :P [[Special:Contributions/162.158.50.34|162.158.50.34]] 13:02, 17 October 2016 (UTC)
* I don't believe you, no-one except Randall Himself is that smart ;-) Anyways, hope the explanation I added helps some [[Special:Contributions/162.158.92.191|162.158.92.191]] 13:40, 17 October 2016 (UTC)

I like how the 6th panel has no borders. To me it signifies the broadening of her horizons, the going beyond her previous limits, as the realisation sinks in. [[Special:Contributions/162.158.92.191|162.158.92.191]] 14:14, 17 October 2016 (UTC)

I remember reading about a fossil of a spider with its web, but I don't remember where I read about it. I don't suppose anyone else has heard the same? (Ideally someone who remembers the source?) [[Special:Contributions/108.162.238.45|108.162.238.45]] 15:27, 17 October 2016 (UTC)

Anyone think this is the character from the Steroids comic? Looks fairly similar. [[Special:Contributions/108.162.237.88|108.162.237.88]] 16:08, 17 October 2016 (UTC)

123: Centrifugal Force

2016-02-10T22:57:54Z

108.162.237.88: /* Explanation */ "lose all you DNA, so it" to "lose all your DNA, so it"

{{comic
| number = 123
| date = July 3, 2006
| title = Centrifugal Force
| image = centrifugal force.png
| titletext = You spin me right round baby, right round, in a manner depriving me of an inertial reference frame. Baby.
}}

==Explanation==
[[Black Hat]] has strapped {{w|James Bond}} to a centrifuge and claims the {{w|Centrifugal force|centrifugal}} force will be lethal. Bond objects that there is no such thing, but just {{w|Centripetal force|centripetal}} force. The notion of centrifugal force is a common one, as we experience it whenever we turn. Teachers will initially teach Newtonian mechanics in an inertial frame, and in inertial frames the centrifugal force is zero. Instead, a body that moves in a circle does so because of a centripetal force (acting towards the centre of the rotation). This is a reasonable, and correct view, but is a subtle point that many students find hard to grasp as it seems to contradict their personal experience of centrifugal forces. For the sake of exposition, teachers may claim that "There is no such thing as centrifugal force". This however is also a misconception which is addressed in the explanation below:
;Observers' point of view (Black Hat, us, etc.)
:James Bond is moving in a circle, and is therefore accelerating. The force keeping him there is an inward force of contact against the centrifuge, a centripetal force. Via Newton's {{w|Newton's laws of motion#Newton's third law|third law}}, since the centrifuge is pushing Bond inward, Bond is pushing the centrifuge outward. The centrifuge's material is strong enough not to break under this force, however.
;James Bond's point of view
:In James Bond's frame of reference, Bond is at rest. He is kept there by two forces: the above-mentioned inward force of contact against the centrifuge, and an ''outward centrifugal force''. He feels both forces.

As mentioned in the explanation, as the centrifuge rotates faster, the forces needed to keep him in motion get larger, so the force he feels gets larger. This will eventually kill him. The conclusion will be the same regardless of which frame of reference is chosen.

Teachers of mechanics are well aware of this, however in introductory expositions these ideas are often not taught. In theoretical mechanics, one describes the positions and velocities of the particles in a model relative to a frame of reference. This means that a time is chosen to be time 0, and positions are chosen to be (0,0,0), (1,0,0), (0,1,0) and (0,0,1). With these chosen, the position and time of any particle in the system can be described. It is an axiom of Newtonian Mechanics that there exist "Inertial Frames". In an inertial frame a particle will remain at rest or at a constant speed unless acted on by an external force, and Newton's second law takes a simple form: F=ma. The surface of the Earth approximates an inertial frame. In a non-inertial frame, such as one rotating with a giant centrifuge, or moving with an accelerating vehicle, a particle will accelerate, relative to the frame. Newton's second law, when formed in such a frame is much more complicated, as it has terms for the linear acceleration of the frame, the angular acceleration of the frame, the centrifugal force and the {{w|Coriolis force}}. These extra terms are sometimes called "fictitious forces" as they result from the choice of the frame of reference. The mathematics required to describe problems in a non-inertial frame is more sophisticated, and all problems may be solved using an inertial frame. Thus is reasonable that teachers at school level "lie to children" and teach the mechanics in inertial frames.

The final statement by Black Hat is that said by {{w|Auric Goldfinger}} in {{w|Goldfinger (film)|Goldfinger}} in response to James Bond's question "Do you expect me to talk?"

The title text is inspired by {{w|Dead or Alive (band)|Dead or Alive's}} famous song from 1985, "{{w|You Spin Me Round (Like a Record)|You Spin Me Round}}".

Randall feels very strongly that the centrifugal force is a real thing. He links to this comic in the first footnote of his [[what if?|What if?]] article [https://what-if.xkcd.com/92/ One-Second Day], stating that it is a real thing.

As can also be seen in the [https://twitter.com/bohacekp/status/531500491180875776/photo/1 footnote on page 132] in his [[what if?#The book|What if? book]] he will even fight you about it. From the book: 
"Furthermore, if you're on the equator, you're being flung outward by a centrifugal force1."
 "1Yes, centrifugal. I will fight you."
 (The article itself is about what happens if you lose all your DNA, so it has not much to do with this "real" force... The sentence is just stating that the actual weight loss from losing all your DNA is similar to the weight loss you would experience by moving from the poles to the equator due to this force.)

==Transcript==
:[James Bond is strapped to a giant wheel suspended from the ceiling. Black Hat is standing next to two levers.]
:Black hat: How do you like my centrifuge, mister Bond? When I throw this lever, you will feel centrifugal force crush every bone in your body.
:[Same scene, but a closer shot.]
:Bond: You mean centripetal force. There's no such thing as centrifugal force.
:Black hat: A laughable claim, mister Bond, perpetuated by overzealous teachers of science. Simply construct Newton's laws in a rotating system and you will see a centrifugal force term appear as plain as day.
:[Closer shot, only Bond's head is visible.]
:Bond: Come now, do you really expect me to do coordinate substitution in my head while strapped to a centrifuge?
:Black hat: No, Mister Bond. I expect you to die.
{{comic discussion}}

[[Category:Comics featuring Black Hat]]
[[Category:Physics]]
[[Category:Comics featuring Cueball]]
[[Category:Footer comics]]

247: Factoring the Time

2015-11-10T17:45:53Z

108.162.237.88: /* Explanation */

{{comic
| number = 247
| date = April 11, 2007
| title = Factoring the Time
| image = factoring_the_time.png
| titletext = I occasionally do this with mile markers on the highway.
}}
==Explanation==
In this comic, [[Cueball]] is bored, so he is calculating the {{w|Prime factor|prime factors}} of the time shown on the clock. Cueball has been doing this for almost two hours (from 1:00 pm to 2:53 pm). The number 2 is the smallest prime but is not a factor of 253, which is an odd number. The smallest prime factor of 253 is 11, which makes the other factor 23.

His co-worker decides to mess with Cueball and so he switches the clock from 12-hour time (2:53 pm) to 24-hour time (14:53). This makes factorization more difficult, as the time now shown is a four digit number rather than a three digit number. The number 1,453 is actually a prime number and so has no factors but one and itself. Cueball has less than one minute to determine this, which is nearly impossible to do without practice.

In the title text, [[Randall]] claims he applies the same challenge to {{w|highway location marker}}s. At highway speeds (60+ mph), they would show up at least once per minute. Combined with the need to also concentrate on driving, factorizing numbers in the allowed time becomes much more difficult despite the lower numbers on the markers.

==Transcript==
:[One man is sitting at a computer. Cueball sits at a separate desk. There is a clock which reads 2:53.]
:Cueball: 253 is 11x23
:Man at computer: What?
:Cueball: I'm factoring the time.
:Cueball: I have nothing to do, so I'm trying to calculate the prime factors of the time each minute before it changes.
:Cueball: It was easy when I started at 1:00, but with each hour the number gets bigger
:Cueball: I wonder how long I can keep up.
:[Man at desk reaches back and touches the clock.]
:''BEEP''
:[Clock now reads 14:53.]
:Cueball: Hey!
:Man at computer: Think fast.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Math]]

235: Kite

2015-11-10T03:32:55Z

108.162.237.88: /* Explanation */

{{comic
| number = 235
| date = March 14, 2007
| title = Kite
| image = kite.jpg
| titletext = It's easy to regret your awkward conversations but hard to regret the ones you didn't have.
}}

==Explanation==
This comic presents, through a surreal scenario, one of Randall's recurring themes: that it is better to [[458:_Regrets|take a chance]] and make an [[308:_Interesting_Life|interesting]] [[267: Choices: Part 4|choice]].

[[Cueball]] flies a kite, then fixes it to a tree and climbs its string. In real life, of course, the string would not be able to support the weight of a human, but let's ignore that for now. Up in the sky, [[Megan]] appears hanging on a blimp, looking at him throughout the encounter. Cueball wonders about her and considers talking to her, but he does not act. After she has gone, Cueball is alone again; nothing has changed.

The title text explains the meaning of this metaphor. It is easy to regret an awkward conversation you had. In contrast, you don't regret the conversations you didn't have the nerve to start, because their cost is invisible--yet, they may have been missed opportunities, possibly a much higher cost than a simple awkward conversation.

==Transcript==
:[Cueball readies a kite.]
:[Cueball starts to fly the kite.]
:[Cueball continues to fly the kite.]
:[Cueball ties the kite string to a tree.]
:[Cueball grabs the string.]
:[Cueball starts to climb the string.]
:[A scene showing Cueball holding onto the string at a high altitude, against a colour backdrop of the ground, clouds, water and the sky.]
:[Black and white again. Megan comes into view holding onto a small blimp.]
:Cueball's thought bubble: Hey, there's someone else up here. I wonder what her story is.
:[Megan floats to the other side of the panel.]
:Cueball's thought bubble: Maybe I should say hi.
:[Cueball is alone holding onto the string.]

==Trivia==
There is a [https://youtu.be/3fCxyVSzd2k fan made animated version of this comic].

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics with color]]

25: Barrel - Part 4

2015-10-26T23:33:12Z

108.162.237.88: /* Explanation */

{{comic
| number = 25
| date = October 31, 2005
| title = Barrel - Part 4
| image = barrel_part_4.jpg
| titletext = :(
}}

== Explanation ==
In the first three comics of the series, the character explored the ocean in a barrel and then encountered a whirlpool, all with a reaction of innocent wonder. Here, the empty barrel floating adrift, plus the title text and a previous announcement by Randall that this would be the conclusion of barrel boy's story, imply that the character's encounter with the whirlpool brought him to some harm.

This is the fifth in a six-part series of comics whose parts were randomly published during the first several dozen strips. The series features a [[:Category:Barrel|character]] that is not consistent with what would quickly become the [[xkcd]] [[stick figure]] style. The character was in the barrel in part 1-3.

After Randall released the full [http://liveweb.archive.org/web/20070207052159/http://www.xkcd.com/barrel.html The Boy and his Barrel] story on xkcd it has been clear that the original [[Ferret]] story should also be included as part of the barrel series.

The full series can be found [[:Category:Barrel|here]]. But below they are listed in the order Randall has put them in his collection linked to above:
* [[1: Barrel - Part 1]]
* [[20: Ferret]]
* [[11: Barrel - Part 2]]
* [[22: Barrel - Part 3]]
* [[25: Barrel - Part 4]]
* [[31: Barrel - Part 5]]

== Transcript ==
:[The barrel is shown on a grid paper background, floating sideways and empty in a choppy sea.]

==Trivia==
*This was the 26th comic originally posted to [[LiveJournal]].
**The previous was [[37: Hyphen]].
**The next was [[26: Fourier]].
*Original title: "Monday's Drawing"
*There were no original [[Randall]] quote for this comic.
**However three hours after posting the comic he made a new post with the following statement:
:::'''''Barrel series'''''
:::By the way, here are all the barrel comics on a single (easily linked) page:
:::[http://liveweb.archive.org/web/20070207052159/http://www.xkcd.com/barrel.html http://www.xkcd.com/barrel.html]
:::I cheated, and went back and lightened the gridlines in #2. It was just bothering me. I'll try not to do that much. But as I'm not destroying anyone's childhood, I don't feel like I'm really pulling a George Lucas.
:::I mean, I'm not destroying more than one childhood.
:::Oops.
*The link above goes to the archive.
**Since this was not (as he stated in the [[37: Hyphen#Trivia|previous comic]]) the last in the [[:Category:Barrel|barrel series]] the last comic must later have been included.
**Since this last barrel comic [[31: Barrel - Part 5]] involved the [[:Category:Ferret|ferret]], the previous ferret story [[20: Ferret]] must also have been included then.
**Thus making the original ferret a "real" part of the barrel story.
*Randall also confesses that he changed the appearance of the 2nd Barrel comic.
**At this time, that must have referred to the one called [[11: Barrel - Part 2]] although Randall in the page above has moved this to after the first ferret comic.
*This comic was posted on [[xkcd]] when the web site opened on Sunday the 1st of January 2006.
**It was posted along [[:Category:First day on xkcd|with all 41 comics]] posted before that on LiveJournal as well as a few others.
**The latter explaining why the numbers of these 41 LiveJournal comics ranges from 1-44.
*One of the original drawings drawn on [[:Category:Checkered paper|checkered paper]].

{{comic discussion}}

[[Category:Comics posted on livejournal| 26]]
[[Category:First day on xkcd]]
[[Category:Checkered paper]]
[[Category:Barrel|05]]