explain xkcd - User contributions [en]

3001: Temperature Scales

2024-10-24T09:15:41Z

162.158.186.20: /* Explanation */ absolutely need a comma here

{{comic
| number = 3001
| date = October 21, 2024
| title = Temperature Scales
| image = temperature_scales_2x.png
| imagesize = 740x535px
| noexpand = true
| titletext = In my new scale, °X, 0 is Earths' record lowest surface temperature, 50 is the global average, and 100 is the record highest, with a linear scale between each point and adjustment every year as needed.
}}

==Explanation==
{{incomplete|Created by an EXPONENTIAL TEMPERATURE SYSTEM. Do NOT delete this tag too soon.}}

Since the invention of the {{w|thermometer}}, a number of different {{w|temperature}} scales have been proposed. In modern times, most of the world uses {{w|Celsius}} for everyday temperature measurements. A small number of countries (the USA and {{w|Territories of the United States|its territories}}, the Bahamas, Belize, the Cayman Islands, Liberia, and Palau) retain the {{w|Imperial units|imperial system}}, which uses the {{w|Fahrenheit}} scale, which preceded Celsius by just under two decades. The other widely used temperature scale is {{w|kelvin}}s, which uses the same scale as degrees Celsius, but is rooted at {{w|absolute zero}}, making it both useful in scientific calculations and easy to convert to and from °Celsius (which, along with °Fahrenheit, is now officially defined relative to kelvins.) Kelvins have been part of the widely adopted official {{w|metric system}} since 1954. Even in countries that use Fahrenheit, scientific measurements are usually done in degrees Celsius or kelvins.

The comic compares these scales, and a number of others, on [[Randall]]'s scale of "cursedness." The joke is highlighting how different the temperature scales are, and how impractical most of them are. All of the listed scales are real, but may be considered obsolete to varying degrees. Please see also [[1923: Felsius]], a combination of degrees Fahrenheit and Celsius.

{| class=wikitable
! scope="col" | Unit
! scope="col" | Water Freezes
! scope="col" | Water Boils
! scope="col" | Notes
! scope="col" | Cursedness
! scope="col" | Explanation
|-
| {{w|Celsius}} || 0 || 100 || Used in most of the world || 2/10 || The Celsius (°C) scale was devised by Swedish astronomer {{w|Anders Celsius}} in 1742, and revised to its current version a year after his death, in 1745. 0°C represents the freezing point of water, and 100°C represents the boiling point, both under {{w|standard atmospheric pressure}}. The Celsius scale is now defined in terms of the Kelvin scale. By the given "cursedness," it is regarded as one of the two least problematic temperature scales.
|-
| {{w|Kelvin}} || 273.15 || 373.15 || 0K is absolute zero || 2/10 || Kelvin (written with a lowercase 'k' as a unit, or as 'K', without the degrees symbol '°') is a unit of temperature devised by {{w|Lord Kelvin}} in 1848. It uses the same scale as Celsius but is shifted by 273.15 to set absolute zero at 0K (based on the {{w|Boltzmann constant}}.) While kelvins are very useful for {{w|thermodynamics}} and material physics, it can be unintuitive. Kelvin and Celsius are the most commonly used units in scientific measurements and calculations.
|-
| {{w|Fahrenheit}} || 32 || 212 || Outdoors in most places is between 0–100 || 3/10 || Fahrenheit (°F) is officially used in a few countries and informally in several others. It originated in a time when factors of 360 were favored in science over powers of ten, which is why the freezing and boiling points of water are set 180° apart. Devised around 1724, {{w|Daniel Fahrenheit}} chose not to base 0° on the freezing point of water, instead setting it at the coldest temperature he could achieve: the freezing point of an {{w|ammonium chloride}} {{w|brine}} solution. Although these reference points are now considered arbitrary and outdated by modern scholars, the scale gained popularity especially in Anglophone countries, likely because it aligns with everyday weather conditions and is intuitively useful. Its range covers typical temperatures across various latitudes and seasons, and 100°F is close to normal human body temperature. The Fahrenheit scale remains commonly used only in the U.S. (Randall's home country) and its territories, the Bahamas, Belize, the Cayman Islands, Liberia, and Palau.
|-
| {{w|Réaumur scale|Réaumur}} || 0 || 80 || Like Celsius, but with 80 instead of 100 || 3/8 || Abbreviated as °Ré, this system devised by {{w|René Antoine Ferchault de Réaumur}} in 1730 was used in some places until the early 20th century, mostly for cheese-making. The rating (3/8) is a joke on the boiling point of water in this system being 80 instead of 100 as it is in Celsius; converting this to an out-of-ten scale would give 3.75/10, labeling it as more cursed than Fahrenheit but less so than Rømer.
|-
| {{w|Rømer scale|Rømer}} || 7.5 || 60 || Fahrenheit precursor with similarly random design || 4/10 || Abbreviated as °Rø, this scale was created by the Danish astronomer {{w|Ole Rømer}} around 1702. Much like Fahrenheit, it uses the freezing point of ammonium chloride brine as the benchmark for 0°, and the scale is built with factors of 360 in mind with the boiling point of pure water at 60°. Like the Fahrenheit scale, the freezing point of pure water was not originally considered significant by Rømer, but the scale was later updated to fix it to 7.5.
|-
| {{w|Rankine scale|Rankine}} || 491.7 || 671.7 || Fahrenheit, but with 0°F [''sic;'' should be 0°R] set to absolute zero || 6/10 || The Rankine scale (°Ra), devised in 1859 by {{w|William Rankine}}, is to Fahrenheit what kelvins are to Celsius, an absolute scale rather than a relative one. The scale is mostly obsolete, but is still occasionally used in legacy industrial operations where absolute temperature scales are required. It is described as more cursed than the otherwise identical Fahrenheit scale, despite being rooted at a more practical zero point. Another comic, [[2292: Thermometer]], expresses disdain for this scale.
|-
| {{w|Newton scale|Newton}} || 0 || 33-ish || Poorly defined, with reference points like "the hottest water you can hold your hand in" || 7-ish/10 || The famous scientist and mathematician {{w|Isaac Newton}} published this scale in 1701, which was referred to by the the °N symbol. Sadly, the degrees of temperature specified do not correlate exactly with amounts of {{w|heat}}. The cursedness rating (7-ish/10) is a joke about the vagueness of the scale's definition. Very few scientists other than Newton ever used this scale,{{cn}} but it did appear on commercial thermometers around 1758.[https://www.scienceandsociety.co.uk/results.asp?image=10413117&wwwflag=&imagepos=43]
|-
| {{w|Wedgwood scale|Wedgwood}} || –8 || –6.7 || Intended for comparing the melting points of metals, all of which it was very wrong about || 9/10 || Created by the potter {{w|Josiah Wedgwood}} in 1782, the '°W' scale was based on the shrinking of clay when heated above red heat, but was found to be very inaccurate. The comic has a typo, as the scale is called Wedgwood, without the second 'e'.
|-
| Galen || –4? || 4?? || Runs from –4 (cold) to 4 (hot). 0 is "normal"(?) || 4/–4 || The Greek physician {{w|Galen}} suggested a "neutral" temperature around 180 A.D.,[https://www.loebclassics.com/view/galen-temperaments/2020/pb_LCL546.3.xml] during his time as a prominent physician in the {{w|Roman Empire}}. Created by mixing equal parts of boiling water and ice, on either side of this neutral point he described four degrees of heat and four degrees of cold. This range from +4 to –4 is humorously described as implying –100% cursedness, which while technically the least cursed of all the listed scales, is still as unclear as the idea of negative cursedness or cursedness itself. There is no standard abbreviation for Galen's scale.
|-
| {{w|Celsius#History|''Real'' Celsius}} || 100 || 0 || In Anders Celsius's original 1742 specification, bigger numbers are ''colder''; others later flipped it || 10/0 || Most scales' temperatures can be indefinitely large, but have an absolute minimum temperature. By starting at a maximum value and counting down, this scale is indeed cursed, as nearly all possible temperatures (through 1.42x1032K, the maximum physical temperature[https://doi.org/10.4236/jamp.2024.1210198]) will be negative. The cursedness rating (10/0) is a joke on the scale "flipping" the fixed points of modern Celsius. Division by zero is strictly undefined.
The original logic was that zero could be easily calibrated to the height of a column of mercury at the temperature of boiling water, and further measurements then made of the amount it ''reduced'' in height under cooler conditions. This orientation survives in the historic {{w|Delisle scale}}, which predates (and arguably helped inspire) the Celsius scale. The scale originally used by Professor Celsius was only corrected posthumously in 1745, but Delisle's scale was not.
|-
| [https://physics.stackexchange.com/questions/459851/john-daltons-temperature-scale#459863 Dalton] || 0 || 100 || A nonlinear scale; 0°C and 100°C are 0 and 100 Dalton, but 50°C is 53.9 Dalton || 53.9/50 || {{w|John Dalton}} proposed a logarithmic temperature scale in 1802 during his work on what became {{w|Charles's Law}}. The scale is defined so that absolute zero is at negative infinity, with the exponent chosen to match Celsius at 0 and 100. While Dalton temperature is defined for all positive and negative numbers, the nonlinear scale is difficult to work with since the amount of heat represented by a change of one degree Dalton is not constant. Degrees Dalton differs from Celsius by as much as 3.9 degrees between 0 and 100, but diverges much more for more extreme temperatures. There is no standard abbreviation for Dalton's scale.

The rating (53.9/50) is a joke about the unit, as 53.9 Dalton would be 50 degrees Celsius — i.e., the cursedness could be understood as 50/50 (or 10/10, entirely cursed), but perhaps instead as 107.8% (even more than entirely cursed).
|-
| °X || 42.9 || 151.4 || '''Title text:''' "In my new scale, °X, 0 is Earths' [sic] record lowest surface temperature, 50 is the global average, and 100 is the record highest, with a linear scale between each point and adjustment every year as needed." || ''not provided'' || The {{w|Lowest temperature recorded on Earth|record lowest surface temperature on Earth}} as of 2024 is –89.2°C (–128.6°F), recorded at the {{w|Vostok Station|Vostok Research Station}} in Antarctica on July 21, 1983.[https://wmo.asu.edu/content/world-lowest-temperature] The average surface temperature as of 2023, the most recent available, is 14.8°C (58.6°F.)[https://climate.copernicus.eu/climate-indicators/temperature] The {{w|Highest temperature recorded on Earth|record highest temperature}} is 56.7°C (134.1°F), recorded on July 10, 1913 at {{w|Furnace Creek, California|Furnace Creek Ranch}} in Death Valley, California.[https://wmo.asu.edu/content/world-highest-temperature] "Surface" temperatures are measured at 1.5 meters above ground inside a shaded shelter, to accurately represent the temperature of the air, because temperatures closer to the ground are often much different.

{{cot|Derivation and graph}}
To break the scale into two linear parts (below and above 14.8°C), we define two separate equations for each range:

1. Below 14.8°C (from –89.2°C to 14.8°C):
* 0 °X corresponds to –89.2°C
* 50 °X corresponds to 14.8°C

We calculate the slope m₁:

<center>m₁ = (50 – 0) / (14.8 – (–89.2)) = 50 / (14.8 + 89.2) = 50 / 104 ≈ 0.48</center>

Now, using the point (14.8°C, 50 °X), we calculate the intercept b₁:

<center>50 = 0.48 × 14.8 + b₁</center>

<center>50 = 7.1 + b₁</center>

<center>b₁ = 50 – 7.1 = 42.9</center>

Thus, the equation for temperatures '''below 14.8°C''' is:

<center>'''X = 0.48 × C + 42.9'''</center>

2. Above 14.8°C (from 14.8°C to 56.7°C):
* 50 °X corresponds to 14.8°C
* 100 °X corresponds to 56.7°C

We calculate the slope m₂:

<center>m₂ = (100 – 50) / (56.7 – 14.8) = 50 / 41.9 ≈ 1.19</center>

Now, using the point (14.8°C, 50 °X), we calculate the intercept b₂:

<center>50 = 1.19 × 14.8 + b₂</center>

<center>50 = 17.6 + b₂</center>

<center>b₂ = 50 – 17.6 = 32.4</center>

Thus, the equation for temperatures '''above 14.8°C''' is:

<center>'''X = 1.19 × C + 32.4'''</center>

;Freezing and boiling points of water

Freezing point of water (0°C): Since 0°C is below 14.8°C, we use the equation X = 0.48 × C + 42.9:

<center>X = 0.48 × 0 + 42.9 = 42.9</center>

So, '''the freezing point is 42.9 °X.'''

Boiling point of water (100°C): Since 100°C is above 14.8°C, we use the equation X = 1.19 × C + 32.4:

<center>X = 1.19 × 100 + 32.4 = 119 + 32.4 = 151.4</center>

So, '''the boiling point is 151.4 °X.'''

[[File:XvsC.png|400px|center]]

See also [[2701: Change in Slope]] for a general discussion of separate linear scales between three points.
{{cob}}
Due to high and average temperature records now being broken nearly every year as a result of {{w|climate change}}, Randall's new °X scale must be re-calibrated each year. While extreme values like absolute zero or the {{w|Tungsten#Physical properties|melting point of tungsten}} will shift more significantly over time, everyday temperatures will vary less.
|}

=== Trivia ===

Here are the {{w|room temperature}} values for those scales:

{| class=wikitable style="text-align:right;"
! scope="col" | Unit
! scope="col" | Room temperature
|-
| Celsius || 22
|-
| Kelvin || 295
|-
| Fahrenheit || 72
|-
| Réaumur || 18
|-
| Rømer || 18
|-
| Rankine || 531
|-
| Newton || 7
|-
| Wedgwood || -7
|-
| Galen || 0
|-
| ''Real'' Celsius || 78
|-
| °X || 59
|}

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

:Temperature Scales

:[A table with five columns, labelled: Unit, water freezing point, water boiling point, notes, cursedness. There are eleven rows below the labels.]

:[Row 1:] Celsius, 0, 100, Used in most of the world, 2/10
:[Row 2:] Kelvin, 273.15, 373.15, 0K is absolute zero, 2/10
:[Row 3:] Fahrenheit, 32, 212, Outdoors in most places is between 0–100, 3/10
:[Row 4:] Réaumur, 0, 80, Like Celsius, but with 80 instead of 100, 3/8
:[Row 5:] Rømer, 7.5, 60, Fahrenheit precursor with similarly random design, 4/10,
:[Row 6:] Rankine, 491.7, 671.7, Fahrenheit, but with 0°F set to absolute zero, 6/10
:[Row 7:] Newton, 0, 33-ish, Poorly defined, with reference points like "the hottest water you can hold your hand in", 7-ish/10
:[Row 8:] Wedgewood, –8, –6.7, Intended for comparing the melting points of metals, all of which it was very wrong about, 9/10
:[Row 9:] Galen, –4?, 4??, Runs from –4 (cold) to 4 (hot). 0 is "normal"(?), 4/–4
:[Row 10:] ''Real'' Celsius, 100, 0, In Anders Celsius's original specification, bigger numbers are ''colder''; others later flipped it, 10/0
:[Row 11:] Dalton, 0, 100, A nonlinear scale; 0°C and 100°C are 0 and 100 Dalton, but 50°C is 53.9 Dalton, 53.9/50

{{comic discussion}}

[[Category:Charts]]
[[Category:Science]]

2989: Physics Lab Thermostat

2024-09-26T07:39:38Z

162.158.186.20: /* Explanation */ pedantic

{{comic
| number = 2989
| date = September 23, 2024
| title = Physics Lab Thermostat
| image = physics_lab_thermostat_2x.png
| imagesize = 264x296px
| noexpand = true
| titletext = Hopefully the HVAC people set it to only affect the AIR in the room.
}}

==Explanation==
{{incomplete|Created by ChatGPT, an actual bot, with the help of human copyeditors and critics as found on the talk page. Do NOT delete this tag too soon.}}

This comic is about a "physics lab thermostat," which instead of controlling temperature, it adjusts the {{w|Boltzmann constant}} (a constant that links temperature and energy in physics, equal to 1.38×10−23 J/K, where J is {{w|joule}}s, a unit of energy, and K is {{w|kelvin}}s, a unit of temperature.) The dial shows different values for the constant, implying that it can be changed, which is absurd because the Boltzmann constant is a fundamental number that stays the same throughout the universe. In reality, you can't change the Boltzmann constant, so the comic is making fun of the idea of a scientist casually adjusting a fixed law of physics as if it were something simple like room temperature.

If the Boltzmann constant could be changed, it would directly affect how we experience temperature. The constant determines how much energy particles have at a certain temperature. If the constant were increased, more energy would be associated with the same temperature, so everything would feel hotter even if the temperature stayed the same. On the other hand, if the constant were decreased, less energy would be associated with the same temperature, and everything would feel colder than usual. The thermostat dial would thus make things feel colder if it were turned clockwise, unlike regular thermostats. The equivalent energy range relative to the actual Boltzmann constant would correspond to temperatures of 29°C (84°F) on the left, to 15°C (59°F) on the right.

Beyond just how we feel, altering the Boltzmann constant would disrupt all sorts of processes that depend on temperature, like how fast chemical reactions happen or how heat moves around. A higher constant would make particles move faster and carry more energy at a given temperature, while a lower constant would slow things down. There have previously been control panels for properties of the universe in [[1620: Christmas Settings]] and [[1763: Catcalling]]. A thermometer including units compatible with this thermostat (after dividing by 2/3) is shown in [[2292: Thermometer]].

The title text builds on the absurdity of being able to adjust the Boltzmann constant. It suggests that if the constant could be changed, hopefully, it would only affect the air in the room and not the entire universe. Imagining that the HVAC ({{w|heating, ventilation, and air conditioning}}) system could contain such a change to just the room's air shows the ridiculousness of trying to isolate the effects of altering a universal constant.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

:[A black circular dial is shown with a white indicator line at the upper right. The label above the dial, enclosed in a rectangular box, says:]
:Local Boltzmann Constant
:[The two extremes of the dial are labeled as follows, the first value on the left and the second value on the right:]
:1.418×10-23 J/K
:1.351×10-23 J/K
:[The indicator line is pointing to a position on the dial somewhere around 1.375×10-23 J/K (between the 12th and 13th large ticks clockwise out of 19 total).]
:[Caption below the panel:]
:Physics Lab Thermostat

{{comic discussion}}

[[Category:Physics]]

Talk:2968: University Age

2024-08-06T21:39:30Z

162.158.186.20: ?

[[1477]] anyone? [[Special:Contributions/162.158.41.131|162.158.41.131]] 03:29, 6 August 2024 (UTC)
:Not relevant in my opinion. In [[1477: Star Wars]] Cueball is surprised by how fast time seems to flow past him. Not surprised that everything ages at the same rate as the Cueball in this comic. There are more than 40 comics relating to [[:Category:Time|time]] on explain xkcd... [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 06:50, 6 August 2024 (UTC)

Was there a USA political debate this week that I didn't hear about? About. Hear of it's existence. I Assuredly didn't hear it. [[Special:Contributions/172.70.175.121|172.70.175.121]] 06:27, 6 August 2024 (UTC)

On a related note, today I set a new personal best for time spent continuously being alive. I'm still well behind the world records, but I have beaten pretty much all of the current collegeate athletes. [[User:RegularSizedGuy|RegularSizedGuy]] ([[User talk:RegularSizedGuy|talk]]) 07:08, 6 August 2024 (UTC)
:Happy birthday :) [[Special:Contributions/172.70.86.16|172.70.86.16]] 12:59, 6 August 2024 (UTC)

"'''Unfortunately, I have terrible news'''" kind of feels to me like — almost — there is a pop culture reference here that I am missing (I'd say I feel 33% of the way towards that feeling; certainly somewhere less likely than even). It just seems like a little too strong of a statement to be what President Cueball would say in the moment. That said, I can't find any support for such a half-baked theory. Although there is an "I have terrible news" (without "Unfortunately") from [https://www.imdb.com/title/tt2572734/characters/nm0278979 The Office, Season 9, "Vandalism"] ([https://www.youtube.com/watch?v=Eo8RzH-6Tfw&t=614s video]), but it doesn't strike me as particularly significant. 
¶ Apart from that, I sort of expected more emphasis on obscure schemes, like (a) increasing the average altitude of the rival university to increase its velocity for the tiny relativistic effect, e.g. by funding construction of an observatory for its astronomy department; (b) attempting to measure the founding dates more precisely, e.g. what if it were only 1-year-183-days older; (c) merger with the rival, ala the proposed MIT/Harvard mergers of the early 20th century; &c. [[User:JohnHawkinson|JohnHawkinson]] ([[User talk:JohnHawkinson|talk]]) 09:51, 6 August 2024 (UTC)

: I thought the terrible new was that, after sending the rival university on a round trip at relativistic speed, due to an unfortuneate miscalculation, the rival university would collide with Earth while still going too fast, causing the destruction of the planet. --[[User:Itub|Itub]] ([[User talk:Itub|talk]]) 11:51, 6 August 2024 (UTC)

: I think it's more a commentary on the futility of university administration plans and goals, given that actual success for a prestigious university involves mostly decisions entirely out of administration hands. [[Special:Contributions/162.158.90.109|162.158.90.109]] 20:55, 6 August 2024 (UTC)
:: What do you think the universities alluded to were? I'm guessing MIT in 1861 and UMass (originally Amherst) in 1863. [[Special:Contributions/162.158.186.20|162.158.186.20]] 21:39, 6 August 2024 (UTC)

The way I read the "overtaking our rival by 3" part was that part of the "intensive program" was the sabotage of the other university, effectively ending its aging. This would then be the terrible news to share. [[Special:Contributions/172.71.166.219|172.71.166.219]] 14:02, 6 August 2024 (UTC)