explain xkcd - User contributions [en]

2796: Real Estate Analysis

2023-07-04T11:45:36Z

172.70.86.25: /* Explanation */

{{comic
| number = 2796
| date = June 30, 2023
| title = Real Estate Analysis
| image = real_estate_analysis_2x.png
| imagesize = 474x458px
| noexpand = true
| titletext = Mars does get a good score on 'noise levels' and 'scenic views,' but the school district ranking isn't great; the only teacher--the Perseverance rover--is too busy with rock samples to teach more than the occasional weekend class.
}}

==Explanation==
{{incomplete|Created by an EASILY IMPRESSED URBANIST - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

This comic shows a chart ranking locations in our solar system (the eight currently recognised planets and Earth's own moon) along two scales: their walkability and their proximity to shops. As this is a "real estate analysis", this comic mocks real life "real estate analyses" for people who are looking for a new home. Walkability measures the ease of walking as a form of transportation in an area (often related to how urban that area is), and is measured by metrics like the 100-point walk score, with higher numbers representing easier and safer walking. Proximity to commercial shops and eating establishments can likewise be a factor for potential residents looking for a convenient living environment. While no units are provided, proximity can be defined as a number that increases with decreasing distance.

Earth is rated as highly walkable, probably because humans can walk on much of its surface without immediate & continuous existential need for environmental survival gear (so far), and due to the gravity on its surface. Earth also rates high on the "proximity to shops and restaurants" scale because its surface hosts all commercial establishments known to humans; most of businesses are within a few building stories of the surface, though some "shops" on airplanes are up to several kilometers above it.

All other locations are rated as completely unwalkable, and remote from any shops or restaurants. The next closest body, the Moon, typically around 384,400 km away from Earth, is about five orders of magnitude further from shops and restaurants than anywhere on Earth. (A dozen people have actually walked ''on'' the Moon, [https://sei-engagement.pubpub.org/pub/nmjeoom7/release/8 more or less], but none have actually walked ''to'' the Moon, or to wherever else they may want to go from there.) Venus is 108 million km away while Uranus is 2.9 billion, so all these bodies' clustering near the origin on the proximity scale masks a large difference in accessibility. The gas giants Jupiter and Saturn are assessed marginally higher walkability scores than the solid Mercury (where temperatures are extreme, but do briefly pass through the range survivable for humans as the planet rotates); maybe their less-hostile (and, in the case of Ganymede and Titan, physically larger) moons are taken into account here.

Based on Earth's high score on both metrics, Randall makes the claim "I get why this place is so popular". Most humans would agree with Earth being preferable (no human is known to have permanently inhabited any celestial body besides Earth[https://www.planetary.org/worlds/pale-blue-dot]), but would be more concerned with local differences in livability.

Walkability scores on websites such as https://www.walkscore.com/ take into account proximity to restaurants, groceries, and shopping (among other factors, such as proximity to parks, schools, and culture and entertainment venues), so it would be fairly unusual for a location to score high on walkability but low on proximity to shops and restaurants, or vice versa.

The alt text comments that Mars did score high on the 'noise levels' and 'scenic views' scores. Generally, lower noise levels help maintain a calm and relaxed lifestyle, and are therefore a desirable quality for real estate. Due to it having a thinner atmosphere and (almost) zero sources of manmade noise, Mars is very quiet (though [https://www.nasa.gov/feature/goddard/the-fact-and-fiction-of-martian-dust-storms not entirely silent]). However, this extreme lack of noise may turn out to be detrimental to human wellbeing. Access to scenic areas is also generally seen as a positive when assessing property, and the large, barren scenery of Mars has been abundantly documented by the several rovers sent to its surface, resulting in widespread fascination with its serene landscapes (though the ever-present dust, and the need to deal with it, will mar the serenity). Again, though, the sheer emptiness of the landscape might turn out to be a negative rather than a positive.

It then states the 'school district' ranking (proximity to a good schooling system, which is also desirable, especially to families) is rather poor on account of there being only one available teacher - the rover ''Perseverance'' - and it being too busy with its rock samples. ''Perseverance'' is (at the time of this comic's publication) a still-active Mars rover whose main purpose is to examine minerals from Mars' surface and scan them for signs compatible with ancient life: while it could hypothetically serve as a teacher (using its memory banks as teaching material, for instance), doing so would greatly interfere with its main mission if done regularly.

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

:[A graph is shown. Both axes have a label with an arrow and 10 visible ticks.]
:Y-axis: Walkability score
:X-axis: Proximity to shops and restaurants
:[Labels of multiple dots at around (0, 0), clockwise:]
:Mars, The Moon, Mercury, Venus, Neptune, Uranus, Saturn, Jupiter
:[Label of a dot at roughly (9.5, 9.5):]
:Earth

:[Caption below the panel:]
:After doing a real estate analysis, I get why this place is so popular.

{{comic discussion}}

[[Category:Charts]]
[[Category:Astronomy]]
[[Category:Mars rovers]]

Talk:2790: Heat Pump

2023-06-23T01:04:36Z

172.70.86.25:

woah! an xkcd with color what was the last one with color? (im kinda new to xkcd) [[Special:Contributions/172.71.122.48|172.71.122.48]] 21:17, 16 June 2023 (UTC)Erfaniom
:I guess the last one with a lot of color was [[2750]]. More at [[:Category:Comics with color]]. [[Special:Contributions/162.158.167.11|162.158.167.11]] 17:29, 17 June 2023 (UTC)

I suppose color was needed to show the air temperature. Odd, though, that in summer (in the northern hemisphere), the character is trying to increase the indoor temperature. [[User:Davidhbrown|Davidhbrown]] ([[User talk:Davidhbrown|talk]]) 21:27, 16 June 2023 (UTC)
:He's not. He's moving the hot air from inside to the cooler outside. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 22:18, 16 June 2023 (UTC)
::I actully think he's warming the inside, already warmer than outside, by effectively (and literally!) squeezing the heat out of the cooler outdoors air.
::By compressing the cool outdoor air, he increases its temperature (p1v1/t1=p2v2/t2) to warmer than the warm indoor air, creating a squeezebox->room flow of heat energy, then returns to the outside before decompressing and lowering the temperature in his squeezebox below the cool-air temperature in order to create an outdoors->squeezebox flow of energy and repeat. (The comic has the cycle start at roughly half-way through that, and wraps round, but the heat-to-room seemed the most obvious starting place here.)
::Right now, I'd not wish to heat my indoors up (even at 11:30pm, like now), so I agree that it's a funny time of year show heat-adding (rather than heat removing), but it definitely is that. [[Special:Contributions/172.70.86.154|172.70.86.154]] 22:31, 16 June 2023 (UTC)
:::Assumption(?): Indoors is on the LHS and higher, outdoors on the RHS and lower, door opens outwards and steps down to "outside". He COULD instead be cooling a basement apartment with a door that opens inwards (like mine)... however he seems to make a noticeable difference to the red, not the blue, so... probably not. :-/ [[Special:Contributions/172.70.34.160|172.70.34.160]] 02:36, 17 June 2023 (UTC)
::: Since panel 3 shows it at its widest and bluest with "Release", I understand that to mean he's releasing the heat outside from inside - like an A/C does. The weird thing is then showing the reddest/smallest with "Radiate", that word means "make and release heat" to me. The thing is, past experience tells me Randall lives in roughly the same part of the world as me, same climate. That he's in the northern states (like, within a day's drive of the Canadian border), and the Eastern time zone, and it's summer for us. Only heat pumping people should want is pumping heat OUT of the house... [[User:NiceGuy1|NiceGuy1]] ([[User talk:NiceGuy1|talk]]) 04:16, 18 June 2023 (UTC)
::::Releasing the spring. At that point, there's the same amount of heat within the device, but it's spread out more so that the temperature is lower (than it was, but also than the surrounding air, which is also ''negligibly'' compressed outwards of course). NB, it does ''not'' draw air into it.
::::Now he has a cool device, heat naturally flows into it until (sufficiently) equalised after a small wait. Take the outside-cool (and expanded) device inside and compress it (it does not expel air!) to have that amount of heat be in a smaller space and thus a higher temperature. High enough to (quite naturally) flow into the room. Thus low-temperature heat taken from outside and used to increase the higher-temperature heat inside, which is different to what happens if you trap and move cold ''air'' into a warm room. Though perhaps it looks like that on first appearance, except for the colour-cues going all screwy. [[Special:Contributions/162.158.74.96|162.158.74.96]] 09:55, 18 June 2023 (UTC)
::::This all rather assumes that Randall came up with the comic in response to his immediate situation, rather than just musing generally and abstractly on heat pumps and the way they work.[[Special:Contributions/172.71.178.51|172.71.178.51]] 10:20, 19 June 2023 (UTC)
:he's actually heating it, the comic is set in winter. It's a reference to the discussion about regulating heating systems in Germany. I added something about that in the explanation, but I don't think I made the citation right [[User:Marta]] ([[User talk:Marta|talk]]) 05:25, 17 June 2023 (UTC)
::The citation does not appear to strongly relate to the comic to me. I might be curious if Randall had a lot of comics queued and actually published a winter one in the summer, for example. [[Special:Contributions/172.69.59.112|172.69.59.112]] 00:19, 18 June 2023 (UTC)
:::I agree, I think the Germany thing might probably be coincidental. Randall lives in North-Eastern America. It's unlikely, though quite possible, he was inspired enough by such foreign matters to base a comic on it. Still, you never know from whence inspiration may strike, in which case he published when he thought of it instead of when it'd be relevant... [[User:NiceGuy1|NiceGuy1]] ([[User talk:NiceGuy1|talk]]) 04:40, 18 June 2023 (UTC)
::::News of this had not otherwise reached me over the German Ocean (i.e. North Sea), never mind where Randall is, way over the Pond (i.e. Atlantic). Not saying it wasn't a prominant bit of news, in his media feeds, but usually the problem is that something 'popularly heard about' state-side confuzzles anyone in (say) Europe/ex-Europe when used as inspiration for a comic without enough setup to it. Now, ''if'' say Penn./Mass. state legislature were being similarly proactive on such matters, I'd say it might be the cue for this. Otherwise, it might be better as an afterthough/Trivia instead of the lead-on paragraph. But I also don't know enough to know that it ''isn't'' worthy of such prominance, so this is just my thoughts, leaving others to alter it if they so wish... Anybody can do it, after all... [[Special:Contributions/162.158.74.96|162.158.74.96]] 09:55, 18 June 2023 (UTC)
:(I'm not to editing wikis) [[User:Marta]] ([[User talk:Marta|talk]]) 05:25, 17 June 2023 (UTC)
::Nearly right. Simple "insert URL" as a 'number' is single []s, or [<url><space>some text] to have it given linking text (preferable).
::Plus you seem to have not used the four tildes, i.e. <code><nowiki>~~~~</nowiki></code> to sign the above comment (made it correct, for you), plus confusingly replied ''before'' another reply (so I ''originally'' indented you a bit more, as well as it now having that timestamp to make precedence clear, but as soneone disliked the indentatiom I'm rearranging in 'threaded'-order).
::But these are all things you'll pick up, I'm sure, if you're going to be getting [used] to wikis... Welcome! [[Special:Contributions/172.71.178.139|172.71.178.139]] 05:35, 17 June 2023 (UTC)

Wasnt there a "My hobby is to open my refrigerator and when people tell me that doesnt help, I sneak into their house and use their AC?" Comic? I cant find it, but we should link it in the "how leaving a fridge open doesnt help" section [[Special:Contributions/172.71.142.158|172.71.142.158]] 23:36, 16 June 2023 (UTC)
:Sounds like Steven Wright, he has lots of those "my hobby is" jokes. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 13:29, 17 June 2023 (UTC)

I think it's talking about leaving the door open in general i.e. forgetting to close it when getting groceries, not specifically when he's moving the heat pump [[User:Firestar233|Firestar233]] ([[User talk:Firestar233|talk]]) 23:40, 16 June 2023 (UTC)

I can't think of a good reason to say this, but my new fridge doesn't warm up on the back. It warms on the sides. A bad (and quite a PITA reason) is I had to get a new fridge. Protip: don't panic, and do put the sacks of ice into something that won't leak. First time I've met a fridge that doesn't warm on the back.
Btw, red hot blue cold. Pink? Light blue? A light blue a pink? Shrug. [[Special:Contributions/172.70.43.31|172.70.43.31]] 23:57, 16 June 2023 (UTC)

How many trips would this take? I'll leave the exact parameters of the calculation up to you. (Nerd sniping attempt.) ~ Megan she/her [[user talk:megan|talk]]/[[special:contribs/megan|contribs]] 00:20, 17 June 2023 (UTC)
: 42. But stick figures are just lines and have no surface area for heat transfer.
[[Special:Contributions/172.70.134.236|172.70.134.236]] 01:02, 17 June 2023 (UTC)

Currently, the explanation says you use a heat pump to "transfer heat from a relatively cold area to a relatively hot area". I don't know anything about the named "ideal gas law" in order to be sure enough to change this, but isn't that the wrong way around? If an area is ALREADY cold, why would anybody transfer heat FROM it? 04:49, 18 June 2023 (UTC)
:Let's say it's winter, and it's cold outside. It's warmer inside, but not as warm as you'd like it to be, so you need to warm it up. Where are you going to get the heat from? Traditionally you'd use a boiler to heat up water or electric coils, but these use lots of energy. A heat pump is more efficient, it moves some of the heat from the cold air outside to the inside. You need a pump because it won't move spontaneously -- heat always goes from warmer to colder areas. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 09:49, 18 June 2023 (UTC)
:[edit conflict with the above reply, thus repetition, but as I was adding other stuff too...] It's fridge-logic! i.e., that's what fridges do... and if you're living in a cool climate, you can potentially heat your house above "too cold for indoors" temperatures by extracting heat from the "far too cold for indoors" air that is outside. [[Special:Contributions/162.158.74.96|162.158.74.96]] 09:55, 18 June 2023 (UTC)

Technically, it's not the ''ideal'' gas law in play, since air isn't an ideal gas, and the system would behave similarly for closer-to-reality gas behaviour models. But I can't think of a good way of modifying the article to reflect that. [[User:BunsenH|BunsenH]] ([[User talk:BunsenH|talk]]) 16:04, 18 June 2023 (UTC)

Noting you could make hand-crank manual heatpumps that are much easier to use than the one depicted. If it’s doable it’s of meaning because a heatpump can be a big electricity draw, and sometimes electricity is not available. You could also connect a horse, waterwheel, or windmill to it. Making homemade windmills out of bicycle parts is a thing. [[Special:Contributions/172.69.59.147|172.69.59.147]] 20:03, 18 June 2023 (UTC)
:You can make a [https://hackaday.com/2016/08/25/a-refrigerator-cooled-by-rubber-bands/ rubber band heatpump] which works the exact opposite: rubber bands ''heat'' when stretched and ''cool'' when the force is released. This seems counterintuitive, but stretching is adding entropy (as is compressing a gas) and releasing the tension is bringing the entropy back to normal levels again (as is relasing the gas pressure). [[User:IIVQ|IIVQ]] ([[User talk:IIVQ|talk]]) 05:04, 19 June 2023 (UTC)
::The link is to a hand-crank fridge. The rubber bands are on a wheel, and get stretched/released depending on whether they are inside or outside of the fridge. The construction is quite similar to the comic. [[Special:Contributions/172.71.255.21|172.71.255.21]] 13:39, 19 June 2023 (UTC)

Folks seem to be assuming that the red side is "indoors", and the blue side is "outdoors", but in my experience exterior doors tend to swing in, not out. The hinge pins on an outwards-swinging door can more easily be accessed, which makes an out-swinging door a poor choice as an exterior door. [[Special:Contributions/172.70.100.224|172.70.100.224]] 20:26, 18 June 2023 (UTC)
:But why would you have steps leading up to the door from the inside? [[User:Firestar233|Firestar233]] ([[User talk:Firestar233|talk]]) 21:55, 18 June 2023 (UTC)
:Many exterior doors open outwards as a matter of safety, especially emergency exits. It's not a big deal if only one or two people are expected to try to exit in event of an emergency, since whoever opens the door can probably take a step backwards to make way for the door. But if there's likely to be crowding at the door, there isn't room for it to swing inwards. [[User:BunsenH|BunsenH]] ([[User talk:BunsenH|talk]]) 22:28, 18 June 2023 (UTC)
::For sure he is trying to heat up his house. And yes many places doors open in, but not always, and specifically not in public buildings for safety as just mentioned. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 08:34, 19 June 2023 (UTC)
:::Given his obvious lack of grasp of the impracticality of the solution, maybe he's actually trying to cool down the outside.[[Special:Contributions/172.70.162.229|172.70.162.229]] 13:34, 19 June 2023 (UTC)

Maybe not the intent of the comic, but it's interesting how the red/blue for temperature are also the political colors of the united states. After recent schisms, I imagine many people feel like they are walking between huge crowds of red->blue or blue->red slowly trying to build communication like an ant building an anthill grain by grain. [[Special:Contributions/172.71.255.21|172.71.255.21]] 13:39, 19 June 2023 (UTC)
:Interesting to note that Blue and Red are UK political colours (as they are elsewhere), but that here it is Labour (left-leaning, occasionally ''very'' left leaning) as red, Conservatives (right-leaning, occasionally ''very'' right leaning) as blue. Which always amuses me when I see Democrats (right of centre) and Republicans (so right of right of centre that it's not really funny any more) coloured how they are. Also, Libertarians aren't Liberals (UK: yellow, centre-ground fence-sitters), despite the similarity of name. About the only close match are the Greens (green!), but I think your lot might tend to being more militant than ours, at least the politically-inclined ones.
: Anyway, the colours are the usual colours. At least it's less confusing than taps labelled C(old) and H(ot) in the UK, but ''F(roid) et C(haud)'' in France, at least when you see only the "C" first. [[Special:Contributions/141.101.99.85|141.101.99.85]] 14:55, 19 June 2023 (UTC)
::Heh, that reminds me of my confusion as a kid when sometimes bathrooms would be labelled D and H (Damer/Herrer = ladies/gentlemen), and sometimes P and D (Piger/Drenge = girls/boys). [[User:Villemoes|Villemoes]] ([[User talk:Villemoes|talk]]) 12:12, 21 June 2023 (UTC)

Your parlance vary but to me a heat pump is a device that can heat or cool. (strangely, this would be easier to explain if I spoke of 'caloric' and coolth.' A heatpump is not an air conditioner except that it actually is when it wants to be: it can both move energy into a space and out of the space. Refrigerators only move energy out. Air conditioners only move energy out, (for the standard way to install them) the argue about summer and winter? Stop being silly. Here the outdoor temp has varied a lil in the past ten days. I think from a low of 45F (light jacket weather) to a high of 92 (uncomfortably warm). Here, to keep it comfortable inside at this time and (similar weather in the fall) I need to cool from about 3-7 pm and heat from about 3-9 am. If you live in a country that has rationing, my sympathies. "But apartment manager!! the toilet is frozen over!" "Yeah, doesn't matter. I can't turn the heat on until December 15." Sort of thing.[[Special:Contributions/172.70.130.86|172.70.130.86]] 00:17, 23 June 2023 (UTC)
:¿Que? You sound confused. And pumps (heat- or otherwise) needn't be bidirectional. Perhaps it's easier, even, with something slightly different like a peltier-effect system (with switchable power-flow) than to make a fully reversible source/sink set of radiators and compression/expansion chambers, on top of whatever you do to thaw frosting over of the cool-side, etc. [[Special:Contributions/172.70.86.25|172.70.86.25]] 01:04, 23 June 2023 (UTC)