explain xkcd - User contributions [en]

2790: Heat Pump

2023-06-16T23:29:54Z

172.70.206.194: /* Explanation */ ce

{{comic
| number = 2790
| date = June 16, 2023
| title = Heat Pump
| image = heat_pump_2x.png
| imagesize = 740x400px
| noexpand = true
| titletext = If I'm not going to upgrade to a powered one, I should at LEAST stop leaving the door open so often.
}}

==Explanation==
{{incomplete|Created by a BIG CHUNGUS HEAT PUMPER - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
A {{w|heat pump}} is a system which applies the {{w|ideal gas law}} to transfer heat from a relatively cold area to a relatively hot area, i.e. to heat an insufficiently warm room/building or to cool an insufficiently chilled room/building, even if the outside air is at the opposite heat-gradient for the purpose. The extra energy used to achieve this prevents the {{w|second law of thermodynamics}} from being violated, and is usually assumed to be added to the warmer side of the system. This is why the back of a refrigerator will feel hot, as it maintains the cooler internal temperature (and why leaving its door open does not cool the room that it is in down, just heats it up as it fruitlessly attempts to both heat and cool the same air-mass).

In this comic, [[Cueball]] has a ''manual'' heat pump, and he is manually heating an area by walking from the warm area (colored in ''red'') to a colder area (colored in ''blue''), and "drawing" residual heat into the "bellows" / accordion-shaped device by expanding them to cool them below the outside air temperature (more intense blue). He then returns back to the warm area and compresses the bellows to concentrate heat above the sustained room-temperature (more intense red), then letting it radiate away and increasing room temperature before going back outside to repeat the process of drawing heat out of the cooler air. As expected, this is a laborious process, as captioned in the text below the panel. Manual heat pumps of this kind do not exist in real life, but are partly emulated by devices such as {{w|fire piston}}s. The {{w|air source heat pump}} effectively does the same thing as this comic, but by using components installed across a wall (letting fluids/vapors flow between the two sides) rather than moving physical components through doors.

The title text refers to the problem of having to open the door to carry the device in and out. This would let the warmed air flow out, and cool air flow in, to undo some of the effort used to attempt to increase the difference. In lieu of some device that does not require the door to be opened at all, he should at least promptly close it between each passage through it.

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

:[Cueball indoors (light red background) holding a light red accordion-shaped device in his hands and walking towards an open door.]

:[Cueball outdoors (light blue background) with the door closed, the device is still light red.]

:[Cueball extends the device and it turns blue.]
:''Release''

:[Cueball looks behind while the device has turned light blue.]

:[Cueball walking back inside through an open door, the device is still light blue.]

:[Cueball indoors with the door closed. He squeezes the device and it turns red.]
:''Squeeze''

:[Cueball looks at the door while the device is glowing in bright red.]
:''Radiate''

:[Cueball is leaving the indoors area (now a slightly darker red background) through an open door.]

:[Caption below the panel:]
:Manual heat pumps are such a pain.

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

Talk:2783: Ruling Out

2023-06-01T14:50:08Z

172.70.206.194: New comment

Wow. the amount of citation needed tags is excessive. Here's a fun idea, do like that SMBC comic and actually find and give citations. [[Special:Contributions/172.69.70.72|172.69.70.72]] 19:41, 31 May 2023 (UTC)Bumpf
:Definitely. I fixed one (it should have been ''after'' the comma), during some other edits, but was sorely tempted to remove maybe two of them to just keep the funniest one(s). Whichever that(/they) might be. I expect they'll almost all evaporate in a future edit, though, as there's plenty of editting bound to be done. [[Special:Contributions/172.70.90.219|172.70.90.219]] 19:47, 31 May 2023 (UTC)
::Nice work to whomever on that! Xkcd never fails to make me smile if not LOL, and Explainxkcd never fails to teach cool facts. o7 [[Special:Contributions/172.69.134.147|172.69.134.147]] 21:28, 31 May 2023 (UTC)

I'm pretty sure there has been serious scholarship about the habitable zone of some quasars. Let's see.... Here: https://iopscience.iop.org/article/10.1088/1742-6596/2364/1/012057/pdf Not absolutely certain, but absolutely '''not''' ruled out. [[Special:Contributions/172.69.134.24|172.69.134.24]] 20:02, 31 May 2023 (UTC)
:I think that Cueball's scientific team did a study to discount the possibilities of quasars in the habitable zone of a star, not of a habitable zone around a quasar.[[Special:Contributions/172.71.166.249|172.71.166.249]] 20:52, 31 May 2023 (UTC)
::A quasar could exist in the habitable zone of a star, and if it was particularly dim, it wouldn't make the zone inhabitable. There's no minimum brightness for quasars, is there? For example, [https://iopscience.iop.org/article/10.1088/0004-637X/728/1/26] defines quasars in terms of relative magnitude, so I don't see why a tiny black hole with a small but sufficient accretion disk in translunar orbit couldn't qualify. [[Special:Contributions/172.69.134.162|172.69.134.162]] 20:54, 31 May 2023 (UTC)
:::Relative to their ''entire galaxy!'' Fixed explanation. [[Special:Contributions/162.158.166.175|162.158.166.175]] 09:02, 1 June 2023 (UTC)

I don't know how to properly describe the length of time the Moon's orbit of the Earth has been known. If you think that the moon orbits the earth, but you also think the sun, stars, and planets orbit the earth, do you actually have any way to justifiably say that you know that the Moon orbits the Earth? Also, is it worth pointing out the reasons that the moon is such an obvious thing to know about (i.e. its visibility and prominence to the naked eye, its cultural significance,...)?[[Special:Contributions/162.158.174.183|162.158.174.183]] 20:59, 31 May 2023 (UTC)
:Interesting xkcd (sort-of) reference here. Back when What-If questions started being solicited, I sent in something (roughly) like "When trying to justify the original geocentric theory of the solar system, it is said that it had always 'looked like everything went round the Earth'... What would it have looked like if it had always looked like everything, including the Earth, went round the Sun?" ...which I'm pretty sure never got answered. Probably didn't spark enough possible scope for that good old xkcd magic. But I saw plenty of other good stuff, so no regrets on my part. [[Special:Contributions/172.70.162.251|172.70.162.251]] 23:14, 31 May 2023 (UTC)
::I think your question was particularly difficult to answer in any way other than "Everything ''does'' go around the sun. To see what that looks like, look up." I suppose your question (if I'm understanding what you may be looking for) may be stated otherwise as "How different would the movement of our Solar System need to be in order to make it obvious that everything revolves around the sun (to a layperson observer on Earth)"? [[Special:Contributions/172.70.206.194|172.70.206.194]] 14:50, 1 June 2023 (UTC)

Y'know, I'm not entirely convinced that "tectonically active black holes" is something that we're actually capable of ruling out [[Special:Contributions/172.68.174.190|172.68.174.190]] 22:33, 31 May 2023 (UTC)
:Even if the black hole is tectonically active, its activity is in one direction only: forward, where you can never catch up to it. The damage is extreme, but it's held safely in the boundary of the singularity. [[Special:Contributions/172.70.130.203|172.70.130.203]] 01:10, 1 June 2023 (UTC)

Did anyone else see the connection between this comic and the NASA briefing yesterday on UAPs (Unidentified Aerial Phenomena, their term for UFOs)? In the briefing they discussed that the approach they'd need to take is one of ruling out everything else instead of saying for certain that "this is a UAP". I think that's the entire intent of this joke - to comment on the NASA briefing. [[Special:Contributions/162.158.175.113|162.158.175.113]] 11:50, 1 June 2023 (UTC)

2776: Crystal Ball

2023-05-15T23:12:06Z

172.70.206.194: /* Transcript */ optics (physics)

{{comic
| number = 2776
| date = May 15, 2023
| title = Crystal Ball
| image = crystal_ball_2x.png
| imagesize = 257x336px
| noexpand = true
| titletext = They often use ball lenses to collect light at the ends of optical fibers, so when you look stuff up on the internet you're actually scrying through a crystal ball.
}}

==Explanation==
{{incomplete|Created by SPHERICAL ABERRATION - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

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

:[A bearded wizard with a pointed hat is sitting at a table and investigating a crystal ball. Cueball is sitting at the opposite side.]
:Wizard: Your future is hard to see.
:Wizard: I can make out some hazy details in the center, but the off-axis components are particularly unclear.

:[Caption below the panel:]
:Wizards never did figure out how to fix spherical aberration.

{{comic discussion}}

[[Category:Characters with hats]]
[[Category:Comics featuring Cueball]]
[[Category:Physics]]