1463: Altitude

Explain xkcd: It's 'cause you're dumb.
Jump to: navigation, search


In this comic, Randall is making fun of how oxygen deprivation can lead to reduced mental acuity. In this case, the mental clarity of the researchers devolves as they approach the high altitude telescope, leading to juvenile and almost intoxicated behavior. Dizziness, lightheadedness, impaired judgment, and euphoria are symptoms of oxygen deprivation, or hypoxia. Those researchers would benefit from having a written list or plan developed while they were still functioning at peak mental acuity. Note that high altitude does not lead to severe effects as described in the comic.

Iodine cells are used for wavelength calibrations of high-resolution RV spectra between 501 and 610 nm.

Note that the phrase "low oxygen" refers to the lower partial pressure of oxygen at altitude. The proportion of oxygen at high elevations is still approximately 2/9ths of the atmosphere, the same as at sea level. The altitude sickness is caused by lowered atmospheric pressure which leads to smaller amount of oxygen actually delivered ("pushed") into bloodstream.

The title text refers to a laser guide star a device for focusing telescopes by making artificial reference points in the sky. The reference points are created by shooting a powerful laser into the sky. The concern of the astronomer in the comic is that an imagined "star cat" may be attracted to the laser in the same way that cats playfully chase laser beams projected on surfaces. Cats' reactions to laser pointers were previously explored in 729: Laser Pointer.


Because of low oxygen, astronomers working at high altitude telescopes may need to write down their plans ahead of time while at sea level.
[Some astronomers are inside a sea-level research facility.]
Astronomer #1: Ok, let's head up to the observatory.
[The astronomers drive uphill.]
Astronomer #1: When we reach the summit, we'll check the iodine cell and do a general calibration.
Astronomer #2: Sounds good.
[The astronomers have reached the high-altitude observatory.]
Astronomer #1: My head feels funny.
Astronomer #2: Look at those telescope domes. I hope they don't roll away.
Astronomer #1: Maybe we should tape them down.
[The astronomers are inside one of the domes.]
Astronomer #1: Haha, look at this mirror! My face is huge!
Astronomer #2: I see your face in the telescope! I discovered you!
Astronomer #1: Let's make out!

comment.png add a comment! ⋅ comment.png add a topic (use sparingly)! ⋅ Icons-mini-action refresh blue.gif refresh comments!


Ok, Is everyone on vacation today? or is this explanation that hard? Edo (talk) 19:27, 22 December 2014 (UTC)

The comic was uploaded just minutes before you commented at 19:23. ThePurpleK (talk) 19:36, 22 December 2014 (UTC)
"Ok, Is everyone on vacation today?" Randall was ... --RenniePet (talk) 20:01, 22 December 2014 (UTC)
If you've paid him for something then I won't complain too much about your complaint - if you haven't at least bought one of his books, then what does he owe you? I am always a little disappointed when he fails to update right on time (or for an entire week in the case of the What If? site), but seriously? I bought a $15 book? what's that worth to him? maybe several minutes of his time? He's given me so much more than that over the years - the least I can do is give him a week or two off from my demands for trivia and wit now and then. My apologies if I somehow mistook your comment as a complaint... -- Brettpeirce (talk) 15:42, 23 December 2014 (UTC)
It wasn't a complaint, I was just trying (unsuccessfully, apparently) to be funny. --RenniePet (talk) 04:16, 24 December 2014 (UTC)

Transcript right now assumes two Astronomers. It looks to me like three. 21:03, 22 December 2014 (UTC)

I changed it to 3. 22:36, 22 December 2014 (UTC)
It looks to me like there are two. They just reply to each other more than once. But it is probably not possible to tell from the comic. Kynde (talk) 12:44, 23 December 2014 (UTC)

A laser guide star is a device for focussing telescopes. Cats go crazy chasing lasers. I can only imagine what havoc a star cat might wreck chasing a laser guide star. 21:07, 22 December 2014 (UTC)

The source of the laser is only moving at 1000 miles an hour, but it's going in a huge circle. That's a lot of leverage for our particular lighthouse. -- Seebert (talk) (please sign your comments with ~~~~)
You mean "wreak"? 05:12, 23 December 2014 (UTC)
Of course (s)he did - but this is the interwebs, wear you don't half to used corect grammer or spelink, even Nguyen it getz in teh weigh oven der schtanding -- Brettpeirce (talk) 15:42, 23 December 2014 (UTC)

I may be wrong, but I think all high-altitude observatories are built on mountaintops. So the drawings indicating the astronomers are driving up a hill, at least for the last stretch, is wrong - they'd be driving up a very steep mountain road with lots of zig-zags. --RenniePet (talk) 23:49, 22 December 2014 (UTC)

True story: Stephan James O'Meara's eyeballs are close to where it'd become statistically unlikely for there to be humans with a more perfectly shaped eyeball. He probably sees that 3 of the sky's planets are bigger than a point without an instrument. So from natural ability, being born after '55, and a bit from practice, SJO had about the best night vision of anyone alive in 1985. The guy wanted to be the first human to see Halley's Comet come back. So he traveled from Boston to a 14,000 foot volcano in the middle of the Pacific and brought a telescope so wide that Yao Ming could barely hug it. And bottled oxygen. Even people who can grow enough blood cells and heart-lung athleticism to acclimate completely still have trouble seeing in the dark. Besides some of the best observing conditions on the planet, it was also only 7.5 degrees from the latitude where Halley's Comet passed overhead so there was very little extra air to look through. Also, you have to use peripheral vision. But not too far to the side. And not the ear side, that's the blind spot. And tap the telescope and look for motion. That's the technique. It must've been freezing (it was midwinter and convection of even a human under the opening affects the view) but here is a guy staring through a telescope Yao Ming could barely get his arms around with an oxygen mask to his face. 00:17, 23 December 2014 (UTC)

Did you mean: Stephen James O'Meara -- Google

Am I the only one who's bothered by this? It was funny right up until the "let's make out" comment at the end. Astronomy has a pretty serious sexual harassment problem, and as a woman working in astronomy I'd rather that wasn't made light of. 03:08, 23 December 2014 (UTC)

Don't make a mountain out of a molehill. (Can't sign post as I have no account. Sorry.) (talk) (please sign your comments with ~~~~)
I don't think Randall would consciously make light of such an issue. Sadly, it does make a kind of sense that it would be an astronomical problem, so to speak. Taibhse (talk) 04:17, 23 December 2014 (UTC)
That's assuming one or more of the astronomers is female. They could all be male. 06:03, 23 December 2014 (UTC)
When I read that line I sort of said to myself, "OK, there's a mix of men and women involved." But I didn't assign any sex to the speaker. And I certainly didn't see it as a form of harassment, just a playful silly suggestion. --RenniePet (talk) 08:14, 23 December 2014 (UTC)
They could all be female. Would that make it ok? -- Hkmaly (talk) 13:51, 23 December 2014 (UTC)
As a man, that would make it acceptable -- Brettpeirce (talk) 15:43, 23 December 2014 (UTC)
There are many instances of spontaneous suggestions of making out or getting it on throughout xkcd. All the examples I can think of seem to be lighthearted with not 'deeper meaning' --Pudder (talk) 08:59, 24 December 2014 (UTC)
Thanks for the reference. We don't know enough about the situation depicted to know if harassment is involved, but evidently the issue is real enough that it affects how funny the comic is to some people, which makes it a relevant topic. And it's easy to see, especially in the context of oxygen impairment, that it could indeed be problematic, so I added a few sentences on that. Nealmcb (talk) 16:01, 23 December 2014 (UTC)

Oxygen concentration is constant regardless of altitude? So there is the same quantity of oxygen per cubic meter of atmosphere at sea level as at the edge of the atmosphere? And halfway to the moon? That doesn't sound right... 04:39, 23 December 2014 (UTC)

No. The number of oxygen molecules per volume of air (= concentration) is not constant, but number of oxygen molecules per total number molecules of air (= mole fraction) is practically constant at 21%. As the total air pressure decreases with altitude (i.e. fewer total number of molecules per volume of air), the absolute number of O2 molecules per volume (= concentration) decreases. -- Simon (talk) (please sign your comments with ~~~~)
I'm not sure if it's just way to explain more complex phenomena or if it really works that way in lungs, but I heard/read it's the partial pressure of oxygen which determines how you feel when breathing. Meaning, you will feel same effect in air with same partial pressure of oxygen no matter what the total air pressure will be. -- Hkmaly (talk) 13:51, 23 December 2014 (UTC)
That makes sense, but it doesn't matter whether we talk about partial pressures or concentrations: the partial pressure is proportional to the concentration; it's the total pressure times the mole fraction. -- Simon 19:28, 23 December 2014 (UTC)
Agreed, the term "partial pressure" is just a magic word for lay person and does not explain anything, only confuses general public. Simon's explanation using the decreasing number of oxygen molecules is much more "explanatory". Nyq (talk) 20:35, 23 December 2014 (UTC)
I agree that the term itself doesn't explain anything. Regardless, was confused by the term "concentration". It can be statistical anomaly, but it's also possible "partial pressure" is LESS confusing for general public. Of course, longer explanation is always more "explanatory", but as a downside, it's longer. -- Hkmaly (talk) 13:36, 27 December 2014 (UTC)

What makes this even funnier/more silly (in my opinion) -- these days, with the use of digital cameras/detecting equipment and internet connections, astronomers usually don't even need to go up to these telescopes any more. They can stay at a more breathable altitude and get their data remotely. --Aaron of Mpls (talk) 06:28, 23 December 2014 (UTC)

Sure, tell it to STS-61, STS-82, STS-103, STS-109 and STS-125! :) Nyq (talk) 20:35, 23 December 2014 (UTC)

"The proportion of oxygen at high elevations is still approximately 2/9ths of the atmosphere, the same as at sea level." 2/9ths is a strange fraction, and at 22.22% it is farther from the 20.95% that is the fraction of O2 in dry air than 1/5th = 20%. Just say 1/5th, 20%, or 21%. Don't introduce a more precise but less accurate fraction-- 13:40, 24 December 2014 (UTC)