Man on the moon?

September 5, 2005 9:32 PM

DrunkenSciFiFilter- What would happen if a human being, dressed in only like a tee shirt and let's say some cargo shorts, was suddenly on the surface of the moon? Details!
posted by xmutex to science & nature (24 comments total)

No time to give a detailed account of the agony, but here's the links I usually point people to when talking about exposure to the vacuum of space:

- Geoffrey Landis: Human Exposure to Vacuum.
- NASA Ask an Astrophysicist: How would the unprotected human body react to the vacuum of outer space?
posted by brownpau at 9:36 PM on September 5, 2005

The quick version: your blood would boil and you'd die.
posted by Wild_Eep at 9:43 PM on September 5, 2005

brownpau's second link seems to contradict the boiling blood thing. Why would your blood boil, anyway? I don't understand that. It seems quite cold from all accounts.
posted by xmutex at 9:49 PM on September 5, 2005

The quick version: your blood would boil and you'd die

Actually, both of brownpau's links specifically state that your blood won't boil. Their short version is that your tissues swell, your venous blood swells, circulation stops.

I'd always thought that the scene in 2001: A Space Odyssey when Dave blasts himself into the airlock and shuts the door was unrealistic; I assumed that he'd die instantly. But the above links indicate that you really would have a good 8 seconds of mobility before the convulsions, etc. start.
posted by gsteff at 9:52 PM on September 5, 2005

Probable answer: he would pass out shortly after deposition on the moon. The balance of opinion is that he would absolutely not explode, his blood would not instantly boil, his eyeballs would not pop out of his head. He would keel over quite shortly from lack of oxygen, probably swell up a little bit from internal pressure, die within a few minutes, and then slowly dessicate over the course of ensuing months. Bottom line is our skin is strong and the body is a pretty tight system, hydraulics-wise, so the most dramatic thing likely to happen to him in the short term is dying due to lack of oxygen. There are some that think it would be a bit more dramatic, eyes bug out and maybe go totally bloodshot, body swells markedly and perhaps becomes one big contusion, tongue forces out of the mouth and swells - Total Recall, basically. I tend to see this view as an excess of enthusiasm for drama. I'm guessing it would be dead boring, except for that first ten or twenty seconds of "oh my God what's happening" and the brief but amusing attempts to breath, clawing at the throat etc. prior to loss of conciousness. Then it's just a somewhat puffy guy, in cargo shorts and a tee shirt, dead on boring lunar dust, slowly drying out.

Almost everything you'll read on the net will derive from the following:

http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html

I'd say nobody really knows though because there have been to the best of my knowledge no experiments with long-term exposure to vacuum. Short term, up to the point that oxygen deprivation kills you, experiments suggest you would probably live without significant or lasting harm.
posted by nanojath at 10:01 PM on September 5, 2005

Oh, and xmutex: do you know nothing about physics at all or are you just being funny? If the former, read up on vapor pressure.
posted by nanojath at 10:07 PM on September 5, 2005

nanojath- I know a little. And I'm genuinely curious here.
posted by xmutex at 10:09 PM on September 5, 2005

Arthur C. Clarke argued quite strenuously in several short stories that humans could survive short exposures to the vacuum. This seems to be supported by Brownpau's first link. In animal experiments "survival was the rule if recompression occurred within about 90 seconds."

They would have done more experiments, but PETA commandos destroyed the lab.
posted by LarryC at 10:21 PM on September 5, 2005

xmutex - Basically, when you lower the pressure exerted on a substance (like in a vacuum), the vaporization temperature (read: boiling point) also is lowered.

For an example, given the right conditions, it is possible to 'boil' water at room temperature.
posted by anarcation at 10:24 PM on September 5, 2005

xmutex: the temperature at which things boil is greatly affected by the pressure. My CRC handbook doesn't tell my the temperature that water boils at in hard vacuum, so I don't know the number.

But it is quite possible to get things to boil at very low temperatures if the pressure is very low. For instance, at 50 mbar (which I don't think is even close to a vacuum), water boils at 89 F.
posted by teece at 10:30 PM on September 5, 2005

Atmospheric pressure at sea level is about 15 pounds per square inch. I've walked to an altitude of less than 6 pounds per square inch -- more than half way to outer space -- with no ill effect.
posted by JackFlash at 11:36 PM on September 5, 2005

I've walked to an altitude of less than 6 pounds per square inch -- more than half way to outer space -- with no ill effect.

Fascinating. Tell us more.
posted by wsg at 2:06 AM on September 6, 2005

What color tee shirt?
posted by rob511 at 2:21 AM on September 6, 2005

The moon's surface is not the same as outer space.
It's not in a vacuum, it does have gravity and atmosphere.
posted by bat at 3:35 AM on September 6, 2005

Gravity, yes. Atmosphere, no. The gravity isn't strong enough to retain one...
posted by brundlefly at 3:41 AM on September 6, 2005

I remember reading a report, possibly in one of Clarke's non-fiction works about vacuums, that a Russian cosmonaut's space suite had a total failure on the arm while on a space walk. They have/had pressure cuffs at the elbow/shoulder, so he didn't die. But his arm was exposed to a nearly total vacuum for a number of minutes. The results were reported as swelling and brusing from some of the surface capillaries bursting. But no long term damage.

Also, the Moon has so little atmosphere it is counting as having none. Some measurements put the total mass of the atmosphere at only 10,000kg (or 22,046lb if you're at Earth's G level) (The Moon’s atmosphere). To compare, the Earth's atmosphere is about 5.1 * 10^18 kg in mass (Earth's atmophere).
posted by skynxnex at 7:14 AM on September 6, 2005

You might have more immediate issues with the temperature than the vacuum. According to a website I arrived at from a quick trip to Google, the moon can be "-387 Fahrenheit (-233 Celsius), at night, to 253 Fahrenheit (123 Celsius) during the day." In other words, you might have to worry more about freezing or boiling from temperature and not the vacuum.
posted by mikeh at 7:27 AM on September 6, 2005

I'm not absolutely sure, but I don't think, that you'd spend that short time fighting to breathe. Your wheezing, fighting to breathe reflex is triggered not by lack of oxygen but presence of carbon dioxide. In particular, if you walk into a room full of pure nitrogen, you'll happily breathe it, notice your vision going dim, pass out, die. It's really weird trying to breathe in from a balloon filled with pure carbon dioxide -- you breathe a little bit, and your muscles simply stop! It's not horrible and unpleasant, just strange to encounter this rebellion.

Related question to the original: what would a glass of beer do, carried along by this drunkenSciFi guy? Spoiler below.

don't look

think about it first!

first it boils, then it freezes.
posted by Aknaton at 7:44 AM on September 6, 2005

You might cook in the sun, and would for damn sure get a hellacious (or spectacularly fatal) sunburn from unfiltered UV.

But vacuum is an excellent insulator, so if you're in the shadows your major heat loss will be conductive through your feet, or whatever other bits of you are touching the lunar ground.
posted by ROU_Xenophobe at 7:45 AM on September 6, 2005

I'm not absolutely sure, but I don't think, that you'd spend that short time fighting to breathe. Your wheezing, fighting to breathe reflex is triggered not by lack of oxygen but presence of carbon dioxide.

That is only true until the partial pressure of oxygen in your blood gets down to 60 mmhg from its usual value of 95-100. How long this takes depends on several things such as the individual's metabolic rate and how much oxygen is in the air they have been breathing. This is referred to as the hypoxic drive and takes over in some forms of lung disease when people chronically have elevated carbon dioxide levels in their blood (Pickwickian syndrome, for example). Giving extra oxygen to these patients can actually make them stop breathing.

/off topic
posted by TedW at 10:10 AM on September 6, 2005

Also, the vacuum would suck the air out of our spaceman's lungs; as anyone who has ever had the wind knocked out of them knows, the stretch receptors in your chest will then trigger a mad desire to breathe in long before hypoxia or hypercarbia takes over. Of course breathing in will be impossible in a near-vacuum, so I think there will be plenty of struggling to breathe.
posted by TedW at 10:14 AM on September 6, 2005

TedW writes "Also, the vacuum would suck the air out of our spaceman's lungs..."

I don't think so. You could probably hold your breath in a vacuum, but it would damage your lungs, along the lines of pulminary barotrauma in scuba divers. You'd probably be better off exhaling...
posted by mr_roboto at 12:52 PM on September 6, 2005

Perhaps you could hold your breath in a vacuum. I would guess the appropriate experiments have never been done. Assuming you could, the first time you opened your airway to try and breathe in the air would still escape your lungs. In other words, you would have to hold your breath until you died or passed out.
posted by TedW at 2:07 PM on September 6, 2005

You can probably fit a couple kilos of moon rocks in cargo shorts, by the way. They will seem much lighter on the moon, too.
posted by ikkyu2 at 7:28 PM on September 6, 2005