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What man-made objects can be seen from space?

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gerontius grumpus
65673.  Sat Apr 15, 2006 11:17 am Reply with quote

Please let me humblise most apologetically Norb. I should take more care to read the whole posting.

 
Feroluce
68595.  Fri May 05, 2006 5:31 am Reply with quote

Has anyone mentioned the polders in the Zuider Zee?
I can see them on a map of the world on the other side of the room (not quite the same thing, but you get the point).

 
dr.bob
68624.  Fri May 05, 2006 7:00 am Reply with quote

It's a myth that parts of the human body, or the entire body itself, would explode on exposure to the vacuum of space. They would only experience a pressure difference of 1 atmosphere at most, and divers experience larger pressure differences than that with no ill effects (unless you count the bends).

Interestingly enough, when the Galileo probe was sent to Jupiter, it was used in an experiment to detect intelligent life on Earth. Since it had to fly by Venus a couple of times to pick up enough momentum, they decided to use its camera on its last fly-by of the Earth to see if they could detect any signs of intelligent life.

Unsurprisingly they were unable to image any of the things that are famously viewable from space, like the Great Wall. Of all the pictures they took, only one showed any evidence of intelligent life. A photo of part of Australia showed a huge agricultural field with a definite right-angled corner which was unlikely to have been created naturally.

So, there is intelligent life on Earth, but the only evidence of it is in Australia. Oh the irony! :)

 
samivel
68626.  Fri May 05, 2006 7:02 am Reply with quote

lol

 
Celebaelin
68645.  Fri May 05, 2006 8:10 am Reply with quote

dr.bob wrote:
It's a myth that parts of the human body, or the entire body itself, would explode on exposure to the vacuum of space. They would only experience a pressure difference of 1 atmosphere at most, and divers experience larger pressure differences than that with no ill effects (unless you count the bends).

It's different though isn't it? Wouldn't the rapid vapourisation caused by exposure to a (near) vacuum cause sudden large gas pressures in eg the intestines and lungs (maybe some other bits but that'd be enough). Freeze drying is achieved by exposing a spray to a vacuum so maybe some of the bits would freeze solid and stomachs, blood vessels etc might burst in a similar way from the rapid expansion of water into ice (maybe).

 
iluphade
68654.  Fri May 05, 2006 9:25 am Reply with quote

It might have been mentioned before, but surely the main highways (in Belgium atleast) should be visible from space? (Belgium being the most lightpolluted country and all that :-( )

 
dr.bob
68671.  Fri May 05, 2006 10:41 am Reply with quote

Celebaelin wrote:
It's different though isn't it? Wouldn't the rapid vapourisation caused by exposure to a (near) vacuum cause sudden large gas pressures in eg the intestines and lungs (maybe some other bits but that'd be enough).


Rapid vapourisation? Parts might get frozen, but that's not going to cause huge pressure differences.

Celebaelin wrote:
Freeze drying is achieved by exposing a spray to a vacuum so maybe some of the bits would freeze solid and stomachs, blood vessels etc might burst in a similar way from the rapid expansion of water into ice (maybe).


I doubt it. If a gas is exposed to a vacuum it will rapidly expand and lose pressure. Boyle's law says that the loss of pressure will produce a proportional loss in temperature.

So, if you close you mouth and pinch your nose, your lungs only have to withstand a pressure of 1 atmosphere. If you open your mouth and nose, your lungs may well freeze over, but that will be caused by the drop in pressure so they'll be even less likely to explode.

Your blood vessels will not be exposed to the vacuum as they're a sealed system internal to your body. Or, in other words, if your blood vessels are exposed to the vacuum, then you've got other problems :)

 
Tas
68672.  Fri May 05, 2006 10:46 am Reply with quote

Any fluids open to vacuum (err....eyeballs) will freeze over.
I dunno if they will pop as ice forms in and around them?

:-)

Tas

 
Celebaelin
68684.  Fri May 05, 2006 11:20 am Reply with quote

dr.bob wrote:
Rapid vapourisation? Parts might get frozen, but that's not going to cause huge pressure differences.

Any bodily fluid encountering a vacuum (including sweat) is going to evaporate and expand to fill the space available according to

PV=nRT

T will drop sharply during the process. Your mouth, nostrils and anus will form 'nozzles' limiting the escape of the evaporating gasses. The evaporating liquids will draw energy from their surrounding ie your body/the rest of the liquid volume to become sufficiently energetic to evaporate. It depends how rapid the evaporation is. How long can you hold your breath for? And don't forget to block Uranus, I mean your anus, or you will quite literally fart yourself to death (unless you explode first).

Quote:
Your blood vessels will not be exposed to the vacuum as they're a sealed system internal to your body. Or, in other words, if your blood vessels are exposed to the vacuum, then you've got other problems :)

Not sure about this, your capilaries might not withstand the (possibly sudden) pressure differential as normally air pressure is working in their favour. You might start hemorrhaging from, well, everywhere, which wouldn't be good for you. Especially as the leaking blood would then start to evaporate accelerating the cooling process. Even if cardiovascular integrity is uncompromised the cooling effect that will result from evaporation from non-sealed systems (no seal is perfect anyway so it's a question of extent) and from radiation of heat to the surroundings (call it a 370K difference in temperature for the sake of argument) will freeze your blood within a relatively short timescale.

All in all I'd rather be in, say, Southern France. With a nice cool drink. And some seafood. And garlic bread.

 
eggshaped
68686.  Fri May 05, 2006 11:26 am Reply with quote

Quote:
And don't forget to block Uranus, I mean your anus, or you will quite literally fart yourself to death.


Celebaelin, is this a throwaway remark or could you actually fart yourself to death? - i'd love to think it was true.

 
Celebaelin
68687.  Fri May 05, 2006 11:34 am Reply with quote

I think it's a distinct (!) possibility. By which I mean to say that yes, in a vacuum I think you could/would vent gas from your gastro-intestinal tract and respiritory system via your anus, and possibly only your anus, until you died. That is unless something more catastrophic along the bursting/exploding/freezing lines happened first.

There is quite a strong voluntary sphincter involved but the first 'escape' might be the first and last straw so to speak.

 
Feroluce
68907.  Mon May 08, 2006 3:18 am Reply with quote

I'd love to think that if you were to fart and burp in that situation, you'd flip inside out :D

 
Linda
68908.  Mon May 08, 2006 4:31 am Reply with quote

Have they ever shoved anything animalish out of an air lock to see what would happen?

Linda

 
Celebaelin
68921.  Mon May 08, 2006 7:22 am Reply with quote

Not as such, ground tests were done to asess the risk to astronauts.

Quote:
Could You Survive?
The best data I have comes from the chapter on the effects of Barometric pressure in Bioastronautics Data Book, Second edition, NASA SP-3006. This chapter discusses animal studies of decompression to vacuum. It does not mention any human studies.
page 5, (following a general discussion of low pressures and ebullism), the author gives an account of what is to be the expected result of vacuum exposure:
"Some degree of consciousness will probably be retained for 9 to 11 seconds (see chapter 2 under Hypoxia). In rapid sequence thereafter, paralysis will be followed by generalized convulsions and paralysis once again. During this time, water vapor will form rapidly in the soft tissues and somewhat less rapidly in the venous blood. This evolution of water vapor will cause marked swelling of the body to perhaps twice its normal volume unless it is restrained by a pressure suit. (It has been demonstrated that a properly fitted elastic garment can entirely prevent ebullism at pressures as low as 15 mm Hg absolute [Webb, 1969, 1970].) Heart rate may rise initially, but will fall rapidly thereafter. Arterial blood pressure will also fall over a period of 30 to 60 seconds, while venous pressure rises due to distention of the venous system by gas and vapor. Venous pressure will meet or exceed arterial pressure within one minute. There will be virtually no effective circulation of blood. After an initial rush of gas from the lungs during decompression, gas and water vapor will continue to flow outward through the airways. This continual evaporation of water will cool the mouth and nose to near-freezing temperatures; the remainder of the body will also become cooled, but more slowly.
"Cook and Bancroft (1966) reported occasional deaths of animals due to fibrillation of the heart during the first minute of exposure to near vacuum conditions. Ordinarily, however, survival was the rule if recompression occurred within about 90 seconds. ... Once heart action ceased, death was inevitable, despite attempts at resuscitation....
[on recompression] "Breathing usually began spontaneously... Neurological problems, including blindness and other defects in vision, were common after exposures (see problems due to evolved gas), but usually disappeared fairly rapidly.
"It is very unlikely that a human suddenly exposed to a vacuum would have more than 5 to 10 seconds to help himself. If immediate help is at hand, although one's appearance and condition will be grave, it is reasonable to assume that recompression to a tolerable pressure (200 mm Hg, 3.8 psia) within 60 to 90 seconds could result in survival, and possibly in rather rapid recovery."

http://www.sff.net/people/Geoffrey.Landis/vacuum.html

And the Nazis are known to have used similar apparatus for experimentation and execution of humans.

http://www.anomalous-images.com/text/NAZNWO52.TXT

I believe the Japanese also indulged in a bit of death by vacuum in China after their invasion of 1931 but I haven't found conformation of this as yet. Just other unpleasant stuff that they did.

btw beware when googling Japanese vacuum torture though to be honest the hits that you get are unlikely to be more offensive than what you're actually searching for in this case.

 
dr.bob
68928.  Mon May 08, 2006 8:34 am Reply with quote

So it's been scientifically proved, then. Being exposed to a vacuum is not a whole lot of fun, but it doesn't cause you to explode.

I wonder if that's worth a GI question at some stage?

 

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