Why vacuum doesn't pull matter apart despite lowering boiling points

  • Context: Undergrad 
  • Thread starter Thread starter mrquantum
  • Start date Start date
  • Tags Tags
    Space
Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
Sign up Log in
7 replies · 3K views
mrquantum
Messages
14
Reaction score
0
I just found out that if you're exposed to the vacuum of space, you won't explode, but rather you'll die less excitingly from a lack of oxygen. So much for the scientific accuracy of total recall!

How is that a vacuum doesn't "pull" matter apart given that lowering pressure can decrease boiling/melting points? Doesn't a really low pressure equate to really low boiling points? Is it because the vacuum in space isn't perfect?
 

Discussion

Astronomy news on Phys.org
mrquantum said:
How is that a vacuum doesn't "pull" matter apart given that lowering pressure can decrease boiling/melting points? Doesn't a really low pressure equate to really low boiling points? Is it because the vacuum in space isn't perfect?

Space has very low pressure which lowers the boiling points - yep.
It also has a very low temperature so liquids exposed to space will probably just freeze.

But you've got to remember that your intuitions about boiling will not work for low-pressure boiling.

A balloon filled with hot water and gasses placed in space would just expand until it's elasticity balances the internal pressure - so it is possible for the skin of the balloon to be strong enough that the internal pressure does not drop low enough for the water to boil.

The idea is that your skin is such a container - ergo, you puff up but you don't explode.
You will, however, leak from various orifices that won't close well enough to balance the pressure difference. What happens will depend on the substance and how much etc...

And I have to go make dinner now - thanks for that!
 
The Daily Cognition article is excellent isn't it?
The bits talking about the question go like this:

In the absence of atmospheric pressure water will spontaneously convert into vapor, which would cause the moisture in a victim's mouth and eyes to quickly boil away.

The same effect would cause water in the muscles and soft tissues of the body to evaporate, prompting some parts of the body to swell to twice their usual size after a few moments. This bloating may result in some superficial bruising due to broken capillaries, but it would not be sufficient to break the skin.

...

Within seconds the reduced pressure would cause the nitrogen which is dissolved in the blood to form gaseous bubbles, a painful condition known to divers as "the bends."


It's the quick lateral thinking in the examples that strikes me.
 
For those not familiar with the film "Event Horizon", for my money one of the most (few) enjoyable sci-fi horror films, the airlock scene is, albeit dramatized, a good example of how even a realistically portrayed exposure to hard vacuum can still have gut-wrenching effect on the viewer. Though it doesn't quite deliver the punch that a sudden cranial burst can elicit.
 
mrquantum said:
I just found out that if you're exposed to the vacuum of space, you won't explode, but rather you'll die less excitingly from a lack of oxygen. So much for the scientific accuracy of total recall!
I assume that you know that most sci-fi uses bogus science. The Myth Busters have a grand ole time proving those things right or wrong.
 
Surely not! Does that mean lightsabers aren't real?

I'm kidding. I was just adding a little whimsy to my question about phase transitions in a partial vacuum.

I know spaceships aren't real. A human could never even get into space.
 
Clearly this thread has run its course.

Locked.