[James Hamlin]

James Hamlin  asked the Naked Scientists:
   
Hi, Chris

I have heard the term "vacuum of space" if this is the case, can we use this pressure to rid our atmosphere of unwanted greenhouse gases or smoke? Like a straw in a balloon. We may need to wait for carbon nano-tubes.

And with that, could we also use these "tubes" as pnuematic space elevators? Such as at the bank drive up teller. 

What do you think?

[graham.d]

Hi James. Unfortunately such a system can't work. What you think of as "sucking" is really the higher pressure side "pushing". A vacuum is the absence of anything pushing back! The earth's atmosphere has pressure as the result of gravity acting on all the air molecules. The gravity also keeps the atmoshere on the earth. As you go higher the pressure gradually gets lower until there is a negligible amount of atmosphere. Having a pipe extending into space would behave exactly as the air outside the pipe. The pressure inside the pipe would be the same as outside and reduce in the same way as you went higher. In the same way as the air outside the weight of air inside the pipe would produce the same pressure gradient.

I hope this explains it.