January 28, 2007
[the air up there] 10:11 AM
Aside from slogging through what is sure to be very lengthy Wikipedia articles, I'm not really sure where to start looking for answers to this nagging but trivial question that popped into my mind last night:
How did scientists know that re-entry into the ozone layer would require heat shields? How did they know where the ozone layer stopped and started? Did they know space was a vaccum, or did they just hedge their bets and plan for all scenarios?
I'm sure the actual obvious answer is that "satellites" collected data, but I'd like to think there was a cauldron of minds in the 50's and 60's that debated the very nature of our atmosphere. Who was right? Who was wrong? How does one go about getting the right ceramic tile that can withstand an invisible volcano?
Well, they know that anything going at high speeds - including things on ground level, like trains, bullets, and fast cars - through anything that isn't a vacuum generates heat due to friction. The more speed, and the thicker the medium through which you're traveling, the more heat. So it was an easy bet that space shuttles would get burned pretty good.
As for where things start and stop. Far as I know, that is mainly done by looking at refraction: different chemicals bend light in different ways, and a trained eye can see how/where. Also there's density, which can again be seen by refraction, but also worked out by calculating gravity, etc.
Ditto for space being a vacuum.
Also, the horizon provides some clues.
Caveat emptor: I'm a bloody terrible physicist.
Posted by: Michael at January 28, 2007 5:07 PMOn the vacuum question, I think people living in mountainous areas have known for thousands of years that air pressure drops based on altitude. After a couple of years in La Paz and the opportunity to scale a couple of peaks in the Andes, I've got pretty good first-hand experience with the issue, as well as the pathetic state of my own fitness. Shouldn't have been that hard for someone to graph out the drop in pressure to the point where the air pressure becomes irrelevant.
Posted by: Chuck at January 28, 2007 5:38 PM
