Is outer space empty?
May 11th, 2009 by Grandpa OddballCopyright © GetOddNews and Grandpa Oddball May 11, 2009. All rights reserved.
Now imagine that we remove the box. The space that was inside the box is still there but it is harder to visualize. What we do is imagine the box is there in order to describe a volume of space. In order to figure out if an amount or volume of space is empty what we do is pretend we have a box surrounding the volume and look inside the imaginary box. We can then move our imaginary box around and look at what’s inside it in order to figure out if different regions of space are empty.
Let’s put our imaginary box on the lawn in the backyard. The box is now sitting on the surface of the Earth and as we have seen it is full of little air atoms and molecules so it is not empty. Let’s now imagine that we have a rocket available
and we shoot the box up in the sky on top of the rocket.
Because the force of the Earth’s gravity gets smaller the higher we go then less and less air is around to full the box because the force of gravity is less the higher we get (see the post on what is gravity?). So the box has less air in it and because there are less atoms and molecules hitting things then the air pressure is also less but the box isn’t empty.
In fact the box never gets empty no matter how high you get. There is always a stray atom or molecule floating around inside the box but when you get high enough there are so few of them that even all together they cannot push very hard. We say then that the pressure is very low. When the pressure gets very very very low we call this a vacuum. Normally when people think of a vacuum they think of a vacuum cleaner as sucking things into it but this is wrong. What actually happens is just the opposite of blowing up a balloon. By removing the air inside the vacuum cleaner the air outside the vacuum cleaner pushes things into the cleaner.
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