Adding to original question:
Q: Maybe the government is conspiricising (probably bad spelling), and gravity isn't actually 9.8m/s^2. How would we know?
Because it's basic kinematics that anyone can verify for themselves. Just drop a ball and measure it's rate of acceleration.
Oh, right. That was obvious. :lol:
Also, using the gravity idea, are we now assuming that space has mass?
No. Where did you get that idea?[/quote]
That wasn't the right question. The right one is "Why doesn't the air fall out of the Earth?"
A 150 ft wall would only hold 150 ft of air, because over time any fluctuation in the air would cause pressure of upward force to move the air, constantly refilling the voids the flucuations create, and this force would give the air momentum, allowing it to surpass these voids and go to the real void. While this would explain wind, it doesn't explain why planes that fly over 150 ft in the air don't become weightless and just go in one direction forever?