re: #38 jaunte

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Brief explanation of the physics involved:

airplane engines do not make airplanes rise into the air. The propeller blades are shaped, and angled, in such a way that when they rotate they bite into the air and pull the plane forward, much like a drill bit does in rock.

As the plane moves forward, the air its flying through must split; some goes under the wing, some goes over the wing. The wing is shaped in such a way that the air going over it has a farther distance to travel than the air going under the wing. Different speeds = different pressure. That makes lower pressure above the wing than below, creating a vacuum effect. The hole in the air above the wing sucks the plane upwards.

Hotter air has more space between molecules; at 120º, the air is too thin for the hole in the air to be “empty” enough to make a vacuum. The plane doesn’t get sucked upwards. Ergo, gravity pulls it down.