When you launch something into orbit … you have launched it, via rocket thrust, so powerfully fast and high and far that when gravity’s pull finally slows the object’s forward progress enough that it starts to fall back down, it misses the Earth. It keeps on falling around the Earth rather than to it. As it falls, the Earth’s gravity keeps up its tug, so it’s both constantly falling and constantly being pulled earthward. The resulting path is a repeating loop around the planet.
I don’t get it.
I mean, “falling” in this instance is something different from gravity’s “tug”? If I jump out of an airplane I will fall to Earth, right? I thought I was falling because of gravity’s tug, because I was being drawn toward the center of greatest mass. The orbiting body is falling away from the Earth (“around the Earth”?) yet being constantly tugged back toward it? “It starts to fall back down,” Mary Roach says. What prevents the object from finishing what it started?
If gravity is strong enough to slow the launched object’s forward progress, why isn’t it strong enough to pull that object back home?
How can an object “miss” the Earth? That’s a pretty big target, especially right up close. Has a barn door beat by orders of magnitude.
Mary Roach is attempting an explanation in layman’s language, avoiding math, which, admittedly, I wouldn’t understand either, but what does “falling” mean here? Although a gravity-free experience is often termed “free fall,” what does falling mean if there is no destination for the fall? If there were no atmosphere (with all its buffeting) would your fall toward and ultimately onto Earth be a different experience from gravity-free falling? If you weren’t looking toward it would you know you were falling toward anything?
source: Packing for Mars: the curious science of life in the void by Mary Roach