Suffice to say that no, no time elapses between dropping and falling, but at the same time no, no signal or interaction has to propagate upward from the ground to Wile E. I'm going to skip ahead a bit here, because I don't feel like explaining the entire theory of general relativity, and it won't be that useful in answering the question anyway. Because it implies that somehow a "signal" of some kind is getting from the ground to Wile E. As in zero time elapses between dropping and falling. Not after a very small interval of time, but absolutely instantaneously. To the absolute limit of our ability to measure it - and our ability to measure it is really good, since we used electromagnets and lasers and other expensive science things - when an object is dropped, it begins falling instantaneously. We can then construct a set of very, very precise experiments with very fine tolerances - probably involving electromagnets and lasers or something - to test this hypothesis.Īnd then we can find that we're totally goddamn wrong. steps off the cliff and when he begins to fall will be equal to or more than the distance between him and the ground divided by the speed of light. Given that fact, it makes sense to hypothesize that the time between the moment when Wile E. We can approach the problem naively by remembering that all propagating phenomena in the universe are limited by the speed of light. But just how much time does elapse, in real life, between stepping off a cliff and beginning to fall? Coyote runs off a cliff, floats in mid-air long enough to hold up a sign that says "Help," then begins to fall.Ĭlearly that's an exaggeration. We can then ask what the speed of that interaction is by putting it in these specific terms: How much time will elapse between your changing your position relative to the ground and your beginning to fall? We call that "gravity." We can call it, in the most generic sense, an interaction: you and the Earth are interacting somehow, and that's what's keeping you from floating freely. You're not floating freely, so clearly something's going on. Please feel free to move on if this strikes you as tiresome.Ĭonsider the Earth, and you on it. This is a far more interesting question than it might seem at first glance, and it deserves some attention because it tells us something fundamental and wonderful and just bloody awesome about the universe.īut I don't know how to tell the story succinctly. This is the winning comment from the reddit discussion from /u/RobotRollCall
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