OK, I understand why science fiction(and fact) uses a spinning space station (colony, etc) to simulate gravity for the people inside, but I didn’t study physics in school (I preferred biology–all that dissecting, and chemistry–I loved blowing stuff up). My question is: if someone in the spinning construct jumps up, wouldn’t that remove them from the influence, leaving them floating above the spinning floor? I hate to imagine the poor helpless guy watching a distant wall, waiting for it to slam into him at high speed as the floor spins beneath him.
The man stays on the walls for the same reason water stays in a quickly-spinning bucket - inertia. Things in motion want to stay in motion going in a straight line. So the spinning space station is moving the man, and the man’s mass gives him inertia. Since the walls of the space station prevent him from going in a straight line, he goes in as close to a straight line as he can - around in a circle around the axis of rotation of the station. To jump or climb stairs, he must overcome that inertia in exactly the same way you must overcome gravity. In fact, Einstein proved that the conditions produced by acceleration (turning, remember, is acceleration) are indistinguishable from the conditons produced by gravity. So spinning space stations sound like a good idea to simulate gravity in freefall or even zero gravity. Being able to look up and see people walking upside-down sounds neat, too.
Thanks, but that didn’t really answer the question: If he did overcome the inertia (say by jumping up), is there anything pulling him back down before the wall slams into him, or in the case of an open cylinder (in other words, no roof above him) he slams into the floor on the opposite side?
He’d need to do more than jump up to overcome his inertia. He’s still moving. When he was against the floor, he was going in a circle. When he jumps away from the floor, he’d start moving in a straight line, but he’d still be moving along. So, he’d come back to the floor fairly soon, almost as if under the influence of gravity.
In order to get the effect you want, the astronaut would have to run around the ring in the opposite direction of its spinning. Once he gets going fast enough to cancel the motion of space station, then jumping up would leave him hovering while the floor of the station rushes underneath. This would be cool, up til the point where the next airlock rushes up and smacks him in the face.
Centrifugal comes from the same root as fugitive, the Latin fugere, to flee. So with a centrifugal force, you’re fleeing from the center.
The astronaut feels a centifugal force due to the spinning of the space station. The outer wall of the space station presses up against his feet with a centripedal force.
Not quite… Einstein assumed that acceleration was equivalent to gravity, and then went on to prove a bunch of other interesting stuff. Experiments do bear out his assumption, though.
The equivalence principle only applies to a completely uniform gravitational field. Anytime tidal gravitation comes into play it no longer exactly holds, unless there is only one test object and it’s a dimensionless point particle.
Actually there is a way to distinguish them. Two things side-by-side falling because of the gravity created by the mass of an object, say the Earth, all fall towards the center of the object and therefore slightly off parallel to each other. Two things falling due to acceleration would fall perfectly parallel.
Two things… First, Saltire was right. He isn’t traveling in a circle – he is going in a straight line, which is shifting from moment to moment. Assuming a vacuum, if he jumped, he would go forward and presumably impact the wall/floor at a later point. This later point would depend on how much force he jumped with, his mass, the radius of the station, it’s velocity, etc.
Second, that last example was assuming a vacuum. Don’t forget that all the air inside the station is probably being dragged along as well because of the internal walls and so on. This air would drag him along in its direction as well. Assuming, of course, that the station isn’t perfectly ring shaped and near-frictionless… the air inside would probably hold a lot more still in that case.
The station is spinning to generate centrifugal (?) force which creates an artificial gravity.
Man inside is spinning at same speed as the station, so is the air. (Recall that fly inside a car, buzzing around, as the car travels at 80 mph? Fly cannot fly at 80 mph.)
The inertia of the man is traveling in the direction of the spin no matter which direction he walks in. The force presses him against the furthest point of the spin i.e.; the outer wall or always ‘down.’ He may not walk up a vertical wall and expect to stay there. Centrifugal force always tries to throw things away from the center of the spin in a direct line.
If he jumps up or walks into an open elevator shaft that ends on the outer rim, he will not break loose of the force because everything, including him, is moving in the direction of spin and affected by it. He will fall ‘down,’ being hurled away from the center of spin.
Now, make the central hub or spin point big, say 50 feet in diameter and shove him into the middle of it and he will be weightless because he is at the exact center of the spin. Eventually, air currents generated by friction within the hub would grab him and cause him to move, with increasing speed, outward from the center point. Put the hub in a vacuum and he would require assistance to leave the zero point.
