... other celestial bodies, would I be able to take a tennis ball and make it orbit around my body?
2007-12-30 14:54:45 · 8 answers · asked by Anonymous in Science & Mathematics ➔ Astronomy & Space
I mean, I'm almost rotund enough to do it in my living room, but all I usually can manage is about 1/4th of a full orbit.
2007-12-30 14:57:31 · update #1
Nobody's done the numbers yet, so here they are. The only problem is that the human body is very irregular in shape, so let's assume a spherical human body (on the rotund side) of mass 100 kg (about 220 pounds weight on earth).
Suppose you release the ball in a circular orbit of radius 1 meter (a bit more than arm's length). The orbital parameters are the following:
period = 21.4 hours
speed = 0.082 mm/sec
(This speed is about 1 inch in 5 minutes.)
So the period isn't all that long. The speed, however, is extremely small. If you gave it a speed higher than 0.116 mm/sec, the ball would escape; so you'd have to release the ball very very carefully. (It's not the place for Roger Clemens.)
-- edit
Faesson -- This would not work in a spacecraft, because the gravity of the spacecraft and heavy equipment within would make for a very complex gravitational path. (If the spacecraft and all of its contents form a spherically symmetric shell around you, then the orbit would work; but spherically symmetric spacecraft are as rare as spherically symmetric people. The one advantage of the spacecraft is that if you throw the ball too hard, it will bounce off the walls instead of disappearing into the distance.)
2007-12-30 15:36:12 · answer #1 · answered by Dr Bob 6 · 1⤊ 0⤋
The answer is yes.
If, in a region, there is zero gravity, or, more practically, if the force of gravity on all directions are about the same, thus summing up to zero anyway, then for a tennis ball beside you, you are the sun and it is a planet.
But to answer the question fully, we must know first the initial (kinetic) energy of the "planet". KE=1/2 mv^2, so the faster the "planet" is, the greater its energy. There is an energy that is just enough so that the "planet" would escape from you and would fly out into the great beyond. Below this energy, the "planet" may take one of two options, depending on its initial energy - if it has a high energy, its path around you would be an ellipse, and if it does not have enough energy to follow an elliptical path, it would follow a parabolic path and fall into you (we hope not in your face, though).
2007-12-30 15:01:52 · answer #2 · answered by pecier 3 · 1⤊ 0⤋
Interesting question. Theoretically it would be possible but practically it would be too hard. The orbital speed would be extremely small because the force between you and the tennis ball would be really tiny.
Right now I'm too lazy to actually do the calculation of the orbital period, but it would be fun to see how long it would take to orbit you at arm's length. Let's see -- I'll make a wild guess of the top of my head; I'll bet it would take hundreds of years.
Remind me to come back later with the calculation...
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I went through a really crude estimate in my head before I fell asleep and discovered that my guess was way off. The period is just hours, not centuries. So I agree with the answer computed below. Interesting.
2007-12-30 15:05:16 · answer #3 · answered by Steve H 5 · 1⤊ 0⤋
You would also orbit the tennis ball, since you both have mass. It would be an extremely slow orbit, though. If you hit the tennis ball at any noticable speed it would totally escape your gravitational field, so be careful.
2007-12-30 15:05:36 · answer #4 · answered by Anonymous · 1⤊ 0⤋
Perhaps - if you threw it out there at just the right angle and just the right velocity (less than escape velocity). Of course you might have to wait for a few centuries for it to turn around and come whizzing back past you (ADDED actually around you) in its highly elliptical orbit. Probably not worth the wait.
2007-12-30 15:06:17 · answer #5 · answered by Larry454 7 · 1⤊ 0⤋
yes you can make the ball orbit you infact the only resion it cant orbit you on earth is because the earths gravity is stonger then yours. so if you can find a place were your gravitation pull is the strongest the ball will orbit you.
2007-12-31 00:56:27 · answer #6 · answered by Tony 2 · 0⤊ 0⤋
i think you are over-thinking this.
you don't really need to be 'out in the furthest reaches' to experience that.
astronauts in orbit have micro-gravities. If all the other forces cancel out, the ball should orbit (albeit weakly) around you.
2007-12-30 15:39:22 · answer #7 · answered by Faesson 7 · 0⤊ 0⤋
No shut up
2008-01-02 20:29:29 · answer #8 · answered by Anonymous · 0⤊ 0⤋