#ANIMATED UNDERHAND THROW GIF FULL#

If you threw it at a modest ten meters per second, it's still going to be many kilometers ahead of you by the time it gets back to the ISS orbit forty five minutes later. So it travels around the Earth slightly faster than the ISS in the first half of its orbit, and ends up ahead of you by the time it crosses the orbit of the ISS half an orbit later. If you throw it towards the Earth, then a quarter of an orbit later, the direction of your throw, and so of the extra velocity, is in the same direction as the ISS itself is traveling. Yes, half an orbit later, it will cross the track of the ISS, but because it is faster than the ISS, it will be ahead of the ISS.Īnother way to see it - this is less accurate because it doesn't take account of the changing pull of gravity depending on your distance from the Earth - but it gives a first rough approximation of how it works for small velocities. Kepler's second law of equal areas in equal times - an object in an elliptical orbit will go around the Earth faster when it is closer to the Earth, and slower when further away - so completes the part of its orbit closest to the Earth more quickly than the ISS. However, that doesn't work, even in the most ideal situation, because by throwing it towards the Earth, you make it orbit closer to the Earth and so it goes around it faster (by Kepler's second law, of equal areas in equal times). After all you threw it towards the Earth and half an orbit later it's returning from the direction of the Earth. In practice, it's very hard.įirst, you might, very naturally again, think it's going to return half an orbit later. Now that we know it won't hit Earth, what about trying to catch it? Can we throw it in such a way that it comes back to our hand a bit like a boomerang? You should find it is above the opposite side of the world. And then check where it is 45 minutes later. You can check where the ISS is right now using ISS tracker. Half an orbit later (45 minutes for the ISS) then both the ISS and your ball will be traveling over the Atlantic just south of the UK.įor instance if you throw it ten meters per second towards the Tasmanian sea relative to the ISS right now, then forty five minutes later, it is still traveling 10 meters per second in that same direction relative to the ISS - but because you are on the opposite side of the Earth now, that direction now points out of the Atlantic back to the ISS. If you throw a ball towards the Earth from the ISS you'd think it would fall into the Tasmanian sea. After all it is traveling towards the sea, so no matter how slowly it travels, surely it will get there eventually.īut of course, it is in orbit as well with an orbital speed of over seven kilometers per second, and your feeble throw has hardly changed its orbital speed at all. Suppose the ISS is passing just south of Australia. It has a perigee - time when it's closest to the Earth a quarter of an orbit after you threw it, then returns across the orbit of the ISS half an orbit later, and has an apogee, furthest from Earth, three quarters of an orbit after you throw it. If the orbit of the ISS is perfectly circular, your ball's orbit will be more elliptical.

#ANIMATED UNDERHAND THROW GIF FULL#

It crosses the orbit of the ISS roughly half an orbit after you throw it, and crosses it a second time, a full orbit later. Depending on where it is, roughly half the time it travels towards the Earth relative to the ISS and roughly half the time it travels away from the Earth. So it doesn't keep going towards the Earth. The extra velocity you gave it with your throw is in the same direction as before, but because of the orbit, that direction now points away from the Earth and directly back towards the ISS. Let's look at what happens half an orbit later (about 45 minutes later).

This astronaut is throwing something out of the ISS. However, we aren't used to throwing things in orbit, and our intuitions can often lead us astray. So, it is natural to think that no matter how slow it is, it would get there eventually. Depends what you mean by hitting the Earth.įirst, if you throw a ball towards the Earth - yes it's traveling that way when you throw it. Can an astronaut throw a ball to the Earth? The answer is Yes, and No.

Animated underhand throw gif