No, we are not talking about any such William, nor chewing gum, I really mean what happens when an object goes round the Earth without falling down.
My young mind could not figure it out. How COULD an object NOT fall, and just go round? Surely gravity would get it in the end?
Many years later, when I was about 14, I got an A-Ha! solution (ask Martin Gardner, Bless 'im!). And now on this blog, I am calling AIM#2.
Here's how the object does it, let's call it a cricket ball.
What happens when you throw it straight up? It comes down on your head, of course!
What happens if you don't throw it straight up? It always comes down just out of reach in that pond over there.
What happens if you throw it parallel to the ground (horizontally, I mean)? It still comes down, but this time it rolls under the only car visible, again, just out of reach, of course.
If you throw it harder horizontally, it will still come down, but this time it will land much further away, and roll onto the nearby freeway.
This is because the ball comes down in a curve, a well-defined curve, as dictated by Newton's Laws.
Well, we all know that the earth is curved too, don't we?
So the ball travels in a curve, and the earth, as the ball travels, curves down under it.
So, what if the speed of the ball is so big, that any falling it does, is compensated for by the curvature of the Earth, curving away underneath? Theoretically, it would never come down, in that case! This, my loyal reader, is, in essence, what 'orbit' is.
You never see it with cricket balls because 1) it is very hard to throw them at such a high speed, and 2) air resistance will always slow it down.
BUT, in space, where there is no air, and the spaceships have rockets to give them the great speeds needed, it is VERY possible.
And that, indeed, is what 'orbit' is.
There is a relation between height of the orbit and the speed needed to keep the object in orbit, though. In short, the higher the orbit, the slower the object has to go.
Reasoning thus, Arthur C. Clarke (author of 2001: A Space Odyssey) came up with the idea of the communications satellite, which are orbiting satellites that travel so slow that in relation to a fixed point on the earth, they are still. They stay over that point all the time. How can this be? This is easily answered too, because orbit depends upon the relation between the 'falling away' of the earth due to curvature, not to speed relative to any point on it. The fact that these satellites turn around the Earth at the same speed as the Earth itself turns around daily,
is the whole key to it. Their 'orbit speed' is the same as the Earth's speed on its axis, so they appear stationary in the sky.
This whole idea now forms the basis of the communications revolution, and without it, we would not have satellite TV, weather satellites, GPS etc.
Pity about poor Mr Clarke, he could have made a fortune, but neglected to put a patent on his idea, so he gets nothing!
My young mind could not figure it out. How COULD an object NOT fall, and just go round? Surely gravity would get it in the end?
Many years later, when I was about 14, I got an A-Ha! solution (ask Martin Gardner, Bless 'im!). And now on this blog, I am calling AIM#2.
Here's how the object does it, let's call it a cricket ball.
What happens when you throw it straight up? It comes down on your head, of course!
What happens if you don't throw it straight up? It always comes down just out of reach in that pond over there.
What happens if you throw it parallel to the ground (horizontally, I mean)? It still comes down, but this time it rolls under the only car visible, again, just out of reach, of course.
If you throw it harder horizontally, it will still come down, but this time it will land much further away, and roll onto the nearby freeway.
This is because the ball comes down in a curve, a well-defined curve, as dictated by Newton's Laws.
Well, we all know that the earth is curved too, don't we?
So the ball travels in a curve, and the earth, as the ball travels, curves down under it.
So, what if the speed of the ball is so big, that any falling it does, is compensated for by the curvature of the Earth, curving away underneath? Theoretically, it would never come down, in that case! This, my loyal reader, is, in essence, what 'orbit' is.
You never see it with cricket balls because 1) it is very hard to throw them at such a high speed, and 2) air resistance will always slow it down.
BUT, in space, where there is no air, and the spaceships have rockets to give them the great speeds needed, it is VERY possible.
And that, indeed, is what 'orbit' is.
There is a relation between height of the orbit and the speed needed to keep the object in orbit, though. In short, the higher the orbit, the slower the object has to go.
Reasoning thus, Arthur C. Clarke (author of 2001: A Space Odyssey) came up with the idea of the communications satellite, which are orbiting satellites that travel so slow that in relation to a fixed point on the earth, they are still. They stay over that point all the time. How can this be? This is easily answered too, because orbit depends upon the relation between the 'falling away' of the earth due to curvature, not to speed relative to any point on it. The fact that these satellites turn around the Earth at the same speed as the Earth itself turns around daily,
is the whole key to it. Their 'orbit speed' is the same as the Earth's speed on its axis, so they appear stationary in the sky.
This whole idea now forms the basis of the communications revolution, and without it, we would not have satellite TV, weather satellites, GPS etc.
Pity about poor Mr Clarke, he could have made a fortune, but neglected to put a patent on his idea, so he gets nothing!
No comments:
Post a Comment