Earth spin

[gsalih]

Earth is spinning around thousands of miles an hour, so when we jump for a few seconds, shouldn't we land miles away?

[CanadysPeak]

Earth is spinning around thousands of miles an hour, so when we jump for a few seconds, shouldn't we land miles away?

Yep, and we do. Trouble is, the earth does too, so it looks like we came down in the same spot.

[gsalih]

But when we are in the air we are not in contact with the moving earth, so how comes we are travelling at the same speed as the earth whilst in air?

[Fuqin]

imagine your in a passenger aircraft , its flying at say 900km per hr if you get out of your seat and jump up you don’t hit the back of the aircraft , you just go up and down because you and the air craft are travelling at the same speed. : )

[gsalih]

Thanks for your replies, i know that but i am more looking for a scientific explanation.

[CanadysPeak]

Thanks for your replies, i know that but i am more looking for a scientific explanation.

OK. F = ma describes the situation. From some imaginary reference point where we are close enough to think the earth flat, we see the earth moving to the left at about 1000 miles per hour. You, standing on the earth, are also. There are no left right forces acting on you, so you have no acceleration (change in motion) left-right. You jump up. You come down. There never were any left-right forces acting on you, so there was no acceleration. Your left-right position didn't change. This was first noted by Galileo back in , well a long time ago.

Now, if we back off far enough that we could see the earth rotating, we get a slightly different story. When you jump up, you keep your old velocity, but not your old acceleration. You would come down a few thousandths of an inch away (I don't really know how far. It includes rotation and I don't feel like calculating it this morning, but it's not far.). Still close enough enough for ordinary work.

You can see this by taking a tennis ball and getting on a subway car. Toss it up and it'll come down where it started. Now do this as you round a tight curve and you'll see it miss a little. Most subways don't go fast enough to see a big difference; you might have to go ride the carousel at the amusement park.

[Fuqin]

I don’t think its much more complex than what has previously been exsplained , however maybe you want to know what role s gravity and electromagnetism play in this but I think basically you’ve got
Inertia :- http://en.wikipedia.org/wiki/Inertia
Friction :- http://en.wikipedia.org/wiki/Friction

[Lincoln]

I disagree with nothing Canadys said, however, I may offer a different spin on it. Unfortunately, I do not think Fuqin's post is the right way to think about the problem.

The real issue is inertia. If you sit on the Earth, while the Earth is turning, the surface of the Earth is moving and so are you. If you jump up, the Earth continues to move and your speed parallel to the surface of the Earth is unchanged. Yes, you move upwards and downwards, but the parallel motion is unchanged.

In order for you to end up miles away, you'd have to be moved by your contact with the Earth and not your inertia. Were that not true, you'd also see the following strange behavior. Throw a ball. In the world in which you are moving due to contact with the Earth, the ball would move as long as it touches your hand. However, once it isn't touching your hand anymore, it would no longer have a reason to move and it would then fall directly to the ground. The reason the ball continues to move at the speed it did when it left your hand is inertia.