# Crazy physics problem

1. Aug 20, 2011

### Himal kharel

suppose a plane stays over a point in earth . if it remains there can it travel to other place as earth rotates. if this was possible why planes needed horizontal displacement to travel from one place to another?

2. Aug 20, 2011

### xts

Could you say it a bit more clearly?
Certainly, something remaining there cannot be here...

3. Aug 20, 2011

### 101111001101

So you mean if a plane is levitating up while the earth rotates? So if the plane is stationary above US and the Earth rotates, it could wait for a few hours and would end up above London. Sure. Now, imaging you are on the surface of the Earth in the US and are looking at the plane above you. You rotate with the Earth's surface and what do you see? You see the plane travelling forwards, towards London. In fact the situation you described is just another way of looking at what is really going on... And you can change the relative velocity between the Earth's surface the the plane so that you can travel from London to US without having to wait for a long time, go over continental Europe, Asia, Pacific Ocean and then to US. In that case you are racing against the Earth's rotation.

Plane moving over the Earth's surface and the Earth's surface moving under the plane are the same thing. Don't forget, there is still relative velocity between the plane and air and you would still be experiencing the same thing as you would if you considered the plane to be moving over the Earth's surface.

Last edited: Aug 20, 2011
4. Aug 20, 2011

### shayaan_musta

Because if you want to go from one place to another place and you levitate on Earth and then wait for your destination, it takes too long time. Isn't it?
Science provides easiness to life. Therefore there is only a fool person who levitate in air and let the Earth move to reach its destination.

5. Aug 20, 2011

### xts

@101-and other-bits:
Not that direction!
You may start to levitate near Gatwick and stop levitate 6hrs later close to JFK - actually many people do that every day.

6. Aug 20, 2011

### 101111001101

Yeah my bad. The sun rises in say Japan (just a convention) first, then proceeds on to Europe and then the Americas. So if you hover over London, you'd fly above the Atlantic to the Americas, not in the other direction.

7. Aug 20, 2011

### Drakkith

Staff Emeritus
Realize that movement is relative to another location. Even a helicopter hovering over a landing pad is in motion when viewed from the Sun, the Moon, the Space Shuttle, ETC. But I'm assuming you mean that the plane is heading opposite the rotation of the earth. Since the rotational velocity of the Earth, at the equator at least, is 1600 km/h, very few planes even travel that quickly. (Mach 1, the speed of sound, is only 1236 km/h at sea level) Perhaps the most important reason they do not do what you were asking is because the air itself is traveling with the rotation of the Earth and planes have to overcome that drag. Hence they need engines and horizontal displacement.

8. Aug 21, 2011

### Lsos

Since the plane is traveling with the rotation of the earth, it would first have to slow down in order to "hover in place" and wait for another point on earth to rotate underneath it.

Unfortunately, the plane would be the only thing that's slowing down, where as the air would keep on rotating....and physics doesn't distinguish between the plane being in place and the air moving, or vice versa, and so it will cost you the same in terms of fuel and time.