# eli5: The Concorde could travel at a cruising speed of 1350mph, the Earth spins roughly 1000mph. If the Concorde matched the speed of the earth exactly, how high would it have to be to stay in roughly the same spot?

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eli5: The Concorde could travel at a cruising speed of 1350mph, the Earth spins roughly 1000mph. If the Concorde matched the speed of the earth exactly, how high would it have to be to stay in roughly the same spot?

In: Planetary Science

All movment are relative, there are no absolute frame of reference so the question need to specify relative to what. Consider if you are on a ship that move, are you in the same spot if you stand still, you will move relative to an island beside the ship. If you walk on the ship so you are still relative to the island you will move relative to the ship.

Earth orbit the sun at 30km/s, that oribts the milky way at 230 km/s, that move towards the great attractor at 600km/s. So the answer can simply be it is impossible to be in the same spot.

Rotation is measured in revolution per unit of time not a speed like miles per hour. You can measure the tangential speed of a point but that will differs depending on the distance from the axis of rotation.

Earth rotate once in close to 24 hours or in about 4 minutes less depending on what you compare to, the sun versus far away stars. The tangential speed speed on the equator is around 1000 mph but is zero on the poles. the speed is aproximalty cos (latitude) * 1000 mph.

This mean any plane can keep a constant position on earth relative to the sun or stars by just flying close enough to a pole. It do not need to be airplanes, as long as you can move in a circle around the pole it is possible. You can do that by walking. A human walk at approximaly 3.2 mph. That is the trangetal speed at 89.82°. That is 20km from a pole and the circle circuflence is 126km or if you like 78 miles. There are some rounding error in the calculation because 12* 3.2 = 76.8 miles.

So it all depend on what you mean at the same spot, it will either be easy int eh right location or impossible.