Does Earth's rotation affect flight times?

07 August 2011

Question

Does Earth’s rotation alter flight times? Since the Earth is spinning, if you take off from one place and fly in the same or opposite direction to that in which the Earth is turning, what impact does that have on the time it takes you to fly somewhere? What about the fact that the aeroplane is moving? Is there a relativity effect because the aeroplane is moving faster than the people who are on the ground?
-Bansi

Answer

Dominic - Taking the first part of the question, the atmosphere is moving with the surface of the Earth below it, because there's friction between the surface of the Earth and the atmosphere. And so, as the atmosphere is moving with the Earth, when you fly up into it, you continue to move with the surface of the Earth.

The rotation of the Earth also creates weather systems, because the equator is moving very fast in order to get round a whole revolution every day, whereas areas close to the poles have to move less far. That difference in speed at different latitudes creates, for example, hurricanes and other weather systems. That leads to upwelling wind systems, which mean that, when you're flying across the Atlantic for example, it's much faster to go from the US to Britain than to go from Britain to the US.

Dave - You get stable high-speed winds high up, called the jet stream, which is moving with the Earth towards the East; this contributes significantly to reducing the flight times going from the States to the UK, because an aeroplane is travelling with the prevailing wind and therefore confronts less air resistance or drag.

Dominic - Going on to relativity, whenever you're moving at high speeds, time appears to run slow for you. That's called the time dilation principle and so, whichever direction you're moving in this plane, you're moving at high speed, and that will mean that the time would dilate slightly and you will age slightly less quickly. That won't depend from where you're going, that will depend upon the amount of time you spend in the air, and how fast you're going.

Comments

1. You say the air moves with Earth because of friction? Can you explain how friction works on a gas? And how come a moving car does not carry air along it (friction) but encounters air resistance (at considerably less speed than 1600 km/hr)?
Plus, air density varies... so upper layers would move at different speeds with the higher being slower, no?
2. If an airplane flies west (Earth spins easterly) then the plane would have to fly against air (a friction-full medium) that is moving at 1600 km/hr. How is that done? I know that as an airplane takes off it moves Easterly (together with the Earth) at 1600 km/hr. To turn Westerly, what should it do? Slow itself up relative to Earth speed? How?

Try this - drive your car along the road. As it is moving, open the window. Stick you arm out. Feel anything? Now you know how friction works with a gas...

This is out of my depth but im curiouse.

okay right now i'm kind of picturing the layer you see created petrols that when petroly oily substances are on surface of the water. (no idea why)

Is there a point as you get higher and higher into the atmosphere that the effects do change and that the travel time does get effected?

If the atmosphere moved with the earth, you wouldn't see clouds moving. The earth is rotating at 1,000 mph. Planes do not only fly with the prevailing winds. If a commercial plane, at top speed, can fly 600 mph, it doesn't make sense that a plane can even reach its destination. It would always be moving away from it, 400 mph faster. That's also generalized, as the earth supposedly rotates faster at the equator, and slower as you reach the poles. In fact, it would also make it nearly impossible to land. Ever try jumping out of a moving car?

The atmosphere does indeed move around with the Earth. Winds, or aeroplanes, moving contrary to that direction have velocity over and above the intrinsic rotation.

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