# 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

### Earths rotation with atmospere

If it wasn't like that then it would mean that say helicopter howering at one particular spot for one hour would appear or land somewhere else. Sounds unreal.

### Earth rotation

Sounds like to me the spinning ball earth theory is unreasonable when analyzed with the true science of natural laws.

### earth rotation

I noticed how misleading the answer given above to the question as to whether the rotation of the earth affects airplane flight times was. It said that because the atmosphere allegedly rotates with the earth, planes are 'carried along' with the moving air and thus don't have to compensate for rotation. But surely that only works if you're flying in the direction of rotation? If you're flying in the opposite direction shouldn't your journey time be far shorter?

### No, the answer is not misleading, you are mistaken...

Hi Paul

I regret that the misleading element here is, unfortunately, you. The answer above is correct, but let me add further information, which might help you to appreciate why you are mistaken.

If you fly "with" the wind - i.e. in the direction of the Earth's rotation - then you will do less work against the headwind and cover the ground more rapidly. Conversely, if you fly into the headwind, for every mile you move forward, the wind moves you back a set distance; hence it's harder to fly west than east.

### Air moving with Earth, airplane flight

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?

### Friction and a gas...

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...

### Wow

Lol, Newton explained all of this hundreds of years ago, jesus christ

### To those who are bothered by people’s curiosity

Last I checked every question is a good question, while the user may not have been aware of the answer, that doesn’t give you the right to be an asshole. Curious minds have been the basis of all knowledge, for all of history. Just because you’re so “smart” doesn’t mean you should act like everyone else who isn’t aware shouldn’t ask questions. At one time you asked the same question yourself, you’ve questioned everything you know as of now. Just a thought.

### This is out of my depth but

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?

### This makes zero sense

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?

### You've neglected real vs apparent velocity...

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.

### Example

Let's say you were sitting on a bus and throwing a ball up. The ball would then fall directly down to your hand. Why wouldn't the ball fall back from you? Now you were throwing the ball forward at a speed a lot less than that of the bus, it would then hit the front of the bus and fall down. Why wouldn't the ball fall before hitting the front of the bus? The answer to these questions is because you and the ball are moving at the same speed with the bus. Doesn't matter how high you threw the ball upwards or how fast/slow you threw the ball forwards, it would not fall backwards. Same with airplane, wind direction and speed will speed up or slow down your airplane. Not the Earth's rotation because you and airplane are already moving at the same speed with the Earth in space.

### Earth rotation and airplane flight times

Like others, I'm trying to get my head around this. It's said that the earth's atmosphere rotates at the same speed as the earth and that a plane at cruising altitude is either carried along with it (if it's flying in an easterly direction) or has to counter it (if it's flying westwards). There's also the factor of wind strength and direction which can presumably either accelerate or slow down the plane's progress.
I checked flight times for non-stop flights from/to San Francisco and Paris. Typical SF-Paris times are 10hrs 35m to 10hrs 55m. Paris-SF times given as 11hrs 30m and 11.45m.
The shorter W-E times are normally explained as being due to favourable westerly winds.
I'm not sure what the rotational speed of the earth is at these latitudes (SF and Paris). I'm guessing it's at least around half of the speed at the equator i.e. 500+ mph.
The air distance between SF and Paris is given as being around 5,580 miles. The typical cruising speed for a long-distance commercial aircraft is given as between 550-575 mph.
That would take a plane a little over 10 hours (allowing for the slower speeds for ascent and descent) to cover between 5500 and 5750 miles.
So apart from the contrary wind factor which is said to account for the slightly longer flight times from east to west, planes are covering the same distance in the same time regardless of whether they are flying with or against the rotation of the earth.
How is that possible?