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Assuming that a place in Europe is exactly on the opposite side of the earth than Sydney. Now I want to take a plane to travel there. Does it matter if the plan flies with the rotation of the earth or counter the rotation of the earth? i.e. Does it matter if the plane flies westbound or eastbound?

Intuitively I would say it does matter, because if I fly against the earth rotation the goal, in this case Sydney is coming nearer. On the other hand, maybe the plane is still in the atmosphere and therefore part of the earth rotation.

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I read "does the rotation of the Earth affect TIME TRAVEL" :P –  Gurzo Feb 16 '12 at 10:34
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Maybe I'll ask this question in 30 years (hopefully). –  RoflcoptrException Feb 16 '12 at 11:33
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Interestingly, while the earth's rotation turns out to be negligible for traditional aircraft, it has much more of an effect for things that go vertical (i.e. rockets). This is why NASA and the European Space Agency have launch sites near the equator. They can more easily get into an orbital path since the earth is "pushing" them in that direction. –  Kris Harper Feb 16 '12 at 13:35
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Not as much as wind does I would imagine. –  hippietrail Feb 16 '12 at 13:35
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France is part of EU and has quite a few Overseas regions: Martinique and Guadeloupe islands in Caribbean Sea, French Guiana (from where Ariane V is launched), Réunion and Mayotte in Indian Ocean close to Africa). Seems that French Polynesia, Saint Pierre and Miquelon (close to Canada) are also voting for elections in European Parliament (and maybe still New Caledonia, for a few years). –  FelipeAls Feb 16 '12 at 20:55

3 Answers 3

up vote 24 down vote accepted

This actually depends on quite a few factors. I wondered this once many years ago, and asked around quite a bit. Didn't have Travel.SE back then ;)

The earth is rotating at a rather fast speed - and any point on the earth is therefore actually 'moving' (it's all relative). Since the points on the equator have further to travel, they're moving even faster than at the poles.

Now, of course, the air is dragged around WITH the earth, thankfully, otherwise the poor chaps on the equator would have wind speeds in the opposite direction of near the speed of sound ;)

However, when you're in a plane, consider that it can take nearly an hour longer to fly across the Atlantic in a westerly direction ('against' the spin) than 'with' the spin.

When you're flying with the spin, and by relation, with the wind, you're not flying 'into' a force that's going the other way, as you are when you fly against the spin. The earth is also dragging you with it - or rather, it's dragging the atmosphere, and you in it.

However, what you'll tend to find is that it's actually far more dependent in reality on the existence of jetstreams - where the air up there is moving faster than at ground level, and can boost the plane's speed if going in the same direction. Of course, in the other direction you do well to avoid the jetstream, as it would slow you down.

To put it in words more eloquent than my own, I'll borrow a quote from Aerospaceweb.org, which first, you must consider yourself to be running....

Stop running. If you were to jump straight up in the air, would the Earth rotate beneath you? (Those who do believe that the Earth rotates around them may want to stop reading right now.) No, because when you left the Earth's surface, you were traveling at the same speed as the surface, so, in essence, the Earth matched your speed through space while you were in the air! The same condition holds true for an airplane as it travels from Los Angeles to Bombay. If we were to ignore the winds, no matter which direction you flew from Los Angeles, the speed of the aircraft relative to the Earth would be the same. While the aircraft's speed through space would change, the effect of the Earth's rotation remains constant, and in effect is "cancelled out" no matter which direction you travel. In other words, the speed of the rotation of the Earth is already imparted to the aircraft, and the Earth matches that speed during the entire flight. (Of course, in the case of spacecraft, these speeds become very important.)

So, the end result of that long discussion is that the rotation of the Earth has no effect on the travel time of an aircraft. Actually, it is the headwinds and tailwinds that cause the change in travel times. Sometimes it is hard to believe that the winds can have that much effect, so let us consider the problem a bit more in depth. In the example given, the flight from Bombay to California (east) is 23% shorter than the trip from California to Bombay (west). This means that the speed of the trip east must be 23% faster. The prevailing winds pretty much anywhere that we are talking about blow from west to east, so when we are traveling east, we get a speed gain, and when we travel west, we get a speed penalty. Now, if we are to assume that the winds are identical on both days we fly, then the wind speed only needs to be equal to 11.5% of the aircraft's speed! This would cause a difference between the speed to the west and speed to the east of 23%! The cruise speed of the extended range Boeing 777 is about 550 mph (885 km/h) at 35,000 ft (10,675 m). This means that the winds only need a speed of about 65 mph (105 km/h) (good kite weather). Believe it or not, 65 mph is a very typical wind speed at such a high altitude. Speeds of over 100 mph (160 km/h) are not uncommon. If we wanted to make things more complicated, we could consider a region of high speed flow called the jet stream that flows eastward, and if an aircraft can take advantage of these winds, then the travel time can be reduced further.

Also note this LIVE amazing display of the prevailing winds in the USA, which affect all this.

So what is the bottom line? The direction you travel in relation to the rotation of the Earth does not affect the travel time of an aircraft, and, more importantly, a mere 65 mph wind is more than enough to cause a difference in travel time of five hours when you are traveling long distances!

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+1 I remembered about a physics theory back in high school. A fly that flies in car does not affected by the speed of the car. The reason is simple: the fly moves relatively to the car. So I believe your answer is correct. –  Rudy Gunawan Feb 20 '12 at 10:18
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"In other words, the speed of the rotation of the Earth is already imparted to the aircraft, and the Earth matches that speed during the entire flight. " This is not true. For example, suppose you start at the north pole and fly South to the equator. Then, in the absence of wind, the Earth would rotate under you. –  nibot Mar 29 '12 at 17:03
    
@nibot Isn't that just the special case of the speed of rotation of the Earth at the poles is zero? –  ghoppe Mar 29 '12 at 18:30
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But then you fly to somewhere where the surface velocity is not zero. –  nibot Mar 29 '12 at 22:32

It does make a difference. One way the speed of the plane is added to Earth's rotation, one way it's subtracted from Earth's rotation. Special relativity says t' = t*sqrt(1-v^2/c^2). Going with the rotation you have a higher v and thus time passes slower.

You'll need an atomic clock to measure the difference, though. For practical purposes Mark Mayo's answer is right.

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I believe the experiment was done. Quite famous at the time. (Though I'm not old enough to remember it.) –  Tom Hawtin - tackline Feb 18 '12 at 1:42
    
@TomHawtin-tackline: No. The experiment I'm aware of involved putting an atomic clock on a plane and flying it around the world. (And it was repeated for television this century.) In this case I'm talking about flying two atomic clocks halfway around the world and comparing them. The former measures the time difference between flying and stationary (and also the effect of being at jetliner altitudes), the latter measures the time difference between going with and against the spin. –  Loren Pechtel Feb 18 '12 at 5:01
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If this does make any difference, it will be much smaller than the purely special relativistic prediction because of frame-dragging effects. –  David Z Feb 26 '12 at 8:08
    
Loren's answer is the true answer. The difference is so minute (atomically sized actually), that you would never notice. For the other example of someone jumping straight up, he/she would technically have the earth move beneath them, but at the atomic (or smaller) scale. To experiment this is simple: put a robot that jumps on a mile long moving track. Say the track (and therefore the robot) is moving at 50kph, when the robot jumps he will be something like a few mm back from where he originally jumped. Now take that, and scale it to planetary scale! This should put things into perspective for –  user2877 Jul 31 '12 at 4:21

To make it a little more complicated and add to Mark Mayo's answer, the jet streams are caused by the fact that the earth is rotating via the Coriolis effect, so in fact you could argue that yes, the rotation of the earth does affect the travel time, but perhaps not in the way you'd expect.

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Well, it's technically not just the Coriolis effect. That's part of it, but global heating patterns are actually the primary reason for the formation of the jet streams. This is why prevailing winds in the tropics are actually opposite of prevailing winds at subtropical latitudes. The primary cause of prevailing winds is not the rotation of the Earth at all, but rather the fact that air gets heated up faster near the equator due to the higher incident angle of the sun there. –  reirab May 27 at 19:41

protected by Ankur Banerjee Feb 14 '13 at 8:31

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