# Is the flight time affected by the earth’s rotation if we go East- vs. Westward?

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Let’s assume we are flying at the same speed of let’s say 600 mp/h eastward and with 600 mp/h back westward: Will there be a difference in flight time?

Please ignore other factors like jetstream/windspeeds etc. for the main part and and only focus on the rotation

Now i don’t know how the speed of an Aircraft is measured/calculated but if the speeds are the same the destination should be coming closer to us and therefore we’d be faster to reach our destination, right?

Or do i have to imagine it in a sense that we are not “detached” from the earth’s movement, even while we are mid-air and are always moving at a constant speed with it and therefore it won’t matter?

Will it be easier to accelerate in one or the other direction? Will going 600 mp/h east take the same power as 600 mp/h going west?

I am so confused and i can’t even pinpoint as to why.

In: 3

The atmosphere spins along with the Earth, so you aren’t going to gain/lose speed just by going with or against the Earth’s spin. If this wasn’t the case we’d constantly be experiencing 1000mph winds.

No, the Earth’s rotation isn’t the reason; it’s the jetstreams. Basically they are strong wind currents that flow from West to East, at certain angles in the Earth. They are pretty strong winds so not only the direction of the flight, the weather will play a role in how fast you go.

> Or do i have to imagine it in a sense that we are not “detached” from the earth’s movement, even while we are mid-air and are always moving at a constant speed with it and therefore it won’t matter?

This is closer to the truth, though not *exactly* true, and it’s as true as you can get while “ignoring other factors like jetstream” (but the jet stream is a direct result of the Earth’s rotation).

On the ground, the air is moving with the Earth’s rotation at roughly the same speed as the ground. If it weren’t, you’d be experiencing a very strong wind (since most winds in Earth’s atmosphere don’t come anywhere close to Earth’s rotation speed at the latitudes where most humans live). When you say there’s a “wind out of the east at 2 m/s”, what you mean is “the air is moving eastward at 2 m/s less than the ground is, which *looks like* the air moving west relative to the ground”. Whenever there *is* a difference, friction between the ground and the air tends to reduce it, which is why strong winds are rare (and why the atmosphere as a whole co-rotates).

High aloft, though, the jet streams move eastward significantly faster than the ground does. They’re powered by the Earth’s big atmospheric cells, which create north-south winds thanks to differences in the Sun’s heating. The Earth’s rotation – which, from a ground-based perspective, we observe as the [Coriolis force](https://en.wikipedia.org/wiki/Coriolis_force) – tends to bend these north-south winds to the east or west, and since the original winds are quite intense, the jet streams are too, and form a continuous west-to-east blast of wind that circles the globe.

To go further, we need to know a bit more about planes.

A plane has two relevant speeds: *airspeed* (the speed at which the air is moving over its wings) and *ground speed* (the rate at which an object tracing its path on the ground would be moving). They are often different. For example, if there’s a strong headwind, a plane that isn’t moving relative to the ground (0 ground speed) has a positive airspeed, because wind is moving over the wings. Airspeed and ground speed differ by at most plus or minus the wind speed, with airspeed = ground speed + wind speed for a headwind and airspeed = ground speed – wind speed for a tailwind.

(This is why airports have many runways: a plane needs to hit a particular airspeed to take off, so they orient into a headwind to achieve that speed without having to move too fast along the ground.)

Just before it fires up its engines to take off, a plane’s ground speed is zero. That means the plane is co-rotating with the Earth. As it accelerates, gaining ground speed, it is changing its speed relative to that rotation – it’s co-rotating slightly faster if its groundspeed is eastward, or slightly slower if its groundspeed is westward.

Once it’s aloft, planes usually target a particular airspeed based on the characteristics of the aircraft and its flight plan (like how much drag it experiences, or whether it’s in a hurry). If it’s moving with the wind, the same airspeed corresponds to a greater ground speed, meaning that eastward-moving planes (which move with the jet streams) have a greater groundspeed than westward moving planes do. Similarly, if it’s moving against the wind, the same airspeed corresponds to a lower ground speed, meaning that westward moving planes have a slower groundspeed.

In that sense – and only in that sense – planes do get a bit of an indirect “boost” from the Earth’s rotation when they go west to east, and go slower going from east to west. But that boost isn’t because they aren’t co-rotating, it’s because they’re moving with winds that are blowing in the same direction the Earth’s rotation. The wind is what matters, and the fact that its ultimate origin happens to be the Earth’s rotation is irrelevant for the purposes of the plane itself.

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There is one other detail here, which is that planes flying north or south *themselves* experience the Coriolis effect. When a plane flies away from the equator, it’s moving from an area where the Earth’s rotation (as seen by the movement of the ground/air) was faster to an area where it’s slower. But the plane still has its original speed. This tends to make the plane’s movement bend slightly eastward relative to the ground/air, although I think the amount of force involved is pretty small and probably near-negligible relative to the rather large other forces already involved in typical flight. (It matters for things that aren’t flying with wings, though – if you’re trying to hit something with a missile you need to account for it.)

It’s the same distance across the surface whichever way you go, what makes a significant difference in time is the speed of the air in relation to the ground. i.e. the wind. Especially the jet stream, which goes west to east, so flying east often doesn’t take as much time as going west.

The rotation of earth doesn’t have a big impact, but your orbital velocity is higher when flying east, which provides a small amount of extra lift.

Yes! The Coriolis Effect must be taken into account when traveling long distances, even if you take away atmospheric effects of Earth’s rotation. When you jump up in the air, you don’t all of the sudden fly East at thousands of miles per hour because you still have the same rotational inertia as you did when you left the ground, but if you are on a plane flying north from the south your position along Earth’s latitude. The distance around the earth at the equator is approximately 24,900 miles, but at 60°, it’s half that. For the sake of making the math easy lets just say it’s 24k miles, that means at the equator, earth spins at 1000 MPH, but if you were at 60°N, Earth spins at 500 MPH, it obviously spins at the same speed in degrees per hour. Disregarding other effects like air resistance, or weather, if you took off in a plane on the equator and few North, your momentum is conserved, as you approach 60°N, you will be flying north, but you will also have to add in the additional 500MPH you had with you going east with you. So as you fly from the equator to the North Pole the Earth will be turning underneath you and you need to take that into account. Snipers, pilots, artillery crew members all have to take this into account when they are shooting long distances.