How does a jet plane travelling in the same direction as Earth's rotation reach its destination?

Above: Image © Gillfoto, Wikimedia Commons


If a jet plane is traveling in the same direction that the Earth rotates in, shouldn't it never reach its destination since the rotation speed of the earth is faster than the speed of the plane?


Interesting question! We know that airplanes can in fact travel eastward (the same direction that the Earth rotates), but does this mean that they are travelling faster than 1600 km/h (roughly the speed of Earth's rotation)? Not really. The thing to understand is that the lower-atmosphere of Earth rotates right along with Earth's surface. So an airplane travelling down a runway at 100 km/h relative to the ground (ground speed) is also moving at about 100 km/h relative to the atmosphere (airspeed). The only difference between an airplane's ground speed and airspeed will be due to wind specifically, how fast the atmosphere is moving relative to the ground. Wind can significantly affect an airplane's ground speed (in very high winds it's even possible for airplanes to be moving forward through the air but backward relative to the ground!), but the winds that airplanes experience are not nearly as fast as the speed of Earth's rotation. Again, this is because our lower-atmosphere rotates right along with the rest of Earth. Just for fun, imagine that our atmosphere did NOT rotate. If that were the case, the wind speed near the surface of Earth would always be about 1600 km/h! A helium balloon released in Paris would be flying over Canada in less than 3 hours! Thank goodness for a rotating atmosphere!

Answered By: Patrick Barks


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