If you run east, are you running faster than if you run west?

Asked by: Paul Mole, Dudley

That depends on what your movement is relative to. Suppose you walk up the aisle of a plane as it’s flying. The plane’s speed doesn’t affect how quickly you reach the cockpit, but it has a big impact on how fast you reach New York.
The Earth rotates approximately 360° anticlockwise on its axis every mean solar day, which translates to over 1000mph at the equator or 650mph at London’s latitude. If you run east, you are indeed adding your own (trivial) speed to the Earth’s rotational speed, but only relative to a point external to this system, like the Sun.
Einstein showed there’s no absolute frame of reference in the Universe; all motion is relative to something else. So while you’re running east at 660mph, you’re also running around the Sun at over 67,000mph and around the galaxy at around 500,000mph. None of which have any effect on your ability to catch a bus.

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