if all motion is relative, how do we know the Earth isn’t stationary with everything else in the Universe rotating around us, albeit in a right weird and in uniform way.
In: Physics
Motion is relative, but acceleration is not. At least not in the same way.
You know how in a spinning carnival ride, you get pushed to the side? Or how, when you’re in a car that’s speeding up, you get pushed back into the seat?
In cases like those, it’s possible to construct a reference frame in which you are stationary, but those reference frames necessarily contain [fictitious forces](https://en.wikipedia.org/wiki/Fictitious_force).
Don’t let the name fool you. Those forces are real. You can still feel and measure them. But they’re not produced by any physical object, they’re just a consequence of the accelerating reference frame. Only non-accelerating reference frames don’t have any fictitious forces.
The Earth is rotating about it’s axis, and revolving around the sun, which is revolving around the galaxy. All of those are accelerations. It’s possible to construct a reference frame in which it is stationary, but such a reference frame will have these fictitious forces.
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