I know an object can be stationary relative to another, but is there anything absolutely stationary in the universe? Or is space itself expanding and thus nothing is stationary?
In: Physics
Being completely stationary in space doesn’t make sense in relativity. There is no such thing as absolute position.
There is no such thing as an absolute frame of reference in our universe.
However, there is a frame where the CMB is at rest.
https://einstein.stanford.edu/content/relativity/a10854.html
Not as far as we understand the universe. As far as we understand the universe there is no absolute frame of reference.
If everything is relative, what if something is spinning a million times a second in space? Surely it is stationary in relation to itself. Wouldn’t centrifugal force show that it is moving?
While all motion is relative to some reference frame, some reference frames are better candidates for an “absolute” reference frame than others.
Relative to the cosmic microwave background Earth is moving ~370 km/s towards the constellation of Leo.
If you launched something into space in the opposite direction and were able to accelerate it to 370km/s, that would make it “stationary” relative to the cosmic microwave background, which is probably as close as you get to absolutely stationary.
All motion is relative. Imagine your standing still on a long treadmill. That treadmill is on a train. That train is on a planet rotating around a star AND spinning on its access. That entire solar system is spinning around the centre of the galaxy. That galaxy is rotating around a much larger galaxy.
Are you really standing still on the long treadmill?
Relative to the part of the conveyor your standing on, yes. Relative to the rest of the treadmill, train, planet, star and Galaxy, no.
Top answers seem to be “correct” without answering you directly, so I’ll offer this:
Can an object be stationary? Yes.
However, there would be no way of *knowing* that it was stationary. No way of verifying it or proving it. For the reasons explained by others. But in an absolute sense, it is *possible.*
As others have said, there is no absolute stationary, everything is relative. You just have a frame of reference that is defined to be at rest.
Also… “Objects” are not stationary either. Objects are made of atoms that have electrons fuzzing around without even clearly defined position, plus, if you buy into string theory, “everything” is bunch of vibrating string-like things.
Only way to be truly stationary is *maybe* to have literally nothing to be relative to. A single dot with no dimensions in endless nothing. Perhaps. If that dot was everything that exists, a whole reality. Or maybe you could define it from other, macro side – while nothing is stationary, array of “everything” can be stationary. Since everything consists of everything so there’s nothing to be relatively in motion to
closest thing i can find/remember that can be ‘stationary’ are lagrange points. essentially theyre spots between 2 different gravitational pulls so the object stays in place. learned this in my astronomy course and it always stuck with me for some reason lol
https://science.nasa.gov/resource/what-is-a-lagrange-point/
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