If any reference frame where we consider the earth to be the stationary centre point, then everything else on the universe is the one that is moving to us.
By looking at the other planets in the solar system
In a hypothetical star system that only contains the sun and earth, which I think is what you're really asking about, there is no meaningful distinction
I mean given some hypothetical mechanism that’s causing this, and some hypothetical means to measure acceleration from each, we could determine which one actually has this extra force component.
Earth's distance from the sun is a consequence of its orbital velocity. If its orbital velocity increased it would be more distant from the sun, if it decreased it would be less distant.
This is the only practical way that the distance between the Earth and sun could change. If the sun simply "moved", Earth would move right along with it. If the sun moved towards us, we would move away from it too as our orbital velocity wouldn't change. If the sun were to suddenly rocket off in a novel direction, the shape of our orbit might become eccentric, though (stretched into an ellipsoid); think "pulled along by a car on a rubber band" action.
So the point is, whatever strange scenario you cook up to change the distance between the Earth and sun, you should be able to tell by looking at the orbital dynamics exactly what's gone on (and thus what exactly has "moved").
On a simpler conceptual level but in practice more difficult to actually observe, you would also be able to tell by looking at the Earth and sun's relationship to other bodies. If the sun went rocketing off in an unexpected way, you could look at its position relative to other nearby stars. Not as easy to figure out as you'd think though, unless the movement was extreme.
It's all relative. Depends on where you are looking from.
Can I say looking from earth?
If any reference frame where we consider the earth to be the stationary centre point, then everything else on the universe is the one that is moving to us.
By looking at the other planets in the solar system
In a hypothetical star system that only contains the sun and earth, which I think is what you're really asking about, there is no meaningful distinction
I mean given some hypothetical mechanism that’s causing this, and some hypothetical means to measure acceleration from each, we could determine which one actually has this extra force component.
Earth's distance from the sun is a consequence of its orbital velocity. If its orbital velocity increased it would be more distant from the sun, if it decreased it would be less distant.
This is the only practical way that the distance between the Earth and sun could change. If the sun simply "moved", Earth would move right along with it. If the sun moved towards us, we would move away from it too as our orbital velocity wouldn't change. If the sun were to suddenly rocket off in a novel direction, the shape of our orbit might become eccentric, though (stretched into an ellipsoid); think "pulled along by a car on a rubber band" action.
So the point is, whatever strange scenario you cook up to change the distance between the Earth and sun, you should be able to tell by looking at the orbital dynamics exactly what's gone on (and thus what exactly has "moved").
On a simpler conceptual level but in practice more difficult to actually observe, you would also be able to tell by looking at the Earth and sun's relationship to other bodies. If the sun went rocketing off in an unexpected way, you could look at its position relative to other nearby stars. Not as easy to figure out as you'd think though, unless the movement was extreme.
I appreciate the thorough explanation, especially when I asked someone that’s vague and not based in reality at all