You can do it by adding more mass in a fixed inertial frame, or by leaving the mass along and changing the reference frame. You cannot decide which happens, which is an insight from relativity.
So, which was the cause? You cannot tell. You simply can do the math and see that it matches the experiment. Only later do humans try to call it cause and effect, because the math and the experiment match so often and so well.
But this all can change if we find an experiment breaking the models.
Before relativity, most people thought time was constant. They were wrong.
So the above poster is correct in what we usually call cause and effect to simply be stronger correlations that match (current) models.
That can all be changed in future understanding of Nature.
Causation: if I do X, what happens to Y? For any well understood physical situation describing X and Y, the laws of physics tell you what happens to Y when you do X. If I swap out a mass on a spring for a heavier mass, physics will predict how much lower it hangs. The cause is me swapping one mass for another. The effect is where it now hangs. That's the whole point. If it wasn't this way, we'd say our physical understanding is wrong.
Having worked on physics projects for decades, the laws of physics at the lowest level are most certainly not this simple or causal.
>For any well understood physical situation describing X and Y, the laws of physics tell you what happens to Y when you do X.
Not true. If I create two electrons from photon collision, and measure one, will it be spin up? No way to tell. Only aggregates about large enough systems give any reliable answer to such questions.
If look for radioactive decay from 10 U235 atoms for the next 5 minutes, will I see one? Again, there is no yes/no answer, only probabilistic ones. There is no underlying causality - only purely random events with no detectable cause. These are the dice that Einstein didn't like.
There's plenty of similar questions that don't have a simple answer - only answers about large aggregates.
Here's [1] a recent result showing causality is no where the neat and tidy thing you think it is. These results are all over modern physics.
For example, the most accurate physical theories, such as QED, get the right answer by summing forwards and backwards in time. In QED the "future" affects results today as strongly as the "past". Causality is a psychological interpretation, but is not in the math
or the underlying theories.
As far as I know, all quantum field theories (which underlie all physics at the moment) all have such ambiguity or uncertainty about causality.
The laws are math models that give answers. But the lowest laws are time reversible or time agnostic for the most part, and the foundational theories require travelling forwards and backwards to get the correct experimental values.
Similarly, the laws of physics at the lowest level are not causal, but probabilistic. Only when aggregated do some experiments seem causal.
From another direction, there's a massive body of literature on what is causal, and can you detect it. Read, for example, Judea Pearl's monograph "Causality" or some of his other stuff, or simply browse wikipedia starting with him.
For example, when you drop a ball, it falls to earth. Quantum mechanically, there is a probability it simply quantum tunnels to another galaxy. That it most often falls to earth becomes a law, but it is imprecise and not completely correct. It's an approximation.
So every law of physics is merely a strong correlation.
And there's currently plenty of experiments trying to disentangle these issues with causality and locality.
So sure, at the freshman physics level causality is a simple thing. But Nature does not follow almost any of those rules with certainty or unerring rigor. Those are approximations and simplifications.
So, which was the cause? You cannot tell. You simply can do the math and see that it matches the experiment. Only later do humans try to call it cause and effect, because the math and the experiment match so often and so well.
But this all can change if we find an experiment breaking the models.
Before relativity, most people thought time was constant. They were wrong.
So the above poster is correct in what we usually call cause and effect to simply be stronger correlations that match (current) models.
That can all be changed in future understanding of Nature.