Is Gravity a Force?

• B
PeterDonis
Mentor
2019 Award
Coriolis?
Sure, why not?

pervect
Staff Emeritus
The centrifugal force does.
I would have to agree that that's a good example, worthy of some thought. And it fits in well with the description of gravity as being an inertial force presented earlier.

At the same time, though, I still believe that thinking of gravity as "just a force" is a bit like wearing blinders. There are a lot of the interesting predictions of General relativity due to geometrical effects that simply aren't included in the "force" picture. Time dilation effects and non-Euclidean spatial geometries are the first two that come to mind.

Some of these interesting geometrical effects do occur in situations that can be described by special relativity, time dilation being one of the principal ones, and certainly one of the easiest to explain.

In the end, I still favor the geometrical approach to special relativity. But it's unclear how to best motivate the geometrical approach, especially at a B level.

I also know that I don't really want to use the rotating disk in special relativity to motivate any sort of B-level discussion.

Dale
Mentor
I still believe that thinking of gravity as "just a force" is a bit like wearing blinders.
I agree, and calling it a real force or a true force is flat out wrong. It is quite clearly in the category of inertial/fictitious forces.

I can see arguments both for and against calling inertial forces “forces”. Your point that they don’t transform right is compelling, but calling them forces anyway has a long history, and they do cause (coordinate) acceleration.

So in the end I don’t take a stance on that, but wherever you classify inertial forces, there you need to classify the gravitational force also. Nobody classifies inertial forces as true forces.

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pervect
Hi, huge thanks to everyone who replied! I posted my question, then went out of town and just returned. It's going to take a bit for me to digest the answers and may have follow up questions, but I did want to at least express my appreciation.

berkeman