# Gravity forces us to move...

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1. Jul 10, 2015

### Stephanus

Dear PF Forum,
I just want to ask a simple question.

Even if we are at rest (ignoring that the earth rotates, evolves around the sun, orbitting SMBH and Milky way orbitting what? Virgo Supercluster? And Virgo Supercluster to what?),
A. So even if we are at "rest" (blue line), are we always moving just like in ST diagram? We move trough time.
B. And gravity curves what? Space? Time? Space Time? And we are forced to move (green line), so that $t_{green}^2-x_{green}^2 = t_{blue}^2$?
If we see the ST diagram, I think gravity just bends time not space. But what I ask, if we are FORCED to move.

2. Jul 10, 2015

### A.T.

Both are distorted, but time is more important for what we perceive as attraction.

3. Jul 10, 2015

### Stephanus

Wow, the respond is so fast. Thanks A.T. Btw, what about the ST diagram. Are we forced to move so that $t_{green}^2-x_{green}^2 = t_{blue}^2$

4. Jul 13, 2015

### Staff: Mentor

Saying "we are at rest" is not well-defined. Motion is relative - there is always a frame where you are at rest in a particular moment, and frames where you are not.

5. Jul 13, 2015

### Stephanus

Thanks for your reply MFB.
But I don't say:
Even if we are at rest
but
Even if we are at "rest".
Because like you said, Motion is relative and there is always a frame where you are at rest,...
Thanks anyway

6. Jul 13, 2015

### Mentz114

Yes. Blue is not moving through space but is 'moving through time' in the sense that the passage of time is experienced as always.
Gravity is curved spacetime.

No we are not forced to move so that $t_{green}^2-x_{green}^2 = t_{blue}^2$. If blue and green are interacting through gravity it becomes very complicated.

7. Jul 14, 2015

### Stephanus

Thanks for the answers

8. Jul 14, 2015

### eurus

We are never at rest

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