# B Relativily the apple can be still and the ground goes up?

1. Dec 7, 2016

### farolero

so i take that the apple doesnt fall but that the ground acelerates up by relativity

this means the earth inflates at a certain rate thing not noticed for the measure instrument inflates simultaneously

but we feel the inertia effects of the ground moving up making things fall and keeping us on the ground

so as einstein said space curves around mass, more exactly space shrinks around mass

by realitvity i can take space shrinks around mass or mass inflates around space

the shrinkig of space around mass decreases squred to the distance of the mass which also explains orbits

so could i take relativity and curving of space this way or is it wrong?

this is backed up by the fact that the universe inflates and that space changes shape around mass

2. Dec 7, 2016

### A.T.

No, it doesn't mean that the earth inflates. In curved space time, proper acceleration away from the center, doesn't imply movement away from the center.

3. Dec 7, 2016

### Ibix

Wrong, I'm afraid.

You can always locally treat a free falling object as still, true. But extrapolating that to a larger region - such as the whole Earth - doesn't work too well. Earth is not expanding. Its radius, area, and volume remain constant.

This is basically a feature of curved spacetime. Trying to generalise descriptions that work well over small areas is not always straightforward - and pretty much impossible without using the mathematical descriptions.

4. Dec 7, 2016

### Andrew Mason

No. Where did you get this idea? The force of the earth on the apple is equal in magnitude but opposite in direction to the force of the apple on the earth. So the apple both accelerate toward their centre of mass but since the earth is so much more massive than the apple (by a factor of about 10
26, its acceleration is about 1/1026th of the apple's acceleration - ie. cannot be measured.

AM

5. Dec 7, 2016

### farolero

but doesnt the whole universe inflate? isnt this a fact?

wouldnt this imply an inertial gravit for what i explained?

the problem with universe inflation is that how do you know its rate if the measure instrument inflates as well?

6. Dec 7, 2016

### A.T.

Outside of galaxies.

7. Dec 7, 2016

### Ibix

The universe is expanding. Measurement apparatus and other bound systems, like the Earth, are not. That's how we can measure the universe to be expanding.

That is a different phenomenon to a ball falling near Earth.

8. Dec 7, 2016

### A.T.

This part is correct. The ground has proper acceleration upwards, while the apple has zero proper acceleration. It just doesn’t imply inflation of the Earth.

9. Dec 7, 2016

### farolero

if the distance between stars increases by inflation due to certain property of space wouldnt this apply to the components of an atom as well being this mostly made of space?

again how can you falsify the earth is inflating if the measure instrument and your eyes inflate as well?

you would just expect an inertia effect that in fact is there as well

this reminds me a lot that certainly the sun revolves around the earth cause your senses tell you so

10. Dec 7, 2016

### Ibix

The distance between atoms doesn't change due to cosmological expansion. The distance between planets doesn't change due to cosmological expansion. The distance between stars doesn't change due to cosmological expansion. The distance between galaxies doesn't change due to cosmological expansion. The distance between galactic clusters does. The difference between that last one and the rest of the list is how we can measure cosmological expansion.

Sure, if the Earth and all are rulers changed scale we wouldn't detect any change. But then why does the ball fall? The distance between the Earth and the ball would scale too. Put too balls next to each other but hang one from a piece of string. How can rescaling make one fall but the other not?

11. Dec 7, 2016

Staff Emeritus
First, it is better (and more congruent with PF policies) for you to ask what conventional physics says than to make up your own theories (like gravity being caused by an expanding earth).

Second, if gravity were caused by an expanding earth, how long before the earth and moon collide? This theory is a non-starter.

12. Dec 7, 2016

### farolero

"Second, if gravity were caused by an expanding earth, how long before the earth and moon collide? This theory is a non-starter."

this wouldnt happen in an shrinking space where this effect decreases with the distance squared

im taking the known things and questioning them and making whatif in order to learn

13. Dec 7, 2016

### Ibix

The problem with this is that you scatter silly ideas around and spend ages investigating why they make no sense. And when you've finished doing that you know no actual physics - just that your ideas were wrong. Open a textbook and learn. Then you'll have the grounding to generate plausible ideas.

14. Dec 7, 2016

### farolero

well if you know something really well you know perfetly why something is wrong or right

i try to find a balance to use stablished ideas and understand them instead of memorizing

the shrinking space model is a curved space in an inflating universe, its the same than einstein said with another words or thats what i think

15. Dec 7, 2016

### A.T.

And three is the same as five, just with another word.

16. Dec 7, 2016

### PeroK

I think Bryan Greene and Brian Cox might have something to do with it!

17. Dec 7, 2016

### Staff: Mentor

18. Dec 7, 2016

### Staff: Mentor

That is not how this forum works

19. Dec 7, 2016

### Staff: Mentor

This thread is going nowhere. On these words of wisdom: