# How GR curved space time works?

Discussion in 'Pseudoscience' started by BdS, Oct 28, 2013.

1. ### BdSRattling cages since inception :)Registered Senior Member

Messages:
437
In GR there is no force being applied to the object, the object is being potential influenced in the curved space-time geometry. The curves are supplying potential energy (not force) or influencing the objects motion into orbit by the curved space-time environment.

Just a layman trying to understand this... did I get GR gravity correct?

A major problem I've got understanding what I said.

lets compare curve space-time to a ball on a hill, the ball rolls down the hill if theres no obstruction... the hills geometry released the potential energy of the ball gradually depending on the hills slope angle, right? But, if there was no gravitational force the ball would not roll down the hill! GR curves in space-time cant supply any energy/motion to anything without there still being a gravitational force. Experiment: Lets go to a region of space where there is no gravity, we place a wooden plank there at the angle of the slope of the hill, we put the ball on the plank, what do you think will happen? I think nothing will happen! the ball wont roll down the plank, because there is no gravity to force it down the plank...

The GR space-time curved geometry wont work without there still being a gravitational force to force the objects down the space-time curves. Without there being a gravitational force the object would just sit on the curve and not move.

I just dont understand GR gravity, probably because of something Im misunderstanding... where am I going wrong?

Messages:
22,846

The way I understand it......
Gravity in the GR model is space/time....It is exhibited in the presence of mass/energy, when that mass/energy curves the space/time.
You say let's go to a region of space/time where there is no gravity.....but the act of going to that region, with a wooden plank, immediately creates the gravity by warping/curving the space/time.

I think it was John Archibald Wheeler who said,
" mass/energy tells space/time how to curve: space/time tells mass/energy how to move" :

Also In saying the above, we do have two models of gravity...Newtonian and GR.
These both describe gravity in the following two methods, [1] The attraction between two masses, that falls off as the inverse square of the distance between them. and [2] The warping/curving of space/time in the presence of mass/energy.
The GR method is the more realistic model, due to the higher precision obtained near very dense objects such as BHs.
But it also has its shortcomings which become obvious at the Planck/quantum scale.

So even though it is the better model, a model is all it is, as distinct from an exact reality as to the nature of gravity.
In essence then, we don't really know what gravity is.

Last edited: Oct 28, 2013

5. ### BdSRattling cages since inception :)Registered Senior Member

Messages:
437
Yes, the ball and plank attract each other, but the ball doesn't roll down the plank.

I dont think that is invalidating my view, because the ball doesn't roll down the plank.

I agree its a great model, I am just trying to understand where I find the model to fail from a physical perspective. It might be helpful to someone else too, if we can point out the where the model is requiring attention.

It can also just be me misunderstanding the model... and hopefully in discussion I will find where my understanding is flawed.

Messages:
22,846
No the ball and the plank create space/time curvature, thus gravity, so yes the ball does roll down the plank.

As space/time curvature is created, that then must invalidate your view.

You misunderstand....I was speaking of GR over Newtonian.

We'll see what others have to say

8. ### SeattleValued Senior Member

Messages:
4,726
This should be moved to the proper forum don't you think?

9. ### originIn a democracy you deserve the leaders you elect.Valued Senior Member

Messages:
10,907
Agreed this should be in the physics and math section.

10. ### LakonValued Senior Member

Messages:
1,117
Interesting question. I've always thought of it (assuming it's the same question) in more succinct terms, ie, what is the motivational force that motivates things to move along curvature ?

Messages:
22,846

In curved space/time, it is the shortest distance between two points...called a geodesic....and of course the mass creates that curvature, which then exhibits the effects we know as gravity.
Again....

"Mass/energy tells Space/time how to curve: Space/time tells mass/energy how to move."

John Archibald Wheeler:

Last edited: Oct 28, 2013

Messages:
22,846
Worth noting that light itself will contribute to the curvature of space/time, albeit by a very tiny amount, due to its momentum.

13. ### Boris2Valued Senior Member

Messages:
1,106
if there was no hill then the ball wouldn't roll down it!

this is basically what you are saying.

if a region of space has no gravity, an "ideal" volume, then this spacetime will be flat.

Messages:
22,846
Which we would change if we visited there with our plank of wood and ball.

15. ### rr6BannedBanned

Messages:
635
gravity = mass-attraction force. imho

A photon may not have a rest mass but it has a mass, that is why it is drawn into a mass.

Down hill is IN

Gravity / mass-attraction a contractive IN force.

I see there being two primary ways of understanding or exhibiting or representing this primal/essence force of Universe:

1) (O)><(O) wherein the outer geodesics surround/embrace every particle individually and integrally as a wholistic set of two, three four or the whole Universe.

In this next scenario the particles are not embraced by gravity rather is just forced that is exchanged between the two particles.

2) O>< O

Photons/EMRadiation is OUT, dispersive, dissassociative, divergent, expansive etc...

Gravity is IN, convergent, associative, contractive etc....imho.

Naught( energy/physical ) is ever lost because of gravity..see 2nd law/principle of thermodynamics.

r6

16. ### LakonValued Senior Member

Messages:
1,117
Double post, deleted.

17. ### LakonValued Senior Member

Messages:
1,117
You need not concern yourself with any further responses to my posts. Thanks. I'm sure you have the common sense to observe this.

Messages:
22,846
Common sense does not come into the equation, it's more the point of you growing up so I will answer/ask/enquire when and where I see fit.

19. ### LakonValued Senior Member

Messages:
1,117
- In fact, most people would agree that common sense should come into every equation and human dynamic.

- Most grown up people WILL in fact agree with what I just said, above.

- You displayed infantile imaturity in your sentence, above.

So again, I have no interest whatsoever in being guided on anything at all by you. Nothing you say to me will cause me to think about it seriously. No good will come out of it. You will be wasting your time and mine. So please leave me alone. I think it's generally forum ettequete, if not rules, that if one makes such a request of another member, that other member should be decent enough to observe it.

Thanks.

Messages:
22,846
I think you are actually delusional.
I maintain what I said previously, and if that pains you, well then I'm truly sorry.
It's not real smart to want to stay ignorant you know, but if you chose to ignore my replies, that's OK too....No skin off my nose.
All the best.

Messages:
22,846
To facilitate your wishes on most occasions, my interests and answers will mainly be with Astronomy, Cosmology, SR/GR, Astrobiology and SETI, some other areas of physics including Quantum mechanics, Climate change, and Evolution.
Perhaps if you make the effort to avoid these areas, you will be lessening the chances of running into me.

22. ### LakonValued Senior Member

Messages:
1,117
Your fourth 'faux pas' (did you look up 'faux pas' yet ? .. LOL ..) is the assumtion that by ignoring your replies one remains ignorant .. LOL !!!

OK, so, from the word go, we have rejection by YOU of the application of common sense, rejection of common decency, violation of commom ettequette, and four self evident, contradictory bloopers. Can you do worse ?

Again, for reasons I won't list at the moment, I have no interest whatsoever in being guided on anything by you. No good will come from it. You will be wasting your time and mine. So leave me alone, OK ?

Thanks. All the best.

23. ### LakonValued Senior Member

Messages:
1,117
I don't care about running into you, and I'm not trying to tell you where to go or what to do, I'm only saying to you that for many aforementione reasons, I have no interest in being guided by, or having dialouge, with you. Why is this so hard for you to deal with ? A psychologist would say you have a rejection complex.

Leave me alone, OK ? No attemped dialouge by you with me will result in anything good.

All the best.