[Yahya A.Sharif (OP)]

If space-time is infinite ,how gravity extends to infinity?
 we know infinity is unreachable because it continues forever and no-one reach a finite point.How gravity extends to infinite distances while  infinity is unreachable? how gravity bends and curve space-time everywhere while space time end is unreachable? for gravity to bend space-time everywhere it should reach its end , how gravity bends space-time end while this end is unreachable?

[Halc]

for gravity to bend space-time everywhere it should reach its end

There is no end to F = GMm/r², so there is no such end to reach.
You seem to be treating infinity as a number, or treating gravity as something that moves at a speed, which it doesn't.  Gravity waves do, and thus gravity waves reach only a finite distance.

[Yahya A.Sharif (OP)]

for gravity to bend space-time everywhere it should reach its end

There is no end to F = GMm/r², so there is no such end to reach.
You seem to be treating infinity as a number, or treating gravity as something that moves at a speed, which it doesn't.  Gravity waves do, and thus gravity waves reach only a finite distance.

Still my question is not answered . does force between two masses placed anywhere in space exists ?
it means for force to exist gravity should be everywhere as well .
Space-time curvature happens due to mass existence , is mass existence effect "curvature"  everywhere ?
how this effect could reach infinity" infinity is not an end or point but something continues forever" while infinity is unreachable?

[Bored chemist]

Still my question is not answered .

Yes it was.

[Yahya A.Sharif (OP)]

Still my question is not answered .

Yes it was.

A mass started to bend the space time around it at time, is it physical that this curvature happens at the same time everywhere?

[Halc]

Still my question is not answered . does force between two masses placed anywhere in space exists ?

You can't 'place' mass in space.  There's no way to create it or destroy it.  So yes, the force exists everywhere, at any distance, even if far further away than can be identified as being from a specific mass.

Space-time curvature happens due to mass existence , is mass existence effect "curvature"  everywhere ?

Yes, of course.  There is nowhere where there isn't mass existing at some distance, even if you choose a spot where there isn't particularly much of it locally.

how this effect could reach infinity" infinity is not an end or point but something continues forever" while infinity is unreachable?

I don't see what is 'unreachable' about a field that doesn't get to zero at some finite distance.

A mass started to bend the space time around it at time

For it to have 'started to' bend spacetime, the mass would need to have 'started', which I suppose might be how you describe things at the big bang moment when all was local.  But otherwise, you can't 'start' a mass, and expect this new mass to have an effect at infinite (or even finite distance) in a short time.  Mass cannot be 'started', so that doesn't work.

[Yahya A.Sharif (OP)]

Hi Halc,
Thanks for your replies,
What I can't understand is a mass has its effect "space time  curvature" everywhere at an instance is not physical
Also there should be a starting moment when mass started to bend space-time it can't be infinitely in the past.
How mass bend space-time infinitely while this infinity in fact is not fixed and continues forever?
If an object is at constant speed it will move forever never reaching infinity, if I want to move an object from point A to point B I have to go through several points to reach point B this what physics says I can't let it jump from point A to point B the same for gravity it can't jump at an instance to infinity"even infinity can't be reached" so how space-time curvature started at a moment and at instance spread everywhere?

Mass cannot be 'started', so that doesn't work.

What about a rotating object with a torque? it start to have energy inside it and mass and energy are interchangeable so we will then have mass started.We didn't simply place energy from an environment to the mass we transferred energy from form to another so we indeed started new mass with its own gravity.

[Bored chemist]

What about a rotating object with a torque?

What about it?
It has the same mass as it started.

There is some validity to you point.
If God suddenly decided to double the mass of the Sun, nothing on Earth would notice for about 8 minutes and it would be about 5 hours before any effect was observed by Pluto.

However there are two issues that stop this being a contradiction of known physics.

No known process could suddenly double the mass of the Sun without bringing the mass in from somewhere else. (That's why I invoked a God to do it)
The range of the effect would still be infinite- it would just take a while to get there.
There isn't anything that would stop the effect of the change in gravity- so it would go on for ever.
It is infinite.

[Bored chemist]

there should be a starting moment when mass started to bend space-time it can't be infinitely in the past.

Yes, the big bang.
And everything was in the same place at the same time, so there was no need for any effect to travel.

[alancalverd]

As far as we know, the gravitational equation appears to be universally true. We also know that a gravitational field bends the path of electromagnetic radiation to the extent that we can observe the effect of black holes.

Now consider a finite part of an infinite universe, populated by various massive particles from atoms to galaxies. If we make this sample large enough (and there is no limit since it is a sample of an infinite universe) it will contain enough mass to appear from outside to be a large black hole with an event horizon, which no information can cross.

We have thus defined a "real" infinity, comprised of an infinite number of mutually nonobservable "virtual" infinities.

This model has characteristics both of Hoyle's "continuous creation" universe, as seen from inside, and the Big Bang hypothesis which allows for the spontaneous creation and expansion of new, virtually infinite, mini-universes, as seen from outside.

[Yahya A.Sharif (OP)]

It has the same mass as it started.

But not the same gravity

If God suddenly decided to double the mass of the Sun, nothing on Earth would notice for about 8 minutes and it would be about 5 hours before any effect was observed by Pluto.

Then gravity is not everywhere since the big bang is the start of every mass every mass effect still didn't reach infinite distances. If its effect didn't reach there then  gravity doesn't exist.

[Bored chemist]

It has the same mass as it started.

But not the same gravity

If God suddenly decided to double the mass of the Sun, nothing on Earth would notice for about 8 minutes and it would be about 5 hours before any effect was observed by Pluto.

Then gravity is not everywhere since the big bang is the start of every mass every mass effect still didn't reach infinite distances. If its effect didn't reach there then  gravity doesn't exist.

There are events in the universe from which the light has yet to reach us.
Are you saying that means those events don't exist?
Or are you saying that light doesn't exist?
Or what?
You really need to make yourself clear.
So far there's is nothing new in what you have said.

[Yahya A.Sharif (OP)]

As far as we know, the gravitational equation appears to be universally true.

The equation is not necessarily to validate the theory.

[jeffreyH]

Was there gravity before the big bang? Yes. Why? Because it was combined with the other forces. Gravity doesn't suddenly spring into existence out of nowhere. It has energy and energy is conserved.

[Yahya A.Sharif (OP)]

No known process could suddenly double the mass of the Sun without bringing the mass in from somewhere else.

But it could double its kinetic energy for a rotating object using a force in fact we didn't just simply take the energy and placed it into the object we transferred it using force the previous gravity will weaken and new gravity will appear

[Bored chemist]

Cut to the chase.
"How does gravity exert its influence infinitely?"
How could it not do so?
What would stop it?

[Bored chemist]

But it could double its kinetic energy for a rotating object using a force

That force would have to be exerted by an object which had mass or by, for example, EM radiation emitted by an object with mass.
In either case, there's a movement of mass, not a creation of mass.

[Halc]

No known process could suddenly double the mass of the Sun without bringing the mass in from somewhere else.

But it could double its kinetic energy for a rotating object using a force in fact we didn't just simply take the energy and placed it into the object we transferred it using force the previous gravity will weaken and new gravity will appear

Very little of the mass of the sun is manifested in its kinetic energy, so to double that would have almost no effect on its mass. The only way to double its kinetic energy is to take that energy from somewhere else, possibly itself.
I can double the kinetic energy of my car by coasting down a hill.  This takes potential energy away from the car and changes that into kinetic energy.  That's a net mass change of zero, so the car exerts no more or less gravitational pull than before.

The field has indeed changed due this rearrangement of the masses involved, and that change is propagated at lightspeed via gravitational waves.  Those waves will never reach sufficiently distant objects.

[Yahya A.Sharif (OP)]

That's a net mass change of zero, so the car exerts no more or less gravitational pull than before.

But the place in which the space-time is curved is different. An example is a battery and an object rotating on an electric motor the gravitational field of the battery will decrease while the gravitational field of the object will increase.

[Bored chemist]

That's a net mass change of zero, so the car exerts no more or less gravitational pull than before.

But the place in which the space-time is curved is different. An example is a battery and an object rotating on an electric motor the gravitational field of the battery will decrease while the gravitational field of the object will increase.

And you would get the same effect if an ant walked from one place to another; from the battery to the motor.
Some mass would move.
So what?