# If gravity seized to exist (Theory)

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So when G becomes null, in this equation

$T=\frac{T_o}{\sqrt{1-\frac {2GM}{Rc^2}}}$

we have

$T={T_o}$

Yes, that is correct. Depending on the equations it may be safer to technically take the limit as the parameter tends to zero.

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Then to answer the OP, one should take all the equations where G appears and show the result for G = 0.

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Then to answer the OP, one should take all the equations where G appears and show the result for G = 0.

Yes, or maybe more technically the limit in which G -> 0 (not that from the top of my head I can think when we need to be more careful than just setting G=0).

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A very non-sensical question.

Like asking 'what would physics be like if physical laws ceased to exist ?'.

You cannot set up a non-physical situation and ask what results physics predicts.

Everything is interconnected. Would the weak force cease to exist if the EM force suddenly disappeared ? We only see them as separate or decoupled at low energies, but above 125 GeV they are one and the same. Similarily, some think that all four forces may be decoupled low temperature remnants of one force at Planck scale energies. Would removing one low temp aspect, such as gravity, also remove the other three forces ? And once you have removed the fields comprising these forces, what of the quantum particles ( bosons and fermions ) resulting from these fields ?

In other words, what's left ?

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A very non-sensical question.

Like asking 'what would physics be like if physical laws ceased to exist ?'.

I kind of agree, but it can still be a useful exercise to change the parameters in a theory to see what would happen. It can give further insight, even though this situation itself in non-physical. One can still calculate things and see what would happen.

Another question that could be interesting is, although this one would be hard to answer properly, what if

$G \approx \frac{c^{3}}{\hbar}$?

That would mean the Planck length is of the order of a meter. Quantum gravity effects would be a major part of our world.

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...

$G \approx \frac{c^{3}}{\hbar}$?

That would mean the Planck length is of the order of a meter. Quantum gravity effects would be a major part of our world.

We would be postulating a strange dark entity that is causing objects as astronomical distances to behave oddly in terms of the way we know gravity to act locally. I am guessing that over such long distances and huge masses the quantum gravity would be washed out and we would be left at a limit with what we currently think of as the simple classical model

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I kind of agree, but it can still be a useful exercise to change the parameters in a theory to see what would happen. It can give further insight, even though this situation itself in non-physical. One can still calculate things and see what would happen.

Another question that could be interesting is, although this one would be hard to answer properly, what if

$G \approx \frac{c^{3}}{\hbar}$?

That would mean the Planck length is of the order of a meter. Quantum gravity effects would be a major part of our world.

I didn't know G could be expressed like this.

The $c^3$ is awkward.

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I didn't know G could be expressed like this.

The $c^3$ is awkward.

The planck units come from ideas like this.

$l_{planck}=\sqrt{\frac{\hbar G}{c^3}}$

It is not so much a new way of expressing G - merely a rearrangement of the definition of the planck length

The planck units are done just by dimensional analysis - ie you set the universal constants in such a way that a simple length is the result.

What AJB is saying is that a toy universe model could be looked at where G is close to equal to $c^3$ over $\hbar$ - that would mean that the planck length (which in our suniverse is very very short 1.6*10^-35metres) would be of macroscopic scale.

The planck length is around the scale at which quantum gravity must be taken into account.

And on the awkward note - there is a $c^5$ in the planck time!

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I thought that G was an empirical constant, not a derivation of other constants.

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I thought that G was an empirical constant, not a derivation of other constants.

As far as we know you are right. It is the Planck scale that is derived from these constants.

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Everything would fall apart. Objects would because millions of molecules. That's what I mean.

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Everything would fall apart. Objects would because millions of molecules. That's what I mean.

Most objects are not held together by gravity. Solar systems and galaxies would fall apart. Planets might if they are spinning fast enough, I guess. Smaller things wouldn't.

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Well that is assuming you believe gravity is doing it. There is an alternate theory involving dark matter. However if this is not correct and its in fact gravity pulling not pushing from outside force humans and all other creatures would fly off earth, planets would most likely lose orbit, and everything would be thrown out of orbit, earth and other planets that depended on a rotation would probably have half the planet one temperature and the other side a different temperature, I am unsure of what would happen with black holes though which are suppose to be at the center of universes, oh not to mention it would seriously screw with the weather on earth since its believed that gravity does have some effect on that as well.

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Well that is assuming you believe gravity is doing it. There is an alternate theory involving dark matter.

Dark matter is not an alternative to gravity - it assumes gravity works exactly as predicted by theory.

h not to mention it would seriously screw with the weather on earth since its believed that gravity does have some effect on that as well.

Yes, I think not having an atmosphere would do that!

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Well that is assuming you believe gravity is doing it

That's the premise. That this is a science question and is to be answered by established science.

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