Alternative views on gravity?

[happy snapper]

Have the current ideas on the way gravity works been proved in any way and does anyone else have any alternative views? I have a few ideas that seem to make sence to me...

Edited November 24, 2009 by happy snapper

[ajb]

General relativity has so far passed every direct and indirect test ever asked of it.

 

This is a real pain.

 

We know that general relativity cannot be a complete theory. This is due principally to two facts

 

i) The solutions to the Einstein field equations are generically singular. This can mean that the curvature blows up to infinity.

 

ii) Quantum effects are not taken into account.

 

The best chance of seeing something beyond general relativity lies in remnants of the big bang and observations of black holes.

 

You should also be aware that at a classical level at least, teleparallel gravity (all torsion no curvature) is phenomenologically identical to general relativity (upon a choice of action).

 

People have also worked on gauging the Poincare group (which contains general relativity as a special case), theories with higher derivatives (curvature terms other than just R in the action, often motivated by renormalisation group flow), gravity in higher and lower dimensions and supergravity to name a few things.

[happy snapper]

Yes but how does it work(gravity) in easy to understand jargon?

[ajb]

According to general relativity the local geometry of space-time is to be identified with the gravitational field.

 

Curvature = Gravity

 

Test particles under free fall follow what are known as geodesics. These are the shortest paths on the space-time.

 

The field equations are

 

Matter/energy content = Local geometry

 

For more details you could look up wikipedia for a starting point.

[happy snapper]

What im looking for is a person to listen to my idea who is educated in physics who can have an open mind and in some ways forget the numbers and listen and give me reasons why not..Numbers dont exist in physics..There a man made way to try to measure what is going on..So at this stage I dont want numbers.Just ideas.I want some one to go step by step with me and agree or not agree with each step.If we get to the last step il be happy

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do these pages self refresh on this website?

[ajb]

What im looking for is a person to listen to my idea who is educated in physics who can have an open mind and in some ways forget the numbers and listen and give me reasons why not..Numbers dont exist in physics..There a man made way to try to measure what is going on..So at this stage I dont want numbers.Just ideas.I want some one to go step by step with me and agree or not agree with each step.If we get to the last step il be happy

 

At some point you would have to "put the numbers in" in order to test your idea. But that can wait, if you have a good idea.

 

What is your idea?

[Klaynos]

Physics is a man made thing to try and predict what is going on... You need maths to predict accurately.

[ajb]

Physics is a man made thing to try and predict what is going on... You need maths to predict accurately.

 

I took "don't want numbers" to mean that he did not want, at least for now to numerically evaluate the theory to test it. For example the bending of light around the Sun and the perihelion of Mercury.

 

Thinking about it, you do not need to do this. An unevaluated mathematical expressions will do fine. They should reproduce the results of general relativity up some correction terms. These in principle could be tested.

 

What you would have to do then is evaluate it or have a reasonable argument to explain why these corrections are small and agree with observation up to current accuracy.

Edited November 24, 2009 by ajb

[happy snapper]

amagine a particle many times smaller than an electron?

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this particle is in motion

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just say yes then i can move on ok

[ajb]

Already we are in trouble.

 

A classical particle is taken to be point-like. That is it has no extent.

 

The "size" is a bit more ambiguous. You could mean the Compton wave-length [math]\frac{\hbar}{mc}[/math] or the effective size due to the scattering cross-section.

 

Or you mean a classical extended body.

[happy snapper]

i said amagine.. call it a particle .. call it something else ..something that size moving?

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can you amagine that?

[ajb]

So I have a small (but extended) object moving in space-time?

[happy snapper]

now amagine 1 atom on its own in deep space..this micro particle moves toward the atom..what will it do?

[ajb]

I would expect them to interact (at least) gravitationally. (Not that I am very happy with the notion of a micro particle in this situation)

 

What do you think?

[happy snapper]

well id say that the chances are that it would enter into the orbit of the atom and exit the other side as it is so small the chances of it hitting an electron or the necleas is remote..? Is this possible?

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sorry about my spelling

[ajb]

I would be very cautious about dealing with gravity on the scales you have presented us.

 

It seems reasonable to expect that gravitational capture, orbits, bound states and scattering are possible, assuming that the micro particle does not interact electromagnetically. On the atomic scale gravity is suppressed by electromagnetic interactions.

 

You could even try looking at the Schrodinger equation for a classical gravitational potential. It would proceed the same as the Hydrogen atom but with a vastly different scale. You should treat gravity as a background.

[happy snapper]

your not getting my point..no one has proved how gravity works only what it does.These people you quote dont know the answer..Is what I say possible

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gravity cannot effect what causes gravity..

[ajb]

I think you are missing the ethos of physics.

 

The best one can really do is produce mathematical models of nature. The best model of gravity is general relativity. In this respect we do know how gravity works, at least on the scales of astrophysics, down to about 1mm or so.

 

We also know what it does in the sense that one can describe the motion of test particles. We can also discuss quantum field theory on curved space-times, although it is very involved.

 

Now, to work out if the micro particle would hit the atom or not is also involved. However, I would say that it is feasible that the cross-section could be small.

 

Anyway, where are you trying to go with this?

 

If you want to say that gravity on the atomic scale has not been experimentally examined in any detail, I agree.

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gravity cannot effect what causes gravity..

 

Gravity is non-linear and so there is "self-interactions".

[happy snapper]

ok .. now that you say it is possible for this m particle to enter and exit the atom untouched.. Now amagine 1 million particles doing the same journey.. what would happen

[ajb]

ok .. now that you say it is possible for this m particle to enter and exit the atom untouched..

 

Not quite what I said. They would scatter, some with small angles some with large angles.

 

It is difficult to imagine that there is no interaction at all.

 

You could probably calculate this to tree level ok.

 

 

Now amagine 1 million particles doing the same journey.. what would happen

 

I imagine similar to above.

[happy snapper]

only particles that could scatter are the particles that hit something

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so most would enter and leave the atom but some would hit an electron or the neclias? yes?

[ajb]

No not quite.

 

Let us assume that the micro particle is light as compared to the electron. So, we assume it only interacts gravitationally, but is not a source itself.

 

The particles in the atom act as sources of the gravitational field. It is this that the micro particle interacts with and scatters. It does not need to hit one of the electrons or the nucleus. In fact, in quantum theory this exact hitting is not a good concept, but even at the classical level it is not needed.

 

Assuming the cross-section is small, most of the micro particles will be scattered only by a very small angle. Effectively "missing the electrons and the nucleus."

[happy snapper]

gravity can not have an effect on what causes gravity

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you keep talking about gravity having an effect on these mp..im trying to explain how these mp create gravity. so you can not have gravity effecting the thing that causes gravity

[ajb]

You really need to expand on this.

 

Use terms I would be familiar with please, remember I have a two degrees in physics. Thanks

[happy snapper]

ok..1 million mp enter the atom.not all exit as some have been stopped in there journey by the parts that make the atom .So less exit than enter YES ?