Questions on Gravity, General Relativity, and Photons.

[anubisrwml]

I've lost sleep over this and I am hoping that someone here can help me to understand or at least tell me that I'm wrong about what I'm about to ask.

 

General Relativity explains gravity as being the bending of space-time, and we know that the larger the mass of an object, and the greater it's density, the larger it's gravitational pull. But my theory is if you were to take the Earth, and enlarge it to the size of the sun, that it would not effect as much gravitational pull as the sun does. This goes into more detail below.

 

We know that energy can be expressed in many forms, through wave forms, and light as primary examples. Photons, which make up gamma rays and other forms of energy is said to have a rest mass of 0. However, slamming two protons together does do something interesting - it creates matter and anti-matter. Where the mass of the two photons for example was 0, the created matter has mass and travels significantly slower than the photon. When combining the matter and anti-matter once more, photons are created (and I'm assuming the same number of photons that was used to create the matter in the first place).

 

But how does this meet up with my first statement? Well, my theory on this is that gravity, as seen in general relativity, is the positive sum of the natural electromagnetic attraction of electrons, protons, and neutrons which holds our atoms together. I am not saying that the sum is of a negative or a positive charge, but rather a combination of the two. I am not sure that when two atoms are pulled together that there isn't remaining electromagnetic attraction that still exists, even if it's weaker, bet it positive, negative or both. And perhaps I'm very off basis here but it seems to make sense in my mind.

 

Further - and building on this idea, the reason I theorize that the sun would have greater gravitational pull than the earth of similar size is that the sun has more energy as well, which exerts it's own presence on gravity. Further, if photons were ever made to come to a rest, with a 0 mass, would it not be possible to fit an untold number of photons together in a small enclosed space? When matter is destroyed, photons are created - and in my mind, if you were to destroy all of the matter of the planet earth, and convert it all to photons, you could then pack them together in a extremely tight formation, such as a black hole. This would explain why light cannot escape, and also goes into the theory of Hawking Radiation where black holes evaporate so to speak - by the loss of escaping photons in the form of energy, even though light itself being made of photons is pulled into the hole. This idea could certainly explain how so much matter can be compressed into such a small space, because photons without mass would take up far less space than matter with mass.

 

This could be due to the concentration of photons in beams of light. We know that you can affect photons with a electromagnetic field, though a beam of light is largely unaffected, but rather a few photons due to the low chance of the effect, do in fact get pulled off course. Thus could photons escape a black hole in the form of radiation.

 

I know this is a bunch of jabber and random thoughts, but these things have been swirling in my head for weeks now and I would really like to know if there's any basis for these ideas, and if these things have been considered and tested. I'm afraid my math isn't strong enough to formulate equations to explain any of this or to even prove it but I would sleep better at night knowing someone at least glanced at it and either dismissed it as nonsense or said I was onto something.

 

 

[ajb]

Look at the shell theorem - in both Newtonian gravity and general relativity. In fact, Newtonian gravity is enough as this comes as a limit of general relativity.

 

Provided you are outside of a spherically symmetric distribution of matter, the gravitational field is exactly the same as if that mass were concentrated at the centre of the body. So, yes, as the Earth is much lighter than the Sun if you 'blew up' the Earth so that it was the same size as the Sun the force of gravity on a test mass at a given radius from the centre (r > radius of Sun) will be less than it would be for the Sun. (I hope that makes sense!)

 

The converse statement follows in the same way if you were to shrink the Sun.

Edited August 3, 2016 by ajb

[Strange]

I've lost sleep over this and I am hoping that someone here can help me to understand or at least tell me that I'm wrong about what I'm about to ask.

 

General Relativity explains gravity as being the bending of space-time, and we know that the larger the mass of an object, and the greater it's density, the larger it's gravitational pull. But my theory is if you were to take the Earth, and enlarge it to the size of the sun, that it would not effect as much gravitational pull as the sun does.

 

 

This is rather ambiguous.

 

Do you mean a Sun-sized planet made of the same stuff that the Earth is? In which case it would have a much greater gravity than the Sun because it would weight about 4 times as much as the Sun (the Earth is much denser than the Sun).

 

Or do you mean the same mass as the Earth, expanded to the same size as the Sun. In which case it would have much less gravitation than the Sun. In fact, by a remarkable "coincidence" it would have exactly the same gravitation as the Earth (at a given distance).

 

Basically, the force gravity is determined by two things: mass and distance. Density doesn't really come into it (part from affecting the distance of the surface from the centre).

[swansont]

Well, my theory on this is that gravity, as seen in general relativity, is the positive sum of the natural electromagnetic attraction of electrons, protons, and neutrons which holds our atoms together. I am not saying that the sum is of a negative or a positive charge, but rather a combination of the two. I am not sure that when two atoms are pulled together that there isn't remaining electromagnetic attraction that still exists, even if it's weaker, bet it positive, negative or both. And perhaps I'm very off basis here but it seems to make sense in my mind.

 

 

 

How do neutron stars work, then?

 

Also, we know that charges do, in fact, cancel. Neutrons and protons decay into each other in certain circumstances, giving off electrons and positrons. All of these charges have to be equal in magnitude for this to work.

[Strange]

 

 

Further - and building on this idea, the reason I theorize that the sun would have greater gravitational pull than the earth of similar size is that the sun has more energy as well, which exerts it's own presence on gravity. Further

 

While it is true that both mass and energy contribute to gravity, in general the effect of energy is insignificant.

 

 

Well, my theory on this is that gravity, as seen in general relativity, is the positive sum of the natural electromagnetic attraction of electrons, protons, and neutrons which holds our atoms together.

 

This is a very common idea. It comes up every few weeks. There are many reasons why it is obviously wrong:

 

• Gravity depends on mass; there is no obvious relationship between charge and mass.
• Electric charges attract and repel; gravity only attracts
• We can block electric fields; you can't block gravity
• The strength of the electric field from a dipole falls off with the third power of distance (I think); gravity falls of with an inverse square law
• And so on

[imatfaal]

This is a very common idea. It comes up every few weeks. There are many reasons why it is obviously wrong:

 

...

 

Agreed - my favourite is that for electro attraction there is attraction between +ve and -ve and repulsion between like charges

Earth and Moon (+ and -)

Earth and Sun (+ and -)

Moon and Sun. (- and -) !

What ever you you distribute +ve and -ve this three way system cannot work - and yet we know that it does.

[MigL]

As to your last assertion that light comes to 'rest' at the singularity of a Black Hole...

Light, by definition cannot come to rest as it is massless.

However it does have momentum, and as a result neither light ( photons ) or any other quantum particle can come to rest at a singularity. It would then have a clearly defined position in space-time, and according to the HUP, its momentum ( and total energy ) could be any value, from zero to infinite. That is one reason I am skeptical of singularities.

[anubisrwml]

I want to thank everyone here who gave answers and really helped put things to rest in my mind, at least on this front. It does show that, thankfully, I need a lot more to study and it's encouraging to know that these things have all been thought of, tested, and already taken care of. We live in our own little universe and sometimes stepping outside we forget that the universe is much larger than we are.

 

Granted now I have even more questions than before, but isn't that the reason behind science? Without asking question, we wouldn't be were we are today. Again, a big thanks for taking the time to point out the errors in my logic and for helping me to understand more than I knew yesterday!

[MigL]

Open threads and start asking all those questions.

Whether answerable or not, we all love a good discussion.