Gravity, Mass, Dark Matter & Energy - Exploring Relationships

[professor]

in energy directly related to gravity as mass is, it seems that it should be according to relativity, but this leads me to the question of why dark matter need be proposed to explain the differences in gravity and mass proportionality of galaxy clusters and such. Is this difference not as simply related to the energies of momentum in relation to each other, or perhaps a sum of many weak forces on each of the particles/bodies in this system. In an atom the graviton seems to come up in similar questions, or is that allready explained by other attractions without the addition of a graviton?

hopefully someone can work out what i am trying to ask, if it is too much of a jumble let me know and i will attempt at a revision, i wanted to get the questions down whilst i had them fresh in my mind.

 

[coalquay404]

In a word, yes, energy and gravity are directly linked. Schoen and Yau proved, for example, that the total mass/energy of a spacetime is non-negative, with the mass/energy equal to zero only in the case of Minkowski space. This duality between mass/energy and gravity effectively means that Minkowski space is regarded as a stable ground state of the gravitational field, and that a spacetime cannot decay (by some bizarre quantum tunnelling effect or otherwise) into a state of lower energy. Witten's spinorial proof of the positive energy theorem is particularly enlightening in this respect.

I'm afraid that I can't quite work out what you're trying to say in the rest of your post, particularly the comments about gravitons, which are completely unneccessary in general relativity. Gravitons appear principally in string theory as massless spin-2 states of the string configuration, but have no role in the classical theory.

 

[Entropia]

It is a valid question to wonder why dark matter is necessary to explain the differences in gravity and mass proportionality of galaxy clusters and other systems. After all, according to relativity, mass and energy are directly related through the famous equation E=mc^2. However, the existence of dark matter is still needed to explain these discrepancies.

One possible explanation is that dark matter is made up of particles that do not interact with light or other forms of electromagnetic radiation, which is why it cannot be detected directly. This means that it does not emit or absorb light, making it invisible to telescopes and other instruments.

Another possibility is that dark matter is made up of particles with a higher mass than ordinary matter particles. This would mean that they have a stronger gravitational pull, which could explain the observed differences in gravity and mass proportionality.

It is also possible that dark matter is not a single entity, but rather a combination of different types of particles or forces. This could explain why it is so difficult to detect and understand.

As for the role of the graviton in explaining these phenomena, it is important to note that the graviton is still a theoretical particle and has not been observed or confirmed. While it is believed to be the carrier of the gravitational force, its existence has not been proven yet.

In conclusion, the relationships between gravity, mass, dark matter, and energy are still being explored and studied by scientists. While the concept of dark matter may seem complicated, it is necessary to explain the discrepancies observed in the universe. As our understanding of these concepts continues to evolve, we may eventually unravel the mysteries of dark matter and its role in the universe.