General Relativity vs. gravitons/force

[crschoen]

Hello. I've been out of college for 10+ years now, but have never lost the desire to learn more. So I've been trying to increase my physics knowledge, which I feel was not very strong despite some college level physics classes (they seemed to focus too much of classical physics in my view).

I have been trying to read simpler books, but often come across questions that I cannot resolve, and not having the benefit of being able to ask anyone else about this stuff thought I would post one such question here.

I think I have a fairly decent understanding of General Relativity now. That is that gravity is equivalent to acceleration, and that gravity is not a force but merely an illusion of force caused by the warping of space-time that causes matter to move along the geodisc. In other words there is no actual force pushing our feet to the floor, but we perceive it to be a force.

Not long after feeling I had a good grasp on this, I read a couple things that seem to contradict General Relativity:

1. Descriptions of four fundamental forces include Gravity. But wait just a second, I thought it was not a force?

2. Gravitons - these are the carriers of the force of gravity. But wait just a second, I thought gravity was not a force?

What puzzles me is that in my readings of General Relativity, it seems like it has withstood every scientific test since it was proposed by Einstein (from the famous solar eclipse in 1919 onward). So why do we have these conflicting concepts of gravitons and gravitational force?

 

[Ich]

In other words there is no actual force pushing our feet to the floor, but we perceive it to be a force.

Well, there is an actual force pushing the floor to our feet. It carries us away from the geodesic.

1. Descriptions of four fundamental forces include Gravity. But wait just a second, I thought it was not a force?

Yes, that is a problem. You could phrase it more neutral and speak about interactions, which does not contradict GR. But still, you have three forces described in a similar way, and gravity described in a fundamentally different way. Nobody knows how the descriptions could be united.

2. Gravitons - these are the carriers of the force of gravity. But wait just a second, I thought gravity was not a force?

There are gravitational waves (at least supposedly), described by the classical theory GR. If you stipulate that these waves come in quanta just like electromagnetic waves are quantized as photons, you can derive the properties of those "gravitons", like mass 0 and spin 2, from the classical field.
Since gravitational waves are geometric perturbations, you could think of gravitons as the quanta of geometric perturbations, and get the semantics straight.
But again, nobody knows how to quantize gravity, so we can't really say how gravitons fit in.

 

[Entropia]

First of all, congratulations on your continued pursuit of knowledge and your interest in physics! It's great to see someone with a passion for learning and understanding.

To address your question, it's important to understand that General Relativity and the concept of gravitons/force are not necessarily contradictory. They are two different ways of understanding and describing the same phenomenon – gravity.

In General Relativity, gravity is described as the curvature of space-time caused by the presence of mass and energy. This theory has been extremely successful in explaining and predicting various phenomena, from the bending of light around massive objects to the existence of black holes.

On the other hand, the concept of gravitons and gravitational force is based on the idea of a particle – the graviton – that mediates the force of gravity between objects with mass. This is part of the Standard Model of particle physics, which describes the fundamental particles and forces in the universe.

So, while General Relativity explains gravity in terms of the curvature of space-time, the concept of gravitons and force explains it in terms of particles and interactions between them. They are two different ways of looking at the same phenomenon, and both have been supported by experimental evidence.

In fact, some scientists are currently working on theories that aim to reconcile these two perspectives, such as the theory of quantum gravity. But for now, both General Relativity and the concept of gravitons/force are valid and useful ways of understanding gravity.

I hope this helps to clarify things for you and encourages you to continue your exploration of physics. Keep asking questions and seeking answers – that's the best way to learn and expand your knowledge.