That can depend on which definitions you are inclined to embrace.
In physics a force can potentially described as a mathematical abstraction that arises when describing the state of motion of observable objects.
That may not be very physically intuitive or informative. So to make the concept of force a little more physical intuitive we can also talk about force fields. Again a mathematics abstraction that can be supported physically and intuitively by actually measuring "forces" on objects within a force field. A measurement of force reverts back to the first description I offered. In other words, forces are measured by describing the state of of motion of observable objects. In this case, objects that are placed within a "force field". The force field can be said to be "physical" simply because it can be physically measured in this way.
Perhaps a better definition of "force" is given by particle theory in which subatomic particles called bosons are exchanged between objects that cause them to move in observable and measurable ways. However, these bosons themselves could potentially be just as abstract as force fields. Although bosons can be "seen" in the laboratory as tracks in particle accelerators.
So that at least three of the forces are described in this way, electromagnetic, strong and weak force. And all these bosons have been discovered, or seen in the lab.
A forth boson called a graviton has been proposed for gravity, but to my knowledge it has not yet been seen in the lab, and may not exist.
r~ wrote:
Is gravity a state of force?
Einstein's General Relativity describes gravity as a curvature of a fabric of spacetime. But once again, the "Fabric of Spacetime" itself is an abstract mathematical object. Whether it actually exists as a physical entity is hard to say.
I personally feel that since Einstein's description of gravity works so well there is no need for a graviton. Perhaps gravity is not a force at all, but simply a curvature of the fabric of spacetime. The only problem is that we don't really have any physical evidence for what would constitute this "fabric" of spacetime.
Because of this it may be possible that the bosons called gravitons actually constitute this fabric. So it's possible that both of these pictures are correct. In other words, gravity is actually caused by gravitons which in turn constitute the fabric of spacetime. I don't think this question has been settled yet. To the best of my knowledge gravitons have not yet been discovered. But I could be wrong about that, I haven't been keeping up on the latest physics journals.
