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A Universe Without Dark Matter?

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Gravity is one of the four fundamental forces of nature, which means it’s not derived from anything else – it just is. At least, that’s according to our presently accepted theories. But this may be about to change.

Physicists today describe the gravitational interaction through Einstein’s Theory of General Relativity, which dictates the effects of gravity are due to the curvature of space-time. But it’s already been 20 years since Ted Jacobson demonstrated that General Relativity resembles thermodynamics, which is a framework to describe how very large numbers of individual, constituent particles behave. Since then, physicists have tried to figure out whether this similarity is a formal coincidence or hints at a deeper truth: that space-time is made of small elements whose collective motion gives rise to the force we call gravity. In this case, gravity would not be a truly fundamental phenomenon, but an emergent one.

The problem is, if emergent gravity just reproduces General Relativity, there’s no way to test the idea. What we need instead is a prediction from emergent gravity that deviates from General Relativity.