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We know from general relativity that mass curve spacetime. One step further of unification would be that mass is curved spacetime. Is this a possiblity? And if not, why?

Qmechanic
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W.E.
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2 Answers2

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The idea that matter might just be curved spacetime dates back to well before general relativity. As far as I know Bernard Riemann was the first person to suggest that the geometry of space (not spacetime - this was before Einstein) might be curved, and William Clifford (of Clifford algebra fame) seized on the idea that all physical phenomena, including matter, might be a result of curvature in space.

The problem is that neither Clifford nor anyone since has ever found a way to make the idea work. The idea resurfaces sporadically then dies away again. If you're interested there is a nice review of the area in Matter from Space by Domenico Giulini, though this is somewhat technical.

John Rennie
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  • More on early thoughts in this direction - Did Gauss and colleagues consider measuring the curvature of the universe? – mmesser314 Nov 03 '21 at 14:38
  • Einstein General Relativity is a theory of gravitation and not matter. More interesting is the questions how gravitation see of feel matter. Imagine, we would see only in spectrum of gravitational waves. What would we see? There would be no reflection but only refraction. The picture would be similar that of light rays going through a different salty water sheets. In that sense, matter for gravitation is a merely local distortion of spacetime but it is not an artifact of curvature itself. – JanG Dec 04 '21 at 18:54
  • That there's no matter inside a black hole or even no inside spacetime has been postulated by other physicists, too. See https://physics.stackexchange.com/a/674311/281096 – JanG Dec 04 '21 at 19:17
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According to Kip Thorne, black holes are just curved spacetime. There's no matter inside a black hole.

https://youtu.be/oj1AfkPQa6M

Doradus
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