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Physicists have gathered evidence that space-time can behave like a fluid. Is space not as immaterial as we thought?

Tuesday 03rd October
Sabine Hossenfelder | Research fellow at the Frankfurt Institute for Advanced Studies and author of blog Backreaction

Physicists have gathered evidence that space-time can behave like a fluid. Mathematical evidence, that is, but still evidence. If this relation isn’t a coincidence, then space-time – like a fluid – may have a substructure.

We shouldn’t speak of space and time as if the two were distant cousins. We have known at least since Einstein that space and time are inseparable, two hemispheres of the same cosmic brain, joined to a single entity: space-time. Einstein also taught us that space-time isn’t flat, like paper, but bent and wiggly, like a rubber sheet. Space-time curves around mass and energy and this gives rise to the effect we call gravity.

That’s what Einstein said. But turns out if you write down the equations for small wiggles in a medium – such as soundwaves in a fluid – then the equations look exactly like those of waves in a curved background.

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