If we could empty the universe, what would be left? The underlying structure of the universe is called spacetime, and is often likened to a fabric. But “spacetime structure is a science fiction term,” says Jonathan Oppenheim, a physicist at University College London. There’s no consensus on what that actually means.
In classical physics, or Albert Einstein’s theory of general relativity, the structure of spacetime does not exist by itself. Instead, spacetime is intertwined with and shaped by mass and energy, giving rise to gravity. Most importantly, Einstein’s equations are continuous, so the classical idea is that the structure must be smooth.
But today, most physicists believe that spacetime must follow the rules of quantum mechanics that govern the behavior of elementary particles and fields. In that case, you can split it into separate chunks or quantize it. So while spacetime appears to be a smooth background against which everything in the universe unfolds, if you can zoom in enough, you’ll see that it’s actually made of something, just like everything else.
The problem is that there is still no evidence that spacetime is quantized. Proving that is somehow difficult, since what we imagine as “pixels” in spacetime, its most fundamental components, are vanishingly small and impossible to directly observe. is.
Therefore, indirect observations remain. The good news is that physicists have devised a series of ingenious experiments that may eventually solve once and for all the question of what space-time is made of.
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