Ask Ethan: What Is The 'Zero-Point Energy' Of Space?
Date: Monday, April 20, 2020 @ 13:20:41 MST
Topic: Science

From Editors' Pick by Ethan Siegel/ Senior Contributor/ Apr 18, 2020

Imagine, if you can, what it would mean to have a Universe with absolutely nothing in it. You could take all the various quanta of matter and energy and remove them, leaving a Universe with no particles or antiparticles of any type. You could remove any sources of gravitation or spatial curvature, reducing your Universe to nothing more than purely empty space. You could shield the Universe from any external electric, magnetic, or fields that exert a nuclear force, eliminating any possible influence they may have on the spacetime you're considering. Even if you do all that, you still wouldn't get "zero" on your balance sheet for the energy of the Universe...

...For any physical system we can dream up, there's always going to be at least one configuration that we can place it in that will have the lowest total amount of energy. For a series of masses isolated from the rest of the Universe, that's a black hole. For a proton and an electron, that's a hydrogen atom in the ground (i.e., lowest-energy) state. And for the Universe itself, that's to set up empty space in the absence of any external fields or sources.

That lowest-energy state is known as the zero-point energy state. For a long time, scientists who studied the Universe assumed that the zero-point energy was zero. Not for any physical reason, mind you, but because we only had two ways to attempt to arrive at it, and both of them gave answers that pointed to problems with any value other than zero...

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