there’s more to “space” than a mere recitation of its particle density. For starters, it’s permeated by fields. Magnetic and electric fields fill the cosmos, and these have the power to influence the motion of every particle with an electrical charge. Space is also penetrated by an unrelenting torrent of photons of all kinds, which are the most prevalent entities in the cosmos. Neutrinos, the second-most common item, also continually rip through the entire universe; a trillion of them pass through each of your fingernails each second. And gravity waves flow everywhere, according to physicists.
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