The largest component of the universe is something we know almost nothing about.
The best and most accurate observations that cosmologists have gathered over decades show that all the matter around us, every single atom we see anywhere in the cosmos, makes up just 5 percent of all that exists. Another 27 percent is dark matter, which holds galaxies together. And everything else — a staggering 68 percent of the universe — is dark energy, a force that is responsible for the expansion of…
