No, This Is Not A Hole In The Universe
“It is absolutely true that billions of light-years away, there are enormous cosmic voids in space. Typically, they can extend for hundreds of millions of light-years in diameter, and a few of them might extend for a billion light-years in size or even many billions of light-years. And one more thing is true: the most extreme ones don’t emit any detectable radiation.
But that is not because there is no matter in them; there is. It’s not because there aren’t stars, gas molecules, or dark matter; all are present. You just can’t measure their presence from emitted radiation; you need other methods and techniques, which show us that these voids still contain substantial quantities of matter. And you definitely shouldn’t confuse them with dark gas clouds and Bok globules, which are small, nearby clouds of light-blocking matter. The Universe is plenty fascinating exactly as it is; let’s resist the temptation to embellish reality with our own exaggerations.”
The Universe, as you may have noticed, is not a uniform place. Just as there are the great cosmic winners, like stars, galaxies, and clusters of galaxies, there are the regions that have to give up their matter to the denser ones. These underdense regions have less normal matter than average, less dark matter, fewer galaxies, stars, and (for the more distant ones) emit no detectable radiation.