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The Final Border Humanity Will Never Cross

posted by Jason Kottke   May 11, 2021

This video focuses on one of my favorite astrophysics facts: 94% of the observable universe is permanently unreachable by humans. (Unless we discover faster-than-light travel, but that’s fantasy at this point.)

This expansion means that there is a cosmological horizon around us. Everything beyond it, is traveling faster, relative to us, than the speed of light. So everything that passes the horizon, is irretrievably out of reach forever and we will never be able to interact with it again. In a sense it’s like a black hole’s event horizon, but all around us. 94% of the galaxies we can see today have already passed it and are lost to us forever.

“Since you started watching this video, around 22 million stars have moved out of our reach forever.” And future generations, billions of years from now, won’t even be able to see any other galaxies or detect cosmic background radiation, making knowledge about the Big Bang impossible.