Once we know what the Universe is made out of to this degree of precision, we can simply apply this to the laws of gravity (given by Einstein’s General Relativity), and determine what the future fate of our Universe is. What we discovered, when we first applied this to the discovery of a dark energy-dominated Universe, was shocking.

First off, it meant that all the galaxies that weren’t already gravitationally bound to us would eventually disappear from view. They would speed away from us at an ever-increasing rate as the Universe continued to expand and expand and expand, unchecked by gravitation or any other force. As time went on, a galaxy would get more distant, meaning that there was an increasing amount of space between that galaxy and ourselves. Since space continues to expand, the galaxy appears to move away at greater and greater speeds, due to the expansion of space.

But there’s an inevitable conclusion that this leads to that’s even more disturbing. It means that, at a particular, key distance from us, the expansion of the fabric of space itself makes it so that a photon either leaving our galaxy towards a distant one or leaving a distant galaxy headed towards ours will never reach us. The expansion rate of the Universe is so great that distant galaxies become unreachable to our own, even if we were to move at the speed of light!