Big Think
2026-07-31 06:00 en
We see our Universe as it is today: 13.8 billion years after the Big Bang. Because of how quickly and how long it’s been expanding and cooling, the Universe is now sparse, possessing less than 1 proton per cubic meter of normal matter on average. Dark matter and dark energy, not normal matter, dominate our Universe’s contents today, and the expansion rate is much lower, around 70 km/s/Mpc, than it was at earlier times. The cosmic microwave background, or the Big Bang’s leftover glow, is a mere 2.7 K, and although galaxies clump together in groups and clusters, the distance between various…