For as long as humans have contemplated the Universe, we’ve marveled at the vastness of it all. Was our Universe infinite? Was it eternal? Or did it spring into existence a finite amount of time ago? Over the 20th and 21st centuries, these existential questions for all-time have, one-by-one, fallen into the realm of science, and now have the best answers we’ve ever been able to assemble.
As of today, in 2024, we can confidently state that we actually know how old the Universe is: 13.8 billion years old, marking time at the start of the hot Big Bang. If we could step back through time, we’d find that the universe as we know it was a very different place early on. Modern stars and galaxies arose from a series of gravitational mergers of smaller-mass objects, which themselves consisted of younger, more pristine stars.
At the earliest times, there were no stars or galaxies, and even farther, no neutral atoms or stable atomic nuclei, going all the way back to the hot Big Bang. Today, astronomers and astrophysicists who study the early universe confidently state its age with an uncertainty of no more than ~1%: a remarkable achievement. READ MORE...
