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Close to 13.8 billion years ago, the first inflation of the universe happens in what we know as the Big Bang. We don't know why or how it happened, but it did. -
The universe very suddenly and rapidly expands in less than a second. It continues to expand and slowly cool from this point onward. -
During recombination, the first neutral atoms formed after the universe had cooled down enough that atomic nuclei could form with electrons. These new atoms produced their own light, and photons could now move freely across space, creating a newly transparent universe. However, the universe would soon fall into darkness again as recombination also ushered in the cosmic dark ages. -
Gravity began to pull gas into massive clouds that would trigger nuclear fusion and as a product, the earliest stars in the universe would form over the next thousands of hundreds of years. These newborn stars emitted ultraviolet light which would ionize the hydrogen surrounding them. This resulted in the epoch of reionization, a very long process of ionizing the universe with the birth of new stars and galaxies that would wrap up around the first 1 billion years. -
800 million years after the Big Bang, the oldest part of our galaxy, its halo, began to form. The thick disk of the Milky Way would also begin to form and gather stars. Two billion years after this, the Milky Way would collide and combine with a dwarf galaxy named "Gaia-Sausage-Enceladus." This merging of galaxies would ramp up the growth of the Milky Way and the thin disk would accumulate the majority of star systems the galaxy has today. -
At this point in the universe's life, there are already hundreds of galaxies, stars, and other celestial objects. It's also mostly ionized now, meaning the universe is back to being transparent once again! However, this process took hundreds upon thousands of years to complete. But this era of reionization allowed for the creation of celestial bodies, such as our very own Milky Way. -
Cosmic Noon is a time in which the development and growth of stars and galaxies hit its peak. During this time, galaxies gained huge amounts of mass, many changing from lumps of gas and stars to the various shapes we see today. -
Five billion years ago, the universe started to suddenly and rapidly grow compared to how it had previously been moving. This was due to a mysterious force known as "dark energy." Scientists know it exists and that it's causing the universe to expand, but they don't know what it's comprised of. It was once thought that gravity might slow down cosmic expansion, but that would be disproven when dark energy was officially discovered in the late 1990s. -
We know that the Earth likely formed 4.5 million years ago, just a little younger than when our solar system is estimated to have formed. The material left over from when our sun changed from a protostar to the main sequence of its life is what was the basis for our planet and the others in our solar system. This material formed into a protoplanet, and from there, the Earth began to slowly change into how we know it today. -
So, with all this history and development, what will happen to the universe in the future? Well, we don't know. There are theories that the universe will grow so much that we'll be unable to see other galaxies from Earth, that the universe will suffer "heat death." Some theories say it'll end in a "big crunch" where the universe will shrink and collapse in on itself. But, definitively? Planets can be destroyed and stars can die, but we don't know what will happen to the universe itself.