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Big Bang Theory
Observations of an enormous cosmic structure, dubbed the "Big Ring," seem to violate the Copernican principle.
For every proton, there were over a billion others that annihilated away with an antimatter counterpart. So where did all that energy go?
One newly discovered, ancient star has a composition unlike any other. Explaining its existence is already blowing astronomers' minds.
Finding it at all was a happy accident. Examining it further may help unlock the secrets hiding within the earliest galaxies of all.
Today, the star-formation rate across the Universe is a mere trickle: just 3% of what it was at its peak. Here's what it was like back then.
Earth wasn't created until more than 9 billion years after the Big Bang. In some lucky places, life could have arisen almost right away.
As early as we've been able to identify them, the youngest galaxies seem to have large supermassive black holes. Here's how they were made.
For 550 million years, neutral atoms blocked the light made in stars from traveling freely through the Universe. Here's how it then changed.
Even after the first stars form, those overdense regions gravitationally attract matter and also merge. Here's how they grow into galaxies.
The first stars in the Universe were made of pristine material: hydrogen and helium alone. Once they die, nothing escapes their pollution.
The first stars took tens or even hundreds of millions of years to form, and then died in the cosmic blink of an eye. Here's how.
The Big Bang's hot glow faded away after only a few million years, leaving the Universe dark until the first stars formed. Oh, the changes!
Atomic nuclei form in minutes. Atoms form in hundreds of thousands of years. But the "dark ages" rule thereafter, until stars finally form.
The first elements in the Universe formed just minutes after the Big Bang, but it took hundreds of thousands of years before atoms formed.
In the early stages of the hot Big Bang, there were only free protons and neutrons: no atomic nuclei. How did the first elements form from them?
In the early stages of the hot Big Bang, matter and antimatter were (almost) balanced. After a brief while, matter won out. Here's how.
For a substantial fraction of a second after the Big Bang, there was only a quark-gluon plasma. Here's how protons and neutrons arose.
In the very early Universe, practically all particles were massless. Then the Higgs symmetry broke, and suddenly everything was different.
In the earliest stages of the hot Big Bang, equal amounts of matter and antimatter should have existed. Why aren't they equal today?
When the hot Big Bang first occurred, the Universe reached a maximum temperature never recreated since. What was it like back then?
Some 13.8 billion years ago, the Universe became hot, dense, and filled with high-energy quanta all at once. Here's what it was like.
Cosmic inflation is the state that preceded and set up the hot Big Bang. Here's what the Universe was like during that time period.
Bang bang all over the Universe.
If the Universe is expanding, and the expansion is accelerating, what does that tell us about the cause of the expanding Universe?
Everything we observe beyond our Local Group is speeding away from us, omnidirectionally. If the Universe is expanding, where is the center?
If you said "with the Big Bang," congratulations: that was our best answer as of ~1979. Here's what we've learned in all the time since.
Einstein's theory of general relativity introduced the concept of space having a shape. So, what is the shape of space?
Back during the hot Big Bang, it wasn't just charged particles and photons that were created, but also neutrinos. Where are they now?
Although we still don't know the question, we know that the answer to life, the Universe, and everything is 42. Here are 5 possibilities.
From the Big Bang to black holes, singularities are hard to avoid. The math definitely predicts them, but are they truly, physically real?