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? — One of the most remarkable achievements in all of human history is the discovery of the scientific story of how our Universe began, evolved over time, and came to be the way it is today. Back in the very early stages of the Universe, we experienced conditions known as the…

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. — Things happen fast in the earliest stages of the Universe. In the first 25 microseconds after the start of the hot Big Bang, a number of incredible events have already occurred. The Universe created all the particles and antiparticles — known (as part of the Standard Model) and unknown (including…

The highest-energy particles could be a sign of new, unexpected physics. But the simplest, most mundane explanation is particularly iron-ic. — Earth, whether we like it or not, serves as a cosmic particle detector on a continuous basis. It isn’t just light waves that travel through the Universe, nor is that light merely joined by gravitational waves and ghostly neutrinos. In truth, cosmic particles and antiparticles of all types are produced…

In 2022, Hubble owned the record for most distant galaxy. Today, that galaxy is down to the 9th most distant object. Thanks, JWST. — One year ago, in 2022, Hubble still held the cosmic distance record.

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. — The story of our cosmic history is one of an expanding and cooling Universe. As we progressed from a hot, dense, uniform state to a cold, sparse, clumpy one, a number of momentous events happened throughout our cosmic history. …

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, the Universe was filled with all the particles, antiparticles, and quanta of radiation it had the energy to create. …

In the earliest stages of the hot Big Bang, there equal amounts of matter and antimatter should have existed. Why aren’t they equal today? — 13.8 billion years ago, at the moment of the Big Bang, the Universe was the hottest it’s ever been in history. Every single known particle exists in great abundance, along with equal amounts of their antiparticle counterparts, all smashing rapidly and repeatedly into everything around them. …

When the hot Big Bang first occurred, the Universe reached a maximum temperature never recreated since. What was it like back then? — When we look out at the Universe today, we see that it’s full of stars and galaxies, in all directions and at all locations in space. The Universe isn’t static, though; the distant galaxies are bound together in groups and clusters, with those groups and clusters speeding away from one…

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. — Looking out at our Universe today, we not only see a huge variety of stars and galaxies both nearby and far away, we also see a curious relationship: the farther away a distant galaxy is, the faster it appears to move away from us. This continues as far as we’ve…