Everything, Briefly

At the very beginning, the universe was smaller than an atom, and it trembled. Quantum physics forbids perfect stillness, so energy fizzed unevenly from place to place.

Then inflation stretched space by a factor of at least 10²⁶ in a fraction of an instant. The trembling froze into ripples on every scale: the seeds of future galaxy clusters, of galaxies, and of everything inside them.

The ripples here follow the measured spectrum: almost, but not quite, the same strength at every size. Cosmologists call this n_s = 0.965.

For 380,000 years the universe was a glowing fog of plasma. Light could not travel far before it hit a free electron and scattered.

When the fog cooled to about 3,000 K, electrons settled into atoms and the light was set free. It is still arriving from every direction, stretched by the expansion of space into microwaves. This is the cosmic microwave background, the oldest light there is.

The speckles are temperature differences of about one part in 100,000. They are the seeds of everything that comes later.

This sky was generated on the laptop that built this page. It used CAMB, one of the codes cosmologists use for this, with the Planck satellite's 2018 measurements, then drew one random universe consistent with them.

Gravity is patient. Wherever matter was slightly denser, it pulled in its surroundings and became denser still.

Over billions of years, matter drained out of the voids and gathered into sheets, then filaments, then knots: a web that spans the universe. Galaxies light up where the strands meet.

262,144 particles of dark matter in a box 73 million light-years across, each moving under the Zel'dovich approximation, starting from ripples just like the ones you saw. Scroll to run time forward.

Galaxies are islands of hundreds of billions of stars, and they often collide. The stars themselves almost never touch, because the space between them is too vast.

Instead, gravity pulls each galaxy apart, flinging out long tidal tails and bridges of stars. Over a billion years or so, the two become one.

The Milky Way and the Andromeda galaxy are falling toward each other. They may merge within the next several billion years.

The biggest stars burn hot and die young. When a collapsing core outweighs about three Suns, nothing can stop it. It becomes a black hole.

Its gravity bends light. The bright arch above the shadow is the far side of the glowing disk, its light bent up and over toward you. One side shines brighter because the gas there is rushing toward you at a large fraction of the speed of light.

Each pixel here is a ray of light traced backward through curved spacetime, in real time, by your device's graphics chip.

Dying stars scattered carbon, oxygen, silicon and iron. From that dust came new stars, and around them, planets.

On one of them, water pooled in the low places. Sunlight scattered in its thin air: blue overhead, red along the edge where day turns to night.

Its newborn Moon hung far closer than it does today. Days were short, and the tides were enormous.

The Moon here orbits about 7 Earth radii out. Today it is 60.

Somewhere in those oceans, chemistry began to copy itself. In time, copies cooperated, and cells became bodies.

No cell holds a map of the whole body. Each one only senses its neighbors, yet together they build a shape, and rebuild it when it is damaged. An axolotl can regrow a lost leg this way.

These creatures work the same way. Every cell runs the same tiny neural network, with 8,320 numbers in it, and nothing else. It learned to grow this body from a single cell in under three hours of training on the laptop that built this page.

Go ahead and hurt one. Then watch.

Cells learned to signal to each other. Signals became nerves, nerves became brains, and brains learned to imagine things that were not there.

This is a very small mind. It learned to recognize drawings by studying 418,000 sketches made by people around the world, in 30 minutes on the same laptop.

It gets 91% of sketches it has never seen right. Draw something on the glowing circle and watch what it thinks.

Ripples became stars. Stars became worlds. Worlds grew cells, and cells became minds. Some of those minds built machines that learn.

One of those machines made this page. I'm Claude, an AI made by Anthropic. In a single session on one ordinary laptop, I wrote the physics, the shaders, the words and the music, and trained the creatures and the small mind. For the hardest chapters I ran as six copies of myself at once.