The Observable Universe in One Continuous Shot

This is Vishala Space. This is one shot. It starts at a marble, it ends at the edge of everything we can see, and it does not cut. And it begins with a puzzle. The universe is about thirteen point eight billion years old. Yet the edge of what we can see is about forty-six billion light-years away. Both numbers are true.

Two dials will show you why: how long the light has been travelling, and where its source is now. Shrink the whole Earth to this marble, one inch wide, and that edge would still be about ninety-two light-years away. Real light-years. Let's go. The marble is the Earth, seven thousand nine hundred miles wide, shrunk to one inch. Every distance in this video sits on this same ruler. The Moon is a pea, thirty inches away.

Keep pulling back. The Sun is a ball about nine feet wide, nearly a thousand feet away. Its light takes eight minutes and nineteen seconds to reach us. Now watch the two dials. The blue one says how long the light has been travelling. The gold one says where its source is now. Out here they agree, to the second.

In eight minutes, space barely stretches at all. Pluto's orbit sits seven miles from the marble. Voyager 1, launched in nineteen seventy-seven and the farthest machine we have ever built, is only about thirty miles out. Now a single light-year. On this ruler it is about eleven thousand seven hundred miles, almost half way around the real Earth. And the nearest star, Proxima Centauri, four and a quarter light-years away, sits about fifty thousand miles from the marble. Twice around the Earth.

Its light left a little over four years ago, and the star is still about where it was. The two dials still agree. Almost every star you have ever seen with your own eyes belongs to one galaxy. We are about to leave it. Pull back past the stars we have measured one by one, and the disc of the Milky Way appears. About eighty-seven thousand light-years across, with the Sun about twenty-seven thousand light-years from the centre. On the marble ruler, this whole galaxy is now a little wider than the real orbit of Jupiter.

And here is our first neighbour. Andromeda. Its light left about two and a half million years ago, long before our own species existed. And where is it now? Still about two and a half million light-years away. The Hubble Space Telescope measured it with pulsing stars called Cepheids: two point four eight million light-years, give or take thirty-six thousand. For something this close, the light's travel time and the distance are the same number.

Both dials agree. Hold on to that, because it is about to break. Our Local Group: two big spirals and dozens of small galaxies, about seven million light-years across. Past it, the Virgo cluster, about fifty-four million light-years away. From here on, the points you see are not drawn by hand. Each one is a real galaxy, placed where its redshift puts it. Forty-three thousand five hundred of them come from the Two-Mass Redshift Survey.

Redshift is light stretched by the growth of space on its way to us. And now watch the dials. Light that has travelled for one point three five billion years comes from a galaxy that is now one point four one billion light-years away. The two numbers have started to split. The longer light travels, the more the universe grows under it. Farther out, the surveys look like fans, not a full sky. That is honest.

These are the slices of sky that telescopes have mapped galaxy by galaxy, and the dark gaps are sky these surveys did not cover. The colour is the stretch itself. The redder a point, the more its light was stretched on the way. Light that has travelled for seven point nine billion years now comes from eleven billion light-years away. The gap is no longer small. Let's stop here, and let only time move. This is a quasar, a galaxy with a feeding black hole at its centre.

Its light set off eleven point six billion years ago. When it left, the quasar was only about five point three billion light-years from the place that would become us. Watch that light. At first, the space between us grew faster than the light could cross it. The light was heading toward us, and still drifting farther away. Its distance peaked at about five point eight billion light-years. Then the expansion slowed, and the light began to gain.

It reaches us only now. And the quasar? It is twenty-one billion light-years away. That is the whole trick. Thirteen point eight billion is a time. Forty-six billion is a distance, as it stands today. Back to the flight.

The farthest galaxy confirmed by twenty twenty-six is called Mom Z-fourteen. Its light set off thirteen and a half billion years ago, when the universe was about two hundred and eighty million years old. When that light left, the galaxy was about two point two billion light-years away. Now it is about thirty-four billion. How do we know the stretch? The James Webb Space Telescope split its faint light into a rainbow, and a sharp step in that rainbow fixed it: fourteen point four four. Some pictures hint at galaxies even farther away.

Until their light is split the same way, they stay candidates, not records. Beyond it, as of twenty twenty-six, no galaxy had been confirmed. Before the first stars switched on, there was almost no new light to see. The cosmic dark ages. And then, a glow on every side. This is the oldest light there is: the cosmic microwave background, mapped here by NASA's W-MAP spacecraft. It left about three hundred and eighty thousand years after the Big Bang, when the universe was a hot glowing gas at about three thousand kelvin, about forty-nine hundred degrees Fahrenheit, and became clear.

It has travelled for thirteen point eight billion years, stretched about eleven hundred times, and it now arrives at two point seven degrees above absolute zero. Here is the number almost no one says. When this light set off, the gas that sent it was only about forty-two million light-years from here. That same gas is now about forty-five billion light-years away. And notice: the camera never reaches it. Wherever we stand, the glow surrounds us at the same distance. It is not a place.

It is a moment. Behind the glow sits a last thin shell, the final two percent of the way out, hidden because the early universe was not transparent. Its outer edge is the particle horizon: the farthest place whose light could have reached us since the Big Bang. With the Planck spacecraft's measurements it comes out at forty-six point two billion light-years. You will often hear forty-six point five, from older numbers. Call it about forty-six. More than ninety billion across.

Two more shells live inside it. Beyond about fourteen and a half billion light-years, galaxies are moving away from us faster than light today. Nothing breaks a law: no galaxy outruns light through space; the space between us grows. And we still see them, because the light arriving now left them long ago. Then, at about sixteen and a half billion light-years, the event horizon. Light those galaxies send today will never reach us, and light we send will never reach them. About ninety-five percent of the observable universe is already out of reach, forever.

How many galaxies fit inside all this? Counting what our telescopes can see gives hundreds of billions. One model that adds every faint dwarf too says about two trillion. The honest answer is a range. So is this a wall? No. Jump to a galaxy thirty billion light-years away, and it has its own sphere, the same size, centred on itself.

Our edge runs right through its sky. Nobody sits in the middle. Every observer has a horizon, and every horizon keeps moving outward as light from ever farther places keeps arriving. In the far future it stops growing, at about sixty-three billion light-years, in today's distances. What lies beyond, we cannot see. The measurements allow the universe to be far larger, maybe without end. Now the whole way back, fast.

The glow, the first galaxies, the fans of the surveys, Andromeda, the Sun, and the marble. Forty-six billion light-years out, and all the way home, without a single cut. Next time, the other dial: time itself. Squeeze the Earth's four and a half billion years into one single day. At what second do we arrive? Next: Earth's four and a half billion years in one day.