Concepts explained
The First Light of the Universe Is in This Room
The snow on an old analogue television. A small part of that noise set out 13.8 billion years ago. The men who caught it first blamed pigeon droppings.
How can such a thing still be around? In order, then.
At first the universe was opaque
The very early universe was too hot and too dense. Light could not travel far: it struck something, bounced, struck again. Like a torch in fog — plenty of light, nothing visible.
Then it cooled. Below a certain temperature the loose particles settled into place, and there was nothing left for light to collide with.
Nothing stops it, so it does not stop. Which is why it is in this room, landing on the back of your hand.
So why can we not see it?
When released it was the bright light of something hot. It is invisible now, because it was stretched along the way.
The universe kept expanding. The light crossed that expanding space, and when space stretches, the ripples riding on it stretch too.
It was pushed outside the window of the sixth piece. The oldest light there is has already left the band our eyes can reach.
The men who first held the oldest thing in existence took it for pigeon droppings. That is why great discoveries so often surface as the error someone was trying to remove. Unexplained noise is not for discarding but for looking into.
The question that remainsThat light ran for 13.8 billion years and landed in this room, and only now has anything recognised it. What does that change?