The reigning theory for the origin of our universe is that around 13.8 billion years ago, the entire visible cosmos was a tiny, very hot, and very dense point in space that was just a few millimeters in size. Then, in just a few fractions of a second, it exponentially expanded. Of course, the theory is known as the Big Bang. I remember as a kid first reading that the static on TV sets comes from the cosmic background radiation remaining from the Big Bang and received by the television's antennae. Now, Big Think has a great explanation of the whole experiment—"How to prove the Big Bang with an old TV set":
Channel 03 was — and if you can dig up an old television set, still is — simply a signal that appears to us as "static" or "snow." That "snow" you see on your television comes from a combination of all sorts of sources:
* thermal noise of the television set and its surrounding environment,
* human-made radio transmissions,
* the Sun,
* black holes,
* and all sorts of other directional astrophysical phenomena like pulsars, cosmic rays and more.
But if you were able to either block all of those other signals out, or simply took them into account and subtracted them out, a signal would still remain. It would only be about 1% of the total "snow" signal that you see, but there would be no way of removing it. When you watch channel 03, 1% of what you're watching comes from the Big Bang's leftover glow. You are literally watching the cosmic microwave background.