Adam Brown

sort of approach that one might say, which is, you know, there was a ginormous explosion that happened, which was the Big Bang.

You know, if you imagine

if we look out in the universe, it's expanding.

If you sort of play the tape backwards, it's contracting.

Eventually it all contracts at 13.8 billion years ago in the Big Bang.

And so that's a very big particle collider indeed.

And so by just examining very closely the Big Bang and its aftermath, we're able to hopefully probe some of these quantities that are very difficult to probe with particle colliders.

The disadvantage is that you can't,

keep running it and adjust the parameters as you see fit it's just like one thing that happened once and now we're having to peer backwards to uh with our telescopes to see what happened but it can give us hints about things that would be inaccessible with any future future information about the distant past that is in principle inaccessible probably not in principle so something happened to the universe uh in it in its evolution which is that

The very early universe, just after the Big Bang, was opaque to light.

We can only see light past about 300,000 years after the big bang.

Before that, everything's so dense, it's like just a dense plasma that light just gets absorbed by.

It's like trying to look through the sun.

And so we cannot see directly anything from before 300,000 years.

Nevertheless, we can infer lots of stuff that happened from before 300,000 years.

In fact, looking at that light, what's called the cosmic microwave background that was emitted at that time, we infer lots of stuff about just due to the patterns of anisotropies that we see in the sky, we can infer a great deal about what was happening earlier.

And most of our confidence about modern cosmology comes from a number of

experiments that starting in the 80s but accelerating in the 2000s really very carefully measured that anisotropy and allowed us to infer stuff before that.

At the information theoretic level, there's nothing inaccessible.

Well, that's a great question.