Figuring out what happened during the first billionth of a billionth of a second after the Big Bang is rather hard, mostly because there’s no light we can see from that time. In fact, there’s no light that we can see from the first 380,000 years after the Big Bang. For most of that time, light was trapped in a plasma, a dense soup of electrically charged particles a lot like the interior of the Sun….
Read more "What I Do: Part II"Physicists are notorious for oversimplifying things in the name of mathematical modeling. There’s the old joke about spherical cows, radiating milk isotropically, which I’ll spare you here, but the reason we do this is that you can often learn an awful lot about something by simplifying it down to the interesting and easy-to-model parts — which are hopefully the same! The trick is knowing which parts can safely be ignored, but if you do that right, you can get an amazing amount of information about something with a very simple model of it….
Read more "What I Do"Astronomy and cosmology involve some big numbers: a hundred million miles to the sun; six trillion miles in a light-year; two million light-years — ten billion billion miles, a one with 19 zeros after it — to the nearest galaxy. These are huge numbers, and it’s hard to get your head around them directly. But with a little bit of work, it’s not too bad. For example, a million isn’t actually that big of a number: get a cube of something small (marbles? BBs?) with a hundred objects on each side, and there are a million of those objects in that cube. Get a thousand of those cubes — a bigger cube, with ten of the smaller cubes on each side — and you’ve got a billion. A million seconds is only 11 and a half days; a billion seconds is 31 and a half years….
Read more "Big Numbers and Really Big Numbers"What’s this picture?
The easy answer is that it’s a computer-generated image from the Millennium Simulation of what we think the universe looks like on the largest scales. That’s not quite true, though. It’s certainly an image from the Millennium Simulation, but it’s not what we think the universe “looks” like, at least not literally; those luminous dots indicate dark matter, not galaxies, meaning they’re not made of anything that actually gives off light of any kind. More importantly, it’s not what we think our universe looks like because it’s not a map of our universe. It’s a map of a fake universe, a wholly simulated construction living inside a computer…
Read more "Faking It"