large-scale structure

Seeing Strands in the Cosmic Web

For the first time, a part of the dark matter “skeleton” of the universe has revealed itself. The discovery strengthens our understanding of the universe’s history and tells us more about the formation of galaxies like our own, billions of years ago.

Current theories about the largest structures in the universe predict the existence of giant structures made of dark matter — the unseen substance that comprises over 80% of the matter in the universe — between most galaxy clusters. Now, for the first time, a team of cosmologists led by Jörg Dietrich at University Observatory Munich has found hard evidence that the long-sought-after strands of dark matter actually exist….

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What I Do: Part II

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….

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What I Do

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….

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Faking It

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…

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