Where were all of the things a long time ago? Can we find out by looking at things now?

Some of my friends and I use big computers to try to find out where stuff was — all of the stuff, in every place out in space — in the first tiny part of a second, at the beginning of time. We do this by looking at where all of the stuff in space is now, and trying to guess what that means about where stuff was before. But it is very hard to do that, even with a big computer….

Read more "Where were all of the things a long time ago? Can we find out by looking at things now?"

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….

Read more "Seeing Strands in the Cosmic Web"

Feynman Lectures, Chapter I: The Most Important Idea in Science

Back to the Feynman lectures! The writing is quite beautiful — Feynman is very clear and readable, while still packing a great deal of information into a small space. There’s no way one blog post of reasonable length could cover all of the ground that Feynman does in each chapter. And this chapter is especially densely packed, because this chapter is setup. After some brief introductory remarks — and some philosophical comments on the nature of science that I’ll get to in a later post — Feynman gives the class a killer hook, and then uses that hook to reel the students (and readers) in through a quick introduction to many, many concepts that will come up again later in the text….

Read more "Feynman Lectures, Chapter I: The Most Important Idea in Science"