Category Archives: Science


This year we give thanks for an area of mathematics that has become completely indispensable to modern theoretical physics: Riemannian Geometry. (We’ve previously given thanks for the Standard Model Lagrangian, Hubble’s Law, the Spin-Statistics Theorem, conservation of momentum, effective field … Continue reading

Posted in Math, Science | 9 Comments

The Universe Never Expands Faster Than the Speed of Light

Breaking my radio silence here to get a little nitpick off my chest: the claim that during inflation, the universe “expanded faster than the speed of light.” It’s extraordinarily common, if utterly and hopelessly incorrect. (I just noticed it in … Continue reading

Posted in Science | 140 Comments

The Big Picture

Once again I have not really been the world’s most conscientious blogger, have I? Sometimes other responsibilities have to take precedence — such as looming book deadlines. And I’m working on a new book, and that deadline is definitely looming! … Continue reading

Posted in Personal, Philosophy, Religion, Science, Words | 59 Comments

The Bayesian Second Law of Thermodynamics

Entropy increases. Closed systems become increasingly disordered over time.┬áSo says the Second Law of Thermodynamics, one of my favorite notions in all of physics. At least, entropy usually increases. If we define entropy by first defining “macrostates” — collections of … Continue reading

Posted in arxiv, Science, Time | 49 Comments

Hypnotized by Quantum Mechanics

It remains embarrassing that physicists haven’t settled on the best way of formulating quantum mechanics (or some improved successor to it). I’m partial to Many-Worlds, but there are other smart people out there who go in for alternative formulations: hidden … Continue reading

Posted in Philosophy, Science | 102 Comments

Spacetime, Storified

I had some spare minutes the other day, and had been thinking about the fate of spacetime in a quantum universe, so I took to the internet to let my feelings be heard. Only a few minutes, though, so I … Continue reading

Posted in Science | 16 Comments

Guest Post: Aidan Chatwin-Davies on Recovering One Qubit from a Black Hole

The question of how information escapes from evaporating black holes has puzzled physicists for almost forty years now, and while we’ve learned a lot we still don’t seem close to an answer. Increasingly, people who care about such things have … Continue reading

Posted in arxiv, Guest Post, Science | 23 Comments

Why is the Universe So Damn Big?

I love reading io9, it’s such a fun mixture of science fiction, entertainment, and pure science. So I was happy to respond when their writer George Dvorsky emailed to ask an innocent-sounding question: “Why is the scale of the universe … Continue reading

Posted in Science | 68 Comments

Yoichiro Nambu

It was very sad to hear yesterday that Yoichiro Nambu has died. He was aged 94, so it was after a very long and full life. Nambu was one of the greatest theoretical physicists of the 20th century, although not … Continue reading

Posted in Science | 11 Comments

Why Is There Dark Matter?

Years ago I read an article by Martin Rees, in which he surveyed the options for what the dark matter of the universe might be. I forget the exact wording, but near the end he said something like “There are … Continue reading

Posted in Science | 53 Comments