Ask physicist Brian Greene anything

Last week, physicist Brian Greene answered a lot of questions—including a few submitted by BoingBoing readers!—at a live event in New York City. If you missed it, you can watch a recording of the event online now.

But wait, there's more! Dr. Greene only had an hour to talk, and a metric crap ton of very good questions—including, again, some from BoingBoing readers—went unanswered. That's why I'm pleased to announce that the World Science Festival has added a new column to their website, called Ask Brian Greene Anything. For the next month, he'll be sifting through leftover questions from the live event as well as new submissions to answer a physics question every day.

Here's the latest:

Q: If nothing can travel faster than the speed of light, then how did the universe become so big and vast in the blink of a micro-second during the big bang? — Carlos Cordoba, Queens, NY

A: You have to be a little careful when invoking the notion that “nothing can travel faster than the speed of light.” Einstein’s special theory of relativity actually shows that nothing can move through space at a speed greater than light speed. But the process that makes the universe “so big and vast” does not involve objects moving through space. Instead, it arise from the swelling — the expansion — of space itself. And nothing in special relativity constrains the rate at which space itself expands. Indeed, in the early moments of the universe, the expansion of space can rightly be said to have exceeded the speed of light, meaning that regions of space were driven apart via the expansion at a greater-than-light speed. Moreover, since the expansion of space is cumulative (the farther apart two points are — the more space there is between them — the faster they rush apart as space expands), even today there’s a sense in which sufficiently distant regions are receding from each other at a greater-than-light speed.

Also, an important reminder: Reader Kevin Harrelson needs to email me in order to claim his free DVD set of Brian Greene's new NOVA series, "Fabric of the Cosmos." You can reach me at

Image: Dark and ordinary matter in the Universe, a Creative Commons Attribution Share-Alike (2.0) image from argonne's photostream