LHC Fun

I'm sorry that I didn't post anything about the Large Hadron Collider starting up on Wednesday. This is an exciting time for high energy physics, even for those of us without direct ties to the experiment. I'm sure lots of you have been following the whole story (Brian Greene's NYT article is a good start), from the cool science the LHC may illuminate to the crackpots filing lawsuits because they're afraid the machine will create black holes that will engulf the Earth.

On the off chance that you haven't seen them, here are a handful of LHC-related tidbits that I've enjoyed recently:

• I showed the LHC Rap in class on Tuesday. I think they enjoyed it.


• For the paranoid, hasthelargehadroncolliderdestroyedtheworldyet.com. (Beware of cheap knockoffs! Whois says that the similar hasthelhcdestroyedtheearth.com was registered later; their answers may be less reliable.)


• To see the very latest, watch some webcams in and around the LHC. Maybe if you watch long enough, you'll see the Higgs!

Good stuff, good stuff. (And really, those webcams are worth checking out.)

Life after physics

All the talk of LHC doomsday scenarios can get you thinking (even though it may be more likely that the LHC will produce dragons than Earth-swallowing black holes or strange matter), and the HTML source of hasthelhcdestroyedtheearth.com has reminded me of an incredible paragraph from a paper by Sidney Coleman and Frank De Luccia ("Gravitational effects on and of vacuum decay". Physical Review D21 (1980) p. 3305).

In the paper, Coleman and De Luccia studied implications of "vacuum decay", the suggestion that the laws of nature that we know have not settled into their final form. Instead, the idea goes, perhaps the laws of physics got "stuck" as the universe cooled down from the Big Bang much a rock falling down a cliff might get caught on a ledge partway down. The rock is likely to be knocked loose in the next big storm or sooner, perhaps with no apparent cause at all. The same thing could happen to physics if we really are stuck in a "false vacuum": whether caused by a specific event or just bad quantum luck, our seemingly eternal laws of physics could come loose ("decay") and fall into a totally different state. Coleman and De Luccia analyzed what might be left after such an event happened, and had this to say about their results:

This is disheartening. The possibility that we are living in a false vacuum has never been a cheering one to contemplate. Vacuum decay is the ultimate ecological catastrophe; in the new vacuum there are new constants of nature; after vacuum decay, not only is life as we know it impossible, so is chemistry as we know it. However, one could always draw stoic comfort from the possibility that perhaps in the course of time the new vacuum would sustain, if not life as we know it, at least some structures capable of knowing joy. This possibility has now been eliminated.

With that quote in mind, it may be disquieting to realize that a fair number of physicists have come to believe that string theory predicts that the universe has something like 10⁵⁰⁰ different choices of "vacuum" and that we might be living in any of them. I don't think we know anywhere near enough to say how likely they are to decay.