I had a bunch of students over for dinner last night, and while I was busy with that, stuff happened in the world. I hate that.
Of course, there’s been a lot of energy expended on trivia like primary elections, but that’s not what I’m talking about. The important news all has to do with physics.
First, via His Holiness, Peter Zoller has been awarded the Dirac Medal from the Abdus Salam International Center for Theoretical Physics. It’s not as big a deal as the Nobel Prize, or anything, but it’s well-deserved recognition, both for Zoller and for the quantum computing sorts of topics he works on. This is some of the coolest work going on in physics, and Zoller is both scary smart and a really nice guy to talk to.
In older news, well, the universe is bigger than we thought, as some new observations may require a revision of the distance to some nearby galaxies. This, in turn, would require a revision of the Hubble Constant, which describes the rate at which distant galaxies appear to be receding from us, due to the expansion of the universe. And if the Hubble Constant changes, that means the universe is older than expected, by about fifteen percent, or two billion years.
“How could we have missed two billion years?,” you ask. Well, these measurements are really, really difficult, and Rob Knop explains why.
Yet, according to this article at physorg.com, the Chandra X-ray observatory just recently confirmed the value of Hubble’s Constant (which is tied to the age of the universe).
So, which is it?
So, which is it?
Oh, it’s probably something close to 72 (that is, the current “standard” value which the Chandra observations support). There are a whole host of different measurements (of which the Chandra result is a new example) which suggest the Hubble constant is somewhere around 75.
I skimmed the preprint that Rob Knop pointed to, and it turns out that it doesn’t seriously advocate a smaller Hubble constant (e.g., 61); it seems to use this instead as a way of arguing that the local distance calibration isn’t as error-free as people think. I think the press release distorts things a bit.
(There was actually a somewhat similar, dramatic announcement back in the mid-90s that the Hubble constant was large and the universe was younger than we thought, based on brand-new HST distance measurements. Which were measurements to a single galaxy, which turned out to be in an unusual situation, so that the later measurements based on more galaxies ended up giving a Hubble constant right around 72… The moral? Be cautious about single measurements, and also about press releases.)