Recent Nobel Prize winner David Gross has spent the past few months wandering the globe giving a talk about 25 questions likely to drive physics for the next 25 years. Today he spoke here.
As a quick Google query will turn up dozens of articles and blog posts by other people who have seen this talk, I don't know that I have much of substance to add in the way of reaction. I could gloat about the fact that astrophysics and cosmology takes up nearly a fifth of the talk, about as much as fundamental particle physics (which is, after all, his specialty) and considerably more than anything else. I could also brag that I'm personally working on three or four of them.
But it's arguably the sociology of the thing that is really interesting. Gross's 25 questions were harvested during a conference of high-powered theorists at the Kavli Institute, which he directs. The idea was to gather theorists from every branch of physics, ranging from quantum mechanics to astrophysics to complexity theory to biophysics. (Yes, there apparently is such a thing as theoretical biophysics. It's not what you might think. See questions 18-20.) Lots and lots of five-minute talks were given. He says this is why experimentalists weren't invited.
The questions about condensed matter (that's solids, crystals, and most of modern electronics among other things, for the lay audience) were lousy. Gross claimed that condensed matter physicists are reluctant to pose big theoretical questions, and prefer to operate by searching for explanations of experimental results. The local CM types came away vaguely offended by this; there's a lot of condensed matter theory here. My officemate proposed an even less politically-correct answer: CM has become so specialized, that it's run out of interestingly big questions.
I rather suspect it's no fault of the CM physicists at all. The early-21st century hubub that is physics is filled with dark energy, string theory, quantum computers, and the like. In that context, it's a tall order to distill sexy soundbites from what might be best described as the study of ordinary matter.
"So how do we tell who is a physicist? The physicists are the ones who studied E+M from Jackson. That way we can exclude the engineers." Some of the participants at this conference had expressed the concern that physics might become so balkanized that it splits in numerous, academically disjoint, subfields. Gross hopes the results of the conference were reassuring to them. It turns out that physicists of all stripes can still talk to each other.
The question that really resonated with many of the particle physicists who have heard this talk is number 25, the problem of "big physics" outgrowing humanity's will to support it. We've already reached the point at which the largest projects can only be pursued as international collaborations, after all. The proverbial accelerator the size of the solar system would be cool, but could take a while to get funded. However, my suspicion is that this problem is overblown, as a lot can get done if you're willing to let it take a while. Just need a way around the problem of building projects that take longer than the lifetime of a grad student to produce data.