The New York Times today has Where is Physics Headed (and How Soon Do We Get There?). It’s an interview by Dennis Overbye of Maria Spiropulu and Michael Turner, the chairs of the NAS Committee on Elementary Particle Physics – Progress and Promise. This committee is tasked with advising the DOE and NSF so they can “make informed decisions about funding, workforce, and research directions.”
The transcript of the interview is rather bizarre, for several reasons. Spiropulu, probably the main person responsible for the recent wormhole publicity stunt, is here the voice of sober reason:
Overbye: String theory — the vaunted “theory of everything” — describes the basic particles and forces in nature as vibrating strings of energy. Is there hope on our horizon for better understanding it? This alleged stringiness only shows up at energies millions of times higher than what could be achieved by any particle accelerator ever imagined. Some scientists criticize string theory as being outside science.
Spiropulu: It’s not testable.
whereas Turner (an
astronomer astrophysicist with no particular background in mathematics) is a big fan of string theory as mathematics:
Turner: But it is a powerful mathematical tool. And if you look at the progress of science over the past 2,500 years, from the Milesians, who began without mathematics, to the present, mathematics has been the pacing item. Geometry, algebra, Newton and calculus, and Einstein and non-Riemannian geometry.
We will have to wait and see what comes from string theory, but I think it will be big.
On the topic of particle physics and unification, there’s
Overbye: You’re referring to Grand Unified Theories, or GUTs, which were considered a way to achieve Einstein’s dream of a single equation that encompassed all the forces of nature. Where are we on unification?
Spiropulu: The curveball is that we don’t understand the mass of the Higgs, which is about 125 times the mass of a hydrogen atom.
When we discovered the Higgs, the first thing we expected was to find these other new supersymmetric particles, because the mass we measured was unstable without their presence, but we haven’t found them yet. (If the Higgs field collapsed, we could bubble out into a different universe — and of course that hasn’t happened yet.)
That has been a little bit crushing; for 20 years I’ve been chasing the supersymmetrical particles. So we’re like deer in the headlights: We didn’t find supersymmetry, we didn’t find dark matter as a particle.
Turner makes the case one often hears these days from string theorists: the field may have given up on unification, but it has moved on to something much less boring:
Turner: I feel like things have never been more exciting in particle physics, in terms of the opportunities to understand space and time, matter and energy, and the fundamental particles — if they are even particles. If you asked a particle physicist where the field is going, you’d get a lot of different answers.
But what’s the grand vision? What is so exciting about this field? I was so excited in 1980 about the idea of grand unification, and that now looks small compared to the possibilities ahead.
Turner: The unification of the forces is just part of what’s going on. But it is boring in comparison to the larger questions about space and time. Discussing what space and time are and where they came from is now within the realm of particle physics.
From the perspective of cosmology, the Big Bang is the origin of space and time, at least from the point of view of Einstein’s general relativity. So the origin of the universe, space and time are all connected. And does the universe have an end? Is there a multiverse? How many spaces and times are there? Does that question even make sense?
Spiropulu: To me, by the way, unification is not boring. Just saying.
The problem with the idea that we’ve moved on to a new, far more exciting time in physics, devoted to replacing conventional space-time and exploring the multiverse, is that there’s no actual way to do experiments about any of this (other than the wormholes…). If this is the vision of the coming NAS report, a possible response from the DOE and NSF may be “That’s nice, we can now shut down all those expensive labs and experiments doing the boring stuff and focus on investigating the wormholes that Google’s quantum computer is producing for us.”
Update: Ars Technica has some refreshing anti-hype: Requiem for a string: Charting the rise and fall of a theory of everything, with subtitle “String theory was supposed to explain all of physics. What went wrong?”
It’s a good explanation of what went wrong with string theory, although one might point out that pretty much the same story was first explained by others in detail 20 years ago.
There definitely seems to be a recent trend in popular science articles to finally admit that string theory unification may simply be a failed and now dead idea. This article gets brutal at times:
The dearth of evidence has slaughtered so many members of the supersymmetric family that the whole idea is on very shaky ground, with physicists beginning to have conferences with titles like “Beyond Supersymmetry” and “Oh My God, I Think I Wasted My Career.”