Dreams of a Final Theory by Steven Weinberg – review

leave a comment »

Simulated trace of a Higgs boson. There are fears even the LHC may not be powerful enough to bring the final theory within our grasp.

Here is an elegant, leisurely and profound contemplation of science by a man who doesn’t know what he is talking about. That last barb is true only in one very limited sense. In every other respect, Steven Weinberg is the perfect guide: he is a Nobel laureate; he woke the publishing world up more than 30 years ago with a stunning introduction to modern cosmology called The First Three Minutes; he was a driving force behind what was going to be the world’s most extravagant experiment; and he explains himself with a fabulous command of language…..
Furthermore, he wrote Dreams of a Final Theory almost 20 years ago. High-energy physics is a fast-moving field (the phrase seems less fatuous and more pertinent when you talk about particle accelerators) but the world is still waiting to find out what the final theory could possibly be, always supposing humans are smart enough to recognise it when they see it, and always supposing a final theory even exists.

First, the problem. It reduces to this: is there an explanation that needs no other explanation to support it? Is there one theory, equation or model that makes sense of why light has a fixed speed and no other; why and how a photon can turn into a speck of something solid; why matter is what it is and not something else; why particles become atoms and atoms become molecules; why a single photon can go through two slits at the same time; and why space yields to matter and makes it go downhill?

Physicists have got a handle on separate mysteries such as special and general relativity, and the electromagnetic and nuclear forces, and have conducted enough experiments in to confirm that – however weird the outcomes – quantum mechanics works. But separately none of these explains why the world is as it is, with space expanding in every direction, and time ticking away remorselessly in one direction, and light cascading across the universe, and solid, palpable galaxies made of atoms held together by invisible, intangible lumps of mass. What exactly happened at the very beginning of space and time that made it inevitable that this universe turned out the way it did?

This is an old question: Weinberg’s contemporaries at Cern started talking about Grand Unified Theory in the late seventies and later introduced the term Theory of Everything. Stephen Hawking famously proposed in 1988 that one day physicists would “know the mind of God”. Leon Lederman wrote a book about the mysterious entity now being pursued at Cern and called it “the God particle”.

And then, as part of the defensive apparatus for the awesomely ambitious Superconducting Supercollider, then taking slow shape in the chalky bedrock of Texas, Weinberg delivered this book in 1992. It is many things: a reflection on the nature of science; a short history of research into the ultimate nature of matter; a lesson in the exquisite conundrums of mathematical physics; a straightforward but tactful defence of Big Science – big on a billion-dollar scale – and a bit of straight talking on what science is not likely to reveal about the mind of God. There is a very instructive essay on what physicists mean when they equate beauty with truth and an expert but not necessarily fair kicking for the philosophers of science.

The surprising thing is that the book doesn’t feel in the least out of date. Since first publication, physicists have demonstrated quantum entanglement and experiments in teleportation; they have built the once-theoretical fifth state of matter, the Bose-Einstein condensate; they have used such technology to slow a beam of light first to bicycle speed, and then to a standstill; they have stopped talking about cosmic string and introduced branes instead; they have extended the idea of a multiverse; and they have identified an entirely new feature called dark energy, that accounts for three quarters of the whole detectable cosmos. So why is his book still a great read?

There are three reasons. One is that Weinberg writes with clarity and an old-fashioned feeling for a good sentence (in the preface, he rather casually drops the names of Tacitus, Edward Gibbon and Samuel Eliot Morison as historians that he reads for pleasure). The second is that he is restating a question that has been on papyrus or in print for at least three thousand years: why is the world as it is and who or what made it that way? Universal and timeless questions have universal and timeless appeal. The third is obvious: the book is still entirely up-to-date because 20 years on, nobody has got anywhere near the discovery of a Final Theory.

Whatever the answer – if there is an answer – rests on evidence of events that might have happened in the first billion trillionth of a second of time, and such a recreation requires a massive accelerator. The SSC was brutally cancelled in the mid-nineties, leaving a large hole in the Texan bedrock. The Large Hadron Collider at Cern in Geneva has only half the design energies that were planned for the SSC, and because of technical problems right at the start, the LHC is still only running at half-power.

And even before start-up, there were hints that the answers from the LHC might not suffice: both the Cern Council and the US theoretical physics community have been making a case for an even bigger machine, called the linear collider. That suggests that the experimental physicists don’t expect a Final Theory in a hurry.

And anyway, says Weinberg, a Final Theory, once found, won’t be the end of science: it will just be the end of one particular kind of science. He makes it clear that he thinks it must be out there, like the North Pole, even if we never reach it.

He contemplates the possibility that we might just not be clever enough to know it when we see it (“It is possible to train dogs to do all sorts of clever things, but I doubt that anyone will ever train a dog to use quantum mechanics to calculate atomic energy levels.”) And he worries just a little bit about the way our daydreams might contract if and when the search comes to an end. Weinberg is the man who famously once wrote “The more the universe seems comprehensible, the more it also seems pointless,” and yes, he talks a little too about how that phrase has dogged him for decades.

Written by physicsgg

July 8, 2011 at 1:46 pm

Posted in High Energy Physics

Tagged with

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: