Last summer Discover was a lead sponsor of the celebration of Albert Einstein at the Aspen Institute in Colorado. Our September special issue on Einstein—“100 Years of Genius Without Limits”—served as a primer for the gathering, four glorious days of talk and think on topics like “Culture in the Age of Space-Time Relativity” and “Einstein the Empiricist and the Frontiers of Condensed Matter Physics.” Heady it was, but no one, no matter what his or her background in science, ever seemed lost. There were meaningful moments of insight from the likes of Nobel Prize–winning physicist Murray Gell-Mann, author E. L. Doctorow, Astronomer Royal Sir Martin Rees, and physicist Michio Kaku, the author of this month’s cover story.
Kaku’s story is an outgrowth of a session at Aspen called “Einstein’s Unfinished Symphony,” which was supposed to be a discussion about the great physicist’s long and unsuccessful effort to come up with a unified field theory—what has become known as a theory of everything. Einstein struggled to reconcile the fact that tiny things at the quantum level (energy packets and matter smaller than an atom) do not behave the same as larger things like desks and planets. Einstein once described aspects of quantum mechanics as “spooky,” and he felt that a new way of understanding physics was necessary to merge the quantum world and the world we see around us into a unified, understandable universe.
On the stage at Aspen were four remarkable physicists: Brian Greene, S. James Gates, Sheldon Glashow, and Lawrence Krauss. Within moments, it was clear that the four were divisible into two worlds as separate as the quantum and the full size. That’s because Greene and Gates are string theorists, and Glashow and Krauss are particle physicists. Greene and Gates believe string theory could accomplish what Einstein was after: one explanation for how all matter, energy, and forces in the universe behave. Glashow and Krauss believe string theory is a fantasy that has been deemed credible for far too long and that string theorists are sucking up the resources and the best students that physics has to offer.
To give you just a glimpse of the convictions involved, we asked Krauss, whose intriguing book Hiding in the Mirror: The Mysterious Allure of Extra Dimensions, From Plato to String Theory and Beyond is coming out in October, to riff a bit on what he’s thinking these days. He e-mailed us:
“String theory may be in a worse position now regarding being testable than it has been at any time in the past 20 years. What we have learned from all of the remarkable activity in this area is that we understand the theory far less than we thought we did, and the ultimate theory is far more complex (those charitable would say far richer) than had been envisaged, and it may not resemble anything that has been discussed to this point. Strings themselves may not even be fundamental objects. It is quite possible that (a) string theory has nothing to do with the universe in which we live or (b) even if it does, that we will never have an empirical way of knowing it. We have new windows opening, which could provide information on fundamental physics, such as the Large Hadron Collider and the Laser Interferometer Space Antenna mission. However, this is largely independent of the work on string theory (outside of the unlikely possibility that extra dimensions will be directly observed at the Large Hadron Collider). Finally, while the mathematical developments that have occurred over the past 20 years have been remarkable, string theory has had little impact on the rest of physics outside of providing new mathematical tools and interesting possibilities for theorists to explore—something that is not without merit, but something that should also not be turned into more than it is.”
Talk like that is why we came away from Aspen asking Kaku, a cofounder of string theory and a keen communicator, to put up or shut up. If we can’t exactly prove string theory is correct, we asked, can we at least see a light down the tunnel of experimentation? Not surprisingly, he had a rich and thoughtful reply. You can read it by turning the page.