Cosmic Bubble Bath

"WHY IS THE UNIVERSE so bubbly?" asks Mercelo Gleiser

Bubbly?

"Look out at the universe," says the physics prof with a hint of Brazilian accent. "It's full of complicated structures, big galaxies distributed in the universe very mysteriously. If you look into deep space, each dot you see is a galaxy." He shifts excitedly from the visible to the hidden. "Let's say the universe is a box. You would expect it to be homogeneous. But that's true only if you look over the large scale. It turns out that the universe is like a bubble bath. Galaxies live on top of the surfaces of the bubbles, and there are voids where there is nothing that's the inside of the bubble."

Now most of us have gotten used to the image of the Big Bang exploding the universe into being some 15 billion years ago. Einstein's mathematical formulations some 70 years ago pointed the way to the theory that George Lemaitre spelled out in 1927. Many people are familiar with the red and blue shifts that, Doppler-like, show the stellar movements that indicate the universe is not yet finished expanding and may eventually stretch so far that it implodes into itself, like bread dough left to rise too long. But a cosmic bubble bath? Where did that idea come from?

As with so much of cosmology's quest to know how the universe got to be the way it is, such images spin off from the ongoing-explanatory tango between the observable and the theoretical in both physics and math. "Mathematical models explain the origins of the universe, how it appears from nothing," says Gleiser who was one of the star professors at last summer's Alumni College on Riddles of Creation. "But there's a big flaw in the argument: Where do the laws we use to build these models come from? We have to develop the physics to explain the origin of these laws. Physics can't do this now." But modern physics can explain more about the universe, current and past, than humankind has ever been able to before. In fact, according to Gleiser, firm cosmological explanations now run clear back to only a hundredth of a billionth of a second after the Big Bang itself. In trying to crack what happened in that split second after the Bang, cosmologists are attempting a unifying picture that would explain every structure in the universe, from the smallest subatomic particles to the vastness of galaxies and intergalactic space. To Gleisr who recently won a Presidential Faculty Fellow Award complete with a $500,000 research grant from the National Science Foundation, the problem of how it all began is as profoundly absorbing as a black hole.

"Let's roll the film backwards," he says, beginning the theoretical journey back to the Bang. Reversing the expansion that astronomers and astrophysicists can measure today, Gleiser takes us back some 14 billion years, to the time when galaxies were first forming out of cooled gas clouds.

Traveling further back to when the universe was a 300,000-year-old infant, Gleiser leads us into the realm of atomic synthesis. Electrons and protons fused into atoms, leaving gamma rays photons produced during nuclear fusion, fission, and radioactive decay to stream around the universe. George Gamow, the nuclear physicist who developed the Big Bang theory in detail during the late 1940s, actually predicted that the universe was full of such "background radiation" from its early history, but the radiation wasn't detected until Bell Telephone Laboratory workers stumbled onto it in 1964. The discovery convinced cosmologists they were indeed on the right path back to the beginning of time.

Now Gleiser jumps to a mere second after the Big Bang, when nucleosynthesis, studied through nuclear physics, glued protons and neutrons together.

We go back even farther, via "strong interaction" physics, to a thousandth of a thousandth of a second after the Bang. Here we encounter the "quark-hadron transition," when subatomic particles called quarks were getting together to form protons and neutrons.

And finally particle physics Gleiser's specialty inches us back to an amazing hundredth of a billionth of a second after the Bang, when quarks floated freely in a kind of cosmic soup. At this point nature's four forces the easily observable gravitational and electromagnetic, and the more hidden strong and weak forces that bind atoms appear as only three, for in what physicists call the first unification, the electromagnetic and weak forces act the same. Physicists can actually replicate this unification with particle accelerators like the one at Fermilab outside Chicago, where Gleiser conducts much of his research.

What they can't do yet in the lab is get any closer to the Big Bang. "Now physics is into speculations," Gleiser reports. The Grand Unification Theory yes, GUT seeks to explain how the strong force would unify with the electromagnetic/weak. And, says Gleiser, the goal of some physicists, including Einstein, is to finally reduce the four forces to one. This, they theorize, is the original state of the universe.

"If that's true, and the forces started to get separated, how did this occur?" Gleiser asks, reversing the journey and entering the realm of his own research. "As the universe expands, gets colder and less symmetric, how did the symmetry get broken?" Through complicated math and computer models he runs in his Dartmouth office, he simulates the breaking of symmetry in the universe and studies the impact. In classes, especially his wildly popular "Physics for Poets," Gleiser pulls out simpler models of the broken symmetries that abound in nature. "Water in a bottle is symmetric, but as it freezes, crystals form, with molecules living in the vertices and nothing in between," he explains. "By cooling water, we broke the symmetry."

And that leads Gleiser back to the cosmic bubble bath: "The bubbly universe looks like broken symmetry."

As the universeexpands, so do theexplanations of howit all began.