On Physics: Religion, Science & Extra Dimensions

In her new book, Knocking on Heaven's Door, Harvard University theorist Lisa Randall explores how physics may transform our understanding of the fundamental nature of the world. She thinks an extra dimension may exist close to our familiar reality, hidden except for a bizarre sapping of the strength of gravity as we see it. She also ponders the makeup of dark matter, unseen particles that have shaped the growth of the entire cosmos. These ideas, once the sole province of fiction writers, face real tests in a new generation of experiments. Sensitive detectors now sniff for dark matter, while the most complex scientific machine ever created, the Large Hadron Collider (LHC), beneath the border of Switzerland and France, smashes subatomic particles into one another at almost the speed of light.

What were your main goals for your new book?

One goal was to describe the science I'm interested in today: the physics happening at the LHC and searches for dark matter. But I also wanted to clarify the nature of science: what it means to be right and wrong, what it means to make measurements, and the roles of uncertainty, risk and creativity.

Do you feel the physics community is on the verge of finding something remarkable?

I certainly hope so. We have a good chance [with the LHC] to see the Higgs particle, which tells us how elementary particles acquire mass. Other deep issues include space-time symmetry and whether there are extra dimensions. We really do have a chance of making inroads on those subjects. There are a lot of bizarre ideas here, from string theory to a "brane" of extra dimensions right next to our own.

Why should we regard these ideas as more than fanciful constructs?

I'm certainly not asking anyone to take on faith any of the ideas that I present. That's part of the point of the book: science proceeds, and we systematically end up with new ideas and explanations, going from the human scales we're very familiar with to scales that are so remote it's hard to have intuition about them. Science is a self-correcting process, too, something that I expect will happen with the recent announcement of neutrinos that may move faster than the speed of light.

Can you describe the essence of your idea about extra dimensions?

There could be more to the universe than the three dimensions we are familiar with. They are hidden from us in some way, perhaps because they're tiny or warped. But even if they're invisible, they could affect what we actually observe in the universe. There are lots of things we cannot see with the naked eye that turn out to be based in reality. Extra dimensions could be relevant to one of the questions we're trying to answer at the LHC: how particles get their mass, and why they have the masses that they do, which are far smaller than physicists would expect them to be. So our idea is there's an extra dimension that's so warped, the masses would be big in one place and small in another. In other words, gravity could be weaker in one place and stronger in another. If so, it could be a natural explanation both for why particles masses are what they are, and why gravity is so much weaker than the other elementary forces we observe. This extra dimension could be separated from ours by a million trillion trillionth of a centimeter.

Is this a parallel yet inaccessible universe?

It interacts with our dimensions only via gravity. And gravity is extremely weak. An elementary particle at ordinary energies exerts negligible gravitational force. But at the LHC, if this idea is right, we would see evidence of this extra dimension. Particles could carry momentum into the extra dimension, and that could actually be observable.

But it's not something you think of as a "parallel universe?"

Technically, yes, it could exist parallel to our universe. But it's not just a carbon copy of our universe, which a lot of people think of when they hear that phrase. If physicists do find solid evidence of extra dimensions, how would that affect our view of the universe and our place in it?
You can have very exotic underlying phenomena, but they still would be consistent with the ordinary rules we're familiar with. At some level, it doesn't change anything. However, it means that at some deep underlying level, there's a much richer universe out there. It's just a wonderful thing to know what our universe is made of.

You describe the LHC as a "stupendous achievement."

Technologically, it's a tour de force. The fact that this thing works is amazing. We're looking for very rare events, so you need a very precise, very well understood machine to make them and detectors to understand what you see. You need an extreme amount of energy focused in a very tiny region to make these collisions happen, allowing the subcomponents of protons—quarks and gluons—to collide directly. And when they do, they can make new forms of heavier matter.Many people feared the LHC would produce a planet-devouring black hole. Scientists took it very seriously, and they ruled out this possibility not only theoretically, but also by looking at collisions of cosmic rays that create this same type of energy. We live in a world where there are many risks, and it's high time we start taking seriously which ones we should be worried about. Physicists showed this particular one is not a risk.

You offer a forthright discussion about religion and its compatibility with science. Why did you decide to broach that subject?

I almost had to in a book titled Knocking on Heaven's Door. But there is real confusion about what it means to be right and wrong—the difference between what spiritual beliefs are and what science is. I felt that if I was going to explain science, it was important to explain those distinctions. I wanted to take seriously the different views of the universe that people have, but to say there really are differences.

You wrote: "The religious part of your brain cannot act at the same time as the scientific one. They are simply incompatible.”

When I say they are incompatible, I mean something very specific: A spiritual belief based on something that isn't based on actual material or cause and effect—the ways we understand scientifically—is just different than science. It's a very specific statement.

When you speak to public audiences, which popular misconception about physics strikes you the most?

You're trying to get me in trouble! It's probably the over-application of quantum mechanics. People think it explains things that it can't. There are a lot of mysteries about quantum mechanics, but they mostly arise in very detailed measurements in controlled settings.

You describe the LHC's giant detectors as works of art. Is probing the nature of the universe just as much an aesthetic endeavor as a scientific one?

Art and science do appeal to some of the same creative instincts. There's an appreciation of something larger than ourselves, which I think both art and science address. However, you can have a beautiful idea in science, and it can be just wrong—not because it's mathematically inconsistent, but because it's not realized in the world.

-Robert Irion (“Opening Strange Portals in Physics,” Smithsonian magazine, September 2011. Image from The Twilight Zone, Spiral Staircase.)

Defining Higgs-Boson: The Celestial Mechanics of The God Particle...

"There are children playing in the streets who could solve some of my top problems in physics, because they have modes of sensory perception that I lost long ago."

-J. Robert Oppenheimer

The Higgs Mechanism:

"Imagine a cocktail party of political party workers who are uniformly distributed across the floor, all talking to their nearest neighbours. The ex-Prime Minister enters and crosses the room. All of the workers in her neighbourhood are strongly attracted to her and cluster round her. As she moves she attracts the people she comes close to, while the ones she has left return to their even spacing. Because of the knot of people always clustered around her she acquires a greater mass than normal, that is she has more momentum for the same speed of movement across the room. Once moving she is hard to stop, and once stopped she is harder to get moving again because the clustering process has to be restarted.

In three dimensions, and with the complications of relativity, this is the Higgs mechanism. In order to give particles mass, a background field is invented which becomes locally distorted whenever a particle moves through it. The distortion - the clustering of the field around the particle - generates the particle's mass. The idea comes directly from the physics of solids. Instead of a field spread throughout all space a solid contains a lattice of positively charged crystal atoms. When an electron moves through the lattice the atoms are attracted to it, causing the electron's effective mass to be as much as 40 times bigger than the mass of a free electron.

The postulated Higgs field in the vacuum is a sort of hypothetical lattice which fills our Universe. We need it because otherwise we cannot explain why the Z and W particles which carry the weak interactions are so heavy while the photon which carries electromagnetic forces is massless.

The Higgs Boson aka The God Particle:

Now consider a rumour passing through our room full of uniformly spread political workers. Those near the door hear of it first and cluster together to get the details, then they turn and move closer to their next neighbours who want to know about it too. A wave of clustering passes through the room. It may spread to all the corners or it may form a compact bunch which carries the news along a line of workers from the door to some dignitary at the other side of the room. Since the information is carried by clusters of people, and since it was clustering that gave extra mass to the ex-Prime Minister, then the rumour-carrying clusters also have mass.

The Higgs boson is predicted to be just such a clustering in the Higgs field. We will find it much easier to believe that the field exists, and that the mechanism for giving other particles is true, if we actually see the Higgs particle itself. Again, there are analogies in the physics of solids. A crystal lattice can carry waves of clustering without needing an electron to move and attract the atoms. These waves can behave as if they are particles. They are called phonons and they too are bosons. There could be a Higgs mechanism, and a Higgs field throughout our Universe, without there being a Higgs boson."

"I maintain that the cosmic religious feeling is the strongest and noblest motive for scientific research. Only those who realize the immense efforts and, above all, the devotion without which pioneer work in theoretical science cannot be achieved are able to grasp the strength of the emotion out of which alone such work, remote as it is from the immediate realities of life, can issue. What a deep conviction of the rationality of the universe and what a yearning to understand, were it but a feeble reflection of the mind revealed in this world, Kepler and Newton must have had to enable them to spend years of solitary labor in disentangling the principles of celestial mechanics." -Albert Einstein (New York Times Magazine, 11.9.1930).

- David Miller ( Article: "Politics, Solid State and the Higgs," Dept of Physics and Astronomy, University College, UK, 2000s. Image: -Woman as Higgs Mechanism, 1930s).