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Scientists Celebrate Breakthrough With Particle Collider

September 10, 2008 at 6:40 PM EDT
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In an effort to understand some of the basic tenets of physics, scientists and engineers fired a beam of protons around a 17-mile tunnel Wednesday -- a successful first run for the world's most powerful particle accelerator. Brian Greene, host of the PBS series "Elegant Universe," explains the feat.

JIM LEHRER: And to Jeffrey Brown.

JEFFREY BROWN: Well, we just saw the cheering for success and the animation of what’s going on at the Large Hadron Collider, as it’s called.

To help us understand what it all means, we turn to Brian Greene, professor of mathematics and physics at Columbia University, and host of the PBS series “The Elegant Universe.” His most recent book is “Icarus at the Edge of Time,” a look at the science of black holes.

Well, before you tell us how it works, maybe it will help to explain what scientists are trying to do. What is this all about?

BRIAN GREENE, Professor of Mathematics and Physics, Columbia University: Well, our goal is to figure out the fundamental particles that make up everything in the universe and the fundamental forces by which they interact.

So, one powerful way to do that is to slam particles together at fantastically high speeds and examine the debris, examine the behavior of the debris. And, in that data, we hope to gain insights into these fundamental questions about the universe.

JEFFREY BROWN: What — what kind of questions?

BRIAN GREENE: There are many of them. A question that we have struggled with for a long time is, what gives particles the mass that they have?

And a proposal was put forward, oh, about 40 years ago, something called the Higgs field. The idea is, we are immersed in a field, much like the electromagnetic fields that make up cell phones and radio broadcasts. And, as particles try to go through the field, this field acts like a molasses that creates a drag force on the particles that gives them the mass that we associate with them.

Now, if this is true, in these collisions, we should be able to chip a little piece of this field off as a little particle, a Higgs particle. And if we find that particle, this will be a moment for celebration in the physics community worldwide.

Recreating energy collisions

JEFFREY BROWN: You know, it's interesting to look at that collider. And everything is on such a large scale, 17 miles. But all of those big things are to look at the smallest things, right? What do you mean...


JEFFREY BROWN: What do you mean when you say that these are -- that the protons are collided? What actually happens? How does it work?

BRIAN GREENE: It really is what the word seems to indicate.

You know, you have these protons that are cycling around the 17-mile-long tunnel. And these magnets will direct them every so often into these head-on collisions. They will simply slam into each other. And when they do that, they don't merely pulverize themselves. They take the energy of impact, and allow that energy to retransform itself into other species of particles.

Now, our hope is, when that energy reconstitutes itself as particles, we will find particles that we as yet have never seen before. And that's the way we can get these key insights.

JEFFREY BROWN: Is it correct to think of this as attempting to recreate that moment to right around or right after the big bang?

BRIAN GREENE: It's a pretty good way of thinking about it.

The energetic collisions that we are talking about would have been commonplace around roughly a millionth-of-a-second after the beginning, after the big bang. So, roughly speaking, in a laboratory setting, we're trying to recreate, as close as we can, a little piece of the conditions that took place way back, just after the beginning of time.

Identifying dark matter

JEFFREY BROWN: Now, you said we might be finding things that we haven't seen before. One of them, I guess, is the so-called dark matter.

BRIAN GREENE: Yes, dark matter is a puzzle that we have struggled with for decades.

When we look at the motion of stars and galaxies, the stuff up there in the heavens that gives off light, we see that they're moving in a pattern that cannot be accounted for if the gravity that's out there is only exerted by the stuff that gives off light. There must be other stuff out there that is dark, not giving off light, that is exerting some gravity to account for what we see.

The puzzle is, what is that dark stuff? The observations show us that 30 percent, roughly 30 percent of the universe might be made up of this dark stuff, but what is it? The Large Hadron Collider has the capacity to identify what the dark matter is.

Again, in these collisions, we may create certain particles. They're called supersymmetric particles. The name is not all that important, but these are species of particles that physicists believe may constitute the dark matter.

So, there is a chance that, when this experiment is finished, we will know what this 30 percent component of the universe actually is, whereas, today, we don't.

JEFFREY BROWN: Now, the head of the installation referred to this as a discovery machine. I have also heard some people referring to it, more darkly, as a doomsday machine. And that is the reference to its potential ability to create black holes, and with all of that -- that that implies in people's heads of -- I don't know what -- sucking the Earth into it.

But explain that to us, and maybe you can debunk that for us.

Causing laboratory collisions


You know, it is possible that the Large Hadron Collider will create black holes. And that may sound odd at first, because most of us, when we hear the phrase black hole, think a big, gargantuan thing in space that is very massive, exerts powerful gravity, and, as you said, kind of pulls things in.

But, actually, black holes can be really tiny, too. As long as you crush enough matter and energy to a very small size, in principle, you can create a black hole.

Now, recently, physicists have realized that these high-energy collisions may cram enough energy into a sufficiently small volume to create a microscopic black hole. And this has caused some concern, this idea maybe this black hole will suck things in, suck in Geneva, Switzerland, the whole world, whatever.

This is not something to worry about. It is an interesting question to raise. But these microscopic black holes, we understand from work of Stephen Hawking, will evaporate in a tiny fraction of a section, before anything dangerous can happen.

And I might also add, on top of that, even if they didn't evacuate that quickly, the collisions that will happen at the Large Hadron Collider are the first time that energetic collisions of that sort will happen in the laboratory, but these kinds of collisions happen all the time in the universe, all around us.

There are cosmic ray particles, particles that stream through space, they rain down on the Earth, the moon, everything else. And they move with such a high velocity that the energy of the collision is greater than the energy of the collisions at the Large Hadron Collider.

So, we have survived these kinds of collisions for billions of years already. We simply haven't done them in the laboratory. That's the difference.


And these collisions, I understand, start up later this year, potentially.

Brian Greene, thank you very much for explaining to us.

BRIAN GREENE: My pleasure.