Saturday, March 22, 2008
Collider may show us what's inside an atom
Over in Europe, scientists are getting ready to turn on a huge machine. In fact, it is the biggest machine that human beings have ever built, and one of the most expensive. The machine is called the Large Hadron Collider, or LHC, and scientists hope that it will help them unlock some of the deepest, darkest secrets of the universe.
What are some of these secrets? It turns out that there are all sorts of things that scientists don't know about the universe. For example, where does "mass" come from? We know that all things made of atoms have mass, but we don't actually know where mass comes from. And speaking of mass, why can't we see lots of it? When we try to measure the mass of the universe, it seems to be a lot heavier than it should be. There seems to be lots of matter in the universe that we can't see. What is this "dark matter", and where is it hiding? And what about black holes? Can we create tiny black holes, and if we can, how do they behave? What can we learn from them? We may be able to answer all of these questions and many more using the LHC.
What is the LHC, and how does it work? It is an incredibly complex machine. But if we start with the basics, we can understand the essence of the LHC.
We have all heard of atoms. We can make water, for example, by combining hydrogen atoms with oxygen atoms. That's easy enough. What is inside an atom? Using fairly simple experiments at the beginning of the twentieth century, scientists were able to discover electrons, protons and neutrons. By the way, protons and neutrons are known as hadrons.
The next question is obvious: What is inside a hadron? This is not so easy a question to answer. But, scientists discovered that they could bash two protons together to learn what's inside. The machine that does the bashing is called a particle accelerator, also known as an atom smasher.
The earliest particle accelerators were very simple and could fit in the palm of your hand. By building bigger and bigger particle accelerators, scientists could learn more and more. The basic idea behind a particle accelerator is simple. You take a particle like a proton, and you put a group of them in a sealed tube. You take all the air out of the tube using a vacuum pump, so the protons don't have anything to run into. Then, using microwave energy (a lot like the energy used in a microwave oven), you accelerate the protons.
Most particle accelerators are shaped like rings, and they contain magnets that steer the protons around the ring and keep the protons bunched together. As the protons accelerate, their speed gets closer and closer to the speed of light.
Protons are incredibly tiny, but at the speed of light they have a lot of energy. To understand this, think about a baseball. If a little kid throws a baseball at you, it probably won't even hurt. If a major league pitcher throws a 100 mph fastball at you, it will hurt a lot. If someone shoots a baseball out of a cannon at 500 mph and it hits you, it will kill you. A proton in a particle accelerator is going 186,000 mph, and it has a lot of energy despite its tiny size.
The Large Hadron Collider is the biggest particle accelerator ever built, and it will create the fastest protons human beings have ever created. Its ring is more than 5 miles in diameter and has a tube 17 miles long. And the LHC actually has two tubes, so that two groups of protons can accelerate in opposite directions. The scientists will then slam the two streams of protons together in the biggest head-on collision ever.
The collision will happen in an underground detector room that is as big as a warehouse. The detector is basically a gigantic, specialized movie camera that can sense all of the debris that flies out from the collision. The debris contains the particles that make up the protons -- things like quarks and leptons. The only reason that we know that quarks and leptons exist is because we have particle accelerators.
Because the collisions in the LHC will be so massive, scientists are hoping that they will see new particles that no one has ever seen before. For example, scientists think there's a particle inside atoms called the Higgs Boson, and that this particle is the thing that gives atoms mass. But scientists have never witnessed a Higgs Boson, so they don't know whether it exists. Scientists also hope that the LHC will have enough energy that they are able to create mini black holes, which will then immediately evaporate because they are so small. And maybe scientists will find new particles that no one has ever imagined before.
Because of these possibilities, scientists all over the planet are excited about the LHC, and thousands of scientists are working on the project. With luck, they can start accelerating their first protons sometime in 2008 and begin making new discoveries. We should learn many new things about how the universe works from the LHC.
The Large Hadron Collider and the Hunt for The God Particle
Its purpose is simple but ambitious: to crack the code of the physical world; to figure out what the universe is made of; in other words, to get to the very bottom of things. Starting sometime in the coming months, two beams of particles will race in opposite directions around the tunnel, which forms an underground ring 17 miles in circumference. The particles will be guided by more than a thousand cylindrical, supercooled magnets, linked like sausages. At four locations the beams will converge, sending the particles crashing into each other at nearly the speed of light. If all goes right, matter will be transformed by the violent collisions into wads of energy, which will in turn condense back into various intriguing types of particles, some of them never seen before. That’s the essence of experimental particle physics: You smash stuff together and see what other stuff comes out.
What scientists hope “comes out” is evidence of the Higgs Boson, the so-called God Particle:
Most physicists believe that there must be a Higgs field that pervades all space; the Higgs particle would be the carrier of the field and would interact with other particles, sort of the way a Jedi knight in Star Wars is the carrier of the “force.” The Higgs is a crucial part of the standard model of particle physics—but no one’s ever found it.