Posted on 06/09/2003 6:11:13 AM PDT by andy224
Atlas holds key to scientists' map of Universe By Mark Henderson A vast cavern is the stage for tests to find the 'God particle'
SCIENTISTS have taken a step closer to finding the “God particle” that is thought to shape the Universe. In a concrete cavern 130ft deep and bigger than the nave of Canterbury Cathedral, they will mimic the high-energy conditions that existed fractions of a second after the Big Bang to study a beam of energy a quarter of the thickness of a human hair.
The vast Atlas cavern, which was completed last week at Cern, the European nuclear physics laboratory on the Franco-Swiss border, will house parts of a giant atom-smasher that is expected to solve the most elusive riddle in physics.
When the £1.5 billion Large Hadron Collider (LHC) is switched on in 2007, it will determine once and for all whether the Higgs boson, a mysterious fundamental particle held to give matter its mass, really exists. If the machine finds the boson, proposed by Professor Peter Higgs of Edinburgh University in 1964, it will prove that the Standard Model for the nature of the Universe is correct. If not, the maxims of modern physics will be thrown into disarray.
The boson was nicknamed the “God particle” by the Nobel laureate Leon Lederman for its centrality to the cosmos. Although it will be so small that its presence can only be calculated, not seen, the search for it requires some of the largest and most advanced scientific instruments designed.
The LHC itself is a ring 17 miles (27km) in circumference, buried up to 100m (330ft) underground, through which streams of protons will be bent by the world’s most powerful magnets and smashed into each other at close to the speed of light.
The new cavern, which will house the Atlas detector for tracking the Higgs and other particles, is 40m (130ft) deep, 55m (180ft) long and 35m (115ft) wide.
However, the proton beam that runs through both devices measures just 10 microns in diameter: less than a quarter of the thickness of the average human hair. Roger Cashmore, a British physicist and Cern’s director of research, said: “It is an astonishing feat of engineering. The consultants were on the verge of saying it was impossible to build. But the Atlas cavern is finished, the biggest of its kind in the world, and these experiments are going to tell us whether we’re right about the Universe.”
The current best guide to the nature of the Universe is the Standard Model, an elegant theory that describes how most particles and forces interact. The Higgs boson is its missing keystone: without it, there is no good explanation for why matter has mass and therefore exists.
According to the theory, the Universe is permeated by a field of Higgs bosons, which consist of mass but very little else. As particles move through the field, they interact with it like a ball dropped into a tub of treacle, getting slower, stickier and heavier. Their ultimate mass depends on the strength of the interaction.
Though mathematics predicts its existence, the Higgs boson has never been detected. It is so heavy that the biggest atom-smashers, Cern’s Large Electron-Positron collider (LEP) and the Tevatron at Fermilab in Illinois, have been unable to generate the high energy collisions needed to reveal it, although they have found hints that it is probably there. This is where the LHC comes in. It is 70 times as powerful as the LEP and seven times stronger than the Tevatron, covering all the energy values at which the Higgs might exist. If it is there, it will find it.
What is more, if the “God particle” proves to be a false deity, the LHC will unlock the secret of what is out there instead. “If it doesn’t find the Higgs, it will find what substitutes for it,” Dr Cashmore said.
Jim Virdee, Professor of Physics at Imperial College, London, and a leading Cern researcher, said: “There has to be something else, beyond what we have found already, that explains mass. We believe it’s the Higgs, but Nature may be smarter than us. Either way, the results will tell us what is the right road.”
The atom-smasher will accelerate protons so close to the speed of light that they become 7,000 times heavier than normal. The beams are bent into a circle by superconducting magnets, cooled by liquid helium at -271.4C, almost a degree colder than outer space.
When the protons collide, they are destroyed in a huge burst of energy. This energy coalesces into very heavy particles, one of which scientists hope will be the Higgs.
As the boson is unstable, it will quickly decay, scattering a characteristic signature of smaller particles and energy. These will be picked up by the LHC’s eyes — the Atlas and a sister detector — which surround the collision points.
The detectors, which stand 22m (72ft) and 15m (49ft) tall respectively, are “giant microscopes” built like onions, with several layers of instruments that track particles and measure energy.
The experiments will generate enormous quantities of data, much of it unwanted. “Colliding two protons is like colliding two oranges,” Dr Lyn Evans, director of the LHC project, said. “You’ll occasionally get a collision between two pips, the interesting bits, but you’ll get a lot of pulp. We need to reject an enormous amount of data to pick out the important bits.” Professor Virdee said that the data generated in one second was the equivalent of what all the world’s telecommunications generated in one year.
Even if this wealth of information proves the existence of the Higgs boson, the LHC will continue to serve scientific knowledge for decades.
“Let’s say we have the Higgs,” Dr Cashmore said. “I’d feel warm and content for a few microseconds, then I’d be asking new questions. Why does it affect different particles in different ways? “It would be spectacularly good to find it — I’m not trying to knock it — but it will pose a whole new set of problems. If we are an inquisitive society, these are the things we ought to be doing."
I must admit I've started the book numerous times before only to toss it aside in frustration. My innate weakness in mathematics makes it very hard to plow through.
Anybody read it?
A common misconception. The Higgs mechanism gives the fundamental particles (such as quarks and electrons) their masses, but most of the mass we see comprises protons and neutrons, whose mass arises primarily from quantum chromodynamics. (Dark matter, which dominates over the "baryonic" matter I mentioned, may or may not get its mass from the Higgs mechanism.)
Yes, but can't claim to have followed all of it.
Good question.
They can because the direct observations we make of the early universe place very tight constraints on what the conditions of the very early universe could possibly have been. The conditions are so incredibly tight, in fact, that for many years they were considered to pose a philosophical problem for physics: how was it possible that conditions in the Big Bang were so "finely tuned" that the universe ended up the way it did? If you make a change in even the 50th decimal place, up or down, in any of a number of variables, you get either runaway expansion or nearly immediate collapse.
Nowadays we don't worry about that problem, because the theory of Inflationary Cosmology accounts for that exquisite balance. This model also makes a number of extremely detailed predictions about the Cosmic Microwave Background Radiation, and these preditions have been verified in stunning detail by recent observations with the WMAP probe.
So we're confident that Inflation is reasonably close to the truth. From there, inferring the conditions close to the Big Bang is a matter of straightforward calculation. If those conditions had been ever so slightly different, the universe would look very different from the way it does now.
According to the theory, the Universe is permeated by a field of Higgs bosons,...
Then I read that:
As the boson is unstable, it will quickly decay...
How can the Universe be permeated by a field of unstable, rapidly decaying particles?
How about we shove about 50 Texas Democratic State Reps in it and then backfill?
PLEASE! Someone can be found who is offended by anything that is posted. ;-)
An interesting assertion, although unrelated to the precedent ironic observations.
What are you wailing about? RWP is still in good standing. If he chooses not to participate, that is his choice (this has happened before).
I think that was needed to make his point(IOW it was related). It is akin to the assertion that we need to spend more money on "Art" and "education". The education system is the epitome of the "spend the people's money" approach. If you spend money and the spending achieves your goal, spend more money for even more benefits. If you spend money and the results are not achieved, spend even more money to fix the "problem".
They decay rapidly in the free state. When bound they live forever, nearly.
We argue about how to do this, what to spend it on. For example, gov't is encouraging consumers to buy homes, encouraging it as much as they can. It might seem like we are each choosing how to spend our personal funds if we don't understand the purpose of money.
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