Tag: LHC

The Higgs boson

Clarity of thought courtesy of The Economist

Like many people I had been aware of the hunt for this strange particle, the Higgs boson.  Like many people as well, I suspect, I really didn’t comprehend what it was all about.

Then in The Economist print edition of the July 7th the newspaper’s primary story and leader were about the discovery of the Higgs announced on the 4th July.  The leader, in particular, was both clear and compelling.  I held my breath and asked for permission to republish that leader in Learning from Dogs.

Well the good people from the relevant department at The Economist promptly gave written permission for their leader to be available here for a period of one year.  Thanks team!

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The Higgs boson

Science’s great leap forward

After decades of searching, physicists have solved one of the mysteries of the universe

Jul 7th 2012 | from the print edition

HISTORICAL events recede in importance with every passing decade. Crises, political and financial, can be seen for the blips on the path of progress that they usually are. Even the horrors of war acquire a patina of unreality. The laws of physics, though, are eternal and universal. Elucidating them is one of the triumphs of mankind. And this week has seen just such a triumphant elucidation.

On July 4th physicists working in Geneva at CERN, the world’s biggest particle-physics laboratory, announced that they had found the Higgs boson. Broadly, particle physics is to the universe what DNA is to life: the hidden principle underlying so much else. Like the uncovering of DNA’s structure by Francis Crick and James Watson in 1953, the discovery of the Higgs makes sense of what would otherwise be incomprehensible. Its significance is massive. Literally. Without the Higgs there would be no mass. And without mass, there would be no stars, no planets and no atoms. And certainly no human beings. Indeed, there would be no history. Massless particles are doomed by Einstein’s theory of relativity to travel at the speed of light. That means, for them, that the past, the present and the future are the same thing.

Deus et CERN

Such power to affect the whole universe has led some to dub the Higgs “the God particle”. That, it is not. It does not explain creation itself. But it is nevertheless the most fundamental discovery in physics for decades.

Unlike the structure of DNA, which came as a surprise, the Higgs is a long-expected guest. It was predicted in 1964 by Peter Higgs, a British physicist who was trying to fix a niggle in quantum theory, and independently, in various guises, by five other researchers. And if the Higgs—or something similar—did not exist, then a lot of what physicists think they know about the universe would be wrong.

Physics has two working models of reality. One is Einstein’s general relativity, which deals with space, time and gravity. This is an elegant assembly of interlocking equations that poured out of a single mind a century ago. The other, known as the Standard Model, deals with everything else more messily.

The Standard Model, a product of many minds, incorporates the three fundamental forces that are not gravity (electromagnetism, and the strong and weak nuclear forces), and also a menagerie of apparently indivisible particles: quarks, of which protons and neutrons, and thus atomic nuclei, are made; electrons that orbit those nuclei; and more rarefied beasts such as muons and neutrinos. Without the Higgs, the maths which holds this edifice together would disintegrate.

Finding the Higgs, though, made looking for needles in haystacks seem simple. The discovery eventually came about using the Large Hadron Collider (LHC), a machine at CERN that sends bunches of protons round a ring 27km in circumference, in opposite directions, at close to the speed of light, so that they collide head on. The faster the protons are moving, the more energy they have. When they collide, this energy is converted into other particles (Einstein’s E=mc2), which then decay into yet more particles. What these decay particles are depends on what was created in the original collision, but unfortunately there is no unique pattern that shouts “Higgs!” The search, therefore, has been for small deviations from what would be seen if there were no Higgs. That is one reason it took so long.

Another was that no one knew how much the Higgs would weigh, and therefore how fast the protons needed to be travelling to make it. Finding the Higgs was thus a question of looking at lots of different energy levels, and ruling each out in turn until the seekers found what they were looking for.

Queerer than we can suppose?

For physicists, the Higgs is merely the LHC’s aperitif. They hope the machine will now produce other particles—ones that the Standard Model does not predict, and which might account for some strange stuff called “dark matter”.

Astronomers know dark matter abounds in the universe, but cannot yet explain it. Both theory and observation suggest that “normal” matter (the atom-making particles described by the Standard Model) is only about 4% of the total stuff of creation. Almost three-quarters of the universe is something completely obscure, dubbed “dark energy”. The rest, 22% or so, is matter of some sort, but a sort that can be detected only from its gravity. It forms a giant lattice that permeates space and controls the position of galaxies made of visible matter (see article). It also stops those galaxies spinning themselves apart. Physicists hope that it is the product of one of the post-Standard Model theories they have dreamed up while waiting for the Higgs. Now, they will be able to find out.

For non-physicists, the importance of finding the Higgs belongs to the realm of understanding rather than utility. It adds to the sum of human knowledge—but it may never change lives as DNA or relativity have. Within 40 years, Einstein’s theories paved the way for the Manhattan Project and the scourge of nuclear weapons. The deciphering of DNA has led directly to many of the benefits of modern medicine and agriculture. The last really useful subatomic particle to be discovered, though, was the neutron in 1932. Particles found subsequently are too hard to make, and too short-lived to be useful.

This helps explain why, even at this moment of triumph, particle physics is a fragile endeavour. Gone are the days when physicists, having given politicians the atom bomb, strode confidently around the corridors of power. Today they are supplicants in a world where money is tight. The LHC, sustained by a consortium that was originally European but is now global, cost about $10 billion to build.

That is still a relatively small amount, though, to pay for knowing how things really work, and no form of science reaches deeper into reality than particle physics. As J.B.S. Haldane, a polymathic British scientist, once put it, the universe may be not only queerer than we suppose, but queerer than we can suppose. Yet given the chance, particle physicists will give it a run for its money.

Copyright © The Economist Newspaper Limited 2012. All rights reserved.

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Before signing off on this very important step forward for physics, here are a couple of footnotes.

First, here’s a video of the announcement that was widely shown on the 4th.

Secondly, the BBC News website had a really good piece on the 12th July written by their science correspondent, Quentin Cooper, called Higgs: What was left unsaid. Here’s a flavour taken from the early part of the article,

So that’s it, search over, Higgs boson found. Almost 50 years after physicist Peter Higgs first theorised it was out there, public elementary number one has finally been captured in the data from two detectors at the Large Hadron Collider at Cern. Case closed. Champagne popped. Boson nova danced.

If only. That handily simplified and heavily fictionalised telling of the tale has helped transform a spectacular scientific success story into one that is also global front page news. Without it the 4 July announcement might not have generated such a frenzy of coverage and so many claims about it being a historic milestone for our species. One particle physicist only half jokingly told me that in future the date may come to be celebrated as Higgs Day, rather than anything to do with American independence.

Don’t get me wrong. What has happened at Cern represents a magnificent accomplishment; big science at its biggest and boldest. And it’s fantastic that it has been perceived and received as being of such importance. It’s just that there is more to the story from the very beginning right through to the, probably false, ending.

For starters, as Peter Higgs himself acknowledges, he was just one of several scientists who came up with the mechanism which predicted the particle which bears his name, but the others rarely get a mention*. As to the finish – well, as small children are fond of saying, are we there yet? There is very strong evidence that the LHC teams have found a new elementary particle, but while this is exciting it is far less clear that what they’ve detected is the fabled Higgs. If it is, it seems curiously lighter than expected and more work is needed to explain away the discrepancy. If it’s not, then the experimentalists and theorists are going to be even busier trying to see if it can be shoehorned into the current Standard Model of particle physics. Either way, it’s not exactly conclusive.

Do take the simple step of clicking here and read the BBC piece in full.

Well done, Mr. Peter Higgs and all those very persistent scientists associated with the Large Hadron Collider; I suspect we haven’t heard the last of this!

And ‘thank you’ to The Economist.

One smart brain!

Black holes, colliders and paradoxes

This is a very strange world that we live in.

It would be fair to say that my knowledge about what I am writing in this Post is minimal to the point of total ignorance.  So why open my mouth and prove it!  Because the conquest of fundamental questions about our world is not only an example of mankind at its greatest but also something of broad appeal.

That is proved by the continuing popularity of the BBC Television Series – Horizon.  In that series there have recently been two fascinating programmes: Who’s afraid of a big Black Hole? and How long is a piece of string? (Readers outside the UK will not be able to view these programmes.)

Here are the programme summaries:

Black holes are one of the most destructive forces in the universe, capable of tearing a planet apart and swallowing an entire star. Yet scientists now believe they could hold the key to answering the ultimate question – what was there before the Big Bang?

The trouble is that researching them is next to impossible. Black holes are by definition invisible and there’s no scientific theory able to explain them. Despite these obvious obstacles, Horizon meets the astronomers attempting to image a black hole for the very first time and the theoretical physicists getting ever closer to unlocking their mysteries. It’s a story that takes us into the heart of a black hole and to the very edge of what we think we know about the universe.

and

Alan Davies attempts to answer the proverbial question: how long is a piece of string? But what appears to be a simple task soon turns into a mind-bending voyage of discovery where nothing is as it seems.

An encounter with leading mathematician Marcus du Sautoy reveals that Alan’s short length of string may in fact be infinitely long. When Alan attempts to measure his string at the atomic scale, events take an even stranger turn. Not only do objects appear in many places at once, but reality itself seems to be an illusion.

Ultimately, Alan finds that measuring his piece of string could – in theory at least – create a black hole, bringing about the end of the world.

Read more of this strange world