Higgs Force: The
Symmetry-Breaking Force that Makes the World an Interesting Place by Nicholas Mee
Literary Review, March 2012
Last December, with the
Internet having been awash with rumours for weeks, saw the official
announcement of the latest results in the search for the Higgs particle from
the fellowship of the ring – the physicists working at CERN’s 27km circular
Large Hadron Collider (LHC). The Higgs is the missing piece of the theory that
describes the behaviour of fundamental particles and the forces that act
between them. It plays a special role in giving all the other particles mass.
The teams running the two giant
detectors at the LHC independently put the mass of the Higgs, which is measured
in what physicists call gigaelectron volts (GeV), somewhere between 116–130 and
115–127 GeV respectively. Although the scope of the search for the Higgs has
now been narrowed, particle physicists demand an extraordinary degree of
precision in their measurements. As the CERN press release made clear, even a
98 per cent chance of being correct is ‘not yet strong enough to claim a
discovery’.
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| Particle collisions at CERN |
If all the data generated by
the LHC were stored on CDs it would fill more than a million every second. This
is one of the more astonishing facts that Nicholas Mee reports in his book Higgs Force. To overcome this problem
detectors are designed to be highly selective about the data passed on for
storage. When the LHC smashes beams of particles together there are a billion
or so collisions per second within the ATLAS detector alone, yet only the data
from a couple of hundred collision events that have the telltale signs of
interesting and possibly new physics are recorded.
The system that performs the
selection process and determines which information is discarded and which is
stored for analysis is called the trigger. Nicholas Mee acts as the trigger as
he selects the tales to tell of those whose work has helped reveal the
structure of matter and the laws of nature, culminating in the present hunt for
the Higgs particle. The result is an intellectual journey that ends at the LHC
near Geneva but begins with the Big Bang 13.75 billion years ago.
When the universe was born
there was only a single force, which Mee calls the Higgs force. Moments after
its birth the temperature began to fall as the universe expanded and the
original force was shattered into four disparate pieces. The strong force would
hold the quarks together in the atomic nucleus, while the weak force would
transmute matter and make the different elements. The electromagnetic force
would bind atoms and control their chemical reactions, and then there was
gravity. Mee focuses on the three forces that matter when it comes to particle
physics – electromagnetism, weak and strong – and attempts the difficult task
of trying to explain how physicists have discerned that although ‘the universe
began in a perfectly symmetrical state, the Higgs broke this symmetry and
enabled the matter that formed within the universe to evolve into complex and
diverse structures’. Without the Higgs particle the universe would have
remained in a state that was ‘homogeneous, lifeless and uninteresting’.
Most people have an intuitive
feel for what symmetry means. They recognise symmetrical patterns when they see
them. However, physicists understand symmetry in terms of transformation, such
as a reflection in a mirror, a rotation around an axis or a translation through
space. An object or a pattern possesses a symmetry if it does not change when
it is transformed in some way. For instance, if a snowflake is rotated around
its centre by sixty degrees (one sixth of a complete revolution), it will
appear exactly the same after the rotation as it did before. In fact all
rotations through multiples of sixty degrees are symmetries of a snowflake.
Symmetry has become fundamental
to the way that physicists view the universe, and an increased understanding of
the symmetries of nature has been one of the major themes in the development of
physics. When a quantity remains unchanged throughout a physical encounter it
helps physicists to disentangle the details of what might be an extremely
complicated event. This is true of the collisions that take place at the LHC.
Mee does an admirable job of explaining all this before tackling ‘spontaneous
symmetry breaking’, which lies at the heart of the Higgs story.
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| Peter Higgs |
This book is far broader and
more accessible than its title may suggest. For instance, we learn that the
scientific investigation of magnetism dates back to William Gilbert, the
personal physician of Elizabeth I. He was one of the first to try to understand
the workings of nature through experimentation rather than philosophical
argument. He concluded from his many experiments that the Earth is a magnet,
explaining why a compass needle points north. Among others that we meet is a
physicist who compared his power to transmute the elements to the mythical
alchemist Hermes Trismegistus; an astronomer who was captivated by the beauty
of a falling snowflake; the British physicist whose work predicted the
existence of antimatter; the theorist who transformed particle physics with his
eightfold way; and Peter Higgs, whose long wait for the discovery of the
particle that bears his name may soon be over.
