THE Creation, according to modern theory, was such a uniformly perfect event
that matter should have been destroyed within an instant of its appearance.
Nothing we now know should ever have been. Yet something shattered that
perfection: our Universe arose because it is quintessentially asymmetric.
Human life itself seems lopsided. The spherical embryo is transformed into a
highly structured being with its organs mirror asymmetric. The molecules of
life, such as amino acids, differ from their mirror images: the milk in Alice鈥檚
looking glass world would have been unfit to drink. Whether we scrutinise life,
the Universe or anything, the deeper we look, the more asymmetry appears.
Indeed, asymmetry is seemingly necessary for anything 鈥渦seful鈥� to exist.
Many physicists now believe that the ultimate source of all asymmetric
patterns may be traced back to a single event that took place within a split
second of the big bang. How nature creates structures and asymmetric patterns
from underlying uniformity is a great unsolved mystery, but one to which the
answers may soon be known. In 2005 at CERN, the European Laboratory for Particle
Physics in Geneva, the largest experiment in history will attempt to recreate
what the Universe was like in its first moments, before the natural symmetry had
been hidden. 快猫短视频s there believe that when the true symmetries of Creation
are known, the way that nature broke them will also become clear.
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There is direct evidence that the stuff of which we are made is but half of a
symmetric whole. 快猫短视频s speak casually of antimatter, the faithful opposite
of matter, and a symmetry so perfect that when any particle of matter meets its
antiparticle, mutual annihilation occurs. It is the romance of this mutual
suicide pact and the accompanying burst of energy that has made antimatter so
beloved of science fiction writers. Physicists at CERN can even watch this
energy appear, confirming time and again matter鈥檚 vulnerability to antimatter.
They also see the converse, where a large enough concentration of energy
coagulates into matter and antimatter. We believe this is how the basic
particles of the material world first emerged.
A perfect Creation, with its symmetry untainted, would have led to matter and
antimatter in perfect balance. The next instant would have seen a mutual
annihilation as they recombined鈥攊n other words, a symmetrical Universe
would have vanished as soon as it had appeared. Such a uniform cosmic soup could
hardly have led to our asymmetrical Universe, where antimatter appears to be all
but absent.
Mainstream cosmology has it that the Creation was barely completed before
something interceded, and the perfection in which every atom of substance had
been counterbalanced by a precise antipartner was lost forever. This broke the
symmetry between matter and antimatter with the result that after the great
annihilation, a small proportion of the matter was left over. Those remnants are
what have formed us and everything around us. We are the material rump of what
must have been an even grander Creation.
Matter defeating antimatter was a necessary step for there to be anything at
all. Yet this alone was not enough. If that had been the end of it, the material
Universe would have been merely a bland plasma of particles with none of the
elements. A multitude of natural asymmetries have made the cosmos what it is.
What is increasingly exciting physicists is that there appears to be a common
culprit for all of them.
The simplest element, hydrogen, formed first and the force of gravity
collected it into vast clumps, stars, where the heavier elements so necessary
for life were cooked up. Our own Sun has been in this stage for 5 billion years,
transmuting hydrogen and radiating sunlight to Earth. This warmth has energised
the chemical and biological processes of life, which have needed that vast time
span to create creatures with the complexity of humans.
Asymmetry has been essential to this. The warmth of the Sun is the radiant
glory of the electromagnetic force, which we feel across 145 million kilometres
of space. Yet, the 鈥渨eak鈥� force, which helps to transmute hydrogen, has a sphere
of influence smaller than the dimensions of a single atom. As its name suggests,
it is weaker than the electromagnetic force, and this enfeeblement is what has
enabled the Sun to survive long enough for us to arrive.
Different these forces may be, but we have evidence that in the searing heat
of the big bang they were identical. Only as the Universe cooled have the
electromagnetic force and its weak sibling taken on their separate identities.
This asymmetry is directly related to another: that whereas photons, which carry
the electromagnetic force, are massless, their counterparts for the weak force,
鈥淲 particles鈥�, are more massive than iron atoms.
Differences in mass are also responsible for the lopsided structure of atoms.
More than 99.95 per cent of the atom鈥檚 mass resides in the nucleus. This
positively charged heart is too heavy to be easily stirred, and so provides the
anchor for the solidity of matter. But the electrons, with their trifling mass,
are liberated to pass from one atom to another. They flow as current down wires,
power the modern world and drive the chemistry of life. This asymmetry in mass
is crucial to the structure of materials.
It appears to be mass, the ill-understood inertia that gives every particle
its identity and properties, that disturbed the original harmony of Creation and
may even be the source of all asymmetry. This notion is attributed to Peter
Higgs of the University of Edinburgh. To illustrate his ideas, we can turn to
magnetism, though Higgs applied them to the whole Universe.
When left to their own devices, physical systems seek to attain a state of
lowest energy. To do so, they may change their phase, as when liquids freeze,
giving up energy as heat, or when individual magnetic atoms in a lump of iron
line up to make it magnetic.
In iron and other metals, every electron is spinning and acts like a tiny bar
magnet, the direction of its north-south magnetic axis being the same as its
axis of spin. For a single isolated electron this axis could point in any
direction. This is an example of the rotational symmetry of three-dimensional
space, in which any direction is as good as any other.
But when electrons are housed in a lump of iron, neighbouring electrons
prefer to spin in the same direction as one another, because this minimises
their energy. The preferred direction of all the little magnets then becomes the
north-south axis of the whole magnet. It is a classic example of hidden
symmetry in that the laws of physics for single spinning electrons have no
preferred direction whereas those for a magnet clearly do.
This is how electrons in iron behave when cool. But heat the iron above 900
掳C and the extra energy will liberate every spinning electron from the
entrapment of its neighbours. The spin axes of these mini magnets will point in
random directions again鈥攔otational symmetry is restored and the bulk
magnetism disappears. Cool the metal and magnetism will return.
Instead of heating the magnet to liberate the spins, suppose we stay in the
cool magnetic phase and give the spins a small pulse of energy so they wobble.
It is possible to make the shared direction of spin鈥攊n effect, the local
magnetic north鈥攙ary in a regular, wavelike way throughout the metal. These
variations are known as spin waves and, just as electromagnetic waves are
bundled into photons, so spin waves are bundled into 鈥渕agnons鈥�. And just like
photons, magnons act like particles.
Imagine for a moment what would happen if mythical creatures had evolved
inside the magnet. They would interpret its unchanging features as 鈥渆mpty
space鈥�. In developing descriptions of their universe, they would be unaware of
rotational symmetry because they would experience a preferred direction in
space鈥攖hat due to the ubiquitous magnetism. They would regard this
asymmetry as the natural order.
After some time, a scientist among the creatures realises that empty space is
not really empty but has a structure (which we recognise as the magnetic
spinning electrons). Furthermore, the scientist realises that this structure
combined with the fact that the creatures are living below 900 掳C has given
rise to asymmetry: the underlying laws are really symmetric.
At first this is just an idea, but the creatures work out that they can test
it by injecting a large enough pulse of energy for magnons to appear. These
would be all the evidence needed to reveal the underlying structure.
It turns out that these creatures might not be mythical. They could be
us鈥攖heir predicament is an analogy for our own. Higgs鈥檚 theory is built on
the idea that the vacuum is really a structured medium. What we call mass is a
result of interactions with this all-pervasive stuff, known as the Higgs field.
The analogues of magnons are 鈥淗iggs bosons鈥濃�攑article-like manifestations
of the structured vacuum.
Discovering a Higgs boson would be the first direct evidence that we are en
route to revealing the true symmetries of the Universe. It would confirm that
the masses of the fundamental particles arise from their interactions with the
Higgs field. And we would be able to look back to see how the hot, symmetric
Universe behaved before mass hid it from view.
For the creatures in the magnet, 900 掳C was enough to reveal the true
symmetry. For us it is more like 1017 掳C. To recreate the energies that
correspond to such temperatures, thousands of scientists and engineers are
working at CERN to build the Large Hadron Collider, which is due to power up
about five years from now.
Like the mythical creatures who suddenly have the existence of the magnet
revealed to them, and with it gain enlightenment as to the true nature of their
universe, so we can anticipate revelations from the Large Hadron Collider within
ten years. It鈥檚 a tantalising prospect. For the first time, we may come to see
the ultimate foundations of reality.