Inside the atom (left) lies the nucleus; inside the nucleus, neutrons and protons;
inside each of them (top right), three quarks. The search for elemetary matter continues.
An image of one of CERN’s recent collisions: the first proof of the Higgs field?
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“By
convention there is colour, by convention sweetness, by convention bitterness, but
in reality there are atoms and space”
Democritus,
Greek philosopher (c.460-c.400 BC)
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Do
the secrets of the universe lie within the atom? Could a 27-kilometre tunnel reveal
the deep truth?
Reverse the film of
our universe’s history, and things seems to get mighty strange in the last reel.
What began in physical harmony, propitious for planets, humans and domestic appliances,
has reverted to hell: temperatures hotter than the sun’s core, an exotica of hysterical
matter, forces rupturing asunder. Nudge the reel a bit further on, and the image
abruptly switches from fury to a vague and peaceful nothing.
It is not an ending—or rather a beginning—that satisfies too many people. Though
little headway has been made exploring this peculiar transformation of nothing into
hot and very excited everything, the issue has not been absent from scientific minds.
If only to combat the allure of a “God particle” bent on generating the cosmos, science
has searched for an alternative: not just a history of before the big bang, but some
deeper reason for why, out of unfathomably chaotic stuff, should emerge a place where
a hair-dryer works.
Gabriele Veneziano is one of those who believes an answer may have been found. According
to this leading Italian theoretical physicist, a deeper reality lies “under” the
one we perceive. Superstrings, to be precise, vibrating away in 10 or 11 dimensions,
creating and composing the entire universe from their minuscule shudders.
Deciphering his account of how the universe came to be reads like an odyssey through
20th century physics. Superstring theory, and its many cousins in the domain of elementary
particle physics, are offshoots of the two great theoretical inventions of the century’s
first decades—general relativity and quantum mechanics. On the basis of the first,
a convincing picture of the universe could be drawn back to an initial point, or
“singularity,” of massive, possibly infinite density. Through the quantum world,
vast leaps could be made in penetrating the atom, the components of the atom (protons,
neutrons and electrons), and then, colossal equipment and minds permitting, the components
of the components of the atom.
Slam and see
At that point, the two theoretical roots join as one. Assuming the universe is created
in a blazing, primordial soup, then clearly the most basic units of matter will be
those that prevail. Finding out what rules govern them is then the golden bridge
towards understanding how the universe was made.
Until the end of last year, a palm-sized pipe wrapped in potent magnets and circling
beneath the Franco-Swiss border was the world capital for such investigations. Along
this 27-kilometre pipe, a pair of electrons would pass 11,000 times a second—close
to the speed of light—before hurtling to a splintering collision. Such is CERN, the
European laboratory for nuclear research. The principle is simple: slam and see.
Behind the principle lies a very basic formula, Einstein’s E=mc2, which establishes an equivalence
between energy and mass. Accelerate a subatomic particle like an electron or proton,
crash it into a partner, and the energies accumulated in its light-speed dash will
be scattered into more massive, very short-lived particles—exactly the sort of particles
that reigned in the early universe before gluing together as space cooled.
The appetite of scientists has naturally not abated. By 2005, a new accelerator is
due to be operating at CERN: the Large Hadron Collider, armed with a magnetic field
100,000 times that of the earth, interspersed with six-storey high detectors and
able to take subatomic conditions back to those which held in the universe’s first
picosecond (10-12 seconds). “We are going to be able to probe distances inside matter
which are perhaps ten times smaller than we’ve seen before,” explains John Ellis,
a senior physicist at the laboratory.
Through theoretical work and experiments at this and other accelerators, scientists
have already disaggregated the atom and the forces that rule its movements into a
menagerie of over 60 particles. A story of the universe has emerged: a tale of descent
from high to low energy, in which primitive forces split (creating electricity),
and unstable fundaments of matter convert their mass into the astonishing energies
inhabiting every atom.
The
staircase of universes
But
the story is far from complete. It may be very well to enumerate and calculate the
powers of quarks and spins of photons, yet how could such an encyclopaedic set of
characteristics sprout so level-headedly from a meltdown? Perhaps more importantly,
where does gravity fit in? Its supposed force-carrier, the graviton, has never been
observed. The force itself appears alien to quantum theory. And its strength for
each atom is derisory compared to the belligerence of the nuclear and electromagnetic
forces: how else could a chair buttress you from the entire gravitational attraction
of the planet?
In search of an answer, the scientific community has appealed to the notion of unification.
The deeper one gets into the interstices of matter, they argue, the more sweeping
and elegant the formulae may become.
The lust for a unified theory behind nature has prime targets in sight. In a last
gasp of CERN’s old accelerator, the first experimental indications emerged of the
so-called Higgs field, an arena of force like the electromagnetic field with which
species of particles interact (or do not) and win their very unique masses. “Imagine
you’re cooking pasta,” says Ellis, “and you add olive oil. When it cools, the olive
oil separates out. What we’re trying to do in the new collider is boil the water
so that we can see the differences evaporate.”1
Yet this still leaves the gravitational conundrum unresolved. John March Russell,
a physicist at CERN, enthuses over one mind-bending possibility: that gravity is
so weak in comparison to other forces because much of it is swallowed into other
dimensions. Should this be the case, he says, the new collider may reveal more than
just new particles: energy might be sucked away into the nether-world, or even more
radically, tiny black holes may form for a fraction of a second.
Such extra dimensions would appear to make elementary particles that bit more baffling,
but the opposite is probably true: it may offer the first proof that strings exist.
“Theoretically, the gravity problem and string theory fit together very nicely,”
argues March Russell.
But what precisely are these magical strings? For around 30 years, theorists have
laboured over rival sets of formulae explaining how string-like phenomena, around
10-32 cm in length and thus invisible to all possible experiments, generate the entirety
of known particles and forces, including gravity. If true, it would be the deepest
theory ever encountered: the overarching law breathing form and function into the
universe.
Unfortunately, their infinitesimal size and supplementary dimensions have given the
theory an air of high abstraction, but Veneziano, also of CERN, is undaunted. For
him, the epoch of creation might have to be rewritten. “I see the big bang as a way
to put string theory to the test. When you get very close to time zero, strings simply
cannot fit into space.”
The results are revolutionary. No infinitely dense singularity could exist at the
start of the universe because of the strings’ irreducible size. Instead, a “pre-history”
must be sketched in. “This could be a very long pre-history starting with an almost
trivial, infinite universe filled with gravitational waves that barely interact at
all,” says Veneziano. “The beginning of the process ending in the big bang is the
occurrence of an overdense region leading to the formation of a black hole.” Within
this hole, trapped waves start to interact in the form of strings. An early relative
of gravity causes a lightning expansion of space, and at some critical and obscure
moment, the era of strings cedes to the big bang, thus begetting the era of particles,
planets and us. “What we have for most of the time before and after the big bang
is a classical evolution,” he says.
Major problems remain, above all in explaining why the underlying strings (or any
other fundamental theory for that matter) do not lead to an utterly different set
of physical laws. But the thought is still a giddy one—that reality migrates along
a staircase of universes, each step recumbent on the one before. “In the world today,
the castle is destroyed—it’s a heap of rubble,” declares Ellis, “but the original
structure may well be unique and in some sense very beautiful and simple.”
1. Another target
for research might also usher in a new unity. This branch of theory, known as supersymmetry,
speculates that a fundamental balance exists throughout the quantum realm, and that
at high energies the “superpartners” of known particles will flit into observation. |
