Faster than the Speed of Light
Joao Magueijo at Cafe Scientifique,
Live Theatre, 15th March 2004
Review by Caspar Hewett
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2004 reviews
This event was the contribution of the now well-established Café Scientifique to
Newcastle Science
Festival 2004 and a great opening to the week it was. The speaker
Joao Magueijo, is a
Reader in Theoretical Physics at Imperial College, London and author of
Faster Than the Speed of Light: The Story of a Scientific Speculation.
He opened by explaining
how Einstein’s theory of relativity is the foundation of every other theory in
modern physics and that
the assumption that the speed of light is constant is the foundation of that
theory. Thus a constant speed
of light is embedded in all of modern physics and to propose a varying speed of
light (VSL) is worse
than swearing! It is like proposing a language without vowels.
For Magueijo relativity is not really difficult to grasp and a constant speed of
light is the start point. To
help to visualise this he invited the audience to imagine driving alongside a
car made of light. Since the
speed of light is constant it does not matter what you do in terms of
accelerating or decelerating the
light car will still have the same relative speed to you. This counter-intuitive
notion led Einstein to
propose that speed and time must be variable - in particular that time advances
at different rates for
objects moving relative to each other. The speed of light, c, thus is a speed
limit - it is not possible to
go faster than it. This is quite annoying - especially from the point of view of
space travel. Although it
is very fast compared to the speed at which we do things, c is slow compared to
the size of the
Universe - there is a disparity of scale especially considering the length of
human life.
Those proposing a VSL have been described as the punk rockers of physics, but
the notion is not
without precedent. Einstein himself proposed a VSL theory in 1911, but abandoned
it. Like any
assumption in science the constant c is not dogma - all theories are open to
revision in the light of
experimental or observational evidence.
So, why propose a VSL? According to Magueijo a number of problems in physics led
to the VSL
theory - primarily in the area of cosmology. In 1930 Edwin Hubble discovered
that the Universe is
expanding. This means that space is literally being created between the
galaxies. Hubble was observing
the creation of distance. Reading time backwards this suggested that the
Universe was increasingly
small the further back in time we go, and led to the conclusion that everything
started from a point - The Big Bang. Magueijo drew attention to the horizon
problem this gives rise to - at any time the
Universe has a finite age and thus there is only a finite time for information
to travel through it and
things can only travel a finite distance. This means that we can only see to the
horizon of the Universe
and cannot be affected by anything beyond this. The closer in time (and space)
we are to the Big Bang
the smaller that finite distance is. If we allow for c to be higher earlier in
the Universe then information
could travel faster. Magueijo claimed he had a hangover when he first considered
this - it must have
been some headache!
Magueijo drew attention to Dirac’s complaint in 1968 that there was too much
speculation in
cosmology. It seemed to Dirac that cosmologists were making any assumptions they
fancied, especially
in the light of the possibility that the laws of physics may be varying with
cosmological time. For
Magueijo the fact that we live in an expanding Universe means that it makes
sense to question the
static nature of the laws of physics. However, as a scientist he believes that
it is a matter for experiment
to decide whether any theory is right or wrong.
The second part of the story is related to the ongoing search for a Grand
Unified Theory (GUT) for the
laws of physics. The theory of relativity is 100 years old next year and it was
Einstein’s great dream to
find a GUT. However there has been a 100% failure rate so far. The fact that
this has still not been
solved is another reason to abandon constant c. In his theory of general
relativity Einstein showed that
gravity is a property of space-time - the presence of matter warps space-time
and it is this distortion
that we experience as gravity. The other fundamental forces are electro-
magnetism and the strong and
weak nuclear forces, all of which are characterised by quantum effects. For a
GUT gravity needs to be
quantized, but this would mean that time could not be continuous. This gives
rise to the notion of a
granular property of space - As Magueijo puts it ‘Planck space’ is pot holed.
Thus we have to ask what
kind of object would fall through holes in space. In relativity length, like
time, is not absolute - there is
the theory of length contraction which, according to Magueijo needs to switch
off at some point if a
GUT is to be achieved.
Following his engaging introduction the audience were invited to quiz Magueijo
on the VSL theory. A
number of people asked about the experimental support for a VSL and what type of
experiment could
be designed to support or disprove the theory. Magueijo gave a variety of
answers. First he pointed to
the existence of ultra high energy cosmic rays. These particles have been
detected passing through the
earth and represent a contradiction with relativity. Relativity predicts that
there should be a limit to the
energy level possible for cosmic rays and the theory has thus been shown to be
wrong. Further
evidence comes from astronomical observation - astronomers look into the past
when they look into
space and have been measuring and observing quasars. Reconstructing the speed of
light in the past it
seems that it was slightly higher 7 or 8 billion years ago than it is now. This
work has not been repeated
and thus cannot be taken as irrefutable yet. Another experiment Magueijo
suggested to test the VSL
hypothesis is to try to measure how much cvaries from year to year. If c varies
over the history of the
Universe then we would expect a very small variation in the course of a year.
Magueijo pointed to the
way atomic clocks are becoming ridiculously accurate and suggested that, if they
keep improving, we
should be able to measure whether c varies year to year quite soon.
Magueijo was scathing about string theory, describing it as ‘like intellectual
masturbation.’ He doesn’t
like string theory for sociological reasons, his main objection being that it is
completely disconnected
from experiment, making it hard, or impossible, to confirm or disprove. He
conceded that it may be
possible to consider a VSL theory and string theory together, but considered
the notion a strange one.
In contrast, when asked whether there is any mileage left in the ether
hypothesis Magueijo thought that
perhaps there is! The idea of the ether originates with the discovery of the
wave properties of light. The
hypothesis was that, if light is a wave, then it must travel in a medium - the
ether. If it existed the ether
would be a preferred frame of reference for the speed of light - an idea which
does not fit in with
relativity theory, but if there is a VSL the situation may be different.
However, this must be tempered
with the recognition that there is strong experimental evidence against such a
preferred frame of
reference, for example in the Michelson-Morley experiment which was central in
Einstein originally
formulating the constant c hypothesis. Michelson and Morley showed that
different observers measure
light at the same speed - Magueijo was clear that if the VSL theory is correct
the results of such
experiments must still hold at the appropriate scale in this part of the
Universe at this time - if not there
is no justification for adopting such a theory since the experimental evidence
is clear and repeatable.
Expressed with humour and great clarity Magueijo managed to get across some very
complex notions
to a non-expert audience. It was clear from the questions from the floor that
there were a number of
physicists in the audience, but also a good cross-section of the general public.
The high level of
intelligence shown by the audience and expected by the speaker is what I have
come to expect of Café
Scientifique and is what science festivals should be all about. More please!
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