The idea of a variable speed of light, championed by an angry young scientist, could one day topple Einstein's theory of relativity
Einstein's famous equation E=mc2 is the only scientific formula known to just about everyone. The "c" here stands for the speed of light. It is one of the most fundamental of the basic constants of physics. Or is it? In recent years a few maverick scientists have claimed that the speed of light might not be constant at all. Shock, horror! Does this mean the next Great Revolution in Science is just around the corner?
Well, maybe. According to one of those scientists, Portuguese-born,London-based João Magueijo, cracks are appearing in Einstein's theory of relativity - the cornerstone of our present understanding of space, time and gravitation. In "Faster than the Speed of Light"(Heinemann) he describes his personal journey through this controversial and emotionally supercharged field.
into the subject while puzzling over the smoothness of the universe, a property
illustrated by the recent results from the satellite WMAP (Wilkinson
Microwave Anisotropy Probe), showing a snapshot of the universe just 380,000 years after the big bang. Significantly, the infant cosmos appears uniform in temperature and density to about one part in 100,000.
The mystery here is that light can have travelled no more than 380,000 light years by that epoch, yet different patches of the sky shown in the snapshot might be millions of light years apart. As no force or influence can travel faster than light, these various patches can never have been in causal contact. So why are they so similar?
an answer. Perhaps light travelled much faster in the past, enabling forces
to propagate more quickly. In that case, widely separated regions of the
universe could have pushed and pulled on each other, and thus smoothed out
their differences. The theory is easy to state, but it flies in the face
of much accepted wisdom. For a start, cosmologists already line up behind
a very different explanation for cosmic smoothness, called inflation. According
to this scenario, the universe jumped in size by an enormous factor during
the first split second. Any primordial irregularities would then have been
stretched to oblivion. WMAP lends strong support to inflation.
More worryingly, constancy of the speed of light is central to the theory of relativity and the other areas of modern physics that this theory penetrates. Physicists will give up this key set of ideas only after a bitter struggle. Magueijo describes just what a struggle he had personally in convincing his colleagues to take the varying speed of light (or VSL) theory seriously.
Although his work, in collaboration with Andreas Albrecht, was eventually published in a leading scientific journal, Magueijo's theory might have been shrugged aside were it not for some remarkable astronomical observations compiled by John Webb of the University of New South Wales. They centre on the quality of the light coming from distant objects called quasars. Split into a spectrum, quasar light is slashed through with dark lines created when intervening clouds of cold gas selectively absorb certain wavelengths, or colours. On careful inspection, some of these lines decompose into closely spaced sub-lines, called "fine structure." What Webb and his colleagues noticed is that the fine structure in the quasar light is subtly different from its laboratory counterpart. One explanation for this difference is that the speed of light fell slightly between 10 and 6 billion years ago. The effect is tiny - a few parts in a million - but potentially of huge significance.
Taken on their own, Webb's results do not foreshadow the collapse of textbook physics. History shows that when a crack appears in an established conceptual framework, one of two consequences may follow. One is that the old theory gets tweaked a bit to accommodate the new findings, but the basic framework remains intact. The other is the disintegration of the whole edifice, which gets replaced by something radically new. The latter is what happened when Einstein replaced Newton's ideas of space, time and gravitation with his own theory of relativity.
Is it now Einstein's turn to be toppled? It could be. In spite of the entrenched position of the theory of relativity, few physicists would claim that it is the last word. In particular, it cannot readily be united with the other great product of 20th-century physics - quantum mechanics. All attempts to develop a consistent quantum description of gravitation involve fudging Einstein's original theory in some way. So sooner or later observational flaws will probably appear in the theory of relativity. It may be that Webb's quasar data already hint at trouble ahead.
The idea that the speed of light might vary from time to time, or even place to place, isn't new. Several years ago John Moffat of the University of Toronto published a theory along these lines, but his work seems to have been overlooked. For some reason, the flurry of recent papers on the subject has stirred up a scientific hornet's nest, provoking a strong negative reaction from mainstream physicists.
I have some personal experience of this. Last August I published a short note in Nature, co-authored with two colleagues from the University of New South Wales. We applied the VSL idea to the theory of black holes, to see what the implications would be for the laws of thermodynamics. The paper appeared in the northern hemisphere silly season, and so it received extensive media coverage, in spite of its modest scope and technical nature. Almost immediately I was deluged with hostile denunciations from colleagues, in some cases couched in tones of barely concealed anger. What was all the fuss about? This was, after all, just a calculation.
Part of the answer may be due to pique that our work was given such prominence. But there must be more to it than that. Belief in the absoluteness of nature's laws is a deeply-rooted part of the scientific culture: to do science, you have to have faith that something is sacrosanct and utterly dependable. For historical reasons, the absolute constancy of the speed of light forms part of the bedrock on which the scientific edifice is built. Attempts to meddle with that bedrock produce an almost visceral response.
Among the angry
outbursts we received was one legitimate concern. Some physicists
say that the statement "the speed of light has changed" isn't wrong, but meaningless. The problem arises from the fact that speed is a quantity that normally has units attached. For example, the speed of light is measured to be 300,000 km per second, 186,000 miles per second or one light year per year, depending on which distance and time units you choose. These different numbers merely reflect convention. To say that c has varied invites the response, varied with respect to what? One could explain the Webb results, for example, by saying that distances or clock rates have changed, leaving c constant by convention.
To avoid such ambiguities over units, one must make up a ratio of two speeds. It so happens that physics gives us another fundamental unit of speed, composed of two basic quantities - the unit of electric charge on the electron and Planck's constant of quantum mechanics. When this other speed is divided by the speed of light the result is a pure number, known as the fine-structure constant; its value is close to 1/137. It is this ratio - not the speed of light as such - that Webb's results indicate may have changed slightly.
On their own, the astronomical observations can say no more than that. However, if some other branch of physics, such as gravitation, is brought into the picture, then additional, independent, units of speed can be defined. But in any given case, there will be a choice as to what quantities are regarded as fixed in order to define the system of units, and what will be deemed to vary.
well aware of this criticism, and he addresses it competently in his book.
He argues that if the theory that predicts a variation of the fine-structure
"constant" is simple when cast in terms of a varying speed of
light, but very complicated if cast in terms of a varying electric charge,
then it makes sense to use the former description. There is thus an element
of judgement involved in the way the ideas are presented. But this has always
been the case in physics, where simplicity and elegance play a guiding role
in formulating new theories. To my mind, this puts the matter to rest. It
is perfectly meaningful to claim that the speed of light was greater in
the past, whether or not it is
actually the case.
There are other reasons than purely scientific ones why Magueijo's book will raise hackles. Not only is his theory confrontational, so are his opinions about the scientific community. He devotes a lot of space to attacking the peer-review system, university administration, journal policy and some of his colleagues. Although a few of these jibes are probably justified, and young researchers may empathise with them, I found his remarks too coarse and flippant. I sympathise with the author for the rough ride he has received in trying to get his ideas across to a sceptical scientific community, but I believe that on balance the quality control mechanisms for theoretical physics work well. It is only right and proper that unconventional new ideas should be battle-tested before gaining currency; that makes them all the stronger if they survive.
Many readers will enjoy this book's irreverence and iconoclastic message. The work of Magueijo and others could herald the start of a major shake-up in physics, or it may turn out to be a blind alley. We shall have to await the outcome of future research to see. But even if the speed of light is constant after all, there is much fascinating physics and cosmology here, plus some unusual perspectives into the way professional science is conducted.
is professor of natural philosophy in the Australian Centre for
Astrobiology at Macquarie University, Sydney
Then There Was Light,by Richard Panek Natural History Magazine,
2. At the Speed of Light, What if Einstein was wrong?
By Tim Folger regarding Joao Magueijo, DISCOVER magazine April 2003
3. Was Einstein Wrong, by Paul Davies, April 2003, Prospect Magazine
IS beyond the reach of common sense. It is ,in fact, beyond all sense. The
attempt to make sense out of nonsense results in categorical thinking, but
you in the ivy towers of academia are content to issue metaphorical pearls
of wisdom that you expect us "ordinary" thinkers to swallow as a
matter of fact, unexamined. You don't dare attempt to answer the sensible
questions regarding S.R. because you know in your
bones that it is hopeless to make sense out of nonsense. Instead you turn your back on a real dialogue. In deed you turn your back on empirical phenomena and pat yourselves on the back for being above ordinary common sense.
For my purpose
I let the first five paragraphs of your article stand as history. It does
not diminish Einstein that he contradicts what you say about his approach
to science. "..get the math right first and worry about the observational
consequences later." I quote Einstein here, "...as far as the propositions
of mathematics refer to reality, they are not certain; as far as they are
certain, they do not refer to reality." (A.E. Compiled by A.P. French,
Einstein: A Centenary Volume, 252) A.E. to Hermann Weyl, 1923, "Mathematics
are all well and good but nature keeps dragging us around by the nose."
Einstein: A Centenary Volume, 113) I'm sure you recognize that math is, in
and of itself axiomatic, not empirical. When it comes to explaining S.R. us
"ordinary" folk are told
that without calculus we "really" can't understand S.R.
The Lorentz Contraction is not hard to understand. Does it only apply to imaginary sail boat masts or does it apply to empirical phenomena? Is distance contraction optical or objective? Is time dilation subjective or objective? The fact of the matter is that time and distance are as axiomatic as the number one. They have no inherent nature or character as does your sail boat mast, but for the character that we give it.
Light has character. In Dec. 2002 using one clock we can determine how long it takes a quantity of light to pass us. In June 2003 it will take the same quantity of light longer to pass us. this is empirical evidence. The same quantity of light takes longer to pass us because we are moving in the same direction as the light.
If we are celebrating Einstein at the Museum of Natural History, I propose that we return to the basic questions in the dialogue of 1906 for old time sake. A weekend symposium. There are physicists who agree with me.
Dear Mr. Panek,
Thank you for your answer to my letter. I have folded comments into your
Dear Mr. Lavaggi,
Thank you for your letter to the editor of Natural History regarding my article on Einstein and relativity. Regarding the quote of Einstein's about mathematics that you cite--I don't entirely disagree with your point. But I just want to add that while I'm familiar with the quote, I'm also familiar (as I'm sure you are) with the *seemingly* contradictory nature of many of Einstein's quotes, depending on the circumstances as well as his age.
RL: Yes, this is true.
As I think he would have been the first to say--and was the first to say,regarding the application of this idea to science--we need to watch what he does, not what he says.
In that regard, I do think it's a fair summary to say that he arrived at the mathematical bases of special relativity and general relativity first, and sought empirical evidence later, often urging (in the case of general relativity and eclipse observations) the observational astronomers to get out there and look.
RL: I agree with this.
I think it's also fair to say that as time went on, he became more and more impressed with the usefulness of the underlying mathematics in building a theory, and more and more convinced that he'd been doing so all along, despite his earlier disclaimers to the contrary (which, I also think it fair to say, he espoused in an attempt to adhere to what he at the time imagined were positivist principles).
RL: I agree.
Consider for instance his famous statement in the Herbert Spencer in 1933: "I am convinced that we can discover by means of purely mathematical constructions the concepts and the laws connecting them with each other, which furnish the key to the understanding of natural phenomena" (though "[e]xperience remains, of course, the sole criterion of the physical utility of mathematical construction").
RL: I agree with Einstein "[e]xperience remains, of course, the sole criterion of the physical utility of mathematical construction". You gave no response to the section of my first letter which references [e]xperience.
In Dec. 2002
using one clock we can determine how long it takes a quantity of light to
pass us. In June 2003 it will take the same quantity of light longer to pass
us. this is empirical evidence. In March 2003 it will take the light from
one orbit of Io around Jupiter, (between eclipses,) 15 seconds longer to pass
Earth then it did in December,
even though we are closer to Jupiter in March then we were in December. We are not seeing Io, only the light that left Io 40 minutes earlier. The Lorentz contraction tells us that light will pass us at the same speed regardless of our motion. Why isn't the experience we have of Io's light consistent with the mathematics of the Lorentz contraction ?
For some reason the part of your earlier letter regarding Io and Jupiter didn't reach me in the original correspondence. Or perhaps you added it? Either way, I'm not sure I understand what you're saying there, nor did I (or do I) understand what you meant in the section--which did reach me in the original--regarding "how long it takes a quantity of light to pass us," both the "how long" part and the "quantity of light" part. But it doesn't really matter, as my purpose in writing back to you was not to engage in a larger debate about the validity of relativity but simply to clarify what I felt was Einstein's attitude toward his own methodology.
Thanks again for writing,
Natural History Magazine
Dear Mr. Panek,
Are you willing to represent to me and the world that you do not "understand" what "how long" and "quantity of light" means?
If a light shines a beam for one second, there will be 186,282 miles from its leading edge to the end of its tail. How much time will it take for that length of light to pass observers moving relative to each other?
says it will always pass in one second. Galileo says it depends on the direction
and speed of the observer. The Jupiter Moons experiment confirms Galileo.
2. 4/10/03, At the Speed of Light, What if Einstein was Wrong?
To the editor, DISCOVER magazine
Joao Magueijo's idea of (VSL) varying speed of light, opens a door that has been bolted shut and guarded for the past seventy years. When Magueijo says, "The reaction was negative. People either laughed or looked at me like I was mad." He is referring to the reaction of physicists. Indeed, the physics community sees the benign idea of varying light speed as,"..an act of brutality against the framework of Physics," this comment informs us about the psychological underpinnings of a profession that rhetorically prides
itself on being objective and logical. DISCOVER magazine states "Time after time, as we have gained the technical ability to test Einstein's visionary ideas, we have found them to be true." In all the multitude of tests of Einstein's theory, there is not one measurement of light's speed where the light is not manipulated. In all such 'tests' the light being tested is observed after it is reflected and the point of observation is always at rest with the object that is causing the reflection. These are not tests of motion relative to light. Instead These tests prove Robert W. Ditchburn's theory regarding the Interaction between Light and Matter. He states, "An electron bound to an atom can oscillate with a natural frequency.... the light scattered depends on the frequency...of the light wave and also upon the frequency...and the damping constant...of the electron." Einstein's theory of relativity is shrouded in layers of academic doctrine,
with no empirical evidence that the speed of light is not relative, to moving observers.
I do marvel that Tim Folger and Discover Magazine are presenting this article. It states "Magueijo never liked inflation theory. The idea that the universe expanded from a subatomic mote in less than a billionth of a trillionth of a trillionth of a second seemed unlikely at best to him, and there are obvious problems with the theory. It relies on a mysterious inflationary field and a weird antigravity particle called an inflaton, neither of which has ever been detected. Magueijo decided there must be a better explanation, and on that wet winter morning eight years ago, it came to him. Cosmologists wouldn't need to invoke inflation if they could bring themselves to give up one of their most sacrosanct laws, The speed of light is, was, and ever shall be 186,282 miles per second." I do not accept "inflation theory" either. Once Cosmologists give up their "most sacrosanct law," The cosmos reemerges from the shrouds of the 20th century. If Magueijo never liked inflation theory, how could he believe "that for a few moments at the beginning of time, the universe's extreme heat made photons-particles of light-zip along much faster than 186,282 miles per second, at almost infinite velocities. Then, as the universe began to expand and cool, its physical properties abruptly changed"?
If we abandon our most sacrosanct law, special relativity, we are released from the infantile idea of a big bang. If we take a Kantian view, and factor in anthropocentric preoccupation the cosmos becomes breathtakingly simple. Beginning and ending are anthropocentric inventions. Quantum theory may metaphorically approximate physicality. There is no empirical evidence that physicality, was ever non existent.
Spatially, the Cosmos is infiate. Temporally, the Cosmos is immediate, void of past and future. Physicality only exists at the threshold between the future and the past.
We project yesterday and tomorrow by Anthropocentrically interfacing with now. The future and past are part of the anthropocentric invention that implies start and finish.
The farther a light source is away from us, (a million light years) the more chance there is for its light to lose speed and shift red. The red shift of the most distant Galaxies are not the result of motion away from us but rather their stream of light running out of steam. They may be moving one way or another, but we are at the far edge of their transmission range. Galaxies that are farther than the farthest galaxy that we see are simply too far for us to see. This phenomenon causes the illusion that we are approximately in the center of the Universe.