Is the Speed of Light Variable?

This is a bit esoteric, but it’s certain to attract the attention of creationists everywhere. As you know, creationists assert that the laws of the universe are wildly variable, and in the past they were whatever was necessary to make the bible’s history true. In particular, they often assert that the speed of light was much greater in the past, which avoids their distant starlight problem — that is, if the universe were only around 6,000 years old, then how is it possible that we see light from stars and galaxies that are millions of light-years away from us? We’ve discussed this before — see How Old Is The Creationists’ Universe?

We just found an article at PhysOrg which is certain to raise the creationists’ hopes. It’s titled Theory that challenges Einstein’s physics could soon be put to the test. Here are some excerpts, with bold font added by us for emphasis:

The assumption that the speed of light is constant, and always has been, underpins many theories in physics, such as Einstein’s theory of general relativity. In particular, it plays a role in models of what happened in the very early universe, seconds after the Big Bang.

But some researchers have suggested that the speed of light could have been much higher in this early universe. Now, one of this theory’s originators, Professor João Magueijo from Imperial College London, working with Dr Niayesh Afshordi at the Perimeter Institute in Canada, has made a prediction that could be used to test the theory’s validity.

Okay, what would the test be? We’re told:

Structures in the universe, for example galaxies, all formed from fluctuations in the early universe – tiny differences in density from one region to another. A record of these early fluctuations is imprinted on the cosmic microwave background – a map of the oldest light in the universe – in the form of a ‘spectral index’.

Working with their theory that the fluctuations were influenced by a varying speed of light in the early universe, Professor Magueijo and Dr Afshordi have now used a model to put an exact figure on the spectral index. The predicted figure and the model it is based on are published in the journal Physical Review D.

Here’s a link to their published paper: Critical geometry of a thermal big bang. Without a subscription, all you can see is the abstract, so we’ll stay with PhysOrg, which says:

Cosmologists are currently getting ever more precise readings of this figure [the spectral index], so that prediction could soon be tested – either confirming or ruling out the team’s model of the early universe. Their figure is a very precise 0.96478. This is close to the current estimate of readings of the cosmic microwave background, which puts it around 0.968, with some margin of error.

Moving along:

Professor Magueijo said: “The theory, which we first proposed in the late-1990s, has now reached a maturity point – it has produced a testable prediction. If observations in the near future do find this number to be accurate, it could lead to a modification of Einstein’s theory of gravity. The idea that the speed of light could be variable was radical when first proposed, but with a numerical prediction, it becomes something physicists can actually test. If true, it would mean that the laws of nature were not always the same as they are today.

You can see why the creationist will be excited. PhysOrg continues:

The testability of the varying speed of light theory sets it apart from the more mainstream rival theory: inflation. Inflation says that the early universe went through an extremely rapid expansion phase, much faster than the current rate of expansion of the universe.

We’re all familiar with that. Creationists have never, to our knowledge, been able to do anything with that brief moment of inflation. But if the speed of light is variable — oh boy!

We thought PhysOrg had dropped their comments feature a few years ago, but their article has over 160 comments already. That’s quite understandable. Even without the creationists’ interest, this is a fascinating topic.

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13 responses to “Is the Speed of Light Variable?

  1. Remember that the Anthropic Principle is based on the idea that human life is not possible if any of a few physical constants were significantly different from the values which we observe for them.
    Aside from that, how much does this speculation allow for in the speed of light?
    Can the speed of light over the latest (seeming) billion years be faster by a factor of 10? If so, that could account for the light from stars from a billion light years reaching us in only 100 million years. Not anything like what YEC needs. It would take something like a factor of a million over the last 10,000 years to get close to making it interesting for the YEC.
    And, BTW, this shows that real scientists are continually testing their presuppositions. It is not the case that physicists are content with saying, “Einstein said it, so it must be true.” Nor, “We cannot question this because this is the only way that we can justify our dissolute life by denying the Bible.”

  2. Is this really a theory, or more of an assertion or hypothesis for which they are offering but one test.

  3. Not even an hypothesis, just a wild ass bunch of BS that is used to show ignorant people that they are scientific.

  4. In this new hypothesis (or more correctly, wild-assertion) of variable C, what exactly changes? Is it light that has already been emitted, or new light as it is being emitted?

    In other words, say a beam of light is emitted from a star in a galaxy at a time that appears to be 10 billion years ago, and it’s happily traveling along at one million times C. At some point, it starts slowing down to C. If this is a gradual slowing, it should still be slowing today, and this change in speed should be measurable. (Unless the rate of time is also changing, which would complicate things.)

    Or is it just new light being emitted today that is slower?

  5. retiredsciguy says: “If this is a gradual slowing, it should still be slowing today”

    In my old post that I linked to in the first paragraph of today’s post, we have evidence that the speed of light hasn’t changed for the last 168K years.

  6. Imperial College is vastly overrated. One year to get an M.Sc.? Excuse me?

  7. Eddie Janssen

    What (force) would cause the photons to slow down?

  8. There is no point to my arguing this, especially because I don’t know what I’m talking about, but the Times Higher Education Supplement raking of world universities for 2016 rates Imperial College, London as number 8.

  9. It sounds like these guys are just suggesting that rather than inflation of spacetime being, in a sense, faster than light (for an incredibly short period of time), the speed of light itself was faster. My meager understanding of this is not sufficient to understand why this is an improvement on inflation, but at least they have worked a way to disprove their hypothesis. More power to them.

    I don’t see anything in the article that indicates that light speed continues to vary, only that it might have been different in the very early universe, during the big bang itself. Creationists may spin it – perhaps Jason Lisle will weigh in – but it’s relevance to the speed of light over the past 10,000 years appears to be zero.

  10. If the speed of light varies, what does this do to E=mc2? If c were enough greater than it is today as of “Let there be light,” and that equation applied as written, how did the sun not incinerate the earth with its 750,000 times greater energy output?

  11. João Magueijo is a well known physicist (he has a brief write-up in Wikipedia) who has been working on his “variable speed of light” theory for about 20 years. (It has a description in Wikipedia). It offers no comfort to the anti-evolutionists.

  12. The testability of the varying speed of light theory sets it apart from the more mainstream rival theory: inflation. Inflation says that the early universe went through an extremely rapid expansion phase, much faster than the current rate of expansion of the universe.

    The assertion that cosmic inflation isn’t testable is rubbish. What pray tell did they think the Wilkinson Microwave Anisotropy Probe was doing?

    WMAP observations also support an add-on to the big bang framework to account for the earliest moments of the universe. Called “inflation,” the theory says that the universe underwent a dramatic early period of expansion, growing by more than a trillion trillion-fold in less than a trillionth of a trillionth of a second. Tiny fluctuations were generated during this expansion that eventually grew to form galaxies.

    Remarkably, WMAP’s precision measurement of the properties of the fluctuations has confirmed specific predictions of the simplest version of inflation: the fluctuations follow a bell curve with the same properties across the sky, and there are equal numbers of hot and cold spots on the map. WMAP also confirms the predictions that the amplitude of the variations in the density of the universe on big scales should be slightly larger than smaller scales, and that the universe should obey the rules of Euclidean geometry so the sum of the interior angles of a triangle add to 180 degrees.,/blockquote>

    Image of the angular power spectrum data is consistent with inflationary predictions:

    Note the solid line is the PREDICTED angular power spectrum, based on inflationary cosmology

  13. miles standish

    Not a physicist, but seems like the inflation theory would be more to the liking of those desiring a god component to the universe than VSL. In fact, remember a documentary stating that assertion. Inflation was invented just to make things right re/ horizon problem with no attention to the why or how – sort of a god intervention.

    Seems that documentary, in describing the VSL universe creation, insinuated that the universe just kept expanding away into everything was just a collection of light-less, totally isolated meta-particles, leaving a void. But the void was actually the speed of light. And once the speed of light changed again, presto, another big bang. So the total universe is just this wave of one current and past spent universes.