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A report from researchers at Imperial College London suggests that, contrary to Einstein's theories, the speed of light in a vacuum may not be constant. The proposed new theory provides a prediction that could be used to test its validity.
Scientists behind a theory that the speed of light is variable - and not constant as Einstein suggested - have made a prediction that could be tested.
[...] 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.
[Continues...]
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."
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.
'Critical geometry of a thermal big bang' by Niayesh Afshordi and João Magueijo is published in Physical Review D.
Article text (excluding photos or graphics) available under an Attribution-NonCommercial-ShareAlike Creative Commons license.
The above-referenced journal article is paywalled, but arXiv.org has a preprint available.
It is well-worth reading if for no other reason than they posit the actual existence of a warp factor! Its Introduction raises some interesting shortcomings of the current theory:
1. Introduction. In spite of its mathematical simplicity and observational triumphs, the Big Bang model of the Universe remains an unfinished work of art. Many of its late-time successes can be traced to the initial conditions postulated for its early stages, and these are put in by hand, without justification, other than to retrofit the data. The main culprit for this shortcoming is the so-called horizon problem: the cosmological structures we observe today span scales that lay outside the ever-shrinking "horizons" of physical contact that plagued the early universe. This precludes a causal explanation for their initial conditions.
Several extensions of the Big Bang model have been proposed with the aim of opening up its horizons. An early bout of accelerated expansion [1–3], a contracting phase followed by a bounce [4], a loitering early stage [5], and a varying speed of light (VSL) [6, 7] have all been considered. None of these proposals evades the criticism that retrofitting the data is still used to select in detail the primordial fluctuations that the model should produce. Once primordial causal contact is established, work can start on concrete physical mechanisms for spoiling perfect homogeneity (e.g. vacuum quantum fluctuations or thermal fluctuations). Typically it is found that one can produce a wide range of initial conditions including, but not circumscribed to those explaining the observations.
Are there any cosmologists/astrophysicists in the house who can weigh in? Years ago when I was in college, I took several astronomy courses, so I understand enough of the material to get the general idea, but it is well beyond my background to follow the details.
Specifically, if the spectral index is found to match their prediction, does that mean that the speed of light did, or did not, vary? And, if it DID vary, what impact would that have on our current understanding of the universe?
(Score: 0, Disagree) by Anonymous Coward on Tuesday November 29 2016, @06:54PM
So... If a black hole has so much gravity that light can't escape, then surely the speed of gravity's effects are faster than light. And... If the speed of light is constant, then prisms wouldn't work, and the doppler effect of light wouldn't exist. I'm no brainiac, but I've always thought the E=mc2 was flawed.
(Score: 2) by EvilSS on Tuesday November 29 2016, @07:03PM
(Score: 4, Funny) by fido_dogstoyevsky on Tuesday November 29 2016, @08:54PM
So... If a black hole has so much gravity that light can't escape, then surely the speed of gravity's effects are faster than light. And... If the speed of light is constant, then prisms wouldn't work, and the doppler effect of light wouldn't exist. I'm no brainiac, but I've always thought the E=mc2 was flawed.
In a vacuum. You keep leaving out the phrase "In a vacuum".
And the requirement for the chickens to be spherical.
It's NOT a conspiracy... it's a plot.
(Score: 1) by EETech1 on Wednesday November 30 2016, @03:42AM
So, what if everything outside the universe (literally everywhere before the big bang) is something "less" than a vacuum?
Is it possible that light could travel faster through a medium even more "nothing" than a total vacuum?
A medium we have never experienced, and do not understand, could easily exist that plays by a completely different set of rules.
Perhaps dark matter was something that made up the last universe, but was obliterated when the rush of what we call everything went big banging by. Now all that remains is the burned out corpse of a universe that was completely different from anything we can imagine. Different elements, particles, forces, fundamental equations, and theoretical limits, all pushed aside for the ones that we're familiar with.
(Score: 0) by Anonymous Coward on Tuesday November 29 2016, @09:03PM
You're certainly not a brainiac, that's for sure.
(Score: 1, Informative) by Anonymous Coward on Tuesday November 29 2016, @10:00PM
The effects of gravity do propagate at the speed of light. This can be calculated from the decay rate of binary pulars. It is commonly ignored because it's miniscule effect over orbital distances and time periods.
https://en.wikipedia.org/wiki/Speed_of_gravity [wikipedia.org]
Yes, if light cannot escape from a black hole, then neither should the effect of gravity. Black holes are prevented from compacting that much in any non-infinite amount of time by gravitational time dilation.
A prism works because different frequencies of light are diffracted at a different angle by glass. This does not depend on relativity.
The Doppler effect on light - redshift and blueshift, is because an observer moving towards the source of light will observe the troughs and peaks of the wave more frequently, which means the light will appear the have a higher frequency to them. This does not really require relativity to understand.
The more potent question is why you and this moving observer both perceive the same light as traveling at the same speed. The answer is time dilation. Suppose a spaceship is traveling towards you left at 90% of the speed of light. Another spaceship is traveling towards your right at 90% of the speed of light. How fast does it seem they are traveling relative to each other? While intuitively we add the speeds together, 180% of the speed of light does not make sense is 100% of the speed of light is the maximum possible speed. The answer is in the neighborhood of 98% of the speed of light because of time dilation. According to relativity, from your point of view, time is passing more slowly on the spaceships. Speed is distance divided by time. While the distances add as intuition suggests, the time factor is dilated (larger) giving the predicted result.
I hope my explanation helps. Relativity certainly is a difficult subject to wrap one's mind around.
(Score: 3, Informative) by tathra on Wednesday November 30 2016, @05:10AM
its not. a black hole is a location where space is so warped due to gravity that, once you pass the event horizon every direction only leads closer to the center. the laymen's explanation is typically good enough, but its important to know what a black hole really is if you actually want to start considering the implications of hypotheses dealing with them.
(Score: 2) by letssee on Wednesday November 30 2016, @10:39AM
> I'm no brainiac
Obviously! :-)
Just kidding, but might I suggest you read a few wikipedia pages about the speed of light in a medium? This is highschool stuff.
(Score: 2) by Kromagv0 on Wednesday November 30 2016, @01:08PM
I'm no brainiac, but I've always thought the E=mc2 was flawed.
I see someone is an avid reader of Conservapedia [conservapedia.com]. If you haven't read that article you probably shouldn't as you will feel dumber for having done so.
T-Shirts and bumper stickers [zazzle.com] to offend someone