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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: 3, Interesting) by bob_super on Tuesday November 29 2016, @05:41PM
From where I stand, all the mountains look eternal and all the lakes have water.
I went to see other mountains, they seemed eternal too.
I went to see other lakes, they seemed to have water.
All I know is that my world includes eternal mountains and watery lakes. That's what I measure. That's what my grandparents measured.
Why should i accept that it was ever any different?
(Score: 0) by Anonymous Coward on Tuesday November 29 2016, @05:50PM
Lakes definitely can dry up: https://en.wikipedia.org/wiki/List_of_drying_lakes [wikipedia.org]
(Score: 2) by DannyB on Tuesday November 29 2016, @06:33PM
He didn't say the lakes were eternal. Only the mountains.
The lower I set my standards the more accomplishments I have.
(Score: 2) by bob_super on Tuesday November 29 2016, @08:40PM
I did not either.
I said they seem eternal based on my observation today, the same way that any measurement of c is probably going to return the same exact value today.
(Score: 2) by jelizondo on Wednesday November 30 2016, @04:59AM
We sit together, the mountain and me,
until only the mountain remains.
-- Li Po [poetryfoundation.org]
(Score: 5, Touché) by EvilSS on Tuesday November 29 2016, @05:59PM
In 1943 the spot where mount Parícutin sits was a corn field. A decade later it was a 424 meter high volcano. Should everyone who witnessed that assume all mountains are so spontaneous? Should those that didn't assume it was actually eternal?
(Score: 2) by edIII on Tuesday November 29 2016, @08:34PM
Speaking of lakes..... Long Valley Caldera [wikipedia.org]
Over the course of a million years in Northern California there was "flat" land, volcano, caldera, probably nearly a lifetime filling with water (1,000 feet deep), over flowed, eroded and then drained, "flat" land again, hot springs, humans, artificial dam, and then Lake Crowley. Standing in the middle of that area, you could have made all sorts of wrong assumptions based on a single lifetime of collecting data at any one point. Eternally filling with water, eternally overflowing, eternally flat, etc.
The error that bob_super makes is assuming that everything happens within human life spans, or at most some multiples thereof. Many things in our natural world only begin to make sense in geological time spans (controversial as anything over the Bible-range is). Geology is a good place to look at something across long periods of time since we have data and not measurements of light and grand simulations of what may be the truth in far off places we will never see, touch, or directly measure. You can hold a rock and analyze it, but you can't truly say that about the Horsehead Nebula. Likewise, we can simulate the conditions that create the rock and reproduce it, but other than scary black holes at the LHC, we can't reproduce the formation of a nebula over a million years.
To a fly, fluorescent lamps are not constant, but to a human? Solid light. So of course bob_super isn't exactly wrong (the fly or the human's perspective is technically correct at the moment), but he sure ain't right either about his inductive reasoning providing actual truth :)
Technically, lunchtime is at any moment. It's just a wave function.
(Score: 2) by bob_super on Tuesday November 29 2016, @10:23PM
> The error that bob_super makes is assuming that
... his point was clear enough. I didn't want to put a sarc or second degree tag, because I thought I had put enough indicators of narrow-mindedness. Eternal mountains, lakes, how unscientifically dumb are we all supposed to be?
We could measure c all our lives and not find any variation we couldn't attribute to measurement uncertainty, that doesn't exactly tell me that c was the same when the universe was completely different all those billion years ago. With some scientific luck (as in: having something new to ponder), in another 20 or 40 years I'll get to learn that c was definitely measured to change over time, though in such tiny amount that it doesn't clash with the observable parts of our universe which we know fit Relativity.
(Score: 4, Interesting) by VLM on Tuesday November 29 2016, @10:59PM
other than scary black holes
Speaking of black holes if the speed of light were not constant in spatial coordinates then wouldn't rotating black holes radiate a shitton of energy as the event horizon wiggles every rotation? So if you can't measure an amazing level of radiation from them, I guess there must be no variance based on location, which is interesting as a requirement of whatever theorem is proposed.
(Score: 2) by edIII on Wednesday November 30 2016, @12:58AM
That is damn interesting, and thank you for posting.
Technically, lunchtime is at any moment. It's just a wave function.
(Score: 2) by martyb on Wednesday November 30 2016, @01:54PM
Very interesting! Definitely gets my thought juices going this morning. Am still waking up, but here's a couple ideas:
(1) What if what we now call the speed of light in a vacuum is actually an asymptope [wikipedia.org]?
Think: f(x) = 1/x
In other words, very early on it may have had a lesser (greater?) value and has now nearly flat-lined to its currently-accepted, seemingly-constant speed?
At the beginning of time (/me waves hands), when all of the universe — all the billions of galaxies and supermassive black holes and stars and all that currently exists — are thought to have originated from a single point. Then "Big Bang". And then in an infinitely small amount of time after that, it started expanding. The density of matter at that point would have made a black hole look like aerogel [wikipedia.org]. Further, the thought that the speed of light is a constant pertains to its speed in a vacuum. At that time, there was no vacuum. As I understand it, everything was packed so tightly together that light (photons) were impeded by the Quark-Gluon Plasma [wikipedia.org] that is thought to have existed then. (See also: Quark Epoch [wikipedia.org].)
Then toss in that there were far, far more anti-particles around back then... it took some time for all the foo/anti-foo anhilations to occur.
Looking over the above links, as well as the Wikipedia article on Big Bang [wikipedia.org], suggests to me that if the speed of light were variant back then, someone else would likely have considered it and followed through on its implications. I lack the time at the moment to see if this has actually been pursued.
(2) Separately, what is "length"? If all of matter were universally expanding (every proton, electron, quark, etc.), could it be that the Planck length [wikipedia.org] is time-variant? I seem to recall reading something along these lines several years ago, but cannot recall what the theory/hypothesis was called.
At this point, my brain is freezing up trying to contemplate these things, so I'll close with this somewhat tangetially-related ditty The Siphonaptera (aka "Fleas") [wikipedia.org]:
Again, thanks for the very interesting and thought-provoking idea! It's things like this that make what I do here feel worthwhile.
Wit is intellect, dancing.
(Score: 2) by jasassin on Thursday December 01 2016, @08:18AM
I might remember wrong, but they do. It has already been seen and is an explanation for the seemingly impossible physical divide by 0 error.
jasassin@gmail.com GPG Key ID: 0xE6462C68A9A3DB5A
(Score: 1, Informative) by Anonymous Coward on Tuesday November 29 2016, @06:11PM
From where I stand, all the mountains look eternal and all the lakes have water.
Trump will fix it.
(Score: 4, Insightful) by VLM on Tuesday November 29 2016, @06:52PM
The mountains might be eternal but you look close and you're gonna WTF about ocean bottom seashells on the top of the mountain. Fish skeleton fossils. Ocean ooze turned into limestone. Gets even worse when you slap GPS survey grade equipment up there a couple years and the eternal mountain is moving and changing shape...
Likewise you can see lakes full of water all you want but its trivial to F around with a shovel and look at human scale sediment and determine the lake was gouged out in glacial melt era times. Huh. I live in a glacial area with tons of lakes but not too far from non-glacial areas where the lakes all filled in with muck and are gone.
A lot of science boils down to if you don't look too close there ain't much to see, but once you get the magnifying glass and look real close and start digging in the decimal places a lot of stuff doesn't make any sense unless elaborate and complicate theories are constructed, at which time you can make predictions about what you'll find under your shovel on that other mountain over thar and practically all of the time the prediction works. You might not like some of the implications of those theories but they do seem to predict stuff pretty accurately, mostly.
(Score: 1, Funny) by Anonymous Coward on Tuesday November 29 2016, @08:46PM
Bah! I'll go with my common sense and traditional values while you pie-in-the-sky dreamers scam the government for grant money.
(Score: 2) by VLM on Tuesday November 29 2016, @10:51PM
Its trivially testable, hand out some ancient copies of the Dead Sea Scrolls to one team, and some ancient copies of some obsolete petroleum geology textbooks like an original edition of Levorsen and simply watch and see who strikes oil first...
(well I assume Levorsen isn't still cutting edge anyway)
(Score: 2) by melikamp on Tuesday November 29 2016, @08:13PM
(Score: 3, Interesting) by aristarchus on Tuesday November 29 2016, @08:14PM
“Before I sought enlightenment, the mountains were mountains and the rivers were rivers. While I sought enlightenment, the mountains were not mountains and the rivers were not rivers. After I attained enlightenment, the mountains were mountains and the rivers were rivers.”.
Master Dogen