Faster Than The Speed Of Light?

[Brian Peacock]

Theory challenging Einstein's view on speed of light could soon be tested

The newborn universe may have glowed with light beams moving much faster than they do today, according to a theory that overturns Einstein’s century-old claim that the speed of light is a constant.

João Magueijo, of Imperial College London, and Niayesh Afshordi, of the University of Waterloo in Canada, propose that light tore along at infinite speed at the birth of the universe when the temperature of the cosmos was a staggering ten thousand trillion trillion celsius.

It is a theory Magueijo has being developing since the late 1990s, but in a paper published on Monday he and Afshordi describe for the first time how scientists can finally test the controversial idea. If right, the theory would leave a signature on the ancient radiation left over from the big bang, the so-called cosmic microwave background that cosmologists have observed with satellites.

“We can say what the fluctuations in the early universe would have looked like, and these are the fluctuations that grow to form planets, stars and galaxies,” Afshordi told the Guardian.

The speed of light in a vacuum is considered to be one of the fundamental constants of nature. Thanks to Einstein’s theory of general relativity, it was stamped in the annals of physics more than a century ago at about 1bn km/h. But while general relativity is one of the cornerstones of modern physics, scientists know that the rules of today did not hold at the birth of the universe....

https://www.theguardian.com/science/201 ... -be-tested

[Svartalf]

isn't it already known that depending on the medium, the spead of light is not an absoulte makimum and it's particles going faster than it that release photons in nuclear reactors producing Cherenkov radiation?

[JimC]

isn't it already known that depending on the medium, the spead of light is not an absoulte makimum and it's particles going faster than it that release photons in nuclear reactors producing Cherenkov radiation?

The vacuum speed is a maximum, but in a medium like water, it travels about 30% slower. Beta particles released by radioactive decay can travel at around 99% of the speed of light in a vacuum, so for radioactive decay in water, the particles briefly exceed the speed in that medium. As they brake to an "allowable" speed, they do indeed release their excess energy as Cherenkov radiation.

[Brian Peacock]

I bet the kind of sums needed to pluck evidence of proto-lightspeed from the CMB are devilish tricky.

[pErvinalia]

One thing I have problems grasping is the idea that we can see back to the early universe by looking at distant galaxies. If the universe is say 15billion years old, then looking at stars 14.5 billion light years away shows us what the universe was like at 500million years old. But the light from that time would have long passed us. When it started its journey we were a lot closer than 14.5 billion light years away.

Is this something to do with the expansion of space-time as well as the broadening distances between everything due to so-called dark energy?

[Brian Peacock]

Yes. The kind of spacial mental model explained by Euclidian geometry breaks down when dealing with the curvatures of spacetime. That's why we have to rely on deeper mathematical models. Jim will now provide the equations.

[pErvinalia]

There should be a way of explaining it without equations. I assume it's because "absolute" distance has expanded, therefore light travelled less "absolute" distance in the past than it does now. So even though the universe was smaller 14.5bn yrs ago, light from a star like I described would still take 14.5bn years to traverse that "smaller" distance.

[Brian Peacock]

Have you tried...











... YouTube.

[JimC]

Good question, rEv, about the issue of light travelling through expanding space. Really not sure of the answer...

[Brian Peacock]

It's bloody weird stuff that's for sure. A photon takes c.8 mins to travel from the Sun to the Earth, yet for the photo itself, travelling at lightspeed, it takes no time at all.

[mistermack]

It's bloody weird stuff that's for sure. A photon takes c.8 mins to travel from the Sun to the Earth, yet for the photo itself, travelling at lightspeed, it takes no time at all.

That's only weird to us, because time dilation is so tiny, that we never experience it in our day-to-day lives. (or to be more accurate, we cannot detect it)
That's because the speed of light is such a gigantic number, compared to the speed of humans.

The way I look at it, is that when we are at rest, the energy inside our atoms is constantly whizzing around itself at the speed of light. That's when we are at rest. But when we are moving along at 100 mph, the whizzing would have to happen at c + 100 mph.
It can't do that, so the whizzing has to slow down. If the whizzing of the energy inside you slows, that means that time for YOU slows.
And the same goes for the photon. Travelling at the speed of light, the photon can't whizz AROUND at all. It can only go straight. No whizzing around means no time passes.

[cronus]

Faster than light means going back in time but in the early universe that wouldn't count for much given how little had happened.

[mistermack]

The speed of light is only relevant, when there is STUFF that defines distance.
If all of the stuff in existence doesn't have that property, then the rules are different.
Distance and time go out the window, and with it, the speed of light.

[Feck]

It's bloody weird stuff that's for sure. A photon takes c.8 mins to travel from the Sun to the Earth, yet for the photo itself, travelling at lightspeed, it takes no time at all.

And Why(or more correctly How ) does light "slow down" in a medium like water or glass ? I've Not heard of a good explanation. I've had a lot of people angrily repeating the lies they tell students but no good explanation .

[Brian Peacock]

It's bloody weird stuff that's for sure. A photon takes c.8 mins to travel from the Sun to the Earth, yet for the photo itself, travelling at lightspeed, it takes no time at all.

That's only weird to us, because time dilation is so tiny, that we never experience it in our day-to-day lives. (or to be more accurate, we cannot detect it)
That's because the speed of light is such a gigantic number, compared to the speed of humans....

...but not so big when compared to the speed of love.