http://www.sciencealert.com/the-speed-of-light-might-not-have-always-been-this-slow

The speed of light in a vacuum, or c, is pretty much the most fundamental constant in physics – and according to the general theory of relativity, gravity travels at the same rate.

But a new study suggests that the speed of light might not have always been this speed. In fact, in the early Universe, light might have outpaced gravity, and this new hypothesis could solve one of the biggest problems in physics.

Best of all, unlike a lot of hypotheses put forward in theoretical physics, this one can actually be tested, so we should be able to find out in the coming years if it’s true or not.

So what’s wrong with the speed of light and gravity in the first place? This conundrum comes from the earliest days of the Universe, and something called the horizon problem.

The horizon problem basically deals with the fact that the Universe reached a uniform temperature long before light particles (or photons) would have had time to reach all corners of the Universe.

If the speed of light in a vacuum really is constant, and always has been, then how did the cosmos heat up so fast?

Usually this problem is dealt with by the idea of inflation – which suggests that the Universe went through a huge period of expansion early on.

The hypothesis is that the temperature must have evened out when the Universe was all small and condensed, back when light didn’t have as far to travel, and then it rapidly grew.

That makes sense – except no one knows why inflation started or stopped, and there’s no way of testing it.

An alternative hypothesis has now been put forward by physicist Niayesh Ashfordi from the Perimeter Institute in Canada, and João Magueijo from Imperial College London.

Their idea is this: in the earliest days of the Universe, light and gravity travelled at different speeds.

more at URL

Not again!

This idea pops up once every two to three years.

mollwollfumble said:

Not again!

This idea pops up once every two to three years.

YECs love the idea.

sibeen said:

mollwollfumble said:

Not again!

This idea pops up once every two to three years.

YECs love the idea.

They love the idea of a Big Bang as well.

That’s not a reason to dismiss it.

run in to something similar in a book on antenna theory ~15year ago (speculations about propagation of radio waves, in contracting universe etc)

not that understood’t bein’ dysmathtic, and bit thick too

transition said:

run in to something similar in a book on antenna theory ~15year ago (speculations about propagation of radio waves, in contracting universe etc)

not that understood’t bein’ dysmathtic, and bit thick too

this was discussed a while back.

mollwollfumble said:

Not again!

This idea pops up once every two to three years.

And if it HAS been different in the past, it will proly be different in the future too, perhaps it is continually changing?

bob(from black rock) said:

mollwollfumble said:

Not again!

This idea pops up once every two to three years.

And if it HAS been different in the past, it will proly be different in the future too, perhaps it is continually changing?

Nah, the only explanations consistent with observations are that is was only significantly variable in the first 10^-32 seconds after the big bang. But since there’s no need for it to be variable back then we may as well use Occam’s razor to say that the speed of light has always been constant.

PS, to say that cosmological inflation is untestable is false.
See, for example Planck 2015 results. XX. Constraints on inflation

mollwollfumble said:

bob(from black rock) said:

mollwollfumble said:

Not again!

This idea pops up once every two to three years.

And if it HAS been different in the past, it will proly be different in the future too, perhaps it is continually changing?

Nah, the only explanations consistent with observations are that is was only significantly variable in the first 10^-32 seconds after the big bang. But since there’s no need for it to be variable back then we may as well use Occam’s razor to say that the speed of light has always been constant.

PS, to say that cosmological inflation is untestable is false.
See, for example Planck 2015 results. XX. Constraints on inflation

I note that the Wikipedia entry on cosmic inflation is five years out of date. They should use the data in the paper I linked to.

I wonder whether this means anything.

dv said:

I wonder whether this means anything.

The meaningfulness or otherwise of such self referential statements is a question with no widely accepted answer.

I lean towards “no” myself.

The Rev Dodgson said:

dv said:

I wonder whether this means anything.

The meaningfulness or otherwise of such self referential statements is a question with no widely accepted answer.

I lean towards “no” myself.

LPITW … it would be pretty weird to find out that the speed of gravity and the speed of e/m were different previously but are precisely the same now. I could believe that they approached each other asymptotically, I suppose, such that by now the difference is negligible.

I’s tempted go to mum’s‘n pinch a beer
got some xmas beverages in the fridge
but I ‘ad rasberry cordial’n ol’ feel better
it not so manly thing to say but me I did

The main problem I have with changing speed of light is that it changes the amount of energy in the universe, which violates Noether’s Theorem (among other things).

btm said:

The main problem I have with changing speed of light is that it changes the amount of energy in the universe, which violates Noether’s Theorem (among other things).

does changing phase change any amount of energy

maybe it was another phase we don’t know about

CrazyNeutrino said:

btm said:

The main problem I have with changing speed of light is that it changes the amount of energy in the universe, which violates Noether’s Theorem (among other things).

does changing phase change any amount of energy

maybe it was another phase we don’t know about

what other “phases” of light are there?

JudgeMental said:

CrazyNeutrino said:

btm said:

The main problem I have with changing speed of light is that it changes the amount of energy in the universe, which violates Noether’s Theorem (among other things).

does changing phase change any amount of energy

maybe it was another phase we don’t know about

what other “phases” of light are there?

ones we do not know about yet

what if the state of matter was different during the first moments of the big bang?

CrazyNeutrino said:

JudgeMental said:

CrazyNeutrino said:

does changing phase change any amount of energy

maybe it was another phase we don’t know about

what other “phases” of light are there?

ones we do not know about yet

what if the state of matter was different during the first moments of the big bang?

so pink unicorns then?

• what other “phases” of light are there?

“Stun” and “Kill”…

JudgeMental said:

CrazyNeutrino said:

JudgeMental said:

what other “phases” of light are there?

ones we do not know about yet

what if the state of matter was different during the first moments of the big bang?

so pink unicorns then?

we don’t know what color they are, they could be blue ones

Magueijo and Ashfordi have a predicted CMB value of 0.96478, which is a similar, but not identical figure to the recent reading of 0.968.

How different, slower or faster?

CrazyNeutrino said:

btm said:

The main problem I have with changing speed of light is that it changes the amount of energy in the universe, which violates Noether’s Theorem (among other things).

does changing phase change any amount of energy

maybe it was another phase we don’t know about

Two very good comments.

Yes, phase change of the quantum vacuum releases latent energy that drives cosmic inflation. And that’s one reason why changing the speed of light is seen as an alternative to cosmic inflation.

There are alternatives to general relativity that allow for the speed of light to vary with, for instance, wavelength. But those are likewise not supported by experimental evidence.

btm said:

The main problem I have with changing speed of light is that it changes the amount of energy in the universe, which violates Noether’s Theorem (among other things).

There are at least two resolutions to that problem:

1. Other parts of the Universe may have the speed of light changing in the opposite direction, so that the overall energy is constant.

2. Noether’s Theorem may be wrong. (Should it in fact be called a theorem? It seems more like an assumption to me).

The Rev Dodgson said:

(Should it in fact be called a theorem? It seems more like an assumption to me).

TATE says I’m wrong, she did in fact prove it, so it is a theorem.

Whether it is actually applicable to The Universe (or our neck of the woods of The Universe) is another matter.

If the different speed of light is postulated to explain the lumpy universe why cant the lumps instead come from chaos?

mollwollfumble said:

mollwollfumble said:

bob(from black rock) said:

And if it HAS been different in the past, it will proly be different in the future too, perhaps it is continually changing?

Nah, the only explanations consistent with observations are that is was only significantly variable in the first 10^-32 seconds after the big bang. But since there’s no need for it to be variable back then we may as well use Occam’s razor to say that the speed of light has always been constant.

PS, to say that cosmological inflation is untestable is false.
See, for example Planck 2015 results. XX. Constraints on inflation

I note that the Wikipedia entry on cosmic inflation is five years out of date. They should use the data in the paper I linked to.

Have now fixed Wikipedia.
https://en.wikipedia.org/wiki/Inflation_(cosmology)#Observational_status

mollwollfumble said:

mollwollfumble said:

mollwollfumble said:

Nah, the only explanations consistent with observations are that is was only significantly variable in the first 10^-32 seconds after the big bang. But since there’s no need for it to be variable back then we may as well use Occam’s razor to say that the speed of light has always been constant.

PS, to say that cosmological inflation is untestable is false.
See, for example Planck 2015 results. XX. Constraints on inflation

I note that the Wikipedia entry on cosmic inflation is five years out of date. They should use the data in the paper I linked to.

Have now fixed Wikipedia.
https://en.wikipedia.org/wiki/Inflation_(cosmology)#Observational_status

For instance, before Planck the universe was observed to be flat within “a few percent”. Now we know it’s flat within 0.5%.

mollwollfumble said:

mollwollfumble said:

mollwollfumble said:

I note that the Wikipedia entry on cosmic inflation is five years out of date. They should use the data in the paper I linked to.

Have now fixed Wikipedia.
https://en.wikipedia.org/wiki/Inflation_(cosmology)#Observational_status

For instance, before Planck the universe was observed to be flat within “a few percent”. Now we know it’s flat within 0.5%.

On the page now going to read it during the day looks interesting even if the maths is quite beyond me.

String theory requires that, in addition to the three observable spatial dimensions, additional dimensions exist that are curled up or compactified (see also Kaluza–Klein theory).

How could these additional dimensions that are curled up be uncurled ? and is so what would actually happen