Alan Guth vs Joao Maguelijo

[Jimmyboy]

Has anyone seen the documentary by Joao Maguelijo on discovery about the Horizon problem. He proposes in his theory that the speed of light was greater at the moment of the big bang explaining the unified cosmic background temperature. My question is what is the difference between Alan Guths theory and Joao's. Surley Alan Guths inflation theory would mean a similar increase of the speed of light.. ???

 

[ramparts]

Nope - inflation models occur within pretty standard physics, as far as the speed of light goes. I don't know much about these variable speed of light theories, or how viable they are, but it seems to be a pretty different mechanism - if the speed of light was greater in the early universe, then it's possible for distant regions to be in contact (and equilibrium) with each other without a need for a rapid period of inflation.

 

[Jimmyboy]

Thanks rampart.. If possible could you explain in a simple nut shell Guths inflation theory so i know how it differs to the veriable speed of light theory...

 

[ramparts]

Well, don't quote me on Guth's inflation theory - Guth proposed the thing in 1981 or so, and it's taken a life of its own since (very few theories are owned by any one physicist, and most of the ones that are, are so because they're not very good theories). But the basic idea of inflation is that very early in the universe's history, a tiny fraction of a second after the Big Bang, the universe started accelerating very very rapidly, "inflating", and then after another fraction of a second stopped, and resumed expansion at a more reasonable pace. This proposes to explain why parts of the universe that weren't in contact with each other would all have the same temperature, and also explains how quantum fluctuations in the early universe got blown up, which ended up forming the seeds of galaxy formation much later on.

 

[Jimmyboy]

Have done abit of research and actually alan guths theory does involve velocity faster than light.. Looks like joao is abit of a rip off...

 

[origin]

I am a little confused, you seem to have misunderstood the inflation model or perhaps I am misunderstanding you. You said:

Has anyone seen the documentary by Joao Maguelijo on discovery about the Horizon problem. He proposes in his theory that the speed of light was greater at the moment of the big bang explaining the unified cosmic background temperature. My question is what is the difference between Alan Guths theory and Joao's. Surley Alan Guths inflation theory would mean a similar increase of the speed of light.. ???

The inflation model does not involve a change in the speed of light.

But then you say:

Have done abit of research and actually alan guths theory does involve velocity faster than light.. Looks like joao is abit of a rip off...

This is true that the velocity (actually the rate of expansion) is faster than the speed of light, but again there is no change in the speed of light with the inflationary model.

So clearly there is a huge difference between Joao (changes in the speed of light) and Guth (no changes in the speed of light).

Right?

 

[Jimmyboy]

I think I understand what you are saying, so you are saying in the inflation theory that the universe expanded faster than the speed of light BUT if there where light rays present at the time they would still have travelled at the standard light speed velocity??? if so i just assumed that if the universe expanded faster than light, light would have automaticaly been faster.. obviously not...

 

[ramparts]

I think I understand what you are saying, so you are saying in the inflation theory that the universe expanded faster than the speed of light BUT if there where light rays present at the time they would still have travelled at the standard light speed velocity??? if so i just assumed that if the universe expanded faster than light, light would have automaticaly been faster.. obviously not...

Apparently not It sounds like you've got it down. One thing to consider is that while space itself expanded faster than the speed of light, nothing was actually moving faster than light itself - it's just the background space was expanding. This is a pretty subtle distinction but it's important. Nothing travelled from one point to another faster than light - everything moved away from everything else at those speeds.

 

[rlb2]

I for one think there is a chance that we are measuring the universe the wrong way as a result the Hubble law is actually measuring light from a fourth dimension speed of light perspective, warped space/time. This may be similar to the way that we measure classical physics gravity from a 3D spherical point of view, inverse square law, but over greater distances causing an illusion of a red shift in our measurement and our observations. Or as Hubble would explain "spatial curvature if the redshift correction was made assuming no recession."

So in other words the Steady State Universe may actually exist we are just measuring it the wrong way.

 

[ramparts]

I for one think there is a chance that we are measuring the universe the wrong way as a result the Hubble law is actually measuring light from a fourth dimension speed of light perspective warped space/time similar to the way that we measure classical physics gravity from a 3D spherical point of view, inverse square law but over greater distances causing an illusion of a red shift in our measurement and our observations. Or as Hubble would explain "spatial curvature if the redshift correction was made assuming no recession."

So in other words the Steady State Universe may actually exist we are just measuring it the wrong way.

Inglés, ¿por favor? I think "light from a fourth dimension speed of light perspective warped space/time" is a randomly thrown-together collection of vaguely scientific-sounding words, rather than something that (as its usage in your sentence suggests) can be measured.

For future reference, noun followed by verb is a good place to start. You can throw in direct and indirect objects from there. Good luck!

 

[MeteorWayne]

I've heard all the theories on inflation and I come to the same conclusion every time.
If "space" expanded, then what is space? Is it an invisible 3-dimensional graph necessary for matter to come into existence? ......etc

Spacetime is one single fabric that covers the entirety of our universe.... .

These posts are not related to the topic of the discussion, and have been moved to:

viewtopic.php?f=10&t=17616&start=60

 

[pjay]

Well I tell you what the difference between inflation and other theories is, claiming a change in lightspeed. Although both can account for the almost perfectly isotropic features of the CMB inflation is more in line with observation and theory. Inflation is solidly rooted in the standard theory that so far has resisted all attempts to falsify it. Variable speed of light theories are difficult to reconcile with observation. For all we know the speed of light is a constant. It is possible although not very likely that better observations in the future do show that it's variable over time.

Both theories however are in line with Einstein's theory of special relativity which claims that nothing that has mass can ever reach the speed of light, because it would require an unlimited amount of energy to accelerate to this point. Spacetime does not have mass. So in theory it is quite possible for spacetime to accelerate to speeds faster than light.

If you weigh the alternatives you need a lot of theory because the acceleration of the universe is governed by gravity. Negative pressure coupled with general relativity (the theory of gravity) might therfore explain inflation in a neat way. But since inflation is thought to have occured just shortly after the big bang, you need quantum mechanics to explain many of the effects of inflation. Unfortunately general relativity and quantum mechanics contradict each other.

Something like loop quantum mechanics might show a way out and it would even give sense to the notion of time BEFORE the big bang because spacetime never completely breaks down in a singularity. But that's another subject.

 

[Jimmyboy]

Thanks guys!!! thats cleared that up... and sorry Joao if your reading for calling you a rip off...

 

[astronomy_fan]

I am not familiar with the theories of those two gentlemen but I believe the speed of light may have changed with time. Speed of light is speed of transformation of space properties - magnetic to electric and vice versa. We don't know much about space properties at the time of the Big bang. They may have changed with time. A good analogy could be the changing speed of sound when changing media pressure. In fact I don't believe in "dark mater" and other dark substances and change of speed of light would give me more comfort as explanation of the increasing speed of the Universe expansion.

 

[rpmath]

Has anyone seen the documentary by Joao Maguelijo on discovery about the Horizon problem. He proposes in his theory that the speed of light was greater at the moment of the big bang explaining the unified cosmic background temperature. My question is what is the difference between Alan Guths theory and Joao's. Surley Alan Guths inflation theory would mean a similar increase of the speed of light.. ???

Speed of light is DEFINED to be constant. It is embedded in the way relativity defines space and time.

If you define the distance between A and B in meters as the time in seconds light needs to go between A and B divided by 299,792,458 there is no way you can get another value (well... replace that time by half the time measured by A the light does the path A-B-A to work in a single reference frame and avoid the simultaneity problem... but you still cannot get other value)

To talk about variable light speed you need other definition of distance.

Curvature of space-time is a way to keep that definition:
Light needs more time to go between 2 points if there is a gravity field in its path, so relativity says "gravity expands space" instead of "gravity slows light speed".

The same way if Joao Maguelijo says "light was faster" y can say space "was shorter" unless he has an alternate way to define distance.

 

[TyMoore]

The Speed of Light is a constant only because it is inversely proportional to the square rooted product of two other constants: The vacuum permitivity constant and the vacuum magnetic permeability constnat. The vacuum permitivity constant: epsilon-0=8.854188*10^-12 F/m (Farads per meter) The vacuum magnetic permeability constant is: mu-0=4*pi*10^-7 H/m (Henries per meter.) The speed of light is thus defined (from Maxwell's Equations) to be c=1/sqrt(epsilon-0*mu-0.)

Now having said that, the two physical constants epsilon-0 and mu-0 are properties of the vacuum, specifically the quantum vacuum. Anything that can change either (or more likely both) of those physical constants can change the speed of light. We see this every day: water in a swimming pool distorts images because the water molecules change the vacuum magnetic permeability (it is no longer a vacuum but a medium dominated by water) and the vacuum permitivity (the way the electromagnetic fields interact with the charges of the water molecules.) Light slows down in water...

To speed it up, the optical 'density' of the vacuum must become less...

One can make a mathematical argument that the space-time (the vacuum) within the event horizon of a blackhole becomes assymptotically distorted so that the speed of light increases toward a singularity...

One can certainly argue that the extreme conditions which existed moments after the big bang resulted in conditions which are not conventionally thought of as a vacuum (extreme pressure, radiation, energetic particles...) and that these conditions prevented what we think of as space-time from forming--thus you could end up with a really weird definition for the speed of light--it might even fluctuate briefly--infact, the concept of speed has no meaning at all in the absence of a meaningful definition of space and time...

All bets are off in those extreme conditions.

 

[MeteorWayne]

I personally don't believe that the big bang or a singularity for that matter is correct.

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This post is not related to the subject of the discussion, so has been moved to the same topic as the previous ones.

 

[mjcarpenter]

What I take from Joao's theory, is not so much challenging Guth and inflation, as to point out that we, or rather the physicists involved in these theories/discussions, were taking the speed of light being a constant factor, as a given. Guth presents strong arguments, but, as with almost every new theory, his has some "shortcomings". Guth relies on dark energy to account for some of the expansion of the universe. In addition, his theory for the beginning of the universe we know - quantum tunneling and parent universes - just dont seem to fit with what we "know", as of now. However, I am a believer in the "multi-verse" concept, which Guth's theory backs up quite well.
Joao's theory, being much more controversial and "out there", is also slightly more reasonable - in my eyes - in its assertion that the speed of light, which we know varies according to the medium through which the photons are traveling, may also vary when traveling through a vacuum. This too, along with Guth's theory, would call for the rewriting of our entire understanding of the universe, down to what I believe is the prettiest equation in physics; E=MC^2. While devastating to known physics, I think the confirmation (I realize that inflation has been "confirmed", but that was using other known forces, such as dark energy - as stated above) of one or the other would be the biggest step forward to our understanding of the nature of the universe, as well as our place in it.

 

[Taco_Bob]

I'm not a really big buff on this stuff, but I have had a lingering idea of my own for a while now.
We do know that light slows down a little when it passes from on ambient mass density such as air to a greater ambient mass density such as glass, and the inverse is also true. After all it's how our eye-balls work. So isn't it possible that light travels at "c" within our solar system due to the ambient mass density (AMD) of this solar system and that when it gets far enough away into interstellar space it speeds up? And perhaps on a larger scale, it also "sees" the galaxy in interstellar space as one AMD and then also when it leaves the galaxy and enters intergalactic space; it accelerates even more being within a yet smaller AMD. One way to check this out is to watch for super-novae and hope to see a reflection of one due to gravitational lensing so as to see the same supernova from two directions, thus providing a triangular method of measuring the average speed that the radiation traveled from the blast to here. Such reflections would be extremely faint and it would be difficult to know when to look. I don't believe in the (pounding my chest and grunting) "big bang" theory myself, but my theory would have interesting consequences if the "prodigious paroxysm theory-ification" is true. For instance, at the moment of the big bang, the AMD would be infinite, thus the speed of light: zero. Immediately after, as light gets out into empty space as the AMD drops due to expansion, the AMD would drop to zero, then the speed of light may have become incalculable for the light in the initial flash. Also, gravitaional lensing may have nothing to do with gravity per say, but simply the non-symetrical density that light experiences near by since to one side of the photon is a hyper-dense black hole and to the other, empty space. After all, the same effect may be observed with a sheet of construction paper. For all we really know, gravity itself may not actually have any effect on light at all (if I'm correct). If it did, then no light would have escaped the big bang but (say that thrice with haste) would have been caught up with by substance streaming out.

"We mortals ought never presume to write laws and
expect a Universe of infinite possibilities to obey them." -- Stephen V. McDonald