Originally posted by KazetNagorra
I don't understand how this results in speeds larger than c, care to elaborate?
Just remember, if you strap a rocket to your asss, all the energy of the universe, if you could do that, would not get you even TO the speed of light, much less exceeding it, just extremely close, and what really happens is you make your own 2 dimensional world where you are flatter than a pancake, even though you don't feel it and time goes by inside your craft but the outside world has a different time flow and from their viewpoint, they think you are now immortal, till you slow down to sub relativistic velocities.
Now the idea that distant parts of the universe is separating 3X faster than light just means that space is in some sense 'thinning out' even though it has been pointed out that is a limited analogy.
If you imagine two treadmills that are close together but going in opposite directions and stuff is on both treadmills, the parts will separate but there is no acceleration of the parts, the treadmill is like space, the distance between parts gets greater with no acceleration of the matter at the two distances.
It's almost like space is being 'pumped' in between each atom at the same time, and gives the effect like I mentioned with two treadmills going in opposite directions. As far as the boxes on the treadmils are concerned, they have had no energy added in terms of kinetic energy but they are still separating in distance.
In fact, if you had a billion light year long cord, and had it hooked up to a generator where each end has a large mass, and you have a lot of cord left over, you could in theory generate energy by the simple fact that the cord is being pulled apart, therefore if you resist the unwinding by hooking it to a generator you would get free energy thanks to the expansion of the universe.
The concept of a variable speed of light has been debated also and so far not much change is seen from 10 billion years ago to today, but even a tiny shift would be seen as new physics in action. News at 11🙂
I saw a talk given by Guth a few decades ago and I asked him that same question about exceeding the speed of light, I had used his figures of starting out as essentially a point source and expanding to something say the size of a football (now there is debate over that footballs' shape) in I think it was 10E-34 second. I did a quick calculation and during Q&A I told him that came out to an expansion 22 orders of magnitude greater than the speed of light and he responded and I quote " You did your arithmetic right" and then went into how it was space expanding taking matter with it which IS allowed, space does not have a speed limit.
Of course all that said and done, it has not been absolutely proven that his inflationary theory is correct, it just takes care of most of the observations made on how the universe is actually behaving, where for instance, the MBR (microwave background radiation) is so almost perfectly smooth across the sky, to within one part in 100,000 or so, that could not happen if things had just popped out of the universe at even the speed of light, one side of the sky would start accumulating huge differences because photons or other forms of energy would not have enough time to interact so everthing in the universe would have been independent of one another which is in fact what we do NOT see, so inflation solves that conundrum.
Whether something else comes along that solves the same problems without requireing that kick start is another story. That's what the alternative theories about the variable speed of light is supposed to address, the idea that light went a lot faster in the early days of the universe would also account for the same observations we see today. Problem with that is as best as can be determined as of this date, no such change has been seen. So inflation so far wins by default.
The universe expands faster than the speed of light but matter doesn't care because it has not been given direct kinetic energy to do so like two planets separating because a big rocket was installed on each planet and they separate because of the added kinetic energy, that's the difference.