Faster than light expansion

[Art]

Is the theory that the universe is expanding faster than light a fringe or main stream theory?

How was this calculated? What happens to the rules of causality if this theory is true and how could it be tested?

I should mention I know very little about the subject so try to keep any answers reasonably simple so a 'simple' layman like myself can understand it 

many thanks

[Astronuc]

I think off the top of my head, what we see seems to be traveling at a finite speed, which is less than the speed of light.

Thinking about the "Big Bang", then assuming it started in some small finite volume, the light produced at that point had to travel out ahead of whatever matter had been created up to that time. 

Then accordingly the light traveled outward at 'the speed of light' into 'nothingness' (or the Void) and ostensibly is still traveling outward because there is nothing from which to be reflected or scattered backward toward from where it came.

But that begs one to ask - into what is the universe expanding, and what is/are the boundary condition(s) of the 'physical' universe.

There is perhaps part of the universe we simply cannot 'see'.  Then the question is - "How big is that part which we cannot see?"

Excellent question, by the way!

 

[Orstio]

Is the theory that the universe is expanding faster than light a fringe or main stream theory?

The universal expansion cannot really be measured in terms of internal speeds.  Space and time do not necessarily follow the same laws that govern the things that reside inside them.  What we use to measure expansion is the indirect measurement of redshift of objects that are very far away.  As distance increases, objects tend to be more red-shiftted, which indicates they are moving away at an accelerating rate.  It is believed that the acceleration is caused by the expansion of space and time.  So, it is conceivable that there are objects far enough away that they are moving away at a rate greater than the speed of light due to expansion.

How was this calculated? What happens to the rules of causality if this theory is true and how could it be tested?

Causality would never come into play.  If something is moving away due to expansion so fast that not even its light could ever reach us, then it would never have any effect upon us.  In this scenario, there would be an "event horizon" at the distance where the expansion would cause objects to move away faster than the observable light.  Because it is impossible for us to travel faster than light, we would never be able to "catch up" to the expansion, so no causality comes into play.