[Jon Bondy]

Jon Bondy asked the Naked Scientists:
   
In discussions about Dark Energy, people explain that they detected this (or hypothesize it?) because some energy would be required to expand the universe. 

I've never understood why people believe in the Cosmic Inflation that is reputed to have taken place shortly after the Big Bang.  But, if this Inflation occurred, don't we need to justify that, too, in terms of energy?  What energy was used to perform that Inflation?  How does that compare with the current Dark Energy concept?  It is interesting to note that for a long time, there was debate about whether the universe would expand forever, or would collapse, but no one worried about how that motion would be energized: all of a sudden, we now believe that it is expanding in such a manner that a new source of energy is required.  Is this because the universe is not only expanding, but the rate of expansion is increasing (accelerating)?

Thanks!

Jon

What do you think?

[Phractality]

They call it "dark energy" because they have no idea what it is or where it comes from. There are many models, theories and concepts which attempt to explain it, but none are widely accepted; consequently, they are best discussed in the New Theories section of Naked Scientists. In some multiverse models, dark energy comes into our universe from another universe, so our universe is not a closed system. I have my own model, which contains a detailed description of what dark energy is, where it comes from and what else it does in addition to driving the expansion of space.

[imatfaal]

It is interesting to note that for a long time, there was debate about whether the universe would expand forever, or would collapse, but no one worried about how that motion would be energized: all of a sudden, we now believe that it is expanding in such a manner that a new source of energy is required.  Is this because the universe is not only expanding, but the rate of expansion is increasing (accelerating)?

Yes - for a long time it was thought the galaxies moved simply and either they had a velocity high enough to carry on forever (ie an escape velocity from the rest of the universe) or the velocity was not high enough and they would slowly grind to a halt and start to fall back together.  Neither of these would require a further input of energy.  But when things get faster - ie the expansion is increasing you need a source to drive that.

As Fract said above - no one has detected or even properly theorized dark energy - and there are non-energetic ways of explaining it.   

The inflationary period of the universal expansion is thought to have got its energy from the enormous positive vacuum energy density that the postulated form of the universe would have had - this is the intrinsic energy of empty space.  Sorry it doesn't really get simple.   

[Soul Surfer]

The answer is that no one really knows YET.   Most of the activities within our universe are limited by the laws of the conservation of energy.  There is however one and as far as I can see only one, that is not limited in this way, that is well understood and accepted by all and largely ignored.    All scientists accept that as matter within a collapsing (and probably rotating) black hole progresses towards the hypothetical "singularity", this can be expressed as a point in the very unlikely case of zero rotational energy, or as a ring in the case where there is rotational energy, both potential and kinetic energy will be released, and this release of energy will progress without limit.  That is the point singularity (if it was to happen) has an infinite total amount of energy and not just an infinite energy density.  This clearly means that in the collapse of any black hole there is plenty of energy to create and expand without limit the largest possible universe even having only a few solar masses of matter to start with!

Please note that this is NOT a new theory it is totally within the accepted remit of current science.   On the basis of Occam's razor this is by far the simplest and most likely source of energy to power the expansion of what we see as our universe.  It is currently seen and well accepted that the universe has many more than three dimensions of space and one of time.  It is probably the collapse of these dimensions that we cannot see that powers the expansion of the ones that we can and keeps the whole thing within the rules of the conservation of energy.

To go a bit further into string theory.  Most aspects of the many theories that compose these things have within them a reciprocal relationship whereby as one dimension contracts others expand.  This is also true of information theory (another important feature of many theories)  where time-bandwidth product (a reciprocal relationship)  defines the amount of information.

To take this further would enter the range of new theories.  I can take it a lot further but have not yet been able to put the ideas together well enough to my satisfaction to subject them to peer review.

[yor_on]

Interesting SoulSurfer, but you're postulating other dimensions that somehow doesn't need to obey the laws regulating a singularity there, if I get you right?

Consider a point filled with light, if we could pour infinite 'energy' in it? Would it become infinitly 'big', as seen from the inside? How about a 'virtual particle' then. Also able to have a 'infinite energy'? As I understands it the only thing regulating that 'energy' is that it doesn't fit inside our 'arrow of time'. Assuming that it takes a 'instant' though, it do fits, and so disturb those conservation laws, and, just how many spontaneous 'instants' can a (infinite) SpaceTime have?

'Energy', such a weird idea, and our photon its chalice.

[Soul Surfer]

Mathematical singularities make no physical sense energy levels and densities may get very high but something WILL happen to prevent this.  Its just that we can't be sure what will yet.  I am just suggesting some simple pointers to what might happen without going beyond the limits of the standard models.

[yor_on]

You could actually assume the opposite too Jon. That all energy there is, is regulated through SpaceTime, just as 'gravity'. Assume a ocean of 'unlimited energy' and 'gravity' at the beginning of a BB. Then assume what we have now, then define how that could be possible. In such a scenario the BB would be a limiting factor and the inflation and the later expansion we see should be 'SpaceTimes'  constants strengthening, and possibly weakening again as the expansion seems to accelerate?

On the other hand, any expansion should add up into a accelerating scenario as more 'space' becomes 'available' for further 'expansion'. In a way it seems as a 'run away' scenario thinking of it, as more 'space' comes to be in each moment for further 'expansion'.

It's confusing