Does Dark Energy Exist?

[I_Hate_Infinity]

I know this is a topic still in the realms of theory and we have little data but would my debate my opinion of an external force creating the expansion we see?

Is dark energy really an anit-gravitational force, pushing the Universe outwards? Or is it that the Universe is expanding into a vacuum that is sucking space outwards to fill the void?

What makes us conclude it is an internal force/process acting on space-time to expand it in all directions, instead of an external imbalance that nature is trying to equal out?

An external vacuum should also create the condition of an accelerating, expending Universe that we see, right? If the opposite is true and there is an internal source of repulsive energy, what do we know about it that makes it real? Is 'dark energy' just a label for a the conflicting data from theory (rate of expansion from big bang with only gravity as the pervasive force acting on space-time) and the observed physics (of an expanding universe which is increasing in speed) which makes us believe another force is at work here...

I believe we've allocated about 78% of the constitution of the Universe to Dark Energy, 18% to Dark Matter and 4% to Matter (please correct)

I'd like to here your thoughts on this.

Infinity

[vascop]

There are some things I'm not entitled to have an opinion on because I have not studied them sufficiently, and so it is much more sensible to consult a reputable source, such as a book written by an expert in the field.
This goes for everybody not just me. There are some things you are not entitled to have an opinion about.

[vascop]

OG
Not according to Jim Al-Khalili.

[jim360]

I think vascop has a point, to be fair. It's lovely to see someone asking questions about the Universe and trying to take answers about it on board. However at some point the question you are asking either (a) has no answer even for the experts, or (b) does have an answer but it's very technical and beyond explaining in an AnswerBank post, or (c) does have an answer but you have to be a specialist in the field to understand it. In that case directing you to a book written by such a specialist is really the best place to start.

In answer to your idea of there being a vacuum outside the universe sucking it outwards -- well, that might be possible and I believe might just about fit into a plausible string theory, but you would have to be able to find a way to test this against the simpler 'Dark Energy' Theory, by experiment. I'm not convinced that such an experimental test exists. How could it? You cannot stick your head outside the universe and look. By contrast Dark Energy ought in principle to be measurable and already there are theories in which natural dark energy terms emerge. They're just either way off the anticipated value or only set to the correct value in an ugly manner that doesn't really explain anything.

Dark Energy and the problem of an apparently expanding universe that is accelerating outwards is still very poorly understood. We haven't even solved the problem of Dark Matter yet, although there may be an exciting update in that in the next month or so.

Anyway I'd head over to Jim Al-Khalili's book, or any of Stephen Hawking's, for a full and very readable account. You need far more than 4,000 characters to answer these questions, and far more than just words to explain many of these concepts.

[Old_Geezer]

OK when I've read through the pile of about 30 odd books I've bought and not got around to, I'll consider buying that one ;-)

[jim360]

I just wanted to say that if you've been discouraged from asking questions, please don't be. Just be aware that sometimes the answers are either not known or can't be explained without reference to technicalities.

"Everything should be made as simple as possible, but not simpler." - Einstein

[vascop]

I agree with Jim.
IHI, Keep 'em coming.

[I_Hate_Infinity]

Excellent! I'm sorry for my outburst and it wont happen again... I may have the ultimate question for you though.... Look at the new thread on Science category...

IHI

[beso]

I expect one day scientists will look back on dark energy as we do upon the concept of phlostigen which was an early explanation of fire.

[Old_Geezer]

Hi vascop, I managed to purchase a copy of the book and read chapter 3, which I assume is the piece you referred to.

I read that the universe may have started as an infinite universe. But the definition given seems to be that this is because it would have had an infinite number of points in it each of which is infinitesimal in size. I think that isn't quite what I would describe as an infinite universe. Indeed the description goes on to say that, at this starting point, the universe still has zero volume.

If I am to consider the existing universe I live in as being infinite, then that surely implies it is infinite in volume as otherwise we have a definition problem. (I stress I'm prepared to grant that for a finite volume universe to have an infinite number of points.)

So the problem I have remains with me still. (Although I grant you it maybe it just hasn't been explained enough for my understanding.) A universe that started with zero volume, and which now I'm to consider has infinite volume in the finite time between, must have expanded it's volume at an infinite rate at some point. And that is something I find less feasible than most other conjectures regarding the universe.

If I have to accept infinite acceleration in order to accept an infinite universe then it goes quite low on my list of likely explanations.

Sorry, appreciate this is off the subject of dark matter though.

[I_Hate_Infinity]

I hate infinity :'(