Hi Mark;
Well … hmm … I dunno … Given that no-one understands what Dark Energy is (ie: what gives rise to it, under what conditions it creates force, its interaction to result in the effects we see, etc, etc), I think it might be still valid to say that it exists even if we don't understand it.
The angle I can see (although I am finding it hard to accept myself, and this is only for a chin-wag type discussion), is that the following alternatives to explain the accelerated expansion exist:
i) some mechanism we don't yet even know about (what we don't know);
ii) our measurements are faulty/inaccurate/imprecise so its effects aren't real;
iii) other plausible explanations that have not yet been eliminated;
iv) 'dark energy'
Now, because 'dark energy' is not yet understood (or characterised in any particular specific sense), the label can still be applied to types (i) and (iv) above.
Now, these guys are claiming that they have disproven 'reverse gravity' (which would have fallen into type (iii) above, but is now eliminated). They have also shown that their measurements are accurate and are confirmed to be so, (type (ii) above bites the dust).
Steven raises "an inertia based dark energy free expanding Universe" and Susskind's QFT explanations, which might fall into (iii) above, although it is likely to be argued that neither of these is a 'plausible' hypothesis.
(I'm not too familiar with these hypotheses).
So, if it were to happen that 'dark energy', being defined as the 'catch-all' for what we don't know, and what we can't explain, it could still be argued that it is real. This would be because at the end of the day, something is causing it, so that something must also be real (because we can measure its effects) and that something is the catch-all label called 'dark energy' (the last-man-standing).
Steven;
If I don't quite know what (or the identity of who) is knocking at the door, but I can measure its action's effects (hence they, at least, are real), the only cause in my world of such an effect is real - ie: some kind of force, which I know is real … I've reproduced forces and characterised them for yonks … they are very familiar to me, and are caused ultimately by energy of some kind. So, I'm not sure that the door analogy works for me (?)
(Also guys, I'm easy on all this .. I'm not hung up on it and I'm prepared to admit defeat where a convincing counter is presented, but I think I'm also prepared to let Chris Blake off the hook. Perhaps I initially over-reacted to his claims. Carl's media conspiracy explanation still stands also, of course !
)
Have fun.
Cheers