But that's just devil's advocacy. I'm in the 'space actually expands' camp, although scientifically the observations are as yet insufficient and the theory is underdeveloped. Actually, "expands" is incorrect. It's more like it "reproduces". The additional space between widely separated objects is just like the space that was there before - it doesn't 'thin out.' This may be partially ATM, but it is consistent with Einstein's cosmological constant.
Everyone is entitled to his own opinion, but not his own facts.
That's more like a guess looking forward to the next theory, rather than a ramification of the current ones. It would have to have something to do with why inflation selected a particular hyperslice of spacetime to expand like crazy, and perhaps was even the origin of the local Minkowski geometry-- I don't know if anyone knows which came first, Minkowski or inflation. Such guesses are a good way to motivate new theories, but have less than a stellar track record in the history of science!But that's just devil's advocacy. I'm in the 'space actually expands' camp, although scientifically the observations are as yet insufficient and the theory is underdeveloped. Actually, "expands" is incorrect. It's more like it "reproduces". The additional space between widely separated objects is just like the space that was there before - it doesn't 'thin out.' This may be partially ATM, but it is consistent with Einstein's cosmological constant.
That doesn't mean that necesarily there is something wrong, but it's always healthy in scientific terms to keep an open mind, even if one is not allowed to elaborate the suspicions in this type of 'textbook science only' oriented forum
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The stuff of the cosmos is what it is and it does what it does, and does not care whether or not mortal humans such as ourselves think it is absurd.
Order of Kilopi
Order of Kilopi
I think there is a very important distinction to make here. There never was anything "ATM" about claiming that modern science is wrong. I'll claim that right now: modern science is wrong. Throw me into ATM, I said it! But wait, that isn't ATM-- all scientists know that modern science is wrong, it's a perfectly mainstream attitude. It's what gets scientists out of bed in the morning, in fact.That doesn't mean that necesarily there is something wrong, but it's always hea[lthy in scientific terms to keep an open mind, even if one is not allowed to elaborate the suspicions in this type of 'textbook science only' oriented forum
So what does "ATM" really mean? It means you think science is taking the wrong path to new hypotheses, not that it isn't "right." It is suggesting there is some other hypothesis that is more promising than, say, dark matter and dark energy. That would be ATM, because at the moment it is quite clear that all the progress is being made in the direction of dark matter and dark energy hypotheses. That doesn't mean other directions should not be given fair due, but it certainly means that other directions have to pass muster before we can justify major outlays of resources on them, when the resources directed toward dark matter and dark energy have been so dramatically fruitful so far.
I would say that a certain attitude of dismissing without the benefit of the doubt any alternative that I observe in many modern cosmology apologists is not good science, but that's just my opinion.
There is a world of difference between good science and right science. Good science is always good whereas 'right' science is only right until it is superseded by the new 'right' science.
I think your notion that modern cosmologists should take every single one of the hundreds of ideas they see out there and spend their time turning them from ideas into theories (or debunking them) as unfair. The normal dialogue you get into is something like this:
Alf: I am not a scientist but I have spotted a HUGE hole in the theory you espouse.
Bob: The one I have spent eight years getting my head around?
Alf: Yeah, I just read Wikipedia on it. And I have spotted a flaw you haven't.
Alf: Anyway I have an idea how to fix it. I think that spinning harmonic quintessence, when properly quantised, does the job.
Bob: That doesn't make sense
Alf: You have to use the words like I mean them, not how you hidebound scientific types use them.
Bob: OK explain
...some hours later...
Bob: But that contradicts GR!
Alf: GR is not right then.
Bob: And itself
Alf: You just don't understand....
Bob: And this evidence
Alf: Heck, every little detail! You expect me to have every little detail! You are the scientist YOU do it. I have had the idea, that is the hard part. Now go prove me wrong.
I think you are biased by Forums, real science out there has nothing to do with your depiction.
Yes, Shaula's depiction is more about the interaction between scientists and "flakes". Still, a different depiction with a similar theme is relevant for interactions between scientists:
Mainstream apologist: "Here is a hypothesis that agrees with current observations and guides future observations to test it, and it involves X dark energy and Y dark matter."
Alternative attacker: "But you don't know that is the correct model."
Mainstream apologist: "No one ever does. Did Newton? Let's hear what alternative hypotheses you have, and what observations they agree with."
Alternative attacker:"Umm... (long pause)... All the same, I feel my ideas are being suppressed. I should get more funding, so I can answer your question.
Mainstream apologist: "Answer the question first, then ask for more funding."
ETA: corrected repetition.
Last edited by Ken G; 2011-Feb-11 at 02:56 PM.
I am not trying to start a big argument - just saying that I think the burden of proof should be with the claimant. And now I will shut up before a mod tells me to as this is in danger of hijacking the thread. Ummm, something about expansion?
I would summarize the answer to the OP as being this: the OP presents a false dichotomy, by forcing us to choose between two possibilities that are both oversimplifications, and neither carries the crux of the meaning of our current best cosmological models. However, if forced to choose between them, at least "space itself expands" is a picture that projects the correct GR explanation onto one particular coordinate choice, whereas "objects are all moving away from each other" does not project the correct explanation onto any coordinate choice. The reason for that distinction is that the "objects are moving away from each other" language is so coordinate-dependent that it cannot be the explanation of observed invariants (like redshift), since coordinate choices can never alter the observations. In other words, there is a difference between looking at a correct explanation in language that is only true in one coordinate system (as for "space expands"), versus mistaking a coordinate system as a valid origin of the true explanation (as with "objects are moving away", or even the literal interpretation of "space itself expands"). What's more, there is the possibility that a future theory of space might actually allow us to assert that space itself does indeed expand (or reproduce, if you will), whereas it seems that there is no chance of a future theory that would allow us to say that objects are moving away from each other-- that seems to already contradict what we know.
Now, this is but a tiny sample of what has been a harsh controversy among reknown cosmologists and relativists that has left no winner, simply put, no consensus has ben reached about the OP question even among mainstream cosmologists. It can be argued that these guys know what they are talkng about, know the math, have their phd.'s. I mean they are not using confused "popular explanations" as Shaula said, and yet they don't reach an agreement.
I don't think we can accurately answer that question because in order for us to know if space is expanding wouldn't we have to know where the "end" or the boundary of space is. So, it would most likely be the objects just moving apart in many different "directions"; (if space had directions), due to many different forces acting upon the objects.
Hogg is saying that one does not need space to expand because one can generate a perfectly suitable language by replacing the expansion of space with a mapping into continuously changing reference frames as we consider cosmological events seen by a chain of local observers, which is just another way of saying that comoving-frame coordinates don't have to be viewed as a global system, they can be viewed as a chain of local systems. None of that seems to contradict the prevailing answer that GR + cosmological principle + initial conditions provides the "explanation" of all our observations, including redshifts, and that breaking that answer down into more picturesque and physically suggestive language requires selecting a particular coordinate system and a particular pedagogical angle. None of that is anything but routine in physics-- we avert all problems by simply not taking the pictures we use to understand things too literally, mistaking them for "what is really going on."
Finally, I would point out that none of these different arguments for or against a certain language constitute disagreements about the cosmological model itself, they are pedagogical disagreements about the best ways to think about the cosmological model among experts, and also the best ways to communicate that model to the general public, which can be quite a different issue.
Staticman, if you missed it, Cougar posted a paper near the beginning of this thread that has some commentary on the "argument". It is definitely worth a read. I have been following this cosmological debate for a while now, and it seems to me to be exactly as Ken said, the argument is not about the theory itself. This is not so much a debate on how our observations match with different versions of a theory, it is more a debate about how we should best interpret a single theory. See what you think:
Expanding Space: the Root of all Evil?
Expanding Space: the Root of All Evil -- is definitely worth reading if you're interested in this question of "expanding space". These guys take Chodorwoski to task for being confused. And it sure looks like it to me.
The blog Cosmic Variance, run by cosmologist (not the biologist) Sean Carroll has a brief overview (Does Space Expand?) of the issue appearing in 3 papers, including Hogg's, the Root of all Evil paper, and another one by Peacock. Some of the experts chime into the comments section appearing below the blog entry, and the back and forth is enlightening.
Looks like speedfreek beat me to linking to The Root of All Evil paper.
I knew those papers by Peacock and Lewis, and the blog though I hadn't seen that entry.
It all seems to come down to a problem with the analogies, that's true, I don't deny that, but this seems to be related ultimately with expansion itself seeming a bad picture of the underlying theory, and if expansion IS an interpretation of the theory, why do we base so much of modern cosmology in an interpretation that originates so much diatribe?