From: Twink (neptune@mars.superlink.net)
Date: Wed Nov 26 1997 - 17:39:27 MST
At 17:10:15 Wed, 26 Nov 1997 +1100 (EST) Bradley Graham Weslake
<bgw03@uow.edu.au> wrote:
>I am sorry - I used the term in it's non-empirical sense, which is what
>has caused the confusion. There is such a thing as theoretical evidence
>yes? I don't want to get into semantics; I concede that I worded my
>statement badly. My only excuse is that I generally read the list email late
>at night when, I am beginning to suspect, my mind has already began the
>processes necessary for sleep.
>
>> And why would there be good theoretical
>> reasons if somewhere the theory did not match up with some facts?
>
>If, for instance, there are fairly good empirical results from which
>theoretically pleasing models can be made, but the models do not
>completely and utterly explain all phenomena. This type of thing occurs
>often in a science such as cosmology where a small amount of very
>important observations (microwave background radiation, expanding
>universe, etc.) are the basis for a great deal of theory. An analogy on
>a smaller scale: we don't even understand how our own solor system
>formed, even though we know a great deal about how it works.
You will get no argument from me on the philosophy of science
issue, BUT in this particular case -- positive vs. negative or zero
curvature -- doesn't the latter view cohere with a lot more data
-- however scant the data for either may be?
For the record, I have no problem accepting a theory which is not
supported by shiploads of evidence, but I do have a problem
accepting one that seems to contradict evidence. In this area,
one has to do some major handwaving to avoid some of the
evidence. Also, unlike, say, the example of the neutrino, where
a major item of knowledge seemed to be contradicted by proton
neutron decay, there is nothing like that going on here. In other
words, nothing to warrant acceptance of dark matter on the
scale needed to make the universe closed.
(For those unfamiliar with the neutrino example, what happened is
basically this. In nuetron decay it was discovered that they break
down into an electron and a proton. The paths, from cloud chamber
tracks, between the proton and electron as they fled from the decay
event was not as expected, exactly opposite -- the electron heading
one way which the proton went in the opposite direction. To account
for this Pauli guessed there must be another particle, the neutrino --
so named for it being small and neutral in charge -- that took up the
slack and preserved conservation of momentum. The latter is the
major item of knowledge seemingly contradicted by the evidence.
It could have been that neutrinos were a fantasy, but later
experiments proved their existence. Ergo, Pauli's guess was a
good one. I believe the case with lots of exotic dark matter is NOT
the same. We don't have the same kind of weight with theories of
cosmology. At least, this is my judgment in the matter. Sorry for
the digression and I hope I recalled my history correctly.:)
>> It appears the universe is open, but I'm interested in why, if it does,
>> do some still maintain otherwise. What reasons do they have? And
>> are these reasons valid and tractable? In the interim, we might do
>> well to discuss/try to understand the idea of an open, globally
>> hyperbolic universe -- rather than be shackled to the current
>> Standard model, which might become obsolete.
>>
>> One, but by no means the only, model of an open universe is that
>> of David Layzer. But even if his model is found to be faulty, any
>> good theory of cosmology should be able to account for the fact
>> that the universe has a lot less mass than would needed to close
>> it -- given current observations.
>
>Or be so fitted to other observations that an examination for other
>matter besides the observed matter is warranted.
Certainly, but that position is already spoken for and widely
accepted. We need go no further than the current Standard
Model and its supporters. Let's assume, for the moment,
that they are wrong. What next?
>> An aside: What are the probabilities and how are they
>> measured in this area?
>
>Which probabilities and which area?
You wrote: "There are a multitude of other observed phenomena
which align[sic] well with the theory of a closed universe, as well
as theoretical reasons for believing that such a case is probable."
I'm homing in on the last word and wondering why you think so.
How is a closed universe theory more likely than an open one?
Daniel Ust
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