NetNews Usenet Archive 1992 #27/NN_1992_27.iso/spool/alt/callahan/14076

Text File | 1992-11-24 | 8.9 KB | 188 lines

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From: [e-mail] (J.P.Gardner)
Subject: Re:  Red Shift ( was  Re: Science and god:  Are they incompatible? )
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Date: Tue, 24 Nov 1992 00:16:00 GMT
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The Space Cadet joins a discussion about cosmology, a subject near and
dear to his heart.

>StM says:
>>DJ writes:
>>>  Okay. How do either of you feel about the possibility that Red Shift is not
>>>always an indicator of distance...
>>
>>It's NOT always an indicator of distance.  In the vast majority of cases where
>>we could get independent estimates of distances, however, degree of red shift
>>is closely correlated with distance.

Redshift is a direct indicator of velocity or gravity. The
gravitational effects tend to be small in comparison to velocity, but
are measurable. Objects which are not bound together in gravitational
systems receed from each other due to the expansion of the universe.
This recessional velocity follows Hubble's law which states that
velocity is proportional to distance. There are, however, intrinisic
velocities (also called pecular velocities with respect to the Hubble
flow) which are additional to the expansion velocity.

So, for galaxies and quasars, the redshift is the best way of measuring
distance. Others ways of measuring distance are used to calibrate
Hubble's law, and to determine what component of the velocity is due
to other things, like falling into a dense cluster.

This difference is just being picky, it is _not_ what Halton Arp is
referring to, he is directly challenging Hubble's law.

>>
>>>A certain person's 'peculiar galaxies...'
>>>I can't remember his name off-hand. He wound up going to Europe as he couldn't
>>>get telelscope time here in the US.
>>
>>I'm not familiar with the case in question.  Could you (or maybe DM or one of
>>the other AY types) give us more information on this?  Or a reference?

Reference: _Observational Cosmology_, International Astronomical Union
Symposium #124, eds. A. Hewitt, G. Burbidge and L.Z. Fang, pg. 479ff.
Also, see below.

>>
>    Halton Arp is his name. He said that many quasars appear to be
>connected to galaxies with greatly different red shifts than the galaxy.

The point is he said they appeared that way. He did not do a proper
statistical analysis. This is a mistake that a lot of people make
about a lot of things: making statistical arguments by anecdote.
He finds quasars which appear on the sky to be close to nearby
galaxies, and even finds some which appear to be connected by
tails, arms, etc. But what he doesn't consider is the chance that
this could be a random alignment -- a coincidence. The chances of
such a coincidence _can_ be calculated, and when people _do_
calculate them, they find that the chances are very reasonable.
For example -- see the article on page 499 of the above reference.
In the discussion section following that article, Arp says, "One
can judge for oneself by looking at the picture whether or not the
existence of the line needs to be tested." to which the author
replies, "I can only restate the conclusion of the work described
here, ..., no significant alignment is detected [in this field.]"
(pg. 502.)

Sorry, but looking at pictures isn't science, statistical arguments
are.

>He wanted 4 meter telescope time to find out what, if any, connection
>they did have. After preliminary deep exposures showed he might be correct
>in some instances, he was then denied more time to make absolutely certain.

Four meter telescope time is typically oversubscribed by a factor of 3
to 4. This means that only about 25 to 33 percent of the proposals
submitted get any time at all. When someone is turned down it is
unlikely to be due to conspiracy, it is usually because they wrote a
bad proposal, (or someone else wrote a better one.) There is no shame
in being turned down; it has even happened to me :->. Actually, it
happens to _every_ working astronomer, you just try again.

But if something in your proposal shows that it is unlikely that you
will make good use of the data, then it is unlikely that they will
give you the time for which the taxpayers are paying 3 to 5 thousand
dollars per night.

Now a proposal which would test Hubble's law in a novel way might
well get time -- even if the time allocation committee assumes that
you will just confirm it. But you have to be willing to believe the
data, even if it doesn't give what you expect. This goes both ways;
that is, Arp should believe the data which shows he is wrong.
Such a proposal would have a much better chance, of course, if you
could study something else at the same time.

>I got the impression that if he did find it to be true, some of our
>standard candles for age of the universe would prove wrong in some instances.
>i.e. not all quasars are a long way off, some are attached or imbedded in
>'relatively nearby' galaxies. Which I would say means that some of my
>astronomy knowledge says thats impossible... I see 'proof' on both sides
>of this question. I did see several high-resolution photographs in his
>book that appear to show a hydrogen bridge connecting a quasar and a normal
>spiral galaxy... I have read other claims that say the photograph proves
>nothing... It certainly appears to me to be connected. { I used a magnifying
>glass to suppliment my vision. }

Yes, a disproof of Hubble's law would be a major paradigm shift. There
is a very strong conservatism among scientists about their paradigms.
This is a good thing. If one were to reject very well founded paradigms
whenever some data that appears anomalous is taken, one would never get
anything done, because in the vast majority of cases the data turns out
to be wrong. Scientists wouldn't believe things like this unless they
are confirmed by other groups. Remember cold fusion? If it had been
real, it would have severely changed the paradigms of nuclear physics.
A lot of scientists were skeptical, and it turned out that they were
right, as it was just experimental error. Other groups could not
reproduce the results.

This means that when something anomalous appears that does turn out to
be right -- that is, it is confirmed by different groups and in
different ways -- then there will be some scientists who will go to
their graves refusing to believe the results. Even some well respected
scientists who have made very profound contributions to the field, and
who _ought_ to know better.

This, by the way, is Arp's case. He just can't believe that something
as energetic as quasars can exist -- so they must be nearby and thus
not so energetic.

But even this is good for the field, as it means that when new data
comes along which will test the old, standard, accepted paradigms, it
usually is used to test the paradigm. Thus, I will (when I get around
to it :) compare the data I took to study galaxy evolution, with the
predictions of the steady-state universe theory. Oh, I am quite certain
my data will support the big bang, but I will publish this analysis
either way (probably just with a paragraph in a larger paper.)

Most of these ideas about how science works are discussed in the book,
_The Structure of Scientific Revolutions_ by Thomas Kuhn. It is one of
the classic books on the philosophy of science, and I would recommend
it to anyone interested in how science does and how it should work.

>
>   { I have his book somewhere at home and might be able to find it if you
>     need some of his examples, such as NGC numbers that supposedly have
>     quasars attached. }

Sigh. Often people pushing non-standard or outdated theories or models
turn to the popular press. When they publish in the referreed scientific
journals they are held to the strictures of science -- i.e. good
experimental or observational techniques, proper use of statistics,
etc. In a popular book you can say whatever you want and no one
is around to argue with you.

> Jim Pierce Bach. of Sci. in Applied Computer Science USM - Gulf Park Campus
>             [e-mail]  Disclaimer: Standard.

Hmmm, could I recommend some popular-level books on Astronomy and Cosmology
that _are_ well thought of by most astronomers?

The First Three Minutes -- Steven Weinburg
The Big Bang -- Joe Silk
Galaxies -- Timothy Ferris
A Brief History of Time -- Stephen Hawking
The Milky Way -- Bart Bok and Priscilla Bok
Cosmos -- Carl Sagan
The Physical Universe -- Frank Shu (an undergrad textbook, but very readable.)

Oh, and if you look real hard at the shelf in the Callahan's library that
contains books that haven't been written yet, you might find something
by me. :-)


This is a bit dated, but here is a 1973 direct comparison of Arp and
the standard picture:
Redshift Controversy -- George B. Field, H. Arp, and John N. Bahcall.


--The Space Cadet
Jon Gardner, University of Durham, Physics Dept.
[e-mail]