Re: LIGO.


"cliff wright" <c.c.wright@xxxxxxxxxxxxxxx> wrote in message news:45dd71ce@xxxxxxxxxxxxxxx
Eric Gisse wrote:
On Feb 21, 1:58 am, cliff wright <c.c.wri...@xxxxxxxxxxxxxxx> wrote:

Eric Gisse wrote:

On Feb 20, 11:17 pm, "JanPB" <film...@xxxxxxxxx> wrote:

On Feb 20, 12:50 pm, "EricGisse" <jowr...@xxxxxxxxx> wrote:

On Feb 20, 9:50 am, "JanPB" <film...@xxxxxxxxx> wrote:

On Feb 18, 3:02 am, cliff wright <c.c.wri...@xxxxxxxxxxxxxxx> wrote:
[...]

We now need "missing mass" as WIMPS or MACHOS or something even more
esoteric, "dark energy", mysterious anti-gravity forces and divers other
"odds and sods" like cosmic strings.
Sorry if it offends you, but as a science historian this begins to
remind me of Crystal Spheres and Epicycles and other pre Copernican
machinery.

Yes - I call it "it smells of aether". Clearly the situation in
physics now is very reminiscent of pre-1905.

I don't recall there ever being an experiment that indirectly showed
the aether existed.

As far as dark matter is concerned, we know it is there. It has to be
there unless gravitational lensing has been lying to us.

For some reason I feel dark matter is an irrelevant kludge, like
aether. It just seems to have "data overfitting" and "fudge factor"
written all over it IMHO.

I believe the time for that type of opinion has passed.

http://cosmicvariance.com/2006/08/21/dark-matter-exists/
http://antwrp.gsfc.nasa.gov/apod/ap060824.html

Dark matter, once upon a time, was simply a way of explaining away
what we were expecting.

The idea wasn't without precedent. Pluto's existence was first
inferred through explaining Neptune's odd [at the time] orbit. Black
holes are discovered by explaining the orbits of stars - even though
they are not directly visible.

Then weak lensing showed us that dark matter is everywhere in the
halos of galaxies _everywhere_. It still could be argued that it was
gravity fucking with us. Then the bullet cluster was discovered - dark
matter got a whole lot more substantial.

Then again, a similar process was attempted on Mercury and it took
general relativity to explain it. I do think, though, that the
evidence weighs in enough to make dark matter a viable concept.
Especially when the bullet cluster results shredded competing theories
like MOND [Hell, MOND was simply curve fitting as well - no less
satisfying].

The comparison between dark matter and aether, or various past ideas,
irritates me because the such ideas never had the kind of support that
dark matter does today.

--
Jan Bielawski

Oh Dear! Now who is the professional here.
I know history is "bunk" these days but let's set a few things straight
here.

1. Pluto was discovered accidentally by Clyde Tombaugh when extending
the search for Lowells "planet X" in 1930. It was way outside the
ecliptic (I presume that you know what that is ?) and many magnitudes
fainter than the expected object. As an observing assistant that is one
of the reasons why Clyde had the job, it proved to be much longer and
more difficult than expected and the "professionals" didn't want the
hard work. Clyde did a marvellous job and is deservedly famous, but he
didn't find Planet X and neither has anyone elese since.


Except the only reason people were looking for Planet X was because of
Neptune's unexplainable orbit.


The pertubations, such as they are, of Neptunes orbit are still
largely unexplained.


I highly doubt this is true.


And yes, I have seen the original discovery plates at the Lowell
observatory for myself!


Neat.


2. What the orbital dynamics of some stars show is the presence of a
highly condensed massive object which may, or may not, be some kind of
singularity.


You might like this.

http://www.mpe.mpg.de/ir/GC/index.php


3. The precession of the perihelion of Mercury's orbit had been known
since the late 19th century, it is a very small effect measured in
seconds of arc. Although often quoted as an early proof of relativity it
is not totally "bulletproof" as effects like the dynamics of the solar
wind were not understood at the time. Not to say relativity isn't very
useful where Newtonian Physics breaks down but when putting all one's
eggs in one basket it pays to be very, very careful with your basics.


We didn't even know what made the sun "go" at that point in time.
However, the precession of Mercury's orbit stands as a valid test of
relativity. Like with the Eddington expedition, it does not matter at
this point except as a historical footnote whether or not if what was
seen at that time was correct.

In 2007, observation and theory are entirely compatible.


4. As an astronomer with my own modest observatory, could you please
quote me the catalogue number (NGC etc) of this "bullet cluster" to
which you refer (rather unscientifically) so I can do some research for
myself. Or are you simply referring to a scatter of images?


Google is your friend.


5. I was reliably informed by at least two well respected US
professional astronomers 3 or 4 years ago at seminars at Auckland
University that the effects of "missing mass" increased in proportion to
the scale of the universe being observed. That is it was small in a
typical spiral, larger in a cluster of galaxies and much larger in
superclusters. Were these professionals wrong and if not can someone
please explain why this could not be seen as a property of space/time
or an effect of distance on known forces.


It doesn't surprise me too much to hear that there is more dark matter
in a supercluster than around a galaxy.


Please note I fully accept that gravity deflects light, that is one
thing about which I hope we can all agree. And condensed objects like
galactic nuclei can indeed cause notable lensing effects.

As I get older I realise how true it is that real advances are made by
what A.C.Clarke called "young "scientists, the one's who don't think
that their professor or tutor is the fount of all knowledge.
His job should be to help them to think, unfortunately as I have seen
for myself in 40 years at University these days he is there more to help
them pass examinations.

BTW if you read my earlier posts you will find one very good example of
an historical theory that was highly accepted but proved to be rubbish.
The trouble with people who despise history is that it means they just
continue making the same mistakes (just like economists!).


I value history, I don't reject it. I just don't believe the
comparison is apt.


Cliff Wright.



Perhaps I didn't put that very well.

It will not matter how you put it, Gisse doesn't give a ***.

"Plus some other stuff like proofs, which I don't honestly give a ***
about. " - Gisse, 25 Oct 06

"I don't give a *** about philosophy." Gisse - 16 Nov 06

"perhaps you could explain to me why I should give a ***? " Gisse -20 Nov 06

Until Gisse is force-fed an enema he'll never understand mathematics,
physics or astronomy (subjects which are reliant on proof), he's full of ***.



What the professionals said was
that the relative abundance of "dark matter" vs "normal" matter had to
be increased with scale. It was NOT just a question of the volume of
space involved, but the ratio had to change to "fit" the observations of
intergalactic motion, from individual galaxies, to clusters, to
superclusters.
If this were not so it seems to me that "dark matter" or its equivalent
would have been postulated much sooner as observations showed
discrepancies of motion within galaxies themselves.
Thus either "dark matter" tends to infinity if the universe is
sufficiently large or it is an effect of distance and actually a
characteristic of our space/time which we have not yet seen at a local
scale. In that case mysterious matter may not be needed at all.

IMO the comparison is very apt. The mystery substance apparently
explained the observations but could not be isolated and had some very
unusual characteristics that hadn't been observed elsewhere.
How close an analogy do you need!

BTW I'm sorry to disillusion you, but despite the discovery of a whole
lot of "Plutos" out there recently and the latest computing techniques
the motion of Neptune is still not completely accounted for.

Actually we still don't completely understand what makes the Sun "go"
today. Fred Hoyle's work was almost 60 years ago and things haven't got
much further since, except for solar "Neutrinos" and these just made
things more mysterious.
If it were so we would have fusion power stations supplying our cities
and a lot less worry about global warming.
In fact the only "moderators" and containment we know of for fusion
reactions are 1/10 of a solar mass of hydrogen or so, or the fireball of
a fission bomb (which is very temporary indeed!).

It is I'm afraid very easy to swallow opinion (especially at University)
and take it as hard fact. When your grades depend on basically
regurgitating lectures and set books then the pressure is even harder to
resist.

My long experience of University life has perhaps made me rather cynical
about this, but I have had the experience myself (though not in a
Physics course) of running counter to the opinions of a senior lecturer
and having to do a lot of extra work to get good grades (in the end).

Cliff Wright.
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