Re: LIGO.

Martin Hogbin wrote:

"cliff wright" <c.c.wright@xxxxxxxxxxxxxxx> wrote in message news:45cdc049$1@xxxxxxxxxxxxxxx

Martin Hogbin wrote:

"cliff wright" <c.c.wright@xxxxxxxxxxxxxxx> wrote in message news:45cd6bab$1@xxxxxxxxxxxxxxx


Well this is all very interesting but we still appear to have a non
functional, very expensive apparatus here!


Not yet functional! You have not responded to my latest
post about our bet. I want to place a serious bet. We need to
agree some basis on which the winner is decided otherwise it
could end up as an argument as to who has won. I will not
pay up unless I am sure that you would have paid up had you
lost.

Do you want to place a serious bet or shall we cal it off?



Michelson and Morley used an
old cellar and a realtively simple optical interfernometer, in fact they
had to cut their programme short because someone else needed the cellar.
Perhaps, it being in Dublin, a Guiness delivery was expected.
Strange, I always thought that Semantics were to do with the meaning
of language, but I suppose that mathematicians are running out of mames
for ever more abstruse calculations and logical operations.
None of this however more than partially answers my original question.
Though I see someone has phrased it quite well- In effect what are you
actually measuring and how does propagation speed enter the equation?
Electromagnetism had Maxwell, but can Einstein now join his illustrious
company or not?


Tom has carefully answered your question using the correct
technical language because that is the easiest way to do so.
Many words (such as 'energy' or 'momentum') have much more
precisely defined meanings in technical usage than in everyday
speech. You need to find out what the terms Tom has used mean
in order to get your answers.



Maxwell of course had the advantage of already knowing the approximate
velocity of electromagnetic radiation he did not have to assume it.
BTW how is the nature of the "space/time" positioning of the light paths
determined? Or is it assumed that space is substantially "flat" and
unstressed around the mirrors?
I presume that ant "directional" information depends on the time dealy
of signals and therefore the velocity of propagation, but I stand to be
corrected on that.


You are falling into the trap of expecting distance to be
a 'real' pre-defined thing. We can ultimately only define
distance by how we would measure it. Historically, different
methods have been used. In 1889 one metre was defined as
the distance between two marks on a platinum alloy bar kept
in Paris (this is the constant spacelike proper distance Tom
referred to). On this basis, LIGO would measure a variation
in the speed of light.

However, today one meter is defined as the distance travelled
by light in a specified time. In free space, away from gravitation
and other influences, this gives exactly the same result as using the
metal bar would. In the case of LIGO, because the speed of light
is now defined as a constant, we would now say that the length of
metalwork changes. It all depends on how you choose to define
'distance'.



I fully understand that Einstein's original work as regards
"gravitational radiation" has been much "worked on " since his death 50
years ago, but his name keeps coming up.


An quite rightly so. It is still his theory, unchanged, that is used.
It is just that more details have been worked out.

Martin Hogbin



Ok Martin. How about this? If both LIGO's can produce a signal which
correlates with the observation (using radio or optical techniques) of
some phenomenon. For example an especially close or powerful gamma ray
burst or supernova event. Then I will gladly stand corrected and pay
you the $50 US (about $74 NZ). However if by the end of 2011, an extra
year please note, no correlated signal which can be independently
checked is received then you owe me $50. The correlated event is
required based on the alleged signals detected by Weber (or was it
Wagner) back in the 1970's which turned out to be unrepeatable.
Does that seem fair to you?


I would prefer a generally accepted statement from the scientific
community that gravity waves have been detected. That I why I
suggest that we find an independent referee.


Actually you know I have quite a lot of background in practical Physics
even though my degree was in the history of Technology. I spent most of
my career as an electronics design engineer, and I am an active Amateur
astronomer.
I have most defintely tried NOT to fall into the "trap of distance"
problem. However since Einstein and Quantum mechanics fail to agree on
so many points I get a definite inkling that this whole experiment might
be falling into difficulties beacause of the difference between "macro"
real world conditions and the behaviour of the universe at a quantum level.
At a macroscopic level it is patently absurd to suggest that distance is
not "real".


Perhaps 'real' is not the right term to use. What I am saying is that,
at any scale, we must define what we mean by distance before we
can argue about it. The best way to define exactly what we mean is
say how we would measure it. In 1889 the meter was defined one
and today it is defined another.


From my reading it appears that the hypothetical "gravity wave" will
have a longer wavelength than most EM radiation used today and this
necessitates very large (Km size) detectors.
If that isn't Macroscopic what is?


Agreed, but we must still define what we mean by 'distance'.


I must confess though Martin that as an old time practical experimental
type I still have reservations about the apparent inability of many
theoroticians to explain the basics of their ideas by analogy or some
form of modelling.


Who are these people who cannot explain their ideas?
Einstein's theory of general relativity has been explained in
many ways by may different people.


If they can't visualise what is happening well enough to explain it to
someone with say basic University level Physics and a reasonable
education background then I am always left with a "emperor's new
clothes" suspicion.


Firstly, I am not sure how you can tell if someone else is
visualising what is happening.

Secondly GR is not easy to visualise because it takes place
in 4-dimensional spacetime. Imposing a 3-dimensional
Euclidean space on the subject and then trying ti visualise
what happens is doomed to failure.



In my 40 years at university I have attended lectures by many visiting
scientists well known internationally in their fields of Physics,
Astronomy and Cosmology and have found that those who can do useful work
can ususally come up with a very good explanation of it to a good
general audience.
Total theoreticicians were another breed however and only exceptional
individuals seemed to be able to communicate their ideas.
A bit of Latin is in order here "Quis Custodiet Ipsos Custodies"
( roughly "Who Guards these Guardians").


Oh dear. I hope you are not going to turn out to be one of those
who claim that science is a great conspiracy to defraud the
public.



In a field which I did a lot of work, Acoustics I came across an
instance where the "scientific establishment" refused grants on the
basis of "bad science" to projects which are now in general use.
Look up electronic noise cancellation, otherwise known as "Essex Noise
Reduction" sometime.
Experiences like that shake one's faith in the judgement of some menbers
of the scientific community for good.


Nobody claims to get everything right all of
the time but GR has been subject to nearly
100 years of scrutiny and passed all tests so
far with flying colours.


I really hope this produces some result for us. If they can detect
"something" when something big goes "bump" then it will be well worth
the money.


Yes, I hope something happens.

Martin Hogbin


Hi Martin. Just had time to read and inwardly digest your latest.
I think I now see the whole nub of our differences, such as they are on the nature of "proof" in science.
A big problem is of course what constitutes a "general acceptance" by the scientific community? Then we have the bigger problem of who constitutes a "Neutral referee" Potential for even further arguments here I fear.
You have probably noted that I am a great believer in experiment as the only "real" proof of theory. That is why I suggest that an independent
check on potential sources of "gravitational waves" has to be a condition of a claim of sucessful detection. It might in an extreme case even be a previously unobserved phenomenon but the correalation is all!

An apparatus as delicate as LIGO is inherently prone to noise problems of all kinds and sooner or later some correaltion might turn up between the two LIGO detectors purely by chance.
Since many GR theorists careers are riding on LIGO, I merely suspect that they are as human as anyone else and we all know that we often see what we expect, as any amateur astronomer knows all too well.
After all the "real" universe is what all our theory is supposed to be modelling and Not vice versa.

No I'm not one of those people you speak of with regard to science being a con job. Just as well that it usually isn't. Religion and Politics are quite enough in that department.
I might add that it would be remarkable if I gave up many hours of my time to listen to a lot of Con men while spending a lot of my time in retirement building telescopes and observatories and researching the history of electronics, one of my pet subjects, if I was anti science.
The fact is most people think of me as fanatically pro Science especially the local Creationists and members of the anti Space lobby.
regards Cliff Wright.
.