Re: LIGO.

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?
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". While at the level of quantum effects it is obviously quite a different thing, otherwise how could a device like a tunnel diode or any very rapid switching semiconducting device operate.
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?
After all the intention of the experiment is not like a CERN type particle accelerator where one is concentrating the maximum energy in the minimum volume, but just about the absolute reverse.

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.
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.
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").

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.
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.

Best Regards Cliff Wright.

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