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| Science Forum Index » Physics - Research Forum » LIGO/Virgo status & estimated detection rates... |
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| eric gisse... |
 Posted: Wed Jul 29, 2009 11:15 am |
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Jonathan Thornburg [remove -animal to reply] wrote:
[...]
That was an excellent discussion of the subject.
People who harp on the non-detection of gravitational waves need to sit down
for a minute and think about the event frequencies and how small they are
even for best-case scenarios. Patience is the key here, not "we didn't see
anything immediately. Mothball the facilities!"
To add, the Einstein at (no spam) home people have published the results of their search
through 66 days of S5 data. Unfortunately nothing was found.
http://lanl.arxiv.org/abs/0905.1705/ |
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| Oliver Jennrich... |
| Posted: Fri Jul 31, 2009 3:06 am |
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clifford wright <c.c.wright at (no spam) paradise.net.nz> writes:
[quote:5221b7f4d9]Many thanks for your very clear summary of the position with
Gravitational wave detectors at present. As an engineer however I have
also noted the problems with beam intensity effects etc that they have
already had, I wonder if they can push the sensitivity quite as high in
practice?
[/quote:5221b7f4d9]
What do you mean with 'quite as high'? LIGO operates at the design
sensitivity (with a few exceptions here and there) so they already did
push the sensitivity to where it was expected to be.
Mind you, that alone is a phantastic achievement.
[quote:5221b7f4d9]Although I remain sceptical of the existence of such "radiation"
feeling that other localised effects could produce similar
observations, such as localised electromagnetic forces, I do feel that
the direction of future research should be aimed at space based
measurements. Basically we need wide band detectors, which as has been
shown are simply not practical on the Earth's surface.
[/quote:5221b7f4d9]
Let's take a look: LIGO has about 2 frequency decades sensitivity. In
the electromagnetic world, the equivalent would be a telescope from near
IR (1 micrometer) to soft x-ray (10 nm). I guess any optical
astronomer would call that 'wideband' (well, not quite, they would
probably call it 'overwhelmingly wideband').
LISA's bandwidth will be about 4-5 decades, that would be equivalent of
an optical instrument sensitive from near IR to gamma rays.
[quote:5221b7f4d9]In any event we are working "blind" since we still have no coherent
theory of gravitation. Therefore we need to look at such potential
forces over as wide a range as possible.
[/quote:5221b7f4d9]
For all practical purposes of GW detection, GR is good enough.
[quote:5221b7f4d9]In any event I am hoping that something likely to detect events on a
reasonable time scale can get going before too long! I'm no longer a
young man and I would like to see some conclusion before I leave this
universe!
[/quote:5221b7f4d9]
Amen to that!
--
Space - The final frontier |
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| eric gisse... |
| Posted: Fri Jul 31, 2009 3:06 am |
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clifford wright wrote:
[quote:54fb849197]Many thanks for your very clear summary of the position with
Gravitational wave detectors at present. As an engineer however I have
also noted the problems with beam intensity effects etc that they have
already had, I wonder if they can push the sensitivity quite as high in
practice?
[/quote:54fb849197]
Ask the people who are doing it. They might know.
[quote:54fb849197]Although I remain sceptical of the existence of such
"radiation" feeling that other localised effects could produce similar
observations
[/quote:54fb849197]
http://nobelprize.org/nobel_prizes/physics/laureates/1993/press.html
[quote:54fb849197], such as localised electromagnetic forces,
[/quote:54fb849197]
Electromagnetic waves are the result of a changing electric dipole
moment whereas gravitational waves are the result of a changing mass
quadrupole moment.
[quote:54fb849197]I do feel that
the direction of future research should be aimed at space based
measurements.
[/quote:54fb849197]
LISA is coming along. And is sensitive to frequencies that LIGO, et.al
are not.
[quote:54fb849197]Basically we need wide band detectors, which as has been
shown are simply not practical on the Earth's surface.
[/quote:54fb849197]
Nothing of the sort has been shown.
[quote:54fb849197]
In any event we are working "blind" since we still have no coherent
theory of gravitation. Therefore we need to look at such potential
forces over as wide a range as possible.
[/quote:54fb849197]
Royal "we", I am assuming. We, as in "the scientific community" we, have
general relativity which have been shown to be quite capable.
[...] |
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