Re: Detection of Gravitational Radiation

Chalky <chalkyspam@xxxxxxxxxxxxxxxx> wrote:
About 30 years ago, terrestrial GW detectors were only sensitive enough
to observe "hammer blow" radiation of indeterminate origin.

I would like to know; have modern detectors:

A) Established whether such "hammer blow" radiation is terrestrial
or extraterrestrial in origin?
B) Detected any expected (more sinusoidal varying) gravitational waves?

The (overwhelming) consensus among experts is that no gravitational
waves (of any waveform shape) have yet been directly detected.

(I recall reading one story about g waves having been detected from our
galactic nucleus, but don't know whether this has been confirmed)

In the early 1970s Prof. Joseph Weber (U of Maryland) claimed to
have detected pulses of gravitational radiation, with some (weak)
evidence that they came from the general direction of the galactic
center. However, other researchers found various flaws in Weber's
data analysis, and (different) other researchers with much more
sensitive detectors were unable to detect such signals. The
(again, overwhelming) consensus among experts now is that Weber's
"detections" were artifacts of the data analysis.

There has been one very convincing, abeit rather indirect, "detection"
of gravitational radiation: The orbit of the pulsar PSR B1913+16 has
been found to be gradually shrinking, at a rate which matches precisely
(within the error bars of about 0.3%) the rate one would expect from
gravitational radiation emission.

There are no known sources of gravitational radiation powerful enough
to have accounted for the size of signals Weber claimed to have
detected. (Indeed, the *huge* amounts of energy involved were one
argument against the hypothesis that Weber's detections were geniune.)

There are major efforts currently under way to build, debug, and
fine-tune gravitational-radiation detectors sensitive enough to detect
the (very faint) signals from sources that we _do_ know to exist.

(There are also parallel theoretical efforts to try to estimate the
likely gravitational-radiation signals from various types of sources.
My own research lies in this area.)

ciao,

--
-- "Jonathan Thornburg -- remove -animal to reply" <jthorn@xxxxxxxxxxxxxxxx>
Max-Planck-Institut fuer Gravitationsphysik (Albert-Einstein-Institut),
Golm, Germany, "Old Europe" http://www.aei.mpg.de/~jthorn/home.html
"Washing one's hands of the conflict between the powerful and the
powerless means to side with the powerful, not to be neutral."
-- quote by Freire / poster by Oxfam

.

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