Did Shakespeare expect gravity before Newton?

Were gravitational waves discovered 22 years ago?

Gravitational waves are predicted by general relativity. In contrast to Newton, who believed that the force of gravity is transmitted instantaneously, Albert Einstein showed that changes in the gravitational field propagate through space at the speed of light.

For decades, scientists have been trying to directly detect these gravitational waves in space - but since the measurable effects are so small, this has not yet been achieved. So far we have only indirect evidence of the existence of gravitational waves: Russell Hulse and Joseph Taylor investigated in the 1970s how the two components of the double pulsar PSR 1913 + 16 orbited each other. These are 2 neutron stars; extremely compact objects that arise in a supernova. They were able to show that their orbital speed slowed down slightly - exactly what one would expect if the objects lose gravitational energy by radiating gravitational waves. The observed slowdown corresponded exactly to the predictions from the general theory of relativity. Hulse and Taylor received the 1993 Nobel Prize in Physics for their discovery.

But direct evidence of gravitational waves is still pending and physicists around the world are looking for them. Such a gravitational wave detector - GEO600 - is for example near Hanover (picture on the right). This German-British project has been looking for gravitational waves since 2005 - so far unsuccessfully. The necessary accuracy for a proof could not yet be achieved.

The first experiments for the direct detection of gravitational waves were carried out from 1958 by Joseph Weber at the University of Maryland (who, by the way, played a key role in the development of the laser). At that time he tried to detect the waves by measuring vibrations on large aluminum cylinders:

Image: GEO600, University of Hanover

However, here too the external interference turned out to be too great to provide evidence - the measurement results were not clear enough. Webers suspected several times that he had detected gravitational waves. However, its results could never be reproduced.

Also in February 1987 Weber reported a detection of gravitational waves. That was remarkable - because it was detected at the same time as astronomers discovered the famous 1987A supernova. And supernova outbreaks are among those events from which one would expect strong gravitational waves!

However, here too, the opinion of the scientific community was divided - many did not believe that Weber had actually measured the gravitational waves of the supernova. His instruments are not sensitive enough for this. Until Weber's death in 2002, he continued to work on improving gravitational wave detectors, thus paving the way for modern experiments and projects. But while he was always convinced that he had measured the waves, that view has never caught on in the scientific community. His work always remained controversial (Weber was still not an outsider in science. His work was valued by many - even if they doubted the results. He received many scientific honors and there has been a Joseph Weber Award for astronomical instrumentation since 2002).

Perhaps that could change now. On Monday a work entitled “Gravitational Wave Sources May Be“ Closer ”Than We Think” by Asghar Qadir appeared on the preprint server arXiv Center for Advanced Mathematics and Physics in Rawalpindi, Pakistan.

In it he shows that the strength of the gravitational waves has probably always been incorrectly calculated until now. Under certain circumstances - when the gravitational waves are generated asymmetrically, they can be much stronger. Exactly such an asymmetry can be found in the supernova 1987A and Qadir calculated that the waves from there could have been stronger by a factor of 10,000 than assumed!

So it is entirely possible that Weber 1987 indeed was the first to directly detect gravitational waves! One would have to look closely and check the experiments and data he had back then. Weber will unfortunately no longer experience a possible rehabilitation - but from a scientific point of view one could learn a lot from a new examination of his experiments.

Gravitational waves are predicted by general relativity. In contrast to Newton, who thought that the gravitational force is transmitted instantaneously, Albert Einstein showed that changes in the gravitational field at the speed of light are caused by ...