By David Larousserie

Posted today at 01:19

From g. on the right, the 2017 Nobel Prizes in Physics Barry Barish, Kip Thorne and Rainer Weiss, in Stockholm, in December 2017.

” We did it ! “ This February 11, 2016, in Washington, David Reitze savored the applause triggered by this exclamation. They salute a feat expected for a century, achieved thanks to a vast international collaboration of some thousand physicists.

But how long and difficult it was for this alliance called LIGO / Virgo to observe the first gravitational waves on Earth, this extraterrestrial signal that makes space-time vibrate when large compact masses, like black holes or neutron stars , are turning around at crazy speeds.

“The experiment almost died several times”, notes Harry Collins, a sociologist of science at Cardiff University, who has been involved in the field since the 1970s.

In fact this “experiment” consists of three instruments, two in the United States to form LIGO, of which David Reitze is the spokesperson, and one in Italy for Virgo, a Franco-Italian collaboration at the origin. Their chaotic stories are very intertwined and begin in the 1970s. “At that time, astrophysicists knew little about general relativity. They were therefore rather hostile to this community ”, recalls Jean-Pierre Lasota, physicist, co-author of Gravitational waves (Odile Jacob, 2018). It is true that, in the sky, no one had yet seen objects so massive that only this theory could describe, like black holes or neutron stars. In Gravity’s Shadow (University of Chicago Press, 2004, untranhooly-news.comd), Harry Collins even recalls that the term “observatory”, the “O” of LIGO and Virgo, went badly among astronomers. The climate is also weighed down by the announcements of Joseph Weber who, in 1969, claims to have detected waves, without this being confirmed by others.

Gravitational waves, a distortion of space-time.

“We were called crazy! “, remembers Alain Brillet (CNRS gold medalist), originally from Virgo with his Italian colleague Adalberto Giazotto (who died in 2017, a month after the Nobel Prize celebrating the first detection of gravitational waves). “We believed in it but it took forty years to demonstrate it …”

Parasitic noise and misunderstanding

It all starts in the United States. For the 1968-1969 school year, Rainer Weiss, physicist from MIT (Massachusetts Institute of Technology), future Nobel fellow in 2017, is preparing his first general relativity course which he discovers “Just one day before his students”, as he explains for the records of Caltech, the California Institute of Technology. This is where he came up with the idea of ​​precisely measuring the variation in distance between two masses using an optical measurement called interference. He did not know at the time that the Russians in 1962 also proposed this idea. Or even that Joseph Weber has a similar pattern in his notebooks.

You have 75.52% of this article left to read. The rest is for subscribers only.