Gravitational waves are ripples in the fabric of
space-time generated by violent events such as the
collision of massive objects like black holes. They
travel across the Universe stretching and squeezing
space-time as they go. However, their effect is so
weak that even Einstein doubted we would ever be
able to detect them.
“Our observation of gravitational waves
accomplishes an ambitious goal set out over five
decades ago to directly detect this elusive
phenomenon and better understand the Universe,
and, fittingly, fulfills Einstein’s legacy on the 100th
anniversary of his General Theory,” said LIGO
executive director David H Reitze.
The waves observed by the team were generated
by the collision of two black holes, about 29 and 36
times the mass of the Sun, which occurred 1.3 billion
light-years away. As gravitational waves travel at the
speed of light, this means they have taken 1.3 billion
years to reach Earth.
The results will open up future opportunities to
learn more about the nature of black holes, neutron
stars and other astronomical bodies, and to look
deeper into the Universe.
“With this discovery, we humans are embarking on
a marvellous new quest,” said LIGO co-founder Kip
Thorne. “The quest to explore the warped side of the
Universe – objects and phenomena that are made
from warped space-time. Colliding black holes and
gravitational waves are our first beautiful examples.”
A technician inspects one of the
LIGO detector’s laser-reflecting
mirrors for dust particles or any
other contaminantsPHOTO: CALTECHCOMMENTLORD MARTIN REES ASTRONOMER ROYAL
How big a deal is this discovery?
It’s one of the great discoveries of the decade, up there
with the detection of the Higgs particle, which caused
huge razzmatazz three years ago. The Higgs particle was
a capstone to the standard model of particle physics,
developed over several decades. Likewise, gravitational
waves, vibrations in the fabric of space itself, are a
distinctive consequence of Einstein’s General Relativity.Why has it taken us so long to detect them?
The problem with gravitational waves is that their detection
requires large, expensive and amazingly sensitive
instruments. In the LIGO detectors, intense laser beams
are projected along 4km-long pipes and reflected from
mirrors at each end. By analysing the light beams, it’s
possible to detect jitter in the distance between the mirrors,
as ‘space’ expands and contracts. The amplitude is
exceedingly small: tens of millions of times smaller than the
size of a single atom.What can we learn in the future from ‘listening’ to
gravitational waves?
What is so exciting about the LIGO event is that the form
of the ‘chirp’ exactly matches what was computed on
the assumption that General
Relativity is correct. So it’s given us
firmer vindication of General
Relativity than we’ve had from
other evidence. This initial
detection will stimulate wider
efforts to exploit this
fundamentally new kind of
astronomy,
probing the
dynamics of
space itself.