Detection of gravitational waves on 11th Feb, 2016 by LIGO (Laser Interferometer Gravitational Wave Observatory) Project

1. Gravitational Waves …
A Breakthrough after a
Century
2016
A Review By Atiqa Ijaz Khan
Co Author: Faiqa Ijaz Khan
LAHORE, PAKISTAN DATED: 15TH
FEB, 2016

2. Gravitational Waves … A Breakthrough
after a Century
(Courtesy: YouTube press release)
11th
February, 2016, a breakthrough has been made in scientific history as for the most unexpected
discovery of the century. 400 years ago, when Galileo put up his telescope to the night sky, he
opens up the door for the era of observational astronomy. Back in 1916, Albert Einstein, a year
after his most astonishing theory of General Relativity (1915) about the concepts of Gravity, he
predicted the most amazing specs to see through Universe, i.e. the “Gravitational Wave” goggles.
Efforts made in 1970s has concluded in 1992 when LIGO, Laser Interferometer Gravitational
Wave Observatory project was remarked. The precision/accuracy of LIGO can be understood by
an example, to measure the distance between the nearest star to the Sun (at 3 3/4 light years away;
the distance light travel in a year), LIGO is able to quantify it by the width of human hair, that’s
incredibly mind blowing. Rainer Weiss says, a physicist at the Massachusetts Institute of
Technology (MIT) in Cambridge, who described the original idea for LIGO in paper in 1972.
“People thought we were crazy,” when physicists asked NSF (National Science Foundation) to
spend $300 million on an instrument for such an insane idea of the time. Facing the harsh criticism
from lawmakers and creating a havoc, Congress accepted the idea and construction begins in 1994.
The aspects behind the LIGO, an L-shaped observatory, in order to lessen the local noise
disturbance, the arms are about 4 km apart from each other. One lab is in Hanford, Washington

3. and other at Livingston, Louisiana, built by California Institute of technology (Caltech) and MIT
for US National Science Foundation.
The working concept is somewhat pretty simple to understand. As the laser beam fires up, it split
up into two parts of “L”, moving back and forth, at each arm to the detector, fixed with mirrors at
the end. The beam moves with the speed of light (3 x 108
m), as it coincides at each end, it reflects
back to the common junction point of “L”. The time in which both of these beams reaches the
initial point, is the key to the discovery of the gravitational waves. If gravitational waves pass
through them, two laser beams/waves will not combine together to cancel out each other effect so
to be detected by the photo detector. Otherwise, there will be no detection.
Although, it comes empty handed after a decade in 2008. Then the NSF took another bold step of
$205 million upgrade as Advance LIGO (LIGO-2), opened in 2015. Some other gravitational
detectors, like VIRGO, Italy; GEO-600 Germany; TAMA and CLIO, Japan are the 1st
generation
of gravitational detectors. The 2nd
generation is about to work online in next 3-5 years, including
Advance LIGO, LCGT, Japan and LIGO Australia, with 10 times more sensitive.

4. It took 25 years, 16 countries, 1000 scientists
and 02 mirror detectors to make it possible. On
14th
September, 2015, LIGO recorded a wired
sort of signal at 7 milli-second apart, on both
labs. Actually, they captured the variation in
the signal time lap as they reflect back from the
mirrors. The time difference between these two
beams is not the same! Yupieee…that’s it, they
finally detected the century long waited
gravitational waves. About which Einstein, his
self was not sure to be detected by the human
kind as he said: “It is not possible for human to
detect these gravitational waves as they are so
small to be detected”. LIGO team took months
of careful checking and analysis to confirm the
news from every angle and aspect of data.
“We have detected gravitational waves. We did it,” said David Reitze, executive director of the
LIGO, at a press
conference in
Washington, at 11th
Feb, 2016. The
phenomenon was
detected by observing
the merging of two
black holes 1.3 billion
light years ago (when
multicellular life on
Earth was about emerge!) at the most sensitive and sophisticated detectors of the time. The black
holes of approximately 150 km in diameter (more than Hawaii island in width) and 30 times the
mass of sun, known as solar mass (30 x 1.989*1030
kg) in size collides to form a gigantic black
hole that generates these gravitational waves (or the ripples generated in a water tub after a stone

5. thrown in it) in the fabric of space and time. These waves were moving with the half of the speed
of light. As it hits the Earth, the energy potential of that wave was just about 3 solar masses. These
waves produces jiggling jello like effect as they stretches and compresses the space-time in
perpendicular direction. These ripples are so tiny as by 1/1000 of mass of proton (of 10-19
m).
LIGO was able to detect it, just as a chirp, in the signal for about 20 milliseconds only. Its location
was projected to be coming from the southern part of the Universe, Canis Major constellation
(common name ‘Big Dog’). Wao! Professor Kip Thorne, of the California Institute of Technology,
and one of the founding fathers of LIGO says: “The colliding black holes that produced these
gravitational waves
created a violent
storm in the fabric of
space and time, a
storm in which time
speeded up and
slowed down, and
speeded up again….”
.This discovery
derives in with
another reward for the
astronomers, the detection of a binary black holes circling around each other like Earth around the
Sun. To our more triumph, these waves were detected on a photo detector, thus we can hear them
(256-512 Hz). “Before that we were only able to see the universe, but we are deaf in actual, now
the universe has spoken to us and we can hear it. As the frequency of these waves are just under
the human hearing range” (20 – 20 kHz), says David Reitze, executive director of the LIGO.
To keep up the expectations, binary black holes are not the only source of gravitational waves. As
the collision of neutron stars (size of Washington DC), black holes and neutron stars itself, super
nova, cosmic strings of universe by/after the Big Bang are also the source of these kind of waves.
At present, January 2016, the LIGO facility is shut down for further upgrades. It is expected after
that the sensitivity will be 3 times more and we were be able to detect such huge events in every
months to weeks. Thus, it finally settles downs the century long debate and frustration by finding

6. the gravitational waves. Imagine how people perceives after the discovery of radio waves – we
learned how to communicate; like mobile communication, satellite TVs etc., with gravitational
waves, we are opening a whole new picture, who knows what lies ahead us. Moving from the calm
look of universe from the visible window to the more violent behavior through X-rays, now to
audible range of gravitational waves. As the scientists from all over the astronomical society are
going to embraced the initiation of 1st
step into the door of gravitational astronomy after
exploitation of visible to gamma rays to better the understanding of the mechanics of universe and
its fate.