RIPPLES IN SPACE TIME
Gravitational Wave
Introduction:
Gravitational waves are propagating fluctuations of gravitational fields, that is, “ripples” in space-time generated mainly by moving massive bodies. This distortion of space-time travel with the speed of light. Gravitational waves can be detected by devices which measure the induced length changes. The frequencies and the amplitudes of the waves are related to the motion of the masses involved. Thus the analysis of the gravitational waveforms allows us to learn about their source and, if there are more than two detectors involved in observation, to estimate the distance and position of their source and the sky.
Gravitational waves are propagating fluctuations of gravitational fields, that is, “ripples” in space-time generated mainly by moving massive bodies. This distortion of space-time travel with the speed of light. Gravitational waves can be detected by devices which measure the induced length changes. The frequencies and the amplitudes of the waves are related to the motion of the masses involved. Thus the analysis of the gravitational waveforms allows us to learn about their source and, if there are more than two detectors involved in observation, to estimate the distance and position of their source and the sky.
Here space-time is any mathematical model that
fuses the 3-dimensions of space and the one dimension of time in to a single
four dimensional continuum. Space-time diagram is useful in visualizing and
understanding relativistic effects such as how different observes perceive
where and when events occur.
The idea of space-time continuum comes from the ground-breaking work of ‘Albert-Einstein’. One way of envisioning the space-time continuum is to think of a large piece of fabric, such as a sheet. Einstein realized that objects with mass, such as a person or planet earth, create wrinkles in space-time, which creates a dimple in a sheet. Einstein identified the curves in a space-time as ‘Gravity’ but he thought they would be too small to detect.
In February 2016 the direct measurement of gravitational waves are announced. This provides us with a new method for exploring the universe.
From Prediction to Reality: A history of the search
for gravitational waves
1915 -Albert Einstein publishes general theory of
relativity, explains gravity as the warping of space-time by mass or energy.
1916 -Einstein predicts massive objects whirling in certain
ways will cause space-time ripples—gravitational waves.
1936 -Einstein has second thoughts and argues in a
manuscript that the waves don't exist—until reviewer points out a mistake.
1962 -Russian physicists M. E. Gertsenshtein and V. I.
Pustovoit publish paper sketch optical method for detecting gravitational
waves—to no notice.
1969 -Physicist Joseph Weber claims gravitational wave detection
using massive aluminum cylinders—replication efforts fail.
1972 -Rainer Weiss of the Massachusetts Institute of
Technology (MIT) in Cambridge independently proposes optical method for
detecting waves.
1974-Astronomers discover pulsar orbiting a neutron star
that appears to be slowing down due to gravitational radiation—work that later
earns them a Nobel Prize.
1979 -National Science Foundation (NSF) funds California
Institute of Technology in Pasadena and MIT to develop design for LIGO.
1990 -NSF agrees to fund $250 million LIGO experiment.
1992 -Sites in Washington and Louisiana selected for LIGO
facilities; construction starts 2 years later.
1995 -Construction starts on GEO600 gravitational wave
detector in Germany, which partners with LIGO and starts taking data in 2002.
1996 -Construction starts on VIRGO gravitational wave
detector in Italy, which starts taking data in 2007.
2002–2010 -Runs of initial LIGO—no detection of gravitational
waves.
2007 -LIGO and VIRGO teams agree to share data, forming a
single global network of gravitational wave detectors.
2010–2015 -$205 million upgrade of LIGO detectors.
2015 -Advanced LIGO begins initial detection runs in
September
2016 -On 11 February, NSF and LIGO team announce successful
detection of gravitational waves.
Who has received the 2017
Nobel Prize for Physics?
The prize is shared by Rainer Weiss, Barry Barish and Kip Thorne “for decisive contribution to the LIGO detector and discovery of gravitational waves.”
Dr. Weiss- has born in Berlin and now a U.S. citizen- receives half the prize. The remaining half is shared equally by two Caltech scientists- Dr. Barish, Prof. of Physics and Dr. Thorne, Prof., Theoretical Physics.
The prize is shared by Rainer Weiss, Barry Barish and Kip Thorne “for decisive contribution to the LIGO detector and discovery of gravitational waves.”
Dr. Weiss- has born in Berlin and now a U.S. citizen- receives half the prize. The remaining half is shared equally by two Caltech scientists- Dr. Barish, Prof. of Physics and Dr. Thorne, Prof., Theoretical Physics.
WHAT DID THEY DISCOVER?
They are receiving the prize for the discovery of the gravitational waves released by violent events in the universe such as the mergers of black holes. First time this was detected on September 14th, 2015, by the LIGO-VIRGO collaboration. Since then three more detections have been made, the last one on September 28th, 2017.
They are receiving the prize for the discovery of the gravitational waves released by violent events in the universe such as the mergers of black holes. First time this was detected on September 14th, 2015, by the LIGO-VIRGO collaboration. Since then three more detections have been made, the last one on September 28th, 2017.
WHY DO GRAVITATIONAL WAVES MATTER TO
US?
The discovery is due to an extremely delicate experiment. Gravitational waves were predicted by Einstein almost hundred years ago. After about 50 years of experimentation the waves were detected for the first time on September 2015.
The discovery and the repeated detection have made the possibility of gravitational wave astronomy very real. Gravitational wave astronomy is a way of mapping out some of the most violent processes in the universe such as black hole or neutron star mergers that cannot be detected with light or the conventional methods.
The discovery can prove the way of proving the general theory of relativity, so that we can look deeper and deeper in to the universe. It also throws up the possibility of detectors that can look at the begging of the universe.
Gravity is the weakest of the four fundamental forces so only the most extreme events Black holes colliding, Neutron star twirling and Supernova erupting produce detectable waves.
The discovery is due to an extremely delicate experiment. Gravitational waves were predicted by Einstein almost hundred years ago. After about 50 years of experimentation the waves were detected for the first time on September 2015.
The discovery and the repeated detection have made the possibility of gravitational wave astronomy very real. Gravitational wave astronomy is a way of mapping out some of the most violent processes in the universe such as black hole or neutron star mergers that cannot be detected with light or the conventional methods.
The discovery can prove the way of proving the general theory of relativity, so that we can look deeper and deeper in to the universe. It also throws up the possibility of detectors that can look at the begging of the universe.
Gravity is the weakest of the four fundamental forces so only the most extreme events Black holes colliding, Neutron star twirling and Supernova erupting produce detectable waves.
BLACK HOLE COLLIDING:
It is possible for two black holes to collide. Once they come so close that they cannot escape each other’s gravity, they will merger to become one bigger black hole. Such an event would be extremely violent. Black hole merger would produce tremendous energy and send massive ripples through the space time fabric of the universe. The ripples are called gravitational waves.
It is possible for two black holes to collide. Once they come so close that they cannot escape each other’s gravity, they will merger to become one bigger black hole. Such an event would be extremely violent. Black hole merger would produce tremendous energy and send massive ripples through the space time fabric of the universe. The ripples are called gravitational waves.
Neutron star twirling:
Neutron stars, the densest objects in the universe, can rotate up to several hundred times per second. If the star has properly spherical shape then it won’t emit gravitational waves as it spins. Only if the surface is bumpy, the spinning asymmetry would generate gravitational waves.
Neutron stars, the densest objects in the universe, can rotate up to several hundred times per second. If the star has properly spherical shape then it won’t emit gravitational waves as it spins. Only if the surface is bumpy, the spinning asymmetry would generate gravitational waves.
Supernova erupting:
The gravitational waves are emitted from deep inside the core of the star where no electromagnetic radiation can escape. This allows a gravitational wave detection to tell us information about the explosion mechanism that cannot be determined with other methods.
The gravitational waves are emitted from deep inside the core of the star where no electromagnetic radiation can escape. This allows a gravitational wave detection to tell us information about the explosion mechanism that cannot be determined with other methods.
The
gravitational waves that are detectible by LIGO will be caused by some of the
most energetic events in the universe-colliding black holes, exploding stars,
and even the birth of the universe itself. Detecting and analyzing the
information carried by gravitational waves will allow us to observe the
universe in a way never before possible. It will open up a new window of study
on the universe.
LIGO:
LIGO is the world's largest gravitational wave observatory and a cutting edge physics experiment. Comprising two enormous laser interferometers located thousands of kilometers apart, LIGO exploits the physical properties of light and of space itself to detect and understand the origins of gravitational waves.
LIGO is the world's largest gravitational wave observatory and a cutting edge physics experiment. Comprising two enormous laser interferometers located thousands of kilometers apart, LIGO exploits the physical properties of light and of space itself to detect and understand the origins of gravitational waves.
Although LIGO will search for
gravitational waves from space, and it is called an "Observatory",
LIGO is not, strictly speaking, intended to be solely an astronomical facility.
LIGO is truly a physics experiment on the scale and complexity of some of the
world's giant particle accelerators and nuclear physics laboratories. Though
its mission is to detect gravitational waves from some of the most violent and
energetic processes in the Universe, the data it will collect will have
far-reaching effects on many areas of physics including gravitation,
relativity, astrophysics, cosmology, particle physics, and nuclear physics.
Three things truly distinguish LIGO from an astronomical observatory:
Three things truly distinguish LIGO from an astronomical observatory:
First, LIGO is blind. Unlike optical or radio
telescopes, LIGO cannot see electromagnetic radiation (e.g., visible light,
radio waves, and microwaves) nor does it have to because gravitational waves
are not part
of the electromagnetic spectrum
Second, LIGO is the opposite of
round. Since LIGO
doesn’t need to collect light from stars or other objects in the Universe, it
doesn't need to be dish-shaped like telescope mirrors or radio dishes, which
collect and focus electromagnetic radiation to produce images
Third,
LIGO cannot function alone. While an
astronomical observatory can function and collect data just fine on its own
(some do not, by choice), gravitational wave observatories like LIGO cannot operate solo. The only
way to definitively detect a gravitational wave is by operating in unison with
a distant twin so that local vibrations are not mistaken for signals from
gravitational waves.
How LIGO Works:
LIGO is the world's largest gravitational wave observatory. It consists of two detectors situated 1,865 miles (3,002 kilometers) apart in isolated regions in the states of Washington and Louisiana. Each L-shaped facility has two arms positioned at right angles to each other and running 2.5 miles (4 kilometers) from a central building. Lasers are beamed down each arm and bounced back by mirrors, essentially acting as a ruler for the arm. Sensitive detectors can tell if the length of the arms of a LIGO detector varies by as little as 1/10,000 the width of a proton, representing the incredibly small scale of the effects imparted by passing gravitational waves. LIGO has two observatories to act as a check on the other to rule out that potential gravitational-wave signal detection is not due to a local, terrestrial disturbance; both facilities will detect a true gravitational wave moving at the speed of light nearly simultaneously. Although the twin LIGO facilities act as a single observatory, they are not designed for "observing" in the conventional sense. Instead of eyes, the facilities can be thought more of as "ears" listening for gravitational waves, or even as a skin trying to "feel" the slightest of movements.
LIGO is the world's largest gravitational wave observatory. It consists of two detectors situated 1,865 miles (3,002 kilometers) apart in isolated regions in the states of Washington and Louisiana. Each L-shaped facility has two arms positioned at right angles to each other and running 2.5 miles (4 kilometers) from a central building. Lasers are beamed down each arm and bounced back by mirrors, essentially acting as a ruler for the arm. Sensitive detectors can tell if the length of the arms of a LIGO detector varies by as little as 1/10,000 the width of a proton, representing the incredibly small scale of the effects imparted by passing gravitational waves. LIGO has two observatories to act as a check on the other to rule out that potential gravitational-wave signal detection is not due to a local, terrestrial disturbance; both facilities will detect a true gravitational wave moving at the speed of light nearly simultaneously. Although the twin LIGO facilities act as a single observatory, they are not designed for "observing" in the conventional sense. Instead of eyes, the facilities can be thought more of as "ears" listening for gravitational waves, or even as a skin trying to "feel" the slightest of movements.
Advanced LIGO (aLIGO):
The initial technology deployed for LIGO was sensitive to movement of 1/1000 the diameter of a proton, but with an upgrade begun in the 2010s, LIGO's sensitivity was boosted 10-fold. The many enhancements included increasing the power of the lasers from 10 watts to 200 watts and mirror seismic isolation technology improvements. Overall, aLIGO will be able to detect possible gravitational wave-producing events three times farther away than the initial LIGO setup. Accordingly, a far larger volume of space will now be within "earshot" of the LIGO project, with the opportunity to catch far more potential sources of space-time ripple.
The initial technology deployed for LIGO was sensitive to movement of 1/1000 the diameter of a proton, but with an upgrade begun in the 2010s, LIGO's sensitivity was boosted 10-fold. The many enhancements included increasing the power of the lasers from 10 watts to 200 watts and mirror seismic isolation technology improvements. Overall, aLIGO will be able to detect possible gravitational wave-producing events three times farther away than the initial LIGO setup. Accordingly, a far larger volume of space will now be within "earshot" of the LIGO project, with the opportunity to catch far more potential sources of space-time ripple.
The
overall performance of Advanced LIGO is dominated at most frequencies by the
quantum noise of sensing the position of the test masses, with a contribution
at mid-frequencies from the internal thermal noise of the test masses. This
design, with modest enhancements after it enters scientific use, should take
this interferometer architecture to its technical endpoint; it is as sensitive
as one can make an interferometer based on familiar technology: a Fabry-Perot
Michelson configuration with external optical readout using room temperature
transmissive optics. Further advances will come from R&D that is just
beginning, such as the exploration of cryogenic optics and suspensions, purely
reflective optics, and a change in the readout to one which fully exploits our
understanding of the quantum nature of the measurement (e.g., quantum
non-demolition speed meters). These later developments will be timely for
instruments to be developed in the second decade of this century.
Collected By:
Prajna
Preethi Salyan K S
Rachana K
Rashmitha H
Source:
Internet
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