The Laser Interferometer Gravitational-Wave Observatory (LIGO) aims to detect cosmic gravitational waves to enhance astronomical observations. Developed based on Einstein's theory of general relativity, LIGO utilizes laser interferometry to observe changes in spacetime caused by massive objects, confirming predictions about gravitational waves. Additionally, initiatives like the Einstein Telescope and the INDIGO consortium seek to advance gravitational-wave research and establish observational facilities globally.

2. • NOEL BENNY
• VAJID RAHMAN K
• VYSAKH A V
• ABHIN KRISHNA K A
• AKHIEL NAZIM K A
• ALEX TOMY
• AMRITHA P A
• ANAGHA SUNNY

3. The Laser Interferometer Gravitational-Wave Observatory
(LIGO) is a large-scale physics experiment and observatory
to detect cosmic gravitational waves and to develop
gravitational-wave observations as an astronomical tool.
Two large observatories were built in the United States
with the aim of detecting gravitational waves
bylaser interferometry.

7. • In Einstein's theory of general relativity, gravity is
treated as a phenomenon resulting from the curvature
of spacetime. This curvature is caused by the presence
of mass. Generally, the more mass that is contained
within a given volume of space, the greater the
curvature of spacetime will be at the boundary of its
volume. As objects with mass move around in
spacetime, the curvature changes to reflect the
changed locations of those objects. In certain
circumstances, accelerating objects generate changes
in this curvature, which propagate outwards at the
speed of light in a wave-like manner. These propagating
phenomena are known as gravitational waves.

9. • LIGO's mission is to directly observe gravitational
waves of cosmic origin. These waves were first
predicted by Einstein's general theory of relativity
in 1916, when the technology necessary for their
detection did not yet exist. Their existence was
indirectly confirmed when observations of the
binary pulsar PSR 1913+16 in 1974 showed an
orbital decay which matched Einstein's
predictions of energy loss by gravitational
radiation. The Nobel Prize in Physics 1993 was
awarded to Hulse and Taylor for this discovery

10. After the completion of Science Run 5, initial LIGO was
upgraded with certain technologies that resulted in an
improved-performance configuration dubbed Enhanced
LIGO.Some of the improvements in Enhanced LIGO
included Increased laser power
Homodyne detection Output mode cleaner
In-vacuum readout hardware
Science Run 6 (S6) began in July 2009 with the enhanced
configurations on the 4 km detectors.It concluded in
October 2010, and the disassembling of the original
detectors began. By mid-September 2015, LIGO Scientific
Collaboration included more than 900 scientists worldwide

12. • Interferometry makes use of the principle of superposition
to combine waves in a way that will cause the result of their
combination to have some meaningful property that is
diagnostic of the original state of the waves. This works
because when two waves with the same frequency
combine, the resulting intensity pattern is determined by
the phase difference between the two waves—waves that
are in phase will undergo constructive interference while
waves that are out of phase will undergo destructive
interference. Waves which are not completely in phase nor
completely out of phase will have an intermediate intensity
pattern, which can be used to determine their relative
phase difference. Most interferometers use light or some
other form of electromagnetic wave

16. When a gravitational wave passes through the interfer-
ometer, the spacetime in the local area is altered. De-
pending on the source of the wave and its polarization,
this results in an effective change in length of one or both
of the cavities. The effective length change between the
beams will cause the light currently in the cavity to be-
come very slightly out of phase (anti phase) with the in-
coming light. The cavity will therefore periodically get
very slightly out of coherence and the beams, which are
tuned to destructively interfere at the detector, will have
a very slight periodically varying detuning. This results
in a measurable signal

17. Einstein Telescope (ET) or Einstein Observatory, is a proposed third-
generation ground-based gravitational wave detector, currently
under study by some institutions in the European Union. It will be
able to test Einstein's general theory of relativity in
strong field conditions and realize precision gravitational wave
astronomy. The ET is a design study project supported by the
European Commission under the Framework Programme 7 (FP7). It
concerns the study and the conceptual design for a new research
infrastructure in the emergent field of gravitational-waveastronomy.

19. INDIGO, or IndIGO (Indian Initiative in Gravitational-wave
Observations) is a consortium of Indian gravitational-wave
physicists.This is an initiative to set up advanced experimental
facilities for a multi-institutional observatory project in
gravitational-wave astronomy.
ince 2009,the IndIGO Consortium
has been planning a roadmap for gravitational-wave astronomy
and a phased strategy towards Indian participation in realizing a
gravitational-wave observatory in the Asia-Pacific region. IndIGO
is the Indian partner (along with the LIGO Laboratory in USA) in
planning the LIGO-India project.