2. Content
• Historical background
• What are gravitational waves
• Sources of gravitational waves
• Types of gravitational waves
• Detection of Gravitational waves
• Goals of LIGO
• How it Works?
• Detected Results
• LIGO-India: A Planned Joint India-US Detector (2)
3. Historical Background
• It all started with Einstein theory of general relativity, which predicted the
existence of gravitational waves in space time.
• Einstein theory stated that objects cause the fabric of space-time around
them to curve. Moving objects should therefore create ripples in space-time.
• It predicted that the more massive the object, the larger the gravitational
waves it would create.
• In 1974,Russell Hulse & Joseph Taylor discovered the
first binary pulsar system.
4. What are gravitational waves?
Gravitational waves are ripples in the
curvature of space-time, generated in certain
gravitational interactions and traveling
outward from their source.
They travels at the speed of light.
Their strength weakens proportionally to the
distance traveled from the source.
5. Sources of gravitational
waves
Any object with mass that accelerates (which
in science means changes position at a
variable rate, and includes spinning and
orbiting objects) produces gravitational
waves.
The Universe is filled with incredibly massive
objects that undergo rapid accelerations
(things like black holes, neutron stars, and
stars at the ends of their lives), the
gravitational waves produced by these
massive objects can be detected.
6. •What else causes gravitational
waves?
• Supernova and stars collapse into neutron stars.
• Two black holes colliding or orbiting each other.
• Neutron star orbiting a black hole.
• Rotating neutron stars continuous source of waves.
• Colliding galaxies
7. Types of gravitational waves
In order to understand the types of gravitational waves these objects may
produce, LIGO scientists have defined four categories of gravitational
waves, they are:
1.Continuous Gravitational Waves
Produced by a single, spinning massive object, like an extremely dense
star called a neutron star.
2.Compact Binary Inspiral Gravitational Waves
Produced by orbiting pairs of massive and dense (hence "compact")
objects like white dwarf stars, black holes, and neutron stars.
3.Stochastic Gravitational Waves
These are small waves from every direction having random patterns.
4.Burst Gravitational Waves
These waves comes from short duration unknown sources.
8. Detection of
gravitational
waves
LIGO is a collaboration between the California Institute of
Technology (Caltech) and the Massachusetts Institute of
Technology (MIT).
It is funded by the National Science Foundation.
It will function as a national resource for both physics and
astrophysics, and universities and institutions around the
world will be involved.
Two locations:
Hanford, Washington
Livingston, Louisiana
9. Goals of LIGO
•Prove the existence of gravitational waves by direct
measurements.
•Confirm that gravitational waves travel at the speed of light.
•Learn more about black holes by proving their existence and
study their behavior.
•Gain other knowledge about the universe, including more
information about supernova and the big bang.
10.
11. •The distance measured by a light beam to changes as the
gravitational wave passes by.
•The photodetector then produces a signal which shows how the light
changes over time.
•Basically, the laser interferometer converts gravitational waves into
electrical signals.
•LIGO requires at least two detectors, in different locations, operated
in unison, to confirm the results.
•LIGO must detect deviations in distance as small as one thousandth
the diameter of a proton.
•Interferometers used in LIGO are the world's largest precision optical
instruments.
12. This requires very precise
instruments, including the
vacuum tubes, lasers, mirrors,
and mechanical systems
involved in the setup.
LIGO's vacuum system is one
of the largest, with a volume of
about 300,000 cubic feet.
Pressure inside the tubes must
be one trillionth of an
atmosphere so there are
minimal gases to interfere with
the laser beams.
13. Tubes are made of
steel.
Solid-state lasers are
used
Mirrors are suspended
and shielded from
vibrations - so isolated
that they can detect the
random motion of atoms
in the mirror itself.
30+ control systems
involved in keeping
mirrors and lasers aligned
without human
intervention.
15. Why should we care about gravitational
waves?
•Learning about gravitational waves will expand our knowledge of the universe.
•They are thought to remain unchanged by passing through material - can carry
unaltered information about their source.
•Could gain insight into why the universe is the way it is and what it's fate will be.
•Can accurately determine cosmological distances.
•Searching for existence of gravitational waves may uncover new phenomena.
16. Scientists can detect a black hole using gravitational waves - and
how big and how fast the black hole is spinning.
The gravitational waves emitted from each binary system - in
spiral waves - have characteristic frequencies and amplitudes.
These characteristics depend on properties of the system (mass,
orbital period, etc.).
When waves emitted during the merging of two neutron stars
are detected, we will be able to learn more about their structure
and equation of state.
Eventually, we will be able to use the information from inspiral
waves to perform more precise tests of general relativity,
measure the Hubble constant, and understand the geometry of
the space-time around black holes and other objects
18. •LIGO-India is a collaboration between the Laser Interferometer
Gravitational-Wave Observatory (LIGO) Laboratory (operated by Caltech
and MIT) and three Institutes in India
•The Raja Ramanna Center for Advanced Technology (Indore)
•The Institute for Plasma Research (Ahmedabad)
•The Inter-University Centre for Astronomy and Astrophysics (Pune)
These three institutions bring the complementary skills and resources
needed for the success of the project.
• It is located in Hingoli District,
Maharashtra.
LIGO-India: A joint India-Us Detector
