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CURRENT AFFAIRS
(8th to 14th Feb 2016)
GNXX CANA X06A EN16
THIS WEEK … WE DELIBERATE ON ISSUES
GRAVITATIONAL WAVES … A COSMIC REVOLUTION
UNIVERSE
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It is all about space and time
Size of the whole Universe is not known
Development of various physical theories led to the inferences about the composition of the Universe
It includes planets, stars, galaxies
The observable Universe is about 28 billion parsecs (91 billion light years) in diameter at the present time.
 Parsec is a unit of length
used to measure large
distances to objects
outside the solar system
SPACE-TIME
“It is the mathematical model, that combines Space and Time.”
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It has 4 dimensions, 3 for Space and Time is the fourth dimension.
It simplified large number of physical theories
It is not rigid, it is flexible.
It can be distorted and warped as large masses move through it.
GALAXY
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It is the gravitationally bound system of Stars, Stellar Remnants, Dust, Dark Matter, Black Holes etc.
Approximately, 170 to 200 billion galaxies exist in observable Universe.
We are part of Milky Way Galaxy
This Galaxy measures about 1,00,000 to 1,20,000 light years in diameter.
90% of mass is dark matter.
BLACK HOLES
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It is a region of space-time.
It exhibits strong gravitational effects, due to which, particles and electromagnetic radiation cannot escape from it.
It acts like an ideal black body reflecting no light.
It continues to grow, by absorbing mass from its surroundings.
NEUTRON STARS
 These are formed due to the gravitational collapse of a massive star, after a Supernova.
 These are the densest and the smallest stars known to exist in the Universe.
 They are composed entirely of neutrons.
WHAT ARE GRAVITATIONAL WAVES ?
“These are ripples in the fabric of space-time that are produced, when black holes collide and stars explode” You can say, gravitational waves are
produced when objects accelerate.
Gravitational waves were first proposed, 100 years ago by
Albert Einstein, as part of the Theory of Relativity.
MORE ABOUT GRAVITATIONAL WAVES
1. STARS
2. BLACK HOLES
3. NEUTRON STARS
If a star explodes like a
Supernova, gravitational waves
carry energy away from the
detonation at the speed of light
If two black holes collide, they
will cause ripples in the spacetime
If two neutron stars orbit each
other very closely, energy is
carried away from the system by
gravitational waves
WHAT WAS THE EVENT, THAT GOT MEASURED?
Two Black Holes (one, 36 times the mass of the Sun and the other 29 times the mass of Sun), 1.3 billion light years away from Earth, orbiting
around each other collided and merged into a single massive black hole of 62 times the mass of Sun.
 As per the Theory of General Relativity, the pair of black holes orbiting around each other lost energy, through the emission of
gravitational waves.
 As they lost energy, they were gravitationally drawn closer to each other.
 As they became closer, the spinning became faster and they emitted even more gravitational waves.
 By the end of 20 milliseconds, final collision and a dark violent merger took place.
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Now 100 years of speculation, 50 years of trial and error and 25 years of perfection in establishing instruments ended.
HOW WAS IT MEASURED?
LIGO … Laser Interferometer Gravitational-Wave Observatory
Supported by the National Science Foundation operated by Caltech and MIT
These are built 3,000 kms apart, operating in unison
Livingston,
Louisiana
Hanford,
Washington
3000 km
 TWO L-Shaped detectors with 4 km long vacuum chambers.
 When a gravitational wave passes through, it stretches Space in one direction and squeezes Space in the other direction.
… HOW IT WORKED?
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This is the joint effort of 1,000
researches (LIGO scientific
collaboration) from 80 institutions
across 15 countries.
By measuring the interference of the laser, as they bounce between different points.
By this, they can measure, whether the space in between is squeezed or compressed.
It measures the most violent events in the Universe occurring millions of light years away.
It measures the smallest measurement ever attempted by science - a motion 10,000 times smaller than the nucleus.
HOW DOES IT MATTER?
1. It confirmed Einstein’s Theory of General Relativity, published 101 years ago.
2. It gives birth to Gravitational Wave Astronomy.
3. We can now observe collisions between black holes, probing gravity in extreme situations.
4. This is the opportunity to map era of the early Universe, towards the Big Bang.
FINAL WORD
1. Several Indian scientists are associated with this project. IUCAA, Pune & ICTS Bengaluru associated with this project
2. Albert Einstein must be the happiest man
3. It is game changing Cosmic Revolution
4. Case for Nobel Prize in Physics
It is The Beginning of New Era of Gravitational Astronomy !
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