To understand gravitational waves, we have to first understand the concept of gravitational force.
Around 6th century CE, the great astronomer Brahmagupta discussed about gravitational force of the earth.
In the 12th century, through his book 'Siddanta Shiromani' clarified of the basic concept of gravity. Gravity is also discussed in detail in his second book 'Lilavati'.
In the 16th-17th centuries, the Italian astrophysicist Galileo discovered that all objects fall on the earth in a uniform manner.
It is known that Galileo was declared an apostate by the Roman Catholic Church for his astronomical theories and was punished.
In the 17th-18th century, Newton clarified the concept of gravitational force and presented the universal theory of gravity.
The principles presented by him gave a new direction to astronomy.
According to Newton, 'any two bodies of the universe exert a force of attraction on each other, this force is called gravity.
This theory can explain the fall of objects on the earth, the orbiting of the sun by the planets, etc.
According to Newton's theory of gravitation, 'the force of gravity between any two bodies becomes effective immediately' but his theory does not explain the reasons for the force of gravity.
This theory clearly explains the movement of the planets and the fall of objects on the earth.
But Albert Einstein's Special Theory of Relativity opposes the above concept (Immediate Effectiveness). Einstein believed that gravity was a type of acceleration.
It is independent of matter (the body on which the force of gravity is applied).
From this idea originated the general theory of relativity. It was presented by Einstein to the Training Academy in Berlin on November 25, 1915.
Space and time had no role in Newton's gravitational concept, but Einstein, presenting a revolutionary concept, considered the role of space-time in gravity to be important.
His theory completely changed our concept of space time.
Einstein did not consider space and time to be separate. According to him, not only three dimensions (length, width, height) but four dimensions are necessary to know the position of an object.
The fourth dimension is time. When the speed of an object is less than the speed of light, the effect of the fourth dimension is negligible. Hence it is not needed in normal daily life.
According to Einstein's theory, 'To understand gravity, space should be seen as a sheet of rubber that is stretched in the air.
Imagine that a small glass tablet is placed on it. The weight of this light glass bullet will make a small shallow trough in the flexible sheet of rubber.
Now imagine that a heavy iron ball is also placed on the same rubber sheet.
Due to the iron ball, a very deep trough will be formed on the rubber sheet and the small glass ball will roll and go near the iron ball. This gives an easy explanation of gravity.
The objects of the universe are not static. Therefore, the lighter body gets attracted towards the heavier body and does not collide with it, but starts revolving around it.
It is known that according to Einstein's theory of motion, 'Space' joins 'Time' together.
If the speed of an object is less than the speed of light, then this mixture of space and time is not clear.
Therefore, The principles related to gravity get verified even without interrelating space and time.
Because, The speed of all the objects in the universe is much less than the speed of light.
But this theory does not explain the phenomenon of bending of the light of stars approaching the Sun. For this one has to resort to Einstein's theory.
Einstein hypothesized about the existence of black holes on the basis of this principle.
Indian-American astronomer Subrahmanyam Chandrasekhar said on the basis of his research that 'after a certain limit, a heavy star turns into a black hole.
The mass of a black hole can be millions of times more than that of the Sun.
Similarly, Einstein theorized that time passes very fast when moving away from a heavy body. This principle is critical to the accuracy of our smartphone's GPS system.
Einstein tried to prove all these concepts on the basis of gravitational waves. As we know, the existence of gravitational waves was hypothesized by Einstein.
Einstein explained gravitational waves to the distortion in space time caused by the motion of a heavy body.
Just as a boat sailing in a lake produces waves in still water or by throwing pebbles in a pond, waves are produced. Space time is not like water but is inflexible.
It requires the rapid movement of heavy objects to generate the waves of gravitational waves. For example the integration of two massive black holes or neutron stars.
What is a gravitational wave and why was it significant?
After the discovery of gravitational waves, the perspective of seeing, knowing, understanding the universe changed forever.
To understand this, we have to understand that when we look at an object, the rays coming from that object form the image of that object on the retina of our eye. Similarly, Gravitational Waves also necessary to hear.
Scientists are studying to gravitational waves coming from bodies to see and understand the universe. These waves are electromagnetic waves.
These types of waves include electromagnetic spectrum, visible light, X-rays, radio waves, etc. Our knowledge of the universe is based on these waves.
Scientists study the universe through telescopes. These binoculars are sensitive to X-rays, radio waves, visible light.
But electromagnetic waves get obstructed in the path itself. For example, the microwave oven can be prevented from leaving the microwave.
This is the reason why we failed to see the universe coming into effect immediately after the 'Big Bang'.
It is known that due to the vastness of the universe, light generated from a distant object can take millions of years to reach us.
This means that if any light reaches us today, it was produced millions of years ago.
Therefore, This light gives information about the position of that planet at that time. Thus, the importance of gravitational waves becomes clear.
They walk from one end of the universe and reach the other end easily. Therefore, gravitational waves can provide a clear picture of the early stages of the universe.
Through them it became easy to understand the origin of the universe and its journey till its present form.
How are gravitational waves detected?
Gravitational waves are very difficult to detect. After Einstein had speculated about gravitational waves, Russell Hulse and Joseph Taylor obtained an indirect indication of gravitational waves by energy loss in binary pulsar systems.
But it was a very difficult task to directly prove the existence of these waves.
In 1979, the US National Science Foundation provided funding for the California Institute of Technology and the Massachusetts Institute of Technology.
It was through this funding that the construction of LIGO (Laser Interferometer Gravitational Waves Observatory) in Hanford and Livingston started in the year 1999, which ended in the year 2001.
Even after years of intensive study, gravitational waves could not be discovered here.
Hence it was redesigned and made more sensitive than before. It was restarted in the year 2015.
It is 3-4 times more sensitive than the old LEGO and can even detect extremely low frequency frequencies.
In fact, gravitational waves have very high wavelengths and very low frequencies. So it is very difficult to catch them.
What does LIGO mean?
LIGO are L-shaped observatories located at a distance of about 3000 km from each other.
The main purpose of installing two detectors is to keep the search going continuously while avoiding earthquake, traffic etc.
Each side of the L-shaped observatory is 4 km long and mirrors have been installed at the extreme ends of each arm.
This has been done so that the rays of light emitted from the angle L in both the arms reflect from the mirror and have a perihelion at the angle.
The interferometer is L-shaped in English. It is also called Michelson interferometer. Its two arms are called Gives Tuornois Elation Arm.
A laser beam flows through the interferometer. This beam breaks into two halves at an angle of L and flows in both the arms of L.
When gravitational waves pass through the said region, the local space time changes.
This change causes a very subtle change in the effective length of the laser beam passing through the arms of L.
The magnitude of this change can be of the size of a single molecule.
This variation is detected by using the interference property of light. Thus the existence of gravitational waves was confirmed.
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