Gravitational Waves Questions

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Very Short Answers Questions [1 Mark Questions]

Ques. What are gravitational waves?

Ans. A gravitational wave is a ripple in space that is unseen. Gravitational waves travel at light speed (186,000 miles per second). As they pass, these waves squeeze and stretch everything in their path.

Ques. Which are the probable significant sources of gravitational waves?

Ans. Black holes, neutron stars, white dwarf binary star systems, supernovae, and events connected to the Big Bang are all possible significant sources of gravitational waves.

Ques. Researchers have developed a new _____________ source which can be placed in the LIGO detector to double sensitivity.

1. Hot vacuum
2. Cold vacuum
3. Squeezed vacuum
4. Vacuum

Ans. The correct answer is c. Squeezed vacuum

Explanation: Researchers created a new method to improve the Advanced Laser Interferometer Gravitational-Wave Observatory's sensitivity to gravitational waves, which are small disturbances in space-time. A team of researchers from MIT and the Australian National University report on advancements in what is known as the squeezed vacuum source.

Ques. In 2017, the Nobel Prize in Physics was subsequently awarded to ___________ for their contributions to the successful observation of gravitational waves.

Ans. Kip Thorne, Barry Barish, and Rainer Weiss

Explanation: Kip Thorne, Barry Barish, and Rainer Weiss were awarded the Nobel Prize in Physics in 2017 for their contributions to the successful observation of gravitational waves.

Ques. In 1974, the first probable evidence for the occurrence of ________ was detected from the orbital decay of a pulsar called Hulse–Taylor binary pulsar.

1. Radio waves
2. Gravitational waves
3. Infra-red waves
4. Ultrasound

Ans. The correct answer is b. Gravitational waves

Explanation: The orbital decay of a pulsar known as the Hulse-Taylor binary pulsar provided the first probable evidence for the existence of gravitational waves in 1974.

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Short Answers Questions [2 Marks Questions]

Ques. Why are gravitational waves not easily detectable?

Ans. Gravitational waves are difficult to detect. 

• They have a very modest amplitude with a strain of approximately 10^-21 when they enter the Earth, requiring an extremely sensitive detector and diluting the signal from other noise sources. 
• Gravitational waves are projected to have frequencies ranging from 10^-16 Hz to 10⁴ Hz.

Ques. Why cannot classical mechanics comprehend gravitational waves?

Ans. Newton's law of universal gravitation does not indicate the existence of these waves in classical mechanics. This is due to the fact that this rule is predicated on the assumption that physical interactions occur instantly (at infinite speed), demonstrating one of the ways in which classical physics principles cannot explain events including relativity.

Ques. When was the direct evidence of gravitational waves detected?

Ans. In 2015, the first direct evidence of gravitational waves was discovered. The LIGO detectors in Hanford, Livingston, and Louisiana discovered a signal created by the merger of two black holes.

Ques. What is meant by primordial gravitational waves?

Ans. Primordial gravitational waves are gravitational waves that have been observed in the cosmic microwave background (CMB). They were allegedly seen by the BICEP2 system, according to a statement filed on March 17, 2014. However, it was retracted on January 30, 2015 (the signal is entirely due to random dust in the Milky Way).

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Long Answers Questions [3 Marks Questions]

Ques. How did Albert Einstein treat gravity in his theories?

Ans. The gravitational force is treated as a phenomenon emerging from the curvature of spacetime in the general theory of relativity. 

• The existence of matters causes this spacetime curvature. 
• Generally, the greater the concentration of matter, the greater the curvature of spacetime at the volume's boundaries. 
• As celestial objects with mass travel over the spacetime fabric, the curvature changes to reflect their changing positions. 
• Accelerating bodies cause changes in this curvature that propagate outward at the speed of light in a wave motion in some instances. 
• Gravitational waves are the name given to these moving phenomena.

Ques. What is the difference between the concept of gravity in Newtonian mechanics and the General Theory of Relativity?

Ans. The general theory of relativity i.e. Einstein's theory of gravity, varies significantly from Newton's theory of gravity. 

• The fact that Einstein's theory contains the cosmic speed limit: the speed of light, is one of the most essential. Newton assumed that gravity is felt instantly everywhere in the Universe, implying that it moves at an infinite speed. Newton would have predicted that if the Sun disappeared right now, the Earth would quickly recognize the loss of gravitational force and fly out of the Solar System.
• Einstein observed that since nothing, not even gravity, can move faster than the speed of light, the Earth would not feel the absence of gravity for 8.5 minutes, the time it takes gravity to travel from the Sun to the Earth (at 300,000km/s or 6.7 million mph).
• Another difference between Newton and Einstein is that Einstein's theory recognizes that the source of gravity is energy, not mass, as Newton believed. This indicates that all types of energy, including sound and heat, have gravity. Importantly, gravity is a type of energy, hence gravity generates more gravity.

Ques. How to measure Gravity waves?

Ans. Gravitational waves are detected by a gravitational-wave observatory or detector. 

• As a gravitational wave passes Earth, it continues to squeeze and expand space. 
• LIGO can detect gravitational waves, which cause space to move. 
• A LIGO observatory is made up of two extremely sensitive detectors. 
• These four-kilometer-long L-shaped detectors are located in Washington and Louisiana. 
• Each of these detectors, which use lasers and mirrors, may detect small changes in spacetime caused by gravitational waves. 
• Another observatory, the European Gravitational Observatory's detector, which has a similar design as LIGO, is now operational. 
• So far, the world has three operational gravitational wave observatories. 
• This would allow scientists to pinpoint the source of gravitational waves in space. Similar observatories are expected to open soon in Japan and India.

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Very Long Answers Questions [5 Marks Questions]

Ques. What are the properties of gravitational waves?

Ans. The following are the properties of gravitational waves

• Gravitational waves are invisible and cannot be seen.
• They are extremely fast, traveling at the speed of light (186,000 miles per second).
• As they pass, gravity waves stretch and squeeze everything in their path.
• The objects that produce gravitational waves are very far away from Earth and, if they are very weak, may not reach it at all. As a result, these waves are extremely difficult to detect.
• Gravitational waves are caused by destructive and violent events, however, they are considerably smaller when they reach the planet (thousands of billions of times).
• The gravitational waves that reach Earth are the consequence of a billions of light-years-ago event.

Ques. When were gravitational waves first found and how?

Ans. The first confirmation of gravitational waves appeared in 1974, 20 years after Albert Einstein's death. 

• Two scientists detected a double pulsar at the Arecibo Radio Observatory in Puerto Rico. Pulsars appear to be blinking stars from afar, but they are actually planets around fast-revolving neutron stars. 
• These appeared to them to be the same system that had previously been predicted to create gravitational waves. 
• Astronomers believed that this may be a confirmation of Einstein's prediction from many years ago. 
• As a result, they began tracking how the orbits of these stars changed over time. 
• After 8 years, scientists discovered that these stars were moving closer to one other at a rate predicted by general relativity if they were emitting gravitational waves. 
• Since then, many astronomers have attempted to analyze pulsar radio emissions and discovered comparable findings, although these data were obtained by indirect means rather than direct contact. 
• Finally, on September 14, 2015, LIGO (Laser interferometer gravitational-wave observatory) made a breakthrough and proved the existence of gravitational waves, which were caused by the collision of two black holes 1.3 billion light-years away but reached Earth only in 2015.

Ques. What causes Gravitational Waves?

Ans. Gravitational waves are produced by many violent and forceful phenomena in the universe. 

• When two huge speeding objects, like as black holes, neutron stars, or planets, circle one other, something extraordinary occurs. 
• Such motions have the potential to cause ripples across time and space. 
• Gravity waves would move from the source in the same way that water in a pond spirals out when a stone is thrown into it. 
• The gravitational radiation then spreads out from the source, bringing information about its origins with it. 
• Gravity is a wave that contains information about the nature of gravity. The strongest gravity waves are produced by cataclysmic events. 
• Black holes colliding, supernovae, massive stars that burst at the end of their lives, and neutron star collisions are a few examples.
• Other, weaker waves are expected to be produced by the motions of neutron stars that are not perfect spheres. 
• The residual gravitational radiation is thought to be remnants of the Big Bang.

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