Gravitational waves are ripples in the fabric of spacetime created by massive bodies travelling with extreme accelerations. Massive celestial bodies like black holes, neutron stars, galaxies, or quasars are the probable significant sources of gravitational waves. Gravitational waves were first suggested by Oliver Heaviside and Henri Poincaré. Later, Albert Einstein, along with the general theory of relativity, predicted the existence of gravitational waves. These waves transmit energy as gravitational radiation. It is a type of radiant energy, just like electromagnetic radiation. In classical mechanics, Newton’s law of universal gravitation does not point to the existence of these waves. This is because this law is based on the assumption that physical interactions move instantaneously (with infinite speed) – displaying one of the ways the laws of classical physics cannot describe scenarios associated with relativity.
In 1974, the first probable evidence for the occurrence of gravitational waves was obtained from the wave’s orbital decay of a pulsar called Hulse–Taylor binary pulsar. Joseph Hooton Taylor Jr. and Russel A. Hulse were awarded the Nobel Prize in Physics for this remarkable discovery in 1993. On the other hand, the first direct evidence of gravitational waves was detected in 2015. A signal produced by the merging of two black holes was detected by the LIGO detectors in Hanford, Livingston, and Louisiana. In 2017, Nobel Prize in was subsequently awarded to Kip Thorne, Barry Barish, and Rainer Weiss for their contributions to the successful observation of gravitational waves. In this field, detections of gravitational waves are utilised to infer data on the origins of gravitational waves. The sources that can be analysed in this manner include black holes, neutron stars, white dwarf binary star systems, supernovae, and events related to the Big Bang.
Important Gravitational Waves Questions with Answers
1) What are gravitational waves?
Gravitational waves are ripples or disturbances in the spacetime curvature generated by accelerated matter that move as waves from their sources at light speed.
2) How did Albert Einstein treat gravity in his theories?
In the general theory of relativity, the gravitational force is handled as a phenomenon arising from the curvature of spacetime. This spacetime curvature is created by the presence of matter. Usually, the more the concentration of matter, the larger the curvature of spacetime could be at the confines of its volume. As celestial objects with mass move on the spacetime fabric, the curvature varies to show the changed position of those bodies. In some scenarios, accelerating bodies produce variations in this curvature which move outward at the velocity of light in a wave motion. These moving phenomena are called gravitational waves.
3) Gravitational waves were first suggested by _______ and Henri Poincaré.
Answer: Oliver Heaviside
Explanation: Gravitational waves were first suggested by Oliver Heaviside and Henri Poincaré.
4) Why cannot classical mechanics comprehend gravitational waves?
In classical mechanics, Newton’s law of universal gravitation does not point to the existence of these waves. This is because this law is based on the assumption that physical interactions move instantaneously (with infinite speed) – displaying one of the ways the laws of classical physics cannot describe scenarios associated with relativity.
5) In 1974, the first probable evidence for the occurrence of ________ was detected from the orbital decay of a pulsar called Hulse–Taylor binary pulsar.
Answer: gravitational waves
Explanation: In 1974, the first probable evidence for the occurrence of gravitational waves was detected from the orbital decay of a pulsar called Hulse–Taylor binary pulsar.
6) _________ were awarded the Nobel Prize in Physics for the indirect discovery of gravitational waves in 1993.
Answer: Joseph Hooton Taylor Jr. and Russel A. Hulse
Explanation: Joseph Hooton Taylor Jr. and Russel A. Hulse were awarded the Nobel Prize in Physics for the indirect discovery of gravitational waves in 1993.
7) When was the direct evidence of gravitational waves detected?
The first direct evidence of gravitational waves emerged in 2015. A signal produced by the merging of two black holes was detected by the LIGO detectors in Hanford, Livingston, and Louisiana.
8) In 2017, the Nobel Prize in Physics was subsequently awarded to ___________ for their contributions to the successful observation of gravitational waves.
Answer: Kip Thorne, Barry Barish, and Rainer Weiss
Explanation: In 2017, Nobel Prize in Physics was subsequently awarded to Kip Thorne, Barry Barish, and Rainer Weiss for their contributions to the successful observation of gravitational waves.
9) Which are the probable significant sources of gravitational waves?
The probable significant sources of gravitational waves include black holes, neutron stars, white dwarf binary star systems, supernovae, and events related to the Big Bang.
10) What are the two unique properties of gravitational waves?
Gravitational waves have two unique and important characteristics. First, there is no requirement for any form of matter to exist close enough for the gravitational waves to be created by an uncharged black hole binary system which would not release any electromagnetic radiation. Second, these waves can go through any obstructing matter without getting scattered significantly. On the other hand, light rays from faraway stars could be obstructed by interstellar dust. In the case of gravitational waves, they will go through these entities, essentially unconstrained. These features enable gravitational waves to bear information about celestial phenomena that are never detected by astronomers.
11) Why are gravitational waves not easily detectable?
Gravitational waves are not easily detectable. When they enter the Earth, they have a very small amplitude with strain around 10−21, which means that a super sensitive detector is required, and that other noise sources can dilute the signal. Gravitational waves are typically expected to possess frequencies ranging 10−16 Hz < f < 104 Hz.
12) What is meant by primordial gravitational waves?
Primordial gravitational waves are a form of gravitational waves detected in the cosmic microwave background (CMB). They were allegedly observed by the BICEP2 system, a declaration made on 17th March 2014. However, it was withdrawn on 30th January 2015 (the signal can be fully attributed to random dust in the Milky Way).
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Practice Questions
1) What is meant by gravity?
2) What is the difference between the concept of gravity in Newtonian mechanics and the General Theory of Relativity?
3) What is gravitational lensing?
4) What is meant by spacetime curvature?
5) What is the relationship between mass and gravitational waves?
6) What is a black hole?
7) What is meant by acceleration due to gravity?
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