GRAVITATIONAL WAVES
1. Context
Astronomers have made a discovery that confirms the existence of gravitational waves, which sound like the hum at a large gathering. These ripples in space-time were proposed by Albert Einstein over a century go.
2. Gravitational Waves
- Gravitational waves are ripples in the fabric of spacetime. They are disturbances or waves that propagate through space, similar to waves on the surface of a pond.
- Gravitational waves are generated by the acceleration or motion of massive objects, such as colliding black holes, merging neutron stars, or the early moments of the universe's formation.
- According to Eienstein's theory of general relativity, gravity is not simply a force but the curvature of space-time caused by the presence of mass and energy.
- When massive objects accelerate or undergo changes in motion, they create disturbances in spacetime, which propagate outward as gravitational waves.
- Gravitational waves carry energy and momentum and can travel through the universe at the speed of light. They stretch and compress spacetime as they pass through, causing the distances between objects to alternatively increase and decrease.
- However, these changes in spacetime are incredibly small and require highly sensitive instruments to detect them.
- Direct detection of gravitational waves provides a new way to study of the universe.
- By observing and analyzing gravitational wave signals, scientists can gain insights into the nature of massive objects, and the dynamics of cosmic events, and test the predictions of general relativity in extreme conditions.
- Gravitational wave astronomy opens up a new window to explore the cosmos and deepen our understanding of the universe.
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Image Source: DW
3. Gravitational Waves: From Einstein to Recent Detection
Einstein's Proposal (1916):
- Einstein proposed gravitational waves as ripples in spacetime.
- Described gravity as the distortion caused by matter in space and time.
Direct Detection Achieved (2016):
- Scientists successfully detected gravitational waves directly.
- Indirect evidence had been relied upon since the 1970s.
Role of Pulsars in Recent Research:
- Recent research heavily relied on pulsars, dense remnants of exploded stars.
- Pulsars spin at extraordinary speeds and provided crucial data.
Generation and Effects of Gravitational Waves:
- Gravitational waves generated by dense objects in orbital motion.
- Waves physically stretch and compress space-time as they travel.
Data Collection by NANOGrav Collaboration:
- Latest report's data collected by NANOGrav Physics Frontiers Center.
- Comprises over 190 scientists from the United States and Canada.
- Data collected over a 15-year period.
4. Gravitational Wave Background and Black Hole Discoveries
- Universe's gravitational wave background is compared to the hum of a large gathering. Individual voices (waves) cannot be distinguished.
- Gravitational waves generated by distant black holes were initially detected seven years ago.
- Black holes are incredibly dense objects with intense gravity that traps even light.
- Gravitational waves can be produced by the motion of black holes and other massive objects.
- Previous research utilized the Laser Interferometer Gravitational-Wave Observatory (LIGO).
- Recent discovery provides evidence of gravitational wave hum in a smaller frequency range.
- Frequencies are significantly smaller (around 10-12 orders of magnitude) than those detected by LIGO. The wavelengths of these waves span light years.
- The most straightforward explanation involves pairs of supermassive black holes orbiting each other in our cosmic neighborhood.
- Alternative explanations could involve new physics related to the early stages of the universe near the Big Bang (approximately 13.8 billion years ago).
5. About LIGO
- LIGO stands for the Laser Interferometer Gravitational-Wave Observatory. It is a large-scale scientific experiment and observatory dedicated to the detection of gravitational waves.
- LIGO consists of two identical interferometers located in different parts of the United States, one in Livingston, Louisiana, and the other in Hanford, Washington.
- Each LIGO interferometer consists of two perpendicular arms, each measuring 4 kilometers (2.5 miles) in length.
- The interferometers use laser beams split into two and then recombined to create an interference pattern.
- The interference pattern is extremely sensitive to changes in the length of the arms caused by passing gravitational waves.
- When a gravitational wave passes through the observatory, it causes minuscule stretching and squeezing of space, which is detected as changes in the interference pattern of the laser beams.
- LIGO's precise instruments are designed to detect these incredibly tiny changes, allowing scientists to directly observe and study gravitational waves.
- LIGO's groundbreaking detection of gravitational waves in 2015 confirmed Einstein's predictions and opened up a new era of gravitational wave astronomy.
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For Prelims: Gravitational waves, NANOGrav Physics Frontiers Center, Einstein's theory, Black holes, Laser Interferometer Gravitational-Wave Observatory (LIGO).
For Mains: 1. Explain the concept of gravitational waves and their significance in our understanding of the universe. How do they differ from other forms of waves? (250 Words)
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Previous year questions1. Consider the following phenomena: (UPSC 2018)
1. Light is affected by gravity.
2. The Universe is constantly expanding.
3. Matter warps its surrounding space-time.
Which of the above is/are the prediction/predictions of Albert Einstein's General Theory of Relativity, often discussed in media?
A. 1 and 2 only
B. 3 only
C. 1 and 3 only
D. 1, 2 and 3
Answer: D
2. Recently scientists observed the merger of giant 'black holes' billions of light years away from the Earth. What is the significance of this observation? (UPSC 2019)
A. 'Higgs boson particles' were detected
B. 'Gravitational waves' were detected.
C. Possibility of inter-galactic space travel through a 'wormhole' was confirmed.
D. It enabled the scientists to understand 'singularity'.
Answer: B
3. Which of the following statements is/are correct? (UPSC CDS 2017)
1. In June 2016, the LIGO group of scientists announced the detection of a second set of gravitational waves.
2. Gravitational waves were generated due to the merger of two black holes at about 1.4 billion light-years distant.
3. Gravitational waves were inserted due to the collision of two white dwarf stars at about 14 billion light-years distant.
Select the correct answer using the code given below:
A. 1 only
B. 1 and 2 only
C. 2 and 3 only
D. 1, 2 and 3
Answer: B
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Source: The Indian Express
