Gravitational Waves, Doppler-Shift, Cosmic Microwave Background
Refer to the latest edition of Physical Geography Hardcopy/PDF and Current Affairs for the most updated information on this topic.
Evidence for Big Bang Theory: Physical phenomena such as cosmological redshift, and the discovery of cosmic microwave background radiation and gravitational waves, have added weight to the Big Bang Theory.
Doppler-Shift or Redshift and Blueshift
- Redshift and Blueshift describe how light changes as objects in space (such as stars or galaxies) move closer or farther away from us. American astronomer Edwin Hubble was the first to describe the redshift phenomenon (galactic redshift) and tie it to an expanding universe (galaxies are drifting apart).
- Hubble’s law: the farther away galaxies are, the faster they are moving away from Earth ― also known as accelerating the expansion of the universe.
Cosmic Microwave Background (CMD)
- With a traditional optical telescope, the space between stars and galaxies is completely dark. However, a sensitive radio telescope shows a faint background glow. This glow is strongest in the microwave region of the radio spectrum, and hence it is called a Cosmic Microwave Background (CMB).
- CMD, also known as relic radiation (thermal radiation left over from the “Big Bang”), is fundamental to observational cosmology because it is the oldest light in the Universe and can be found in all directions. Its discovery is considered a landmark proof for the concept of “accelerating expansion of the universe” and the Big Bang Theory.
- Albert Einstein predicted the existence of gravitational waves in 1916 in his general theory of relativity. Gravitational waves are ‘ripples’ in the fabric of spacetime caused by some of the most violent and energetic processes in the Universe. (Spacetime: https://www.youtube.com/watch?v=sryrZwYguRQ)
- Massive accelerating objects (such as neutron stars or black holes orbiting each other) would disrupt spacetime in such a way that ‘waves’ of distorted space would radiate from the source (like the movement of waves away from a stone thrown into a pond). These ripples travel at the speed of light through the Universe, carrying with them information about their origins.
Spacetime (NASA) & Gravitational Waves (NASA)
- While the processes that generate gravitational waves can be extremely violent and destructive, by the time the waves reach Earth, they are billions of times smaller. In 2015, The Laser Interferometer Gravitational-Wave Observatory (LIGO), USA, physically sensed the distortions in spacetime caused by passing gravitational waves generated by two colliding black holes nearly 1.3 billion light-years away!
Einstein’s Theory of General Relativity
Importance of Gravitational Waves
- The gravitational waves can work as sirens to measure the expansion rate of the universe and to understand the origin and the future of the universe.
[UPSC Prelims 2012] Which of the following is/are cited by the scientists as evidence(s) for the continued expansion of the universe?
Select the correct answer using the codes:
[UPSC Prelims 2019] Recently, scientists observed the merger of giant ‘blackholes’ billions of light-years away from the earth. What is the significance of this observation?
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