Context:
Scientists from ICTS Bangalore have proposed a new way to measure the Hubble constant
About Big Bang:
- The Big Bang Theory is the leading explanation for how the universe began.
- It says the universe as we know it started with an infinitely hot and dense single point that inflated and stretched
- The universe expanded over the next 13.7 billion years to the still-expanding cosmos that we know today.
About Hubble’s Law:
- In 1929, Edwin Hubble announced that almost all galaxies appeared to be moving away from us. In fact, he found that the universe was expanding – with all of the galaxies moving away from each other.
- This phenomenon was observed as a redshift of a galaxy’s spectrum.
‘Red shift‘ is a key concept in astronomy. The term can be understood literally – the wavelength of the light is stretched, so the light is seen as ‘shifted’ towards the red part of the spectrum.
Something similar happens to sound waves when a source of sound moves relative to an observer. This effect is called the ‘Doppler effect‘ after Christian Andreas Doppler, who discovered that the frequency of sound waves changes if the source of sound and the observer are moving relative to each other.
- This redshift appeared to be larger for faint, presumably further, galaxies. Hence, the farther a galaxy, the faster it is receding from Earth.
- Hubble’s law is considered the first observational basis for the expansion of the universe.
- It serves as one of the pieces of evidence most often cited in support of the Big Bang model.
About Gravitational Waves:
- Gravitational waves are ‘ripples’ in space-time caused by some of the most violent and energetic processes in the Universe.
- Albert Einstein predicted the existence of gravitational waves in 1916 in his general theory of relativity.
- Einstein’s mathematics showed that massive accelerating objects (things like neutron stars or black holes orbiting each other) would disrupt space-time in such a way that ‘waves’ of undulating space-time would propagate in all directions away from the source.
- These cosmic ripples would travel at the speed of light, carrying with them information about their origins, as well as clues to the nature of gravity itself.
- The strongest gravitational waves are produced by cataclysmic events such as colliding black holes, supernovae (massive stars exploding at the end of their lifetimes), and colliding neutron stars.
About Laser Interferometer Gravitational-wave Observatory (LIGO):
- It is the world’s largest gravitational wave observatory
- Comprising two enormous laser interferometers
- It consists of two widely separated installations within the United States, operated in unison as a single observatory.
- LIGO exploits the physical properties of light and of space itself to detect and understand the origins of gravitational waves (GW).
- Unlike optical or radio telescopes, LIGO does not see electromagnetic radiation. But it doesn’t have to because gravitational waves are not part of the electromagnetic spectrum.
- LIGO detected gravitational waves for the first time in 2015
- LIGO – India
- a planned advanced gravitational-wave observatory to be located in India as part of the worldwide network
- concept proposal is now under active consideration in India and the USA
Source: The Hindu (Printed on 05/09/23 – digitally published in July)
Previous year question
Consider the following statements:
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?
[UPSC Civil Services Exam – 2018 Prelims]
(a) 1 and 2 only
(b) 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer: (d)
