1. Detection of microwaves in space.
2. Observation of redshift phenomenon in space.
3. Movement of asteroids in space.
4. Occurrence of supernova explosion in space.
Select the correct answer using the codes given below:
Explanation
The Big Bang theory states that at some point of time the entire space was contained in a single point of very high density and temperature, from where the Universe has been witnessing expansion in all directions ever since. According to Hubble’s law, the expansion of the universe is such that the velocity at which the galaxy is moving away from the observer is increasing with time.
Statement 1 is correct: Cosmic Microwave Background (CMB) is thought to be leftover radiation from the Big Bang, i.e., the time when the universe began. According to the theory, when the universe was born it underwent rapid inflation and expansion. (The universe is still expanding today, and the expansion rate appears different depending on observation). The CMB represents the heat left over from the Big Bang.
Statement 2 is correct: 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). Redshift and Blueshift describe how light changes with movement of objects in space closer or farther from us. While moving away, the light is shifted to the red end of the spectrum, as its wavelength gets longer. While moving closer, the light moves to the blue end of the spectrum, as its wavelength gets shorter. Galactic Redshift is related to the expanding Universe concept.
Statement 3 is incorrect: Movement of asteroids in space is due to gravity and it is not linked with the concept of expansion of the universe.
Statement 4 is incorrect: The occurrence of supernova explosions (powerful stellar explosions in which a single star becomes as bright as 109 stars like the sun) helps in studying the distribution of elements throughout the universe. These elements travel on to form new stars, planets and everything else in the universe. But this is not considered as evidence for the continued expansion of the universe.