Question

Cosmic or galactic year is?
A- Year in which a comet arrives
B- Period taken by earth to revolve around the sun
C- Year in which total solar eclipse occurs
d- Period of sun’s revolution around the galactic centre.

Answer 1

Hint: As the name suggests we are talking about a specific period of time. Time is one of the important parameters in physics and along with space it is taken as one of the dimensions. Cosmic means universe and all about the origin of life. Comet on the other hand refers to masses moving in space under the influence of gravitational forces.

Complete answer:
The first option is incorrect because there is no fixed time for a comet to come near any planet or another heavenly body. So, it is incorrect. The second option is a period taken by earth to revolve around the sun and that is called revolution of the earth. Thus, this option is also incorrect.
Cosmic year or the galactic year refers to the duration of time in space for which the solar system requires to orbit around the centre of our galaxy that is the milky way. The length of one orbit varies from 200-250 million terrestrial years. The solar system moves and the period of the sun’s revolution around the galactic centre

So, the correct answer is “Option D”.

Note:
The solar eclipse refers to the situation in which the moon comes in between the earth and the sun. It is a natural phenomenon and the opposite of it also occurs in the lunar eclipse. The Milky Way galaxy takes almost approximately 220 million to 230 million Earth years, that is, this is the period of the sun's revolution around the galactic centre.