Question

Tarun got to know from his elder brother that sun is the nearest star and is approximately $150$ million kilometers away from the earth. He wanted to know which is the next nearest star and what is its distance from the earth. His tutor told him that the nearest star is proxima centauri and is at a distance of $4.3$ light years from the earth. Tarun does not know what a light year is. Can you tell him?

Answer 1

Explanation

A light year is a unit of measuring distance. It is used to measure distance of other celestial bodies from earth.

1. A light year is the distance a beam of light travel in single earth year.
2. In $1$ second light travel $3\times {10}^{8}m$
3. In $1$ minutes or $60$second light travel$3\times {10}^8\times 60m$
4. In $1$hour or $60$ minutes light travel $3\times {10}^8\times 60\times 60=3\times {10}^8\times 3600m$
5. In $1$ day or $24$ minutes light travel $3\times {10}^8\times 3600\times 24=3\times {10}^8\times 86400m$
6. In $1$ day or $24$ minutes light travel $3\times {10}^8\times 3600\times 24=3\times {10}^8\times 86400m$
7. In $1$ year or $365$ days light travel $3\times {10}^8\times 86400\times 365=3\times {10}^8\times 31536000=94608000\times {10}^8=9.46\times {10}^{15}m$
8. That is $1$ light year is equal to $9.46\times {10}^{15}m$ distance
9. So $4.3$ light year is equal to $4.678\times {10}^{16}m$
10. $1000m=1km$,therefore $4.678\times {10}^{16}m=$ $4.678\times {10}^{13}km$.