Question

State whether true or false, and correct the statement if false:

The distance of the planets and stars from earth is measured in light years.

• A. True
• B. False

Answer 1

The correct option is A True

Explanation

1. The distance of the planets and stars from Earth is measured in light-years.
2. The term light-year is often used in astrophysics to measure the distance between two astronomical objects.
3. Stars or galaxies are very far away from the earth & giving their distances in the kilometers unit becomes very inconvenient.
4. For example, 1 light year in meters can be calculated as
5. We know light travel at a speed of $3\times {10}^{8}m/s$.
6. Therefore in $1$minute or $60$second light travel $3\times {10}^8\times 60m$.
7. In $1$hour or $60$ minutes light travel $3\times {10}^8\times 60\times 60=3\times {10}^8\times 3600m$.
8. In $1$ day or $24$ hours light travel $3\times {10}^8\times 3600\times 24=3\times {10}^8\times 86400m$.
9. In $1$ year or $365$ days light travel $3\times {10}^8\times 86400\times 365=3\times {10}^8\times 31536000=94608000\times {10}^8=9.46\times {10}^{15}m$.

Hence the given statement is true.