PREVIOUSLY ASKED IN:
WBPSC Miscellaneous Preliminary 2023
Answer
Distance
Explanation
A Light Year is a unit of astronomical distance, not time. It is defined as the distance that light travels in a vacuum in one Julian year. Because the universe is incredibly vast, using kilometers or miles becomes impractical. One light-year is approximately equivalent to \( 9.46 \times 10^{12} \) kilometers.
Key Points
- > Despite the word 'year', it measures distance, not time.
- > 1 Light Year = \( 9.46 \times 10^{15} \) meters.
- > The Parsec is the largest unit of distance in astronomy.
- > 1 Parsec = 3.26 Light Years.
- > Sunlight takes about 8 minutes and 20 seconds to reach Earth.
- > The mean distance between the Earth and Sun is 1 Astronomical Unit (AU).
- > The SI unit for luminous intensity is the Candela (cd).
Additional Information
Astronomical Distance Units
| Unit | Main Use | Equivalent |
|---|---|---|
| Light Year (ly) | Distance between stars | \( 9.46 \times 10^{15} \) meters |
| Parsec (pc) | Intergalactic distances | 3.26 Light Years |
| Astronomical Unit(AU) | Distances within solar system | Earth-Sun average distance |
Memory Tips
- The 'Year' Trap: Don't let the word 'year' fool you. Just as a 'foot' measures distance and not body parts, a 'light-year' measures the distance light travels.