Question

Distance travelled by light in a vacuum in one tropical year

Answer 1

As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in vacuum in one Julian year (365.25 days).

Answer 2

The distance travelled by light in vacuum in one tropical year is 9.4 trillion km.

• The tropical year is the time between two successive occurrences of the vernal equinox (the moment when the Sun apparently crosses the celestial equator moving north).
• 1 tropical year =  365 days, 5 hours, 48 minutes and 46 seconds ≈ 365.24 days.
• Tropical year is also known as solar year or year of seasons.
• The distance travelled by light in vacuum is 1,079,252,849 km/hr.
• The number of hours in a tropical year is 8765.818 hr.
• The distance travelled by light in vacuum in one tropical year can be calculated by multiplying the distance travelled by light in vacuum per hour and the number of hours in a tropical year.

• Distance travelled by light in vacuum in a tropical year = 1,079,252,849 × 8765.818 = 9.4 trillion km.

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