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The SI unit used for measuring vast astronomical distances, defined as the distance light travels in one year, is ______________.
Parsec
Light-year
Astronomical Unit
Angstrom
Light-year
A light-year is a unit of astronomical distance defined as the total distance that light travels in a vacuum over the duration of one Julian year. It is used to measure distances to stars and other objects outside our solar system because these distances are too vast to be conveniently expressed in kilometers or miles.
A light-year is a unit of astronomical distance defined as the total distance that light travels in a vacuum over the duration of one Julian year. It is used to measure distances to stars and other objects outside our solar system because these distances are too vast to be conveniently expressed in kilometers or miles.
Think of it like measuring the size of a giant building using the number of steps a person can take in a day; since space is incredibly vast, we use the 'step' of light moving for a whole year as our yardstick.
d=c├Чt тАФ where d is distance, c is the speed of light, and t is time (one year)
1┬аlyтЙИ9.46├Ч1015┬аm тАФ the standard conversion value in meters
The principle is based on the constant speed of light in a vacuum, denoted by c, and the duration of a calendar year. By multiplying the speed of light (cтЙИ2.9979├Ч108┬аm/s) by the number of seconds in a Julian year (365.25├Ч24├Ч3600┬аs), we derive the distance defined as one light-year.
Light-year is a unit of distance, not time.
The speed of light in a vacuum is approximately 300,000┬аkm/s.
One parsec is approximately 3.26 light-years, making it a larger unit than a light-year.
An Astronomical Unit (AU) is the average distance from the Earth to the Sun.
Provides a manageable scale for interstellar distances.
Physically intuitive as it relates to the observable nature of light.
Not practical for small distances within a planetary system.
Calculation requires knowledge of the exact length of a year and the constant speed of light.
Measuring the distance to nearby stars like Proxima Centauri.
Describing the scale of galaxies and the observable universe.
| Feature | Parsec | Light-year |
|---|---|---|
Distance Unit | Parsec (3.26┬аly) | Light-year (9.46├Ч1012┬аkm) |
1 Light-year тЙИ9.46├Ч1015┬аmeters.
Option A (Parsec) is the largest unit of distance used in astronomy.
Option C (Astronomical Unit) is used primarily for distances within the Solar System (~1.5├Ч108┬аkm).
Option D (Angstrom) is an extremely small unit used for measuring wavelengths of light (1┬аA╦Ъ=10тИТ10┬аm).
B is correct тАФ The light-year is the distance light travels in one year, measuring approximately 9.46├Ч1015 meters.
Always check the units: Parsec is the largest, followed by Light-year, then Astronomical Unit; remember 'AU' for solar system and 'ly' or 'pc' for interstellar space.