Which of the following best describes the difference between two different units of distance in space?
1.An AU is useful for measuring objects fewer than 300 light-years
from Earth; a parsec is useful for measuring objects more than 300
light-years from Earth.
2.An AU is calculated by dividing kilometers by 150 million; a light-year
is calculated by determining how long it takes and object to travel
150 million AUs.
An AU is useful for measuring distances within the solar system; a
light-year is useful for measuring distances beyond the solar system.
An AU equals the distance between Earth and the Sun; a parsec
equals the angle between an object's apparent positions when viewed
from two different locations.