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.

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.

Explanation:

Light year is the distance light travels in one Earth year.  1 light year is equal to .

An astronomical unit  (AU) is the average distance between the earth and the sun.  An AU is approximately 150 million km.

A parsec is the distance at which one astronomical unit subtends an angle of one second of arc.  1 parsec is equal to 20600 AU.

the only real purpose of sputnik 1 was to beat the us into space. we were getting close to launching a useful satellite, explorer 1 - which launched on january 31, 1958. the ussr had to beat that, so they launched sputnik 1 on october 4, 19