Question

1. choose the best answer.

why do astronomers measure distances in light - years?
○ because of the great distances in outer space, other measures are hard to understand.
○ this measure is used in honor of isaac newton and his experiments with optics.
○ use of the metric system requires a physical measuring device such as a meterstick.
○ visible light is the only form of energy capable of travelling between stars.

Explanation:

To determine why astronomers measure distances in light - years, we analyze each option:

• Option 1: Outer space has extremely large distances. Using common units like kilometers would result in extremely large numbers that are difficult to comprehend. Light - years provide a more manageable way to express these vast distances. This makes sense as a reason.
• Option 2: The light - year is not related to Newton's optics experiments. So this option is incorrect.
• Option 3: Measuring interstellar distances with a meter - stick (a metric system tool) is impossible due to the scale of space. So this option is wrong.
• Option 4: There are other forms of energy (like radio waves) that can travel between stars, and light - year is a distance unit, not related to the "only form of energy" idea. So this option is incorrect.

Answer:

A. Because of the great distances in outer space, other measures are hard to understand.