Light year is a unit of

Options

A. Time
B. Mass
C. Distance
D. Energy

Answer

To determine what a light year is a unit of, we can break down the problem step by step.

### Step-by-Step Solution:

1. **Understanding the term "light year":**
- A light year is defined as the distance that light travels in one year.

2. **Speed of light:**
- The speed of light in a vacuum is approximately \(3 \times 10^8\) meters per second.

3. **Calculating the total time in seconds for one year:**
- First, we need to calculate how many seconds are in one year.
- There are 365 days in a year.
- Each day has 24 hours.
- Each hour has 60 minutes.
- Each minute has 60 seconds.
- Therefore, the total number of seconds in a year can be calculated as:
\[ \text{Total seconds in a year} = 365 \, \text{days} \times 24 \, \text{hours/day} \times 60 \, \text{minutes/hour} \times 60 \, \text{seconds/minute} \]

4. **Calculating the total distance light travels in one year:**
- Now that we have the total number of seconds in a year, we can find the distance light travels in that time.
- The distance traveled by light in one year is:
\[ \text{Distance} = \text{Speed of light} \times \text{Total seconds in a year} \]
- Substituting the values:
\[ \text{Distance} = (3 \times 10^8 \, \text{m/s}) \times (365 \times 24 \times 60 \times 60 \, \text{s}) \]

5. **Conclusion:**
- Since a light year measures the distance light travels in one year, we can conclude that a light year is a unit of distance.

### Final Answer:
- A light year is a unit of **distance**.

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