A big explosion on the moon cannot be heard on the earth because

Options

A. the explosion produces high frequency sound waves which are inaudible.
B. sound waves require a material medium for propagation.
C. sound waves are absorbed in the atmosphere of moon.
D. sound waves are absorbed in the earth's atmosphere.

Answer

To solve the question "A big explosion on the moon cannot be heard on the earth because," we need to analyze the nature of sound and the conditions in space.

### Step-by-Step Solution:

1. **Understanding Sound Waves**: Sound is a mechanical wave that requires a medium (like air, water, or solids) to travel. It cannot propagate through a vacuum.

2. **Condition of Space**: The space between the Earth and the Moon is a vacuum. There is no air or any other medium present in space.

3. **Implication of a Vacuum**: Since there is no medium in space, sound waves produced by an explosion on the Moon cannot travel through the vacuum to reach the Earth.

4. **Conclusion**: Therefore, the reason a big explosion on the Moon cannot be heard on Earth is that sound waves require a material medium for propagation, and there is no such medium in the vacuum of space.

### Final Answer:
A big explosion on the moon cannot be heard on the earth because sound waves require a material medium for propagation, and there is no medium in space.