Explanation:

Sound Propagation:
Sound is a form of energy that travels in waves through mediums such as air, water, and solids. When an object vibrates, it creates sound waves that travel through the medium by causing particles to vibrate and transmit the sound energy.

Sound Transmission:
- In air: Sound waves can travel through the air, which is why we are able to hear sounds around us.
- In water: Sound waves travel faster in water compared to air due to its higher density.
- In iron: Sound waves can also travel through solids like iron, but the speed of sound is much faster than in air or water due to the closer arrangement of particles.

Sound in Space:
- In space: Sound cannot travel through the vacuum of space because there are no particles to transmit the sound waves. Sound waves require a medium to travel through, and since space is a near-perfect vacuum, there are no particles for the sound waves to propagate.

Therefore, sound cannot travel through space due to the absence of a medium for the sound waves to travel through. This is why astronauts in space cannot hear each other or any other sounds.