Sound Waves Need Medium To Travel | Space Has No Medium through Which Sound Can Travel
Sound travels in the form of waves. These waves need a medium like solid, liquid or air to reach from one place to another place. Also air is needed to reach from the outside of the ear to the inner ear. Sound needed any one of the medium to travel from one place to another. Even though the sounds of radio waves and small waves reach us but without the converters, that change those sounds to normal sounds human beings cannot hear the sound.
If we go far away from the earth to space, there is only vacuum. Even though there are stars, planets distance between these and the human being will be some crore miles. If a person talks from a distance of few meters, there will be no physical medium that carries the sound to the ears. So no sound can be heard. Astronauts who go to space carry some special tools, when they go to outside from the space ship. Without those tools they cannot talk to each other.