Question

why can't we talk in space

Answer 1

space is a vacuum
sound wave being a mechanical wave needs a material medium for propagation
but u can use radio signals using radio converter in the space suit helmet or in the mmu (man manuovering unit) that's what astronaut do

Answer 2

Sound requires a medium to work... As sound is a compression wave if anything like water or air is compressed we can hear the wave generated by it..... As there is no medium in space it's just vacuum..... Sound cannot travel in vacuum ......