Echo, a repeated sound. The term is usually used to refer to sound that is reflected from a surface and returned to its source after a noticeable delay. A person can typically hear his or her own echo where a hard surface, such as the side of cliff, reflects sound waves directly back to the person. The use of echoes to locate objects is called echolocation.
Meteors and meteorites have fascinated human beings for ages, but have you managed to turn your fascination into some hardcore knowledge? Wishing on a star isnâ€™t going to help you now.
While routinely scanning the stars, NASA scientists came across something they didn't expect to see: a vast area of space empty of stars, planets and matter.