The primary responsibilities of human resources are: 1  C - Compensation. 2  H - Human resource development. 3  E - Employee and labor relations. 4  S - Safety and health. 5  S - Staff.
A new technique uses sound waves to levitate objects and move them in mid-air. Credit: Dimos Poulikakos View full size image. View full size image. Hold on to your wand, Harry Potter: Science has outdone even your best Leviosa! levitation spell.
Sound can travel through anything made of molecules-even water! There is no sound in space because there are no molecules there to transmit the sound waves. Electromagnetic waves are different from sound waves because they do not need molecules to travel. This means that electromagnetic waves can travel through air and solid materials-but they can also travel through empty space. This is why astronauts on spacewalks use radios to communicate.