Why does increasing temperature increases vibration of molecules in conductors so it decreases it’s conductivity while in semi-conductors it increases it’s conductivity and no vibrations occurs in the molecules! ?

What happens to light waves from a star as the star moves away from earth?

Samir watches a 100-minute movie on his spaceship. maria's spaceshipe flies in the same direction as samir's spaceship but she observes his move to last 125 minutes and his spaceship to be 40 m long. how long does samir observe his own spaceship to be? according to an observer on earth, planet x is stationary. maria and samir depart earth on their spaceships at the same time, each flying at 0.5c. maria flies toward planet x and samir flies in the opposite direction. according to maria, her voyage to planet x takes 9 years. how many years does marias voyage take according to samir?

Sound is a disturbance that travels through a medium as a