When light waves are emitted by a moving source scientists can measure: the Doppler effect. Scientists extrapolate backwards in time to derive cosmic microwave background radiation particle accelerators . Scientists smash together tiny bits of matter using :

what statement best describes the difference between the sympathetic and parasympathetic nervous systems?

the sympathetic nervous system prepares the body for intense physical activity and is often referred to as the fight-or-flight response. the parasympathetic nervous system has almost the exact opposite effect and relaxes the body and inhibits or slows many high energy functions.