What does an astronomer mean by "the universe"

In a classical model of the hydrogen atom, the electron moves around the proton in a circular orbit of radius 0.053 nm. what is the electron's orbital frequency? what is the effective current of the electron?

Question 1 of 10multiple choice: select the best answer and click "submit."what method of forecasting predicts the arrival time of a storm based on itscurrent speed and other starting variableso a. climatology methodo b. trends methodo c. analog methodod. persistence method

Awave is propagating from left to right in a medium. the particles in the medium are also vibrating from left to right. what kind of wave does this describe? a. longitudinal wave b. transverse wave c. mechanical wave d. electromagnetic wave