What evidence is there that the Universe is expanding?
The Doppler effect, which changes the spectra of of stars and galaxies toward the red or longer wave lengths, tells scientists that the universe is expanding at an ever increasing rate.
The red shift first observed by Edwin Hubble changed the way scientists viewed the universe. The red shift is part of the Doppler affect waves coming toward the observer move toward the blue side of the spectrum as the waves get closer together, and waves move toward the red side of the spectrum as the waves get further apart. Before Hubble's observations of the change in the spectra of stars scientists believed that the universe was static. The belief was that the universe had always existed in its "present" observational state. This view was consistent with the philosophy of material realism that matter and energy are all that has ever existed or ever will exist.
After the observations of the red shift doppler effect were widely accepted the static steady state view of the universe was abandoned. The Big Bang theory began to be developed in response to the empirical evidence of an expanding universe.
Recently ( in 1998) observations of the rate of expansion of the universe is increasing. The observations were based on the spectra of super novas, made by the Lawrence Berkley National Laboratory.
The hypothesis was that the rate of the expansion should be slowing down.
The hypothesis was based on the theory that the universe was eternal and would recycle alternating between Big Bangs and Big Crushes. The Hypothesis was proven wrong by the observations of the supernovas that the rate of universe was increasing.
The changes of the spectra of the galaxies tell scientists that our present universe had a beginning, will have an ending and that matter and energy are not eternal or self existent.