Many cosmologists now think that the age of the universe is likely to be between 12 and 14 billion years. Lower expansion rates have been suggested by other recent studies as well. This seems to mean that the age of the universe is most likely 15-20 billion years. Red shift . Explain by the Doppler Effect .
Same thing works with light as sound.
Both travel in waves. Light reaching us from distant receding galaxies has shifted toward the red end of the spectrum. B. Formation of stars, galaxies, solar systems, planets, etc. Material begins to clump together as it moves away from the center of the Big Bang. Nebular means cloud.