51.3 Why must we study physics 2. The relationships among the physics and other disciplines Ophysics and astronomy astronomical observation physics s1.3 Why must we study physics THE UNIVERSE HE UNIVERSE contains everything that exists-not only the Earth and everything on it, but also all the planets, stars, at them, The sun. at the center of th solar system, is just one of about Galaxies Way, Astronomers have estimate hat there are about 100 billion scientists think that the universe formed about 15 billion years THe Earth and the sola enormous explosion called also think that the universe galaxies in the universe7 §1.3 Why must we study physics 2. The relationships among the physics and other disciplines 1physics and astronomy astronomical observation physics §1.3 Why must we study physics