Add to table of Contents: Star Life diagramPg. 76 Life Cycle of a StarPg. 77 Spectral fingerprintPg. 78 Electromagnetic spectrumPg. 79 Big Bang LabPg. 80 Big Bang TheoryPg. 81

Big Bang Theory The universe was created 13.8 billion years ago from a cosmic explosion. The original matter was small and dense, but we don’t know what it was.

Big Bang, con’t It explains why distant galaxies are traveling away from us at great speeds=expanding. It also predicted the existence of cosmic background radiation-the glow left over from the explosion itself.(discovered in 1964)

Background radiation Polarized light Big Bang Gravity waves – ripples in space time

The Expanding Universe Breaking down the light from celestial objects into its colors has helped us understand the universe. A spectrum can tell astronomers what an object is made of, how hot it is, and its direction and speed. Spectroscopy has revealed the great abundance of hydrogen and helium in the universe.

Red-shifted Stars Spectroscopy revealed the expansion of the universe. When an object moves away from us, the lines in its spectrum get displaced toward longer wavelengths, with the amount of this so-called redshift proportional to the object’s velocity. Edwin Hubble first showed that the spectrum of almost every galaxy is shifted to the red, and that the farther away the galaxy, the greater the redshift. From these observations, cosmologists correctly deduced that the universe is expanding. What would show that galaxies are moving away from us?? How would it be possible to be staying the same distance away if the Big Bang Theory was true?

Edwin Hubble first showed that the spectrum of almost every galaxy is shifted to the red, and that the farther away the galaxy, the greater the redshift. Red-shift shows that the universe is expanding(objects moving away). What would show that galaxies are getting closer to us? Blue-shift would show objects moving toward us.