WHEN YOU WISH UPON A STAR

Spectral lines of elements are unique to each element No other element has these exact spectral lines.

Doppler Effect is a phenomenon which is created as the source of sound moves relative to the observer. In the case of sound, as the police car approaches, you hear a higher frequency.

The same holds true for spectral lines. Similar to the sound changing frequency, the spectral lines shift toward the red or blue. red shift = away blue shift = toward

When the spectral lines shift their spacing remains constant. The faster the star is moving the greater the shift.

Edwin Hubble observed galaxies red shifting, leading him the theorize that the universe was expanding. He determined the rate of expansion was related to its distance.

Are galaxies expanding from each other ? (16 minutes) dark matter and energy Ted Talks We now know that the expansion rate of the univserse increases with distance. 1:38 dark energy We now know that the expansion rate of the univserse increases with distance. This will give you some sense of the size of the universe. This will give you some sense of the size of the universe.

Going back in time, you would reverse the expansion of the universe. At some point the entire universe would be together as one. Simply put, all this stuff would get very hot and explode- BIG BANG.