1. Christian Doppler By Veronica Spaeth
Christian Doppler was born on November 29, 1803 in Salzburg Austria, and died on March 17, He attended secondary school in Linz and because he was not suited to take over the family business, his parents sent him to the University of Vienna where he would study mathematics further.

2. In 1842, Doppler proposed his theory, On the Coloured Light of the Double Stars and Certain other Stars of the Heavens. He was incorrect on many of the points he tried to make, but one point was extremely important:
The Doppler Effect

3. The Doppler Effect explains that waves (whether sound, light, or even those made in water) have a higher frequency, and are smaller, as they approach an object, and they have a lower frequency and are larger as they move away from it.
For example, the siren of a police car sounds higher as it approaches and lower as it leaves an object.

4. Some images of the Doppler Effect

5. How did he do it?
Doppler’s theory was proven in a many different ways. One of the most interesting involved musicians and a moving train.
One way had two people holding the same note, one standing at a set location, and one standing on a train. While both holding the note, the one on the moving train definitely did not match the standing note the entire time.
The other was very similar, but instead of another player holding the same note, a person with perfect pitch recorded the note being played as the train approached, passed right by, and moved away.

6. This is useful in Astronomy because it explains the red and blue shifts that are used to support the Big Bang Theory.
The Red Shift is the increased “electromagnetic” wave frequency, so the Red shift is moving towards Earth.
The Blue Shift is the decreased “electromagnetic” wave frequency, so a Blue shift is moving away from Earth.
Doppler’s theory has done a lot to help expand our knowledge of astronomy.

7. Eratosthenes
Greek poet, athlete, geographer, mathematician, and astronomer.

8. Eratosthenes of Cyrene lived between 276 BC and 194 BC
Eratosthenes of Cyrene lived between 276 BC and 194 BC. During this time he accomplished many amazing things:
He measured the circumference of the Earth, and was extremely close to the actual measurement
He measured the distance to the sun:
804,000,000 stadia.
He measured the distance to the moon: 780,000 stadia.
He figured out these distances during lunar eclipses.

9. The Earth’s tilt
Eratosthenes also figured out that the Earth was tilted on its axis.
Although there is some argument that Ptolemy was the one to come up with the actual value, Eratosthenes came up with an angle of 11/83 of 180 degrees.
This discovery that the Earth is tilted, helps to explain the changing seasons in certain area’s of the world, it is also why some parts of the world are covered in darkness while others are not.