The history of Astronomy!

We expand our knowledge by adding to what people before us discovered.

In science, we do not study Astrology. Astrology is the belief that the location of the stars and planets on the day you were born determines your personality and your life. Not based on any scientific evidence!

The ancient Greeks were some of the first people to try to explain why natural events occurred without reference to supernatural causes. http://www.thalamus-books.com/books_hunt_living_in_ancient_greece.html

Aristotle Observed a shift in stars’ position when viewed from different locations. This is called parallax. It works best for stars that are closer.

Ptolemy Thought Earth was the center of the universe. This is called the geocentric view. People believed him for 1500 years. His observations: The moon and sun appeared to circle the Earth He concluded that the stars must do the same

Ptolemy’s model Notice where the sun is! http://www.shef.ac.uk/physics/people/vdhillon/teaching/phy105/phy105_ptolemy.html Ptolemy’s model Notice where the sun is!

Nicholas Copernicus In the early 1500s, he was a Polish mathematician and astronomer who collected data about the universe with his eyes. Said the moon revolves around Earth and Earth revolves around the Sun! This is the heliocentric view.

Copernicus’ Sun-centered Universe Heliocentric view-the sun is at the center of the universe, and all of the planets, including the Earth, orbit the sun. Correctly explained the movement of the planets around the sun. Better than geocentric view, but still not the best. Copernicus waited to share is heliocentric view until just before he died! Why do you think he would do this?

Tycho Brahe Collected quantitative data about planetary motion for many years. Predicted orbits were not circular. Measured length of a day accurately. His data was used to prove planets orbit the sun!

Johannes Kepler Was the assistant to Tycho Brahe in the late 1500s. Took Tycho’s observation data and used math to explain laws of planetary motion. Distance from sun is related to period of revolution. Proved elliptical orbits.

Kepler’s Heliocentic View

Galileo Galilei Did not invent the telescope, but he improved it and turned it toward the sky. Saw landforms on the moon. Discovered 4 moons of Jupiter. Saw Venus go through phases just like our moon! Helped prove Earth revolves around the sun.

Photo of Venus going through phases like the moon.

Sir Isaac Newton He thought the universe was not changing. Described a relationship between gravity and inertia that keeps the planets in orbit around the sun. Invented a better telescope using mirrors

Albert Einstein Albert Einstein thought the universe was expanding, but he could not get Newton’s math to work with his observations.​ Big ideas: The laws of physics are the same everywhere in the universe. The speed of light is always the same. An objects energy is related to its mass.

Georges Lemaitre Used Einstein’s math to show that the universe is expanding ​ He thought that if the universe was expanding, all matter had to be packed into a small space in the past.

Edwin Hubble: Beyond the Edge of the Milky Way In 1924, Edwin Hubble proved that other galaxies existed beyond the edge of the Milky Way. He observed a redshift! His observations explained that the universe is expanding!

George Gamow Explained that all the elements that make up everything came from exploding stars.

Stephen Hawking He developed theories about how the world began and furthered our understanding of black holes, stars and the universe. He wrote books that explained his theories in simple terms for everyone to understand, including a children’s book. His most famous book, A Brief History of Time, sold more than 10 million copies!