100 Greatest Discoveries Notes

The Planets Move
• Mesopotamians – did lots of astronomy
o Recorded on clay tablets
o First records
o Earliest record of astronomy, Venus
o First record of planet moving
• Greeks – went to Mesopotamians
o Developed vision of solar system
o Planets move around earth
• Nicholas Copernicus – challenged Greek’s Idea
o Fixes sun in center
o Earth moves
o Published book on day of death
• Johannes Kepler – planets didn’t orbit in circles
o Ellipse
o Calculated accurate orbits
• Galileo Galilai
o Telescope
o Mountains on moon
o 4 stars around Jupiter
o Clusters of stars
o Theory supported by facts

Halley’s Comet
• Comets = fear and terror
• Halley found 3 comets following same path every 76 years
• Predicted the comet would come back in 76 years
o Came back, but Halley died

Milky Way Cluster of Stars
• Hershall from musician to telescope builder
• Found Uranus
• Divided sky in sections
• Counted stars
• Milky Way too large to count

General Relativity
Einstein – orbit of Mercury
• Mercury’s change in orbit every century
• Refined Newton’s laws of gravity
• Gravity takes time to travel
• Curved space
• Theory of General Relativity
• Eclipse tested Einstein’s Theory
• He was Right

The Universe is Expanding
• White nebulae
• 1924 Edwin Hubble study white nebulae
• Now called white nebulae galaxy
• Colour changes as galaxy moves
• Finds lots of colours
• Big Bang

Milky Way Emits Radio Waves
• 1930 Carl Jinsky
• 3 forms of radio waves – thunderstorms, earth, 3rd-mysterious?
o Looked like was from sun
o Actually found black hole
Cosmic Radio Waves Background…something
• Arnold Penseus, Robert Wilson
• Measure radiation from milky way
o Two theories at the time
 Big Bang
 Stationary Theory
o Big Bang would leave extra temperature
• They found extra temp.

Gamma Ray Bursts
• 1960’s – made Gamma Ray detectors
• Supernovae produces gamma ray bursts?
• Made new telescope
• Discovered gamma ray bursts a few trillion light years away
• Gamma ray bursts = past animal extinctions?

Planets Orbiting other Planets
• Looks at waves wobbling as it orbits around
• Universe is expanding
• Explosion of Type 1A supernova