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Lecture

establsihing our palce in the universe


Department
Astronomy & Astrophysics
Course Code
AST101H1
Professor
Michael Reid

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September 13, 2011
Introduction: establishing our place in the universe
Earth
4.6 billion years ago, our universe was made of gas and dust. Shortly after,
earth began to progressively form over time but it was not formed to the way
it is today until 3 billion years ago.
70 million years ago, Earth became a vibrant living place until 5 million years
later a rock smashed into Earth making the planet non-living
Extinction has not stopped
Different perspective: earth is small compare to the other planets as seen in
pictures taken from further distances
Threats to Earth from Earth: climate crisis
Space
Space is huge
Galaxy: several hundred billion or even trillion star collection
The light year
Distance light travels in 1 year
Speed of light: 300,000 km/s
1 light year is about 10(13) km (=10 trillion=10,000,000,000,000)
Similarly for a light second, light hour…)
Scale of the Universe
Earth: -o.o4 lt-s
Solar System: -1 lt-hr
Sun -4 lt-s
Nearby starts -10 lt-ye
Milky way -3x10(4) lt-yr
Local gropu -3x106 lt-yr
Universe 1.37x10(-10) lt-yr
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