NATS 1760 Lecture Notes - Lecture 5: Cosmic Calendar, Big Bang, Gravitational Energy
5 Dec 2018
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*light year is not a unit of time, distance light can travel in one year, and that is equivalent to trillion km. Most of our stars are made of hydrogen and helium. Gravitational energy of starts keeps that reactant together. The matter in our bodies came from the big bang which produced hydrogen and helium. All other elements were constructed from h and he in stars (as novae & supernova) and then recycled into new star system, including our solar system. On a cosmic calendar that compresses the history of the universe into 1 year, human civilization is just a few seconds old. Earth is essentially a spaceship earth is moving in many diff ways, the full year for earth to move around the sun. Earth is revolving around the sun at 30km/s. As seen from above earth rotates on its axis in a counter clockwise direction at an avg speed of.
