AST201H1 Lecture 1: AST201 Week 1

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25 Aug 2016
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AST201 Week 1
Introduction
- We live in the Milky Way galaxy but it is not the universe because the universe contains
trillions of other galaxies
- Everything in the universe is grouped together by a universal force of gravity
- Local super clusters can contains thousands of smaller galaxies
- Light takes 8 minutes to come from the sun to the earth – unit of light years
- The further away the object is, the more we see it further back in time/ when the universe
was younger
- Matter is energy and energy is matter
- Most of the mass in the Milky Way is in the center
Contents of the Universe
- Stars, galaxies, planets, gas, dust, comets, asteroids, moons, meteorites
Fritz Zwicky
Studied clusters of galaxies, wanted to figure out how galaxies are moving within
clusters, how clusters move, and how they move together.
Tried to estimate how much matter would have to be in the stars to produce light. Able to
translate this into how much matter was in the star/light, derived mass from looking at the
motion. Mass is higher than the mass you get from the light
- Gravity: An attractive force between two objects
- There is gravity in space, otherwise the solar system and the universe wouldn’t look the
way it does now
Vera Rubin
Studied the Milky Way. Measured how fast the stars were moving as you go further away
from the center of our galaxy.
Prediction – the further away you are the slower things are moving. Vera – the further
you go away from the center the faster things are moving.
Dark matter (cannot be seen) has mass (mass has gravity, gravity causes the motion aka
mass forces motion).
Current results: Dark matter (26.8%), Dark energy - agent that causes the expansion of
the universe (68.3%), and ordinary matter/what we can see (4.9%)
Space is huge and most of it is very empty. Almost all of the rest is dark matter and dark
energy
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