Notes 1.1 The scale of the universe 09/12/2013
1. How did our ancestors imagine earth?
Stationary and located at the center of a relatively small universe.
Sun, moon, planets all revolve around us.
2. What do we know now?
Earth is a plant orbiting an average star in a vast universe.
3. State the full “comic address” of earth.
A. Earth ▯ A planet in our solar system.
B. Our solar system ▯ located a little over halfway from the galatic centre to the edge of the galatic disk In
the Milky Way Galaxy.
C. Milky Way Galaxy ▯ one of the largest galaxies among 40 galaxies in the Local group.
D. Local Group ▯ Located in the outskirts ( a bit far from centre) of the Local Super cluster.
Solar system: A star (sometimes more than one star) and all the objects that orbit it.
Milky Way: Name of our galaxy and used to refer to the band of light we see in the sky when we look into
the plane of the Milky Way Galaxy. ( Has more than 100 billion stars)
Galaxy: A huge collection of a few hundred million to more than a trillion stars, all bound together by
gravity. Local group: A group of 40 galaxies.
Galaxy cluster: A collection of a few dozen or more galaxies bound together by gravity; smaller collection of
galaxies are called groups.
Superclusters: The largest known structures in the universe, consisting of many clusters of galaxies, groups
of galaxies, and individual galaxies.
(clusters of galaxy clusters)
Universe: The sum of all matter and energy.
5. What is within our solar system?
The sun, Planets and their moons, and smaller objects (rocky asteroids/icy comets)
6. Astronomical Distance Measurements
Some distances are so large that km will not function…
a) One Astronomical Unit: is Earth’s average distance from the sun, which is about 150 million kilometers.
(commonly used in solar system)
b) One lightyear(ly): The distance that light can travel in 1 year ▯ 10 trillion km. (commonly used for
distances between stars and galaxies)
▯ NOTE: Ly is a unit of DISTANCE, not time.
Light travels at the speed of light;
300,000 KM PER SECOND; 1 lightsecond=300,000 km 7. If light could make circles around earth, how many could it make in 1 sec? 8.
8. Explain the relationship between