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Our Place in the Universe
Drew Smith
Important Principles
• The Cosmological Principle
▫ The universe is isotropic and homogenous
(it “looks” the same in all directions.)
• The Copernican Principle
▫ Humans are not special observers of the
universe. No place was the “starting point”
of the universe.
What is the Universe?
• The observable universe contains nearly a
septillion stars (1 X 1024).
▫ This is more than the number of grains of
sand on earth.
• These stars are located in at least 80 billion
galaxies.
▫ These galaxies are then clustered, and
superclustered.
Where do we fit? Solar System
Where do we fit? Interstellar Neighborhood
Where do we fit? Milky Way Galaxy
Where do we fit? Local Group
Where do we fit? Supercluster
Where do we fit? Local Clusters
Where do we fit? Observable Universe
The Universe is EXPANDING
• Each object increased in
distance by double, which
means the rate of expansion
is constant across the
universe. However, the
object that began 10 cm
away travelled 10 cm in the
same time that the closer
object travelled 5 cm. It was
twice as far away, so its
recession velocity was twice
as great.
Any Questions?
• Assignment:
▫ Write a story about the origin of earth, the solar
system, the galaxy, the universe, or all of the
above.