Origin of the Universe
•All matter came together at a single point
•An enormous explosion occurred (“Big Bang”)
and the universe began expanding.
•Galaxies are moving away from each other
Wavelengths of light
•Blue light has shorter wavelength
•Red light has a longer wavelength
Red Shift and Blue Shift
• Star is moving away from Earth then
the light wave is slightly expanded
and shifts to red end of light
• Star is approaching Earth then light
wave is pushed together and shifts to
blue end of light spectrum.
Theories of the Universe
Big Bang Theory
• The Universe began with a densely packed
mass and exploded out.
• The Universe continues to expand.
• Evidence found in Red Shift.
-The Steady State
Theory, developed in
1948, concluded the
Universe had no
beginning and no end.
-Steady State Theory
proposes that matter
is being continuously
created. This would
allow the density of
the universe to remain
constant as it expands.
Open Universe Theory
• Such a universe will never end, but will
eventually become very cold and dark because
stars gradually lose all of their energy.
• Galaxies continue to expand because of lack of
gravitational forces between them.
Closed Universe Theory
the universe is closed if it is sufficiently
dense, and therefore possesses
enough gravitational force to stop or
reverse the expansion started by the
• Spiral: They are in the shape of a flat disk with
a bright central nucleus and spiral arms that
extend out from the nucleus.
• The arms of a spiral galaxy have lots of gas and
dust, and they are often areas where new
stars are constantly forming.
• Elliptical galaxies have very little gas and dust.
Since stars form from gas, little star formation
occurs in elliptical galaxies. Most of their stars
are old and red.
• Irregular galaxies are usually found in groups
or clusters, where collisions and near-misses
between galaxies are common