Download Our Expanding Universe File

Our Expanding Universe
8.8E Students are expected to research how scientific data are used as evidence to develop
scientific theories to describe the origin of the universe.
Part I: Scientific Theory
1. On a piece of notebook paper, draw a tree map with three stems. Label one stem as
“Steady State Theory”, one as “Oscillating Universe Theory”, one as “Big Bang Theory”.
2. Read the following selection. Take notes from the reading about each theory and organize
the information in a tree map.
Expert Information: Since the beginning of time, people have tried to explain how the universe
came to be. Several models explaining the origin of the universe have been proposed and
scientists have attempted to find evidence either supporting or disproving these theories.
There are three models that are supported by the scientific community. One model states
that the universe has always looked about as it does now, and its overall composition does not
change. This model avoids the idea of expansion and contraction, and states that as galaxies
move apart, new matter is created in the empty space. This model is called the Steady State
Theory.
The second model states that when the universe began, all matter was located within a
specific region of space. An explosion occurred, sending matter forcibly outward. This model,
called the Oscillating-Universe Theory, suggests that the universe goes through periods of
expansion and contraction. According to supporters of this theory, our universe is now in a period
of expansion.
A third model was proposed by Georges Lemaitre in 1926. The Big Bang Theory states
that all matter in the universe originated in a central location. Then, about 15 billion years ago,
this region exploded and matter was hurled outward from the site of the explosion.
This
expansion has continued ever since.
There is no real scientific evidence to support either the Oscillating Universe Theory or
the Steady State Theory, but observations have been made that support the ideas behind the Big
Bang Theory. In 1924, a scientist named Edwin Hubble observed the light from stars with an
instrument called a spectrograph. His observations of light showed that some stars were moving
toward earth and others were moving away from earth.
The term electromagnetic spectrum refers to the entire range of light radiation, and
includes radio waves, infrared rays, ultraviolet rays, x-rays, and visible light, the light that we
can see. Visible light makes up only a tiny part of the electromagnetic spectrum. When white
light is shone through a prism, it separates out into the colors of the rainbow. This is called the
visible spectrum, and demonstrates that white light is a mixture of all colors. Hubble was able to
show that as a star comes toward Earth, its wavelengths of light are squeezed together. As a
star moves away from Earth, its light wavelengths are stretched apart. This squeezing and
stretching of light is an example of the Doppler Shift. When stars are moving towards Earth,
their light waves compress near the blue end of the spectrum. This is called blue shift. When
stars are moving away from Earth, light wavelengths compress toward the red end of the
spectrum, which is called red shift. Because of Hubble’s observations, the Big Bang Theory is the
theory most widely accepted by scientists today.