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11/28/05
4:46 PM
MAZER
Page 476
Galaxies
How does the universe expand?
SKILL FOCUS
Measuring (8.4)
PROCEDURE
1
Spread the cut rubber band against the ruler without stretching it.
Mark off every centimeter for 6 centimeters.
2 Align the first mark on the rubber band with the 1-centimeter mark on the
ruler and hold it in place tightly. Stretch the rubber band so that the second
mark is next to the 3-centimeter mark on the ruler.
3 Observe how many centimeters each mark has moved from its original
location against the ruler.
MATERIALS
• thick rubber
band cut open
• ballpoint pen
• ruler
TIME
20 minutes
WHAT DO YOU THINK?
• How far did each mark on the rubber band move from its
original location?
• What does this activity demonstrate about the
expansion of the universe?
CHALLENGE How could you calculate the rates at
which the marks moved when you stretched the
rubber band?
Scientists are investigating the origin of
the universe.
After astronomers learned that galaxies are moving apart, they developed new ideas about the origin of the universe. They concluded that
all matter was once merged together and then the universe suddenly
began to expand. The evidence for this scientific theory is so strong
that almost all astronomers now accept it.
VOCABULARY
Add a description wheel
diagram for big bang in
your notebook.
The big bang is the moment in time when the universe started
to expand. Astronomers have calculated that this event happened
about 14 billion years ago. One phase of expansion may have been
very rapid. In a tiny fraction of a second, the universe may have
expanded from a size much smaller than a speck of dust to the size
of our solar system.
Evidence of the Big Bang
Evidence for the big bang comes from various sources. One important
source of evidence is microwave radiation. Astronomers predicted in
1948 that the universe would still be filled with microwaves emitted
shortly after the big bang. In 1965 researchers detected this kind of
radiation streaming through space in all directions.
476 Unit 4: Space Science
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