The Big Bang

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The Big Bang

• Mike Tinker

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Objectives

• Distinguish between a hypothesis, a theory, and a
  scientific law.
• Describe the Doppler effect.
• Summarize the big bang theory of the origin of
  the universe.
• List Evidence for the big bang theory.

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Hypothesis, Theory, Law

• Hypothesis a possible explanation or solution
  to a problem. A hypothesis is based on facts
  which are established through observation.
• Eliminating 20 once plastic water bottles and
  using only 40 once bottles will reduce the amount
  of plastic that ends up in land fills.

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Hypothesis, Theory, Law

• Theory a hypothesis or set of hypotheses that
  is supported by the results of experimentation
  and observation.
• A theory provides a general explanation for
  scientific observations that is consistent with
  known facts
• Life on Earth began as primitive single celled
  organisms.

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Hypothesis, Theory, Law

• Scientific Law A rule that correctly describes
  a natural phenomenon.
• The Law of Gravity

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Light and the Doppler Effect

• In 1665 Isaac Newton discovered the light
  spectrum.
• Sunlight passing through a prism produces a
  rainbow of red, orange, yellow, green, blue,
  indigo, and violet.
• Light travels in waves like sound or waves in the
  ocean.

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Light and the Doppler Effect

• Wave length is the distance from the crest of one
  wave to the crest of the next.
• Red light has the longest wave length.
• Violet light has the shortest wave length.
• Frequency is the number of wave crests that pass
  a point in a given amount of time.
• Which light wave has the most energy.

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Light and the Doppler Effect

• Chemical elements also produce a spectrum if they
  are heated.
• Elements produce their own signature bright-line
  spectrum.
• Chemical composition of a substance can be
  determined this way.

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Doppler Effect

• Scientists have also discovered that as a light
  moves closer to an observer, the wavelengths
  appear shorter. When light is moving away from
  and observer the light waves appear longer. The
  spectrum emitted by the light will shift toward
  the short end (violet) when an object is moving
  toward and shift toward the long end (red) when
  it is moving away.
• The faster light is moving the farther the shift.
• How does a siren sound as it approaches and then
  goes away?

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Big Bang Theory is Born

• Scientists used an instrument called a
  spectroscope to determine what elements were
  present in stars. (Sun 92 hydrogen and 8
  helium and traces of 100 others)
• By looking at the spectral shift given off by
  galaxies, they found that most galaxies were
  moving away from earth.
• After studying the degree of shift, scientist
  found that the farthest galaxies from earth were
  moving the fastest.

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Big Bang Theory is Born

• Some scientists proposed a hypothesis to explain
  the expanding universe.
• Billions of years ago all matter and energy were
  compressed in an extremely small volume.
• About 15 billion years ago a giant explosion sent
  all matter and energy hurling outward in a cloud.
• Some matter gathered into clumps and formed the
  galaxies we have today.
• Today the universe is still expanding.

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Big Bang Theory is Born

• Not all scientists agreed.
• They said for this to be true, energy should have
  spread out evenly through out the universe.
• In the 1960s scientists using radio telescopes
  discovered low levels of energy called background
  radiation. This energy was evenly distributed
  across the universe.

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