the big bang theory. warm up: use your textbook on page 532 to describe the big bang theory. what...
TRANSCRIPT
The Big Bang Theory
Warm Up:
• Use your textbook on page 532 to describe the Big Bang Theory.
• What are 2 pieces of evidence for the Big Bang Theory?
THE BIG BANG THEORY
States that the universe began as a single cosmic explosion about 15
billion years ago.
What Happened After the Big Bang?
• After about 1 million years the universe cooled and H atoms formed
• Gravity pulled atoms (and then larger masses) together to form stars, planets, galaxies, etc.
Evidence for the Big Bang
• The presence of Background Radiation (energy left over from the Big Bang)– Detected as microwaves
– Maintains temp. of universe at 2.7 K
• Galaxies spreading away from the center of the universe (Red Shift)
How can scientists tell that galaxies are moving away?
As stars move away their light waves are stretched
As stars move closer their light waves are compressed
Red light waves are longer
Blue light waves are shorter
Spectral lines from stars (and galaxies) that are moving away will be shifted to the right (red end) of the spectrum
Galaxies seem to be racing away from the center of the Universe.
• Every galaxy seems to be moving away from Earth.
• After examining the Red Shift that appears from distant galaxies astronomers conclude the universe is expanding at tremendous speeds.
Expanding Universe• If the universe is expanding, then
the objects near the very edge of the universe are the oldest objects in the universe.
• The most distant known objects in the universe are over 12 billion light years from the Earth
Let’s look at that first picture again
What Happens Next?
• While the universe is still expanding due to the original force of the Big Bang, gravity is also pulling all matter inward in the opposite direction
What Happens Next?
• Astronomers think 3 possibilities could occur:– The universe could expand forever– The expansion will slow down and
reach its limit– The expansion will stop and then the
universe will contract
Expansion and Contraction is the most favored idea
• Gravitational attraction will eventually slow the expansion
• Matter and energy will eventually be pulled back together into one spot
• Another “big bang” could occur
Um… I think we may have been here before.
• This restructuring may occur once every 80 to 100 billion years.
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