Download dark matter - Aurora City Schools

Origin of Universe
• Universe…all the space, time, energy
and matter that exists
• Because things are so far from Earth,
and light takes so long to travel to
us, when we look in the sky, we
look into the past
• Most of space is empty … um … space
Early thoughts
• Steady State Theory: everything is
now as it always has been and
nothing will ever change…stars,
planets, galaxies are the same as
they always have been and will
never change
• The Scientific Theory at turn of last
century (1900’s)
Early thoughts
• Einstein…1916…theory of general relativity
redefines gravity and space to
space/time
– Implies that universe must be moving
(not static/unchanging), but doesn’t say
expanding or contracting
• Lemaitre…1927…says universe should be
expanding (observed red shift) and
therefore once had a beginning
• People ignored Lemaitre in favor of Einstein
until…
Edwin Hubble, 1929
• Noticed that light from stars is shifted
towards red end of spectrum
• Means they’re
moving away
from us
• More it’s shifted,
faster they’re
moving
•Opposite is blue shift (means it’s moving
towards us)
Edwin Hubble, 1929
• Hubble noticed that most galaxies are
moving away from us and the
farther they are, the faster they’re
moving
• If go backwards, means everything
was in a small point and exploded
and is moving from that point out.
• Was called Big Bang to make fun of it
and the name stuck!
Big Bang Theory
• EVERYTHING (space, time, matter,
energy) was in one small point
(singularity) that “blew up” and is
still moving outwards today
• Not really an explosion, so much as a
very rapid expansion…like blowing
up a balloon
• About 13.7 billion years ago
• Microwave radiation detected in the
1960’s supports this theory. It’s left
over energy from the Big Bang
Penzias and Wilson
• In addition to Hubble’s
evidence
• 1960’s discovered
microwave radiation all
throughout the
universe, but couldn’t
explain where it came
from
• Only possible source is it’s
left over from Big Bang
• Later shown not to be
“evenly spread”
WMAP…background
radiation
Other evidence
• First elements to form should be
simplest….Hydrogen and Helium,
and that’s what most of the
universe is (>99%)!
• Other heavier elements made by stars
(fusion up to Iron) and supernovas
(other heavier elements)
• Called nucleosynthesis
Timeline
• Inflationary period:
– Rapid expansion, temperature billions of
degrees…way too hot even for atoms to exist!
• 10-43 sec after
– .00000000000000000000000000000000000000
00001 seconds
– 4 forces separate (electromagnetism, gravity,
weak nuclear, strong nuclear)
– Rules of physics we know now start to
work
Timeline
• 10-35 seconds after
– Protons and neutrons form
– .00000000000000000000000000000000001
• 10-1 seconds after
– Electrons form
– .01 sec.
• 3 minutes after
– 1st atomic nuclei form Temperature down to 1
billion degrees
• 300,000 years after
– First atoms (H and He)
– Light shines for first time (CMBR)
What’s next?
• Amount of mass will decide what’s going to
happen to the universe:
– May continue expanding forever
– May continue expanding and then stop at some
size
– May expand to a point and then collapse and
explode again
• Hard to measure amt. to of mass. We see
the effects (gravity) of some matter we
can’t see, so we call it dark matter (e.g.
WIMPs)
What’s next?
• Galaxies don’t seem to be slowing down (so
Big Crunch is doubtful, or we’re still in a
period of expansion)
• Open universe: idea that not enough matter
to keep it all together, and things keep
expanding (like molecules from open jar)
• Closed universe: idea that enough mass to
pull everything back in to Big Crunch
• Flat universe….expands to certain size and
stops
• Oscillating Universe: Bang, Crunch, Bang,
Crunch forever and ever