Download What is the Universe Part 1

What is the Universe Part 1
Where did our solar system come from?
• Stars and planets form from interstellar clouds (nebulae)
of gas and dust, mostly made up of hydrogen and helium
• We can see these all over the Milky Way galaxy
• Clouds begin to condense when gravitational pull of the
matter in these clouds grows stronger
• This is likely how our solar system came to be
Where did our solar system come from?
Where did our solar system come from?
• Tiny condensed particles of matter from within the interstellar
cloud that started it all began to clump and bind a few billion years
ago
• As the diameters of these objects grew, they became planetesimals
• As growth continued, some planetismals were destroyed through
meter collisions, but some survived—and became the eight planets
of our solar system
• The third planetismal from the Sun became our Earth
Where did our solar system come from?
• Scientists theorize that the first planet to form
in our solar system was Jupiter, a gas giant and
the fifth planet from the Sun
• Jupiter kept growing larger and pulling
remaining dust and debris from space into its
orbit, as did the other gas giants
Where did our solar system come from?
• This is likely why the
interior planets
(including us)
remained small and
rocky and (initially)
without any satellites
(moons)
• Some debris didn’t get
pulled into a
planetary orbit and
today makes up what
is commonly known as
an asteroid belt
(between Mars and
Jupiter)
What happened to the “extra” matter?
• Some matter did not get
pulled into a planetary
orbit during the
formation of our solar
system
• Meteor= “space trash”
burnt up by our
mesosphere
• Meteorite=“space trash”
that comes in contact
with Earth’s surface
What happened to the “extra” matter?
• Comets= small, icy
bodies with highly
eccentric orbits around
the Sun
• Periodic comets=
repeatedly orbit in the
inner solar system
– Ex: Halley comet,
last seen in 1986,
expected again in
2061 (~75 year
period)
What is a Galaxy?
• Galaxy: Cluster or
bunch of billions
stars. There are about
100 billion galaxies in
the universe.
• Our neighboring
galaxy, Andromeda, is
2.5 million light years
from Earth!
• We belong to the local
group, a cluster of
about 35 galaxies.
What is a Galaxy?
What does the Milky Way look like?
What does the Milky Way look like?
100
billion+
late main
sequence
and Red
Giant stars
make up
the disk,
suggesting
that this is
the oldest
part of the
galaxy
Sagittarius A,
the mass in the
center of our
galaxy is about
2.6 million
times the mass
of the sun and it
believed to be a
super-massive
black hole that
“glows” because
of the hot gas
spiraling into it
The youngest stars in the
galaxy make up the spiral
arms, this is where most star
Edwin Hubble
• Born in small-town Missouri in 1889
• Attended high school in Chicago, excelling at
academics and athletics (broke state high jump
record, Varsity basketball player and boxer)
• Attended college on scholarship, continuing to play
sports and earned two degrees in mathematics and
astronomy
• Went to Oxford University Law School on a Rhodes
scholarship, where he did not continue his studies
in astronomy, but instead studied law.
• He quickly realized that he wasn’t satisfied
practicing law and went back to school for his
astronomy doctorate
Edwin Hubble
• As soon as he finished up his third degree, he was
drafted during WWI and didn’t begin his career as
an astronomer in California until 1917
• First person to…
– See other galaxies
– Develop a system to classify galaxies
– Explain redshifft
– Define the Big Bang Theory
• Hubble also refined Einstein’s theory of
relativity and the two famous scientists got
together in 1931 because Einstein was
grateful for Hubble correcting his mistakes
How do we know the universe is
expanding?
• Edwin Hubble
discovered that
most galaxies have
redshift in their
spectra
• Redshift of an
object in space
depends on distance
from Earth
• The farther away an
object is, the faster
it is moving away
How does the night sky tell us about the
past?
• Because many
galaxies are so
distant, it takes a
long time for their
light to reach Earth
• Ex: When we see
sunlight, we are
really seeing light
the Sun produced
eight minutes
before
Models of the Universe
• Big Bang Theory (Edwin
Hubble): The universe
began as a point and has
been expanding ever since
• NOT really an explosion,
but an expansion
• Steady State Theory (Fred
Hoyle): New matter has
been created such that
when objects in space
move, new objects fill that
void
• Conflicts with the law of
conservation of matter
Big Bang v. Steady State
Which theory is right?
• BOTH theories have observational tests to support
them
• BUT evidence weighs in favor of the Big Bang
• If the universe began as a highly compressed point (as
stated by Big Bang), then high temperature and
pressure would have created a great deal of high
energy radiation
• In 1965, scientists discovered persistent background
noise in radio antenna caused by weak radiation
• This is believed to be remnant of the Big Bang, as the
energy has shifted over time
• Steady State supporters have no explanation of this
What is going to happen to our universe?
1) Closed Universe (Big Crunch)—expansion will
stop and shift to contraction
2) Open Universe—expansion will continue forever
3) Flat Universe (Big Chill)—expansion will slow to
a halt in an infinite amount of time, but never
contract
What is going to happen to our universe?
What is going to happen to our universe?
• The constant interaction between gravity (pressure in) and
expansion (pressure out) will determine what happens
• One approach to determining the fate of the universe is to measure
how much expansion has already slowed, using redshift of distant
galaxies
• Latest evidence: expansion has started to speed up again! We don’t
know what’s causing it!!
• Most evidence points to a flat universe (inflationary model)