Transcript Ch. 26.5: The Expanding Universe

The Big Bang!
The Expanding Universe
•How do astronomers know the universe is
expanding?
•What is the Big Bang Theory & what
evidence supports it?
•How can dark matter be detected?
Origins
• How and when did the:
– Universe form? (Today)
– Solar system / Earth form? (Next week)
– Moon form? (Next week)
How Do We Know?
Hubble’s Law = The farther a galaxy
is away from us, the faster it is
moving away from us
The Universe is EXPANDING!
Evidence: The Doppler Effect (Wavelengths
appear to change based on the motion of
objects)
Doppler Effect
• Red Shift - If waves move away from you
… the waves stretch out or get longer.
Objects moving away from us in space
appear to be red in color.
• Blue Shift - If waves approach you … the
waves bunch up on top of one another …
or shorten. Objects moving away from us
in space appear to be red in color.
Doppler
Effect
A
RED SHIFT – a shift in
absorption lines of star
spectrum to the red
wavelengths
Objects moving away
have longer wavelengths
(red)
B
Which spectrum is from a
star/galaxy that is moving away
from us?
BLUE SHIFT
Objects moving towards
us have shorter
wavelengths (Blue)
What does this spectrum tell you about the motion of the
supercluster of galaxies?
Red Shifts
What is going on here?
•
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Red Shifted Spectrums
Which galaxy is farthest from us?
Which galaxy is moving away from us faster?
Hubble’s Law
More distant galaxies have
GREATER RED SHIFTS –
They are moving away from
Earth with faster velocity
than closer galaxies.
The UNIVERSE IS
EXPANDING!
Big Bang Theory
The universe came into being at a single
moment, in an event called BIG BANG.
All matter & energy of universe were
concentrated into an incredibly hot, small,
mass.
An enormous explosion sent matter and
energy out into space.
When: 15-20 billion years ago
Support for Big Bang
1. Red Shifts tell us Galaxies are
ACCELERATING AWAY from a center
(Expanding)
2. COSMIC Microwave BACKGROUND
RADIATION
Detected in 1965
Faint radiation coming from all directions
Believed to be energy from Big Bang
Evidence for Big Bang
• Red shift - as light from distant galaxies approach earth there is an
increase of space between earth and the galaxy, which leads to
wavelengths being stretched
• In 1964, Arno Penzias and Robert Wilson, discovered a noise of
extraterrestrial origin that came from all directions at once - radiation
left over from the Big Bang
• In June 1995, scientists detected primordial helium in the far
reaches of the universe - consistent with an important aspect of the
Big Bang theory that a mixture of hydrogen and helium was created
at the beginning of the universe
Background Cosmic Microwave Radiation
The Horn antenna in the Bell Telephone Laboratory discovered the universal
microwave background radiation.
What?
• Microwaves
coming at us
from
everywhere,
but no where
specific.
• It’s lingering
energy (echo)
from Big BANG
explosion!
Fate of Universe
A. Expand forever / Galaxies drift apart?
OR
B. “Big Crunch” – Galaxies collapse into a
center?
Depends on how much mass there is in the
universe … which is in dispute.
Dark Matter
Dark Matter = Does not give off radiation & cannot be
detected
Exerts gravitational force on visible matter
Universe may be 90% + dark matter
Why do we think Dark Matter exists? Galaxies are
accelerating faster than they should be (based on the
observable matter in the Universe). The acceleration
due to gravity does not match up with the amount of
matter that we can see. A = F/m (F = ma rearranged)
tells us that there must be more mass … we’re just not
seeing it.
Questions
1.
What theory states that the universe began as an
explosion of an incredibly dense point of matter
2.
According to the theory of Big Bang, how old is our
universe?
3.
Our universe is currently …
a. Contracting b. Expanding c. Staying the same
Questions
1.
What theory states that the universe began as an
explosion of an incredibly dense point of matter
Big bang
2.
According to the theory of Big Bang, how old is our
universe?
15-20 billion years
3.
Our universe is currently …
a. Contracting b. Expanding c. Staying the same
4. What does Hubble’s Law say about the motion of
galaxies?
5.
When scientists look at the spectrum for Andromeda,
our neighboring galaxy, they notice that the lines are
moved over to the blue end of the spectrum.
Andromeda is …
a.
b.
c.
d.
Moving towards us.
Moving away from us.
A constant distance from us.
Not moving.
4. What does Hubble’s Law say about the motion of
galaxies?
Hubble’s Law = The farther a galaxy is away from us, the
faster it is moving away from us
5.
When scientists look at the spectrum for Andromeda,
our neighboring galaxy, they notice that the lines are
moved over to the blue end of the spectrum.
Andromeda is …
a.
b.
c.
d.
Moving towards us.
Moving away from us.
A constant distance from us.
Not moving.
6.
Quasars, are very distant galaxies. When scientists
look at quasars with a spectroscope they would see
the lines on their spectrum shifted to the (RED /
BLUE) end of the spectrum.
7.
How does the red – shift of far away galaxies support
the big bang theory?
6.
Quasars, are very distant galaxies. When scientists
look at quasars with a spectroscope they would see
the lines on their spectrum shifted to the (RED /
BLUE) end of the spectrum.
7.
How does the red – shift of far away galaxies support
the big bang theory?
Red Shifts tell us Galaxies are
ACCELERATING AWAY from a center
(Expanding)
8.
What kind of wavelength on the electromagnetic
spectrum is lingering around like an echo from the Big
Bang?
9.
What are two possible scenarios for the future of the
universe?
8.
What kind of wavelength on the electromagnetic spectrum is
lingering around like an echo from the Big Bang?
COSMIC Microwave BACKGROUND RADIATION
Detected in 1965
Faint radiation coming from all directions
Believed to be energy from Big Bang
9.
What are two possible scenarios for the future of the universe?
A.
B.
Expand forever / Galaxies drift apart?
OR
“Big Crunch” – Galaxies collapse into a center?
Depends on how much mass there is in the universe … which
is in dispute.
10. What is dark matter and how much of the universe do
scientists think may be dark matter?
10. What is dark matter and how much of the universe do
scientists think may be dark matter?
Dark Matter =
Does not give off radiation & cannot be detected
Exerts gravitational force on visible matter
Universe may be 90% + dark matter
Features of Our Solar System
•
•
•
•
•
in a spiral arm of the Milky Way Galaxy
Sun
9 planets
101 known moons (satellites)
a tremendous number of asteroids
– most orbit the Sun between the orbits of Mars and
Jupiter
• millions of comets and meteorites
• interplanetary dust and gases
Relative Sizes of the
Sun and Planets
Solar System Configuration
Origin of Our Solar System
Solar nebula theory
 cloud of gases and
dust



formed a rotating
disk
condensed and
collapsed due to
gravity
forming solar nebula


with an embryonic Sun
surrounded by a rotating cloud
Embryonic Sun and Rotating Cloud
• planetesimals have formed in the inner solar
system
• large eddies of gas and dust remain far from
the protosun
The Planets
• Terrestrial Planets

– Mercury
– Venus
– Earth
– Mars
Jovian Planets




• small, composed
of rock, with metal
cores
– Pluto?

Jupiter
Saturn
Uranus
Neptune
large, composed
of hydrogen,
helium, ammonia,
methane,
relatively small
rocky cores