Size and scale of the Universe Reference Points
• Solar System – Sun,
planets, asteroids,
comets
• Galaxy – hundreds of
billions of stars, gas
and dust
• Clusters of galaxies –
millions of galaxies
• Universe –
everything!
What is the Universe?
• Everything we can know about is part of the universe.
• Everything we do know about is part of the universe.
• Everything!
Galaxies are redshifted!
• In 1903 at Lowell Observatory in
Flagstaff, Arizona, Vesto Slipher was
the first to measure the redshift of a
spiral nebula (now known as a
galaxy).
• Slipher realized that the redshift of the
spectrum of the spiral nebula (galaxy)
meant that it was moving away from
us at a very high speed.
ALL Galaxies have redshifts –
farther from us greater redshifts!
• Many other scientists made
observations similar to
Slipher’s.
• In 1929, Edwin Hubble
and Milton Humason put
their observations together
in a way that led to the first
realization that the
universe changes – in fact,
the universe is expanding!
Addison Wesley IF20.18
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•
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the more distant the object
the farther back in time we are seeing it
the faster it is moving away from us
and the bigger its redshift.
• PROBLEM: What about Newton’s Laws
and Gravity? Shouldn’t everything be
coming together rather than moving apart?
The Universe is four-dimensional
• A good way to think of
the universe is to use
Einstein’s description of
space-time, the four
dimensional fabric that
makes up our universe.
• The universe has three spatial
dimensions (length, width,
height) and one temporal (time)
dimension
SO WHAT IS THE POINT!!
What is Einstein's theory of what the
universe is composed of and how
does it explain gravity and how the
universe is changing?
The Universe and Space Time
SO WHAT IS THE POINT!!
Remember the Universe
composed of a fabric of spacetime is expanding
The Universe and Space Time
• Galaxies are moving
away from us.
• Galaxies that are further
away are moving faster.
• The universe is
expanding!
• The expansion of the
Universe creates more
space and time
Big Bang Balloon
• Work with a partner and follow the
directions
The Universe is expanding
• The redshifts of galaxies is evidence that the
universe is expanding.
Tutorial: Expansion of the
Universe
• Work with a partner
• Read the instructions and questions carefully
• Talk to each other and discuss your answers with each
another
• Come to a consensus answer you both agree on
• If you get stuck or are not sure of your answer ask
another group
• If you get really stuck or don’t understand what the
Lecture Tutorial is asking as one of us for help
The Universe is expanding
• If the universe is expanding, it must have been
smaller in the past.
• If it was smaller in the past, then there must have
been a beginning for the universe
• Working backwards, what would the universe be
like at the beginning?
• Hot, dense, tiny
Mapping Our History
The subtle
slowing down
and speeding up
of the expansion,
of distances with
time: a(t), maps
out cosmic
history like tree
rings map out the
Earth’s climate
history.
STScI
The Big Bang marks the time when
the Universe began
• In the 1940s, based on Hubble’s Law, George
Gamow proposed that the universe began in a
colossal explosion
• In the 1950s, the term BIG BANG was coined by
an unconvinced Sir Fred Hoyle
• The BIG BANG is the event that marks the time
when the universe began.
• The BIG BANG is the event that marks the time
when the universe began – the beginning of the
expansion.
• But what did the universe look like at the
beginning?
• All of the universe as we know it now, was once a
single point-like location of infinite Temperature
and Energy but was NOT composed of any
Matter.
What happened after the Big Bang?
10-44sec
Radiation
Era
10-35sec 10-32sec
GUT
Era
Inflation
Era
10-10sec 300 sec 3x105yr
Electro-weak
Era
Particle Recombination Galaxy and Star
Era
Era
Formation
http://dev.cadre.com.au/Astro_V/Project/Contact_List/
IF23.02
1x109yr
15x109yr
Present
Era
What evidence is there to support the
idea of a Big Bang?
• ~380,000 years after the event of the Big Bang, the
Universe cooled to a temperature of 3,000 K, and light,
which could not propagate until then, began to spread in
all directions.
• Working backwards, we should be able to see some
evidence of this signature of light (blackbody radiation) at
the time of the early universe.
• The light released then, almost 14 billion years ago, can
still be observed now. The 3,000 Kelvin temperature of
the early Universe has dropped to a temperature today of
2.735 K (Blackbody peak in the microwave)-This is
known as the Cosmic Microwave Background
Radiation!!!
The cosmic microwave background
radiation that fills all space is
evidence for the BIG BANG
The microwave background radiation is
evidence to support the ideas that:
• The Universe was once much hotter, denser and
smaller
• There were times during the early universe when
light could not freely travel through space.
• The Universe began during an event we call the
Big Bang.
• The Universe is approximately 14 billion years
old.
Cosmic Microwave Background Radiation
COBE
WMAP
So what does the WMAP (“the best baby
picture of the Universe ever taken”) tell us?
• The first generation of stars in the Universe first ignited only
200 million years after the Big Bang, much earlier than
many scientists had expected.
• The new microwave background observations precisely peg
the age of the Universe at 13.7 billion years old, with a
remarkably small one percent margin of error.
• The Universe includes 4% atoms (ordinary matter), 23% of
an unknown type of dark matter, and 73% of a mysterious
dark energy.
• The new measurements even shed light on the nature of the
dark energy, which acts as a sort of an anti-gravity affecting
the rate of expansion of the Universe. We might not only be
expanding, but the expansion might be accelerating.
The Universe –
Expansion and the Big Bang
• The observation that galaxies are moving away from us,
tells us that the universe is expanding
• The observation of the Cosmic Microwave Background
Radiation supports the idea that the Universe stated with
an event called the The BIG BANG which marks the
time when the universe began its expansion from a
single point-like location of infinite Temperature and
Energy but was NOT composed of any Matter.
• The Universe is a Blackbody and the Cosmic
Microwave Background Radiation tells us that the
current average temperature of the Universe is 2.73K.
Which corresponds with an age of the universe of
approximately 13.7 billion years.
Big Bang Tutorial
• Work with a partner
• Read the instructions and questions carefully
• Talk to each other and discuss your answers with
each another
• Come to a consensus answer you both agree on
• If you get stuck or are not sure of your answer ask
another group
• If you get really stuck or don’t understand what
the Lecture Tutorial is asking as one of us for help
Dark Matter
• All galaxies exhibit the
same problem of “missing”
matter
• Dark Matter
• Does not emit light
• Not mysterious or evil
matter, just not seen
• Possibilities:
Brown Dwarfs, Neutrinos,
Black holes, MACHOS,
WIMPS
Vera Rubin
Discoverer of Dark Matter
We can not see 90% of the matter that makes up our Galaxy!!
Dark matter
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Most of the mass in galaxies like our own Milky Way does not reside in the stars and
gas that can be directly observed with telescopes.
90 percent of the mass in a typical galaxy is "dark matter," a substance that has so far
evaded direct detection.
How can scientists make this astonishing claim? We have yet to detect dark matter, we
can infer its existence from the gravitational pull it exerts on the luminous material we
can see.
So what is dark matter, and how might we find out? Determining the nature and
distribution of dark matter is one of the most pressing open questions in modern
science—it resides at the interface of particle physics, astrophysics, and gravity. Many
candidates for dark matter have been suggested, from the ghostly axion (particles with a
tiny amount of mass) to Weakly Interacting Massive Particles (WIMPs) that weigh in at
100 times the proton's mass.
https://www.youtube.com/watch?v=FpomfWEr5Dk
https://www.youtube.com/watch?v=QAa2O_8wBUQ
https://www.youtube.com/watch?v=gzLM6ltw3l0
DARK MATTER AND DARK
ENERGY
Dark matter tutorial
• Work with a partner
• Read the instructions and questions carefully
• Talk to each other and discuss your answers with each
another
• Come to a consensus answer you both agree on
• If you get stuck or are not sure of your answer ask
another group
• If you get really stuck or don’t understand what the
Lecture Tutorial is asking for help
The visible light from stars
we observe suggests that
the majority of the mass of
the Milky Way should be
concentrated near the
center.
Light from stars
What does observing the light from stars in
other galaxies tell us?
Looks bright at center so
most the mass should be at
the center.
Mass
Distance from the Galactic Center
Distance from the Galactic Center
Because there is a flat
rotation curve there
should be an equal amount
of mass distributed
everywhere throughout the
galaxy’s disk and halo.
Mass
However the flat
rotation curve tells
a different story?
Mass curve
determined from
the rotation
curve
Mass curve
determined
from Light
Distance from the Galactic Center
So which mass curve is
right?
But that is a problem. Where is all
the missing mass and why can’t we
see it?
Amount of Mass
The mass curve determined from the
rotation curve is our current best
model for how the mass of the
galaxy is distributed. Mass evenly
distributed everywhere in the disk
and halo.
Mass curve
determined from
the rotation
curve
Mass curve
determined
from Light
Distance from the Galactic Center
Where is the missing Mass?
Dark matter – massive objects (matter)
that are (is) distributed evenly around the
galaxy in both the halo and disk.
Dark matter activity
• Follow the instructions on the activity
Dark Energy
Is the Universe Static
• Einstein’s General Theory of Relativity predicts
that the Universe must not be static, but Einstein
refused to believe it
• Edwin Hubble began studying the distances of
galaxies and compared them to the speed at
which they were moving away from Earth.
• Then he compared it to the work of a man who
had been making similar observations years
earlier. He found that the galaxies that were
farther away were moving at a higher speed.
The Expansion of the Universe
• Hubble decided that since the Earth must
not be the center of the universe, this must
be true for any galaxy, not just our own.
• This is what led Hubble to the conclusion
that the universe is expanding.
Einstein’s Biggest Blunder
• Had Einstein not created the cosmological
constant he most likely would have
discovered the expansion of the universe
before Hubble.
The Big Crunch
• The Big Bang gives the universe the force
to continue to expand, but it would stand
to reason that gravity would eventually
slow this force down.
• When gravity begins to overpower this
force the universe would begin to contract
The Expansion/Contraction of the Universe
Bottom to Top- The Big Bang
Top to Bottom- The Big Crunch
The Problem with the Big Crunch
• 1998 Announcement that not only was the
Universe expanding, but it was doing it at an
accelerating rate
Type Ia Supernovae
• It was discovered that these supernovae
had a smaller redshift than would be
expected.
• Because these telescopes are looking
back in time the fact that the redshift was
smaller than expected means that they
were moving slower in the past.
Why is the Universe
Accelerating?
• We don’t know
• One would expect the force the caused
the expansion to eventually be
overpowered by gravity
• Because this is not the case something
must be overpowering the force of gravity
or the general theory of relativity has a
major flaw.
Or is Einstein correct?
• So if the explanation is that there is a force
that is overpowering gravity then that
would mean that Einstein was correct in
adding the cosmological constant
The Cosmological Constant
Maybe Einstein wasn’t wrong
Dark Energy
• Quantum Vacuum Energy- particles which
are constantly coming in and out of
existence generate energy
• The problem is that the calculation of this
energy is a problem in quantum
mechanics and the expansion of the
universe is in terms of general relativity
• Accounts for about 70% of the universe.
Dark Energy vs. Dark Matter
While dark energy repels, dark
matter attracts. And dark
matter’s influence shows up
even in individual galaxies,
while dark energy acts only on
the scale of the entire
universe