The Big Bang Determining the origins of the Universe
Transcript
Slide 1
Determining the origins of the Universe
Slide 2
Learning Goals Students will: 1) Understand the theories for
the formation of the universe.
Slide 3
Success Criteria Students will show their understanding of
learning goals by: 1) Listing the evidence for the Big Bang
theory
Slide 4
Introduction http://www.youtube.com/watch?v=zDQzKTedGN E (Nice
4 minute preview) http://www.youtube.com/watch?v=zDQzKTedGN E
http://www.youtube.com/watch?v=PV0ACIykxQI (Big Bang Part 1 Nat
Geo) http://www.youtube.com/watch?v=PV0ACIykxQI
http://www.youtube.com/watch?v=phV-Zpy1BeM (Big bang Part 2 Nat
Geo) http://www.youtube.com/watch?v=phV-Zpy1BeM
http://www.youtube.com/watch?v=fK375XB3v08 (Big bang Part 3 Nat
Geo) http://www.youtube.com/watch?v=fK375XB3v08
http://www.youtube.com/watch?v=gr8zLAxPs-A (Big Bang Part 4 Nat
Geo) http://www.youtube.com/watch?v=gr8zLAxPs-A
Slide 5
Remember Spectroscopy! In the 1800s, astronomers began to
experiment with tools called spectroscopes (or spectrographs). A
spectroscope is a device that divides light into a spectrum of its
component wavelengths. Spectrographs are produced by a spectrometer
Instead of using a prism, many spectrometers break up light into a
spectrum using a diffraction grating some of these are supplied in
the classroom.
Slide 6
Spectra 1)White light produces a complete or continuous
spectrum 2)A heated gas will produce a line spectrum or emission
spectrum each gas has its own pattern of lines (many lines are
invisible because they are seen in the IR and UV wavelengths) 3)A
cool gas interfering with white light will produce an absorption
spectrum. Certain wavelengths of light are removed from a
continuous spectrum
Slide 7
Spectrographs Scientists in the 1800s made the discovery that
light produced by a glowing gas did not produce a full spectrum,
but just a few lines from the light spectrum Spectroscopes showed
that the light from a specific material, such as a glowing tube of
hydrogen, always produced the same distribution of wavelengths
unique to that material. Use the spectroscopes supplied in the
class to look at various gases. Try looking at the suns spectra or
the spectra from a fluorescent light. Hydrogen Helium Carbon
Slide 8
The value of spectra to astronomers It became clear that by
looking at the wavelength distribution from a spectrograph, you
could figure out what kind of elements were in a light source.
Hence you could determine the chemical composition of a star from
its emission spectra. Typically stars are composed mostly of
Hydrogen and Helium. The sun consists of 71% H, 27% He, 1% O and
the last percent is made of C, N, Si, Mg, Ne, Fe and S. Similarly,
the light reflected from a planet such as Jupiter or Venus would
produce an absorption spectra Stars are actually classified by
their spectra. Different spectra are indicators of different
temperatures of stars and ages of stars. Young stars are hotter and
have more hydrogen vs. helium
Slide 9
Modern Spectroscopy Instead of measuring the thickness or
intensity of lines from a line spectrum, Modern Spectroscopy simply
uses computers which produce a graph of intensity vs.
wavelength.
Slide 10
YOU tube lectures on spectroscopy in astronomy This is a 3-part
series. You might find that you want to skip to parts 2 and 3.
http://www.youtube.com/watch?v=sVev5RsKXog
http://www.youtube.com/watch?v=lsxvnVPLR1A &feature=relmfu
http://www.youtube.com/watch?v=lsxvnVPLR1A &feature=relmfu
http://www.youtube.com/watch?v=Bx0SMevn- 0c&feature=relmfu
http://www.youtube.com/watch?v=Bx0SMevn- 0c&feature=relmfu
Slide 11
The Doppler Effect Physicist Christian Doppler discovered that
the frequency of a sound wave depended upon the relative position
of the source of the sound. As a noisy object approaches you, the
sound waves it generates compress. This changes the frequency of
the sound, and so you perceive the sound as a different pitch. When
the object moves away from you, the sound waves stretch and the
pitch goes down. It's called the Doppler Effect.
Slide 12
The Red Shift Astronomers in the early 1900s discovered that
the lines of many stars were shifted right towards the red side of
the spectrum. The explanation for this can be made by comparing the
red shift of light to the Doppler effect on sound waves.
Slide 13
The movement of stars The conclusion is that we can tell if
stars are moving towards or away from the Earth. Notice the
position of the spectral lines have been shifted from the normal
rest position
Slide 14
Steady State Theory Big Bang Theory
Slide 15
The Steady State Theory An unchanging Universe In the early 20
th century, the prevailing theory for the Universe was that the
universe had existed pretty much in its present form for eternity
with little change! The Steady State Theory suggests that there was
no beginning, nor will there be an end to the universe. It believes
that new stars and galaxies form to fill any empty space that has
been left behind by old stars and galaxies moving away from each
other.
Slide 16
The Steady State Theory:Einstein & the Cosmological
Constant The first challenge to the Steady State Theory came from
Albert Einstein who had recently published the Theory of General
Relativity (1915). Einstein recognized that gravity should start to
draw stars and other matter together, causing the universe to
slowly collapse in on itself. Einstein, a believer of the Steady
State Theory at the time, dealt with problem by adding the
Cosmological Constant (1917) to his mathematical equations to hold
gravity back. This constant allowed the universe to remain constant
but would later become in Einsteins own opinion, his greatest
mistake.
Slide 17
The Steady State Theory A Modern Version The modern Steady
State theory was established in 1949 by Fred Hoyle, Hermann Bondi
and Tommy Gold. Theoretical calculations showed that a static
universe was impossible under general relativity, and observations
by Edwin Hubble had shown that the universe was expanding. The
Modern Steady State Theory asserts that although the universe is
expanding, it nevertheless does not change its appearance over time
(the perfect cosmological principle); the universe has no beginning
and no end.
Slide 18
The Steady State Theory A Modern Version Hoyle suggested that
an expanding universe that stays in perfect balance like a pool
kept full to overflowing by a trickle from a faucet. The "faucet"
of the universe would be the continuous creation of matter from
energy. In other words as the universe expands new galaxies and
stars are added to fill voids and the galaxy has the appearance of
never changing. Though Hoyles theory would be proven wrong, he
predicted that the source of all heavy elements in the universe
were the result of fusion reactions within stars.
Slide 19
Slide 20
The Discovery made by Edwin Hubble Edwin Powell Hubble
(November 20, 1889 September 28, 1953) was an American astronomer
who did his best work at the Hooker Telescope (a 110 inch (2.5 m)
telescope the worlds largest at that time) located on Mt. Wilson in
southern California. Hubble was actually a high school teacher and
school basketball coach who later went back to school to obtain his
Ph.D. in Astrophysics. A major breakthrough in our understanding of
the universe took place in the 1920's thanks to Hubble. For
centuries, astronomers believed that the Milky Way made up the
entire universe. Hubble was among the first to show that the fuzzy
patches in the sky seen through telescopes were other galaxies, not
distant parts of the Milky Way.
Slide 21
The Discovery made by Edwin Hubble Hubble conducted a study of
stars and their spectra. He analyzed the red shifts of stars and
more importantly galaxies and determined the distances to stars
using the Hubble constant. Hubble made the amazing conclusion that
all galaxies were moving away from each other AND that the further
the distance of a star or galaxy, the greater its red shift (and
therefore velocity).
Slide 22
Hubbles discovery The bottom spectrum is the absorption
spectrum of the sun, and those above it for galaxies progressively
further away. The pattern of absorption lines shifts further and
further to the right, toward the red end of the spectrum. What does
this mean?
Slide 23
The Universe is Expanding In the 1920s, Edwin Hubble noticed
something interesting. The velocity of a star appeared to be
proportional to its distance from the Earth. In other words, the
further away a star was from Earth, the faster it appeared to move
away from us. Hubble theorized that this meant the universe itself
was expanding !
Slide 24
Hubbles Law The discovery of the linear relationship between
red shift and distance, yields a straightforward mathematical
expression for Hubble's Law as follows: Where v = H 0 D v is the
recessional velocity, typically expressed in km/s. H 0 is Hubble's
constant D is the proper distance measured in megaparsecs (Mpc)
Hubble's Law is considered a fundamental relation between
recessional velocity and distance
Slide 25
The Universe is Expanding Since light coming from more distant
stars and galaxies takes longer to arrive than from nearer stars;
it means that the farther into space we look, the farther back into
time we are looking In other words, looking deeper into space means
we are looking further back into time.
Slide 26
The Universe appears to be expanding from a central location in
the universe. The Universe is Expanding Working backwards using
this rate of expansion, we can estimate the age of the universe.
This means we are effectively looking back in time, looking at
light that was emitted in the early days of the universe. Since the
universe appears to be expanding from a central location we can
hypothesize that if we move back far enough in time we can deduce
that the entire universe expanded from a single point!
Slide 27
The Universe is Expanding The fact that we see all other
galaxies moving away from us does not imply that we are the center
of the universe! All galaxies will see all other stars moving away
from them in an expanding universe. A rising loaf of raisin bread
is a good visual model: each raisin will see all other raisins
moving away from it as the loaf expands.
Slide 28
The Big Bang Theory In the early 20th century, Georges Lematre
was the first scientist to suggest that the universe expanded from
a single point. Later work by mathematicians and astrophysicists
such as Einstein, Freidman and Hubble provided support for the
theory. Russian scientist, George Gamow, one of Friedman's pupils,
was the major advocate of the Big Bang theory. Gamov defected from
the USSR in 1933 and did most of his work in astronomy in the USA
Gamov suggested suggested that the universe must have exploded from
an extremely dense, hot state. In 1950, British astronomer Fred
Hoyle, who co-founded the opposing steady-state theory, ridiculed
Gamows theory with the term the big bang, but the name stuck.
Slide 29
Cosmic Microwave Radiation: P roof of the Big Bang? Together
with colleagues Ralph Alpher & Robert Herman, Gamov predicted
the cosmic microwave background (CMB) radiation, which is a
radiation that should exist throughout the universe as a remnant of
the Big Bang. In the 1960s, two researchers Arno Penzias and Robert
Wilson, tried to eliminate the noise background picked up by
microwave antennae. Unable to get rid of a mysterious background
signal that remained constant in any direction, at any time, they
phoned Princeton University, reaching the team that was looking for
this very type of radiation. It turns out that this background
noise or static was actually the Cosmic Microwave Background
radiation. Stephen Hawking stated that this was the final nail in
the coffin for the Steady State Theory. A map of the cosmic
microwave background radiation note that it is uneven.
Slide 30
The CMB What Is It? What Does It Tell Us? The Cosmic Microwave
Background (or "CMB" for short) is radiation from around 300,000
years after the start of the Universe. A blink of an eye when
compared to the age of the Universe, which is around 13.82 billion
(13,820,000,000) years old. Before this time, the Universe was so
hot and dense that it was opaque to all radiation. Not even simple
atoms could form without instantly being ripped apart into their
constituent protons and electrons by the intense radiation. Thus
the Universe was made of a "plasma", or ionized gas, which is what
the surface of the Sun is made of.
Slide 31
The CMB: radiation remnant of the big bang! Ever since the Big
Bang, the Universe has been cooling and expanding. By around
300,000 years through its life it was cool enough (though still
around 3000 Celsius) for the simplest atoms to form, and it became
transparent. The light from this time has been travelling through
space ever since, and can be detected all around us from here on
Earth or in space. We can measure the afterglow of the Big Bang.
The expansion of the Universe has stretched out the CMB radiation
by around 1000 times, which makes it look much cooler. So instead
of seeing the afterglow at 3000 degrees, we see it at just 3 K
Slide 32
The CMB is Not Uniform! At present, cosmologists are very
interested in small variations in the cosmic microwave background
and these are proving a rich source of information. The Planck
mission, using a satellite launched on 14th May 2009, aims to
measure these variations more accurately than has been achieved
before. This may yield vital clues as to the distribution of dark
energy and other open questions. The Planck Satellite superimposed
over an image of the Cosmic Microwave Background.
Slide 33
Looking for Evidence for the Big Bang Lematre said that this
event would have left behind some signature radiation. Some time
later, scientists began to look for corroboration of this model,
theorizing that light from the beginning of the universe would be
red-shifted to microwave wavelengths (a wavelength of EMR that is
much smaller than light). Astronomers also began looking for the
most distant objects in the universe knowing that they would have
been created soon after the Big Bang.
Slide 34
Evidence for the Big Bang
http://www.youtube.com/watch?v=uyCkADm NdNo (Good Video with a
summary of Big bang evidence this is actually part of an atheism
vs. creationism argument) http://www.youtube.com/watch?v=uyCkADm
NdNo
Slide 35
Evidence for the Big Bang 1) Hubbles Work - the universe is
expanding based on the red shift of stars and galaxies (1920s) 2)
The CMB the left over radiation of the Big Bang predicted by Gamov
was discovered by Penzias and Wilson (1964). 3) Gamow used the new
science of Quantum mechanics (1930s) to predict that the forces of
the Big Bang and nuclear fusion within stars would create an
abundance of H and He in the stars of 75% H and 25% He this is what
we observe from interstellar gases.
Slide 36
Evidence for the Big Bang 4) Gamow also calculated (using the
limited technology of the 1930s and 1940s) that the heat/radiation
left over from the Big bang would leave a background temperature in
the universe of 5K (kelvin) his calculation was close recent
studies of the CMB give a value closer to 3K. 5) Studies by the
Hubble Space telescope show that the most distant galaxies have
very immature structures (elliptical) in comparison with those
closer to Earth (spirals). This suggests that these galaxies are
younger and in their earlier stages of formation. This is also
backed by the fact that most Quasars (which turn into galaxies)
tend to be found only in the most distant reaches of space.
Slide 37
Evidence for the Big Bang 6) Studies of white dwarf stars (the
remnants (cores) of burned out stars show that the oldest white
dwarves are about 13.8 billion years old in line with the estimates
given for the Big Bang. As evidence mounts for the Big Bang, this
theory becomes stronger. At present, much work is being done with
atomic supercolliders (cyclotrons) to determine he forces present
in the earliest instants of the universe. Data and mathematical
predictions give the following predictions for the conditions found
in the Universe just after the Big Bang.
Slide 38
Slide 39
The Formation of the Universe Starting with the Big Bang Today,
when we look at the night sky, we see galaxies separated by what
appears to be huge expanses of empty space. At the earliest moments
of the big bang, all of the matter, energy and space we could
observe was compressed to an area of zero volume and infinite
density. Cosmologists call this a singularity. (In fact matter can
be created from energy E = mc 2 ) What was the universe like at the
beginning of the big bang? According to the theory, it was
extremely dense and extremely hot. There was so much energy in the
universe during those first few moments that matter as we know it
couldn't form. But the universe expanded rapidly, which means it
became less dense and cooled down. As it expanded, matter began to
form and radiation began to lose energy. In only a few seconds, the
universe expanded out of a singularity and began to stretched.
Slide 40
Big bang timeline
Slide 41
The GUT (Grand Unified Theory) Era:10 -43 seconds The universe
begins with a cataclysm that generates space and time, as well as
all the matter and energy the universe will ever hold. For an
incomprehensibly small fraction of a second, the universe is an
infinitely dense, hot fireball. The prevailing theory describes a
peculiar form of energy that can suddenly push out the fabric of
space. All known forces are combined into a single force gravity,
electromagnetism, the strong nuclear force, the weak nuclear force
the grand unified force.
Slide 42
The inflation Era: 10 -38 to 10 -3 seconds At 10 -38 to 10 -33
seconds a runaway process called " Inflation " causes a vast
expansion of space filled with this energy. The inflationary period
is stopped only when this energy is transformed into matter and
energy as we know it. The most basic forces in nature become
distinct: first gravity, then the strong force, which holds nuclei
of atoms together, followed by the weak and electromagnetic forces.
Elementary particles form (quarks, electrons, neutrinos) (These
particles will eventually combine to form protons and neutrons) At
this point there is an almost equal amount of matter and
anti-matter. These two types of matter begin to annihilate each
other but a small excess of matter remains.
Slide 43
The Era of nucleosynthesis: 10 -3 seconds Elementary particles
smash together in this high energy environment to form the first
atomic nuclei mostly hydrogen and helium The universe is still too
hot for the nuclei to capture electrons. (Matter is plasma - hot
ionic gas) It will take another 300,000 years for electrons to be
captured into orbits around these nuclei to form stable atoms. The
ratio of nuclei is 75% H and 25% He one millionth of a second after
the Big Bang, the universe continues to expand but not nearly so
quickly. As it expands, it becomes less dense and cools.
Slide 44
The radiation era: 3 seconds to 300000 years The first major
era in the history of the universe is one in which most of the
energy is in the form of EM radiation. This energy is the remnant
of the primordial fireball, and as the universe expands, the waves
of radiation are stretched and diluted until today, they make up
the faint glow of microwaves which bathe the entire universe.
Matter continues to form for the next 300,000 years and eventually
matter will dominate over radiation.
Slide 45
Beginning the Era of Matter Domination: 300,000 years At this
moment, the energy in matter and the energy in radiation are equal.
But as the relentless expansion continues, the waves of light are
stretched to lower and lower energy, while the matter travels
onward largely unaffected. At about this time, neutral atoms are
formed as electrons link up with hydrogen and helium nuclei. The
microwave background radiation hails from this moment, and thus
gives us a direct picture of how matter was distributed at this
early time.
Slide 46
Era of Galaxies: 300 million years Gravity pulls matter
together and the first stars and galaxies are formed Gravity
amplifies slight irregularities in the density of the primordial
gas. Even as the universe continues to expand rapidly, pockets of
gas become more and more dense. Stars ignite within these pockets,
and groups of stars become the earliest galaxies. This point is
still perhaps over 13 billion years before the present.
Slide 47
Video review http://www.youtube.com/watch?v=xsQ1XmqEe6 M
(Astronomy Magazine Big Bang)
http://www.youtube.com/watch?v=xsQ1XmqEe6 M
http://www.youtube.com/watch?v=mvBFY_FtGfY &feature=relmfu (The
Evidence for the Big Bang in 10 Little Minutes) Great Video SHOW
THIS!!!!!!!! http://www.youtube.com/watch?v=mvBFY_FtGfY
&feature=relmfu http://www.youtube.com/watch?v=ttpkto9Cm5c&
feature=relmfu (Dark Matter)
http://www.youtube.com/watch?v=ttpkto9Cm5c& feature=relmfu
Slide 48
The Four Basic Forces come into Being! One result of the big
bang was the formation of the four basic forces in the universe.
These forces are: Electromagnetism Strong nuclear force Weak
nuclear force Gravity At the beginning of the big bang, these
forces were all part of a unified force. It was only shortly after
the big bang began that the forces separated into what they are
today. How these forces were once part of a unified whole is a
mystery to scientists. Many physicists and cosmologists are still
working on forming the Grand Unified Theory, which would explain
how the four forces were once united and how they relate to one
another.
Slide 49
The Grand Unified Theory (GUT) The latest attempt to produce a
GUT Grand Unified Theory a theory to unify all forces into a single
force is called String Theory for help with this see Mr. Teahen!
Two great places to read about String Theory are: 1)The NOVA (PBS)
series hosted by Brian Greene http://www.pbs.org/wgbh/nova/elegant/
The Official String Theory Website http://superstringtheory.com/
The LHC (Large Hadron Collider at CERN hopes to shed some light on
the Grand Unified Theory Yes, Physics is the means by which we will
solve the mysteries of the Universe. for help with this see Mr.
Teahen!