Transcript The Big Bang

Determining the origins of the Universe
Learning Goals
 Students will:
1) Understand the theories for the formation of the
universe.
Success Criteria
 Students will show their understanding of learning
goals by:
1) Listing the evidence for the Big Bang theory
Introduction
 http://www.youtube.com/watch?v=zDQzKTedGN
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E (Nice 4 minute preview)
http://www.youtube.com/watch?v=PV0ACIykxQI
(Big Bang Part 1 Nat Geo)
http://www.youtube.com/watch?v=phV-Zpy1BeM
(Big bang Part 2 Nat Geo)
http://www.youtube.com/watch?v=fK375XB3v08
(Big bang Part 3 Nat Geo)
http://www.youtube.com/watch?v=gr8zLAxPs-A
(Big Bang Part 4 Nat Geo)
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.
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
Spectrographs
 Scientists in the 1800’s 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 sun’s spectra or the spectra from a
fluorescent light.
Hydrogen
Helium
Carbon
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
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.
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=Bx0SMevn0c&feature=relmfu
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.
The Red Shift
 Astronomers in the early 1900’s 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.
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
Steady State Theory
Big Bang Theory
The Steady State Theory
An unchanging Universe
 In the early 20th 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.
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
Einstein’s own opinion, his greatest mistake.
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.
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 Hoyle’s 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.
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 world’s 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.
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).
Hubble’s discovery
What does
this mean?
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.
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!
Hubble’s 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 = H0D
 v is the recessional velocity, typically expressed in km/s.
 H0 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
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.
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!
The Universe appears to be
expanding from a central location in
the universe.
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.
The Big Bang Theory
 In the early 20th century, Georges Lemaître was the first
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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 Gamow’s
theory with the term – “the big bang,” but the name stuck.
Cosmic Microwave Radiation:
Proof 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
A map of the cosmic microwave background
constant in any direction, at any time,
radiation – note that it is uneven.
they phoned Princeton University,
reaching the team that was looking for
 Together with colleagues Ralph
this very type of radiation.
Alpher & Robert Herman,
Gamov predicted the cosmic
 It turns out that this “background
microwave background (CMB)
noise” or “static” was actually the
radiation, which is a radiation
Cosmic Microwave Background
that should exist throughout
radiation.
the universe as a remnant of
 Stephen Hawking stated that this was
the Big Bang.
the “final nail in the coffin” for the
Steady State Theory.
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.
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
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.
Looking for Evidence for the
Big Bang
 Lemaître 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.
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)
Evidence for the Big Bang
1) Hubble’s Work - the universe is expanding based
on the red shift of stars and galaxies (1920’s)
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 (1930’s) 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.
Evidence for the Big Bang
4) Gamow also calculated (using the limited technology
of the 1930’s and 1940’s) 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.
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.
The Formation of the Universe
Starting with the Big Bang
 Today, when we look at the night sky, we see galaxies separated by
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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 = mc2)
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.
Big bang timeline
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.
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.
The Era of nucleosynthesis:
10-3 seconds
 Elementary particles smash together in this high energy
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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.
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.
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.
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.
Video review
 http://www.youtube.com/watch?v=xsQ1XmqEe6
M (Astronomy Magazine – Big Bang)
 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=ttpkto9Cm5c&
feature=relmfu (Dark Matter)
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.
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!