Transcript Slide 1

Start Simple-Grow complex
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Start simple-Get Complex
From a sunbeam
A World made from light
Light Gets Heavy
Drops of light
Drops to puddles, to streams, to rivers, to
oceans.
• Making a cake from scratch (totally from scratch)
Chemistry: A Simple Beginning
Building Blocks
• By starting from one or a few building
blocks, a multitude of things can be built.
• Legos, tinker-toys, kinetix
• Pennies, beer cans, toothpicks, popsicle
sticks, dominoes, sand
• Bricks, logs, glass are traditional building
materials.
Chemistry: A Simple Beginning
Building Blocks
• By starting from one or a few building
blocks, a multitude of things can be built
CHEMISTRY
It’s all about
building blocks
All built from a few building materials:
Metal, glass, cement, plastic, & wood.
Let’s make a cake from scratch
(totally from scratch)
Proton
Neutron
Electron
E = mc2
E = 1 kg x (300,000,000 m/s)2
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E = 9x10 joules
1 joule = 1 watt for
1 second
E = 9x1016 watts x sec x kilo x 1 hr
1000 3600 sec
E = 25,000,000,000 kilowatt-hrs
Arizona produced & used 58,000,000,000 KW-hrs in 1999
About half a year to produce enough energy to create the
mass used in a cake (1kg).
Cost = about 3 billion dollars
High energy light (photons) are needed to create matter.
2 or 3 volts can produce
visible light, but that’s
not high enough energy.
We need higher
frequency light, which
has higher energy
photons.
The picture tube (also called CRT) that’s in your television or
computer monitor creates light by accelerating electrons with
30,000 volts of electricity to slam into the front of the monitor.
This light has more energy but not enough.
100,000 to 200,000 volts of electricity to accelerate electrons to
strike a metal plate. When the electrons come to a halt, they give
up their energy as high energy light called xrays. But this light still
doesn’t have the energy to create matter.
The voltage needed to create an electron is about one million
volts. This is the voltage that creates a bolt of lightning. This
voltage pushes electrons from the sky to the ground, but the
electrons are slowed down by the air. If they weren’t, it would
be possible that two electrons accelerated by a million volts
striking the ground would give off light of enough energy to
create a new electron.
Electron
Positron
(anti-electron)
Electron and anti-electron (positron) created when high
energy gamma rays with energy of 1 million volts collide.
Proton
Anti-Proton
Proton (+) and anti-proton (-) created when high
energy gamma rays with energy of 938 million
volts collide.
Quarks
+2/3 U
-1/3 D
Proton
Anti-quarks
U U
D
Neutron
D D
U
Quarks of six “flavor” or “colors” and their anti-quarks are created when high
energy gamma rays with energy of about 300 million volts collide.
The neutron
Proton
Electron
Using the building blocks of
neutrons, protons, and electrons
we build the elements
Building elements
Hydrogen-1
Beryllium-4
Helium-2
Boron-5
Lithium-3
Carbon-6
Elements are the new building
blocks
Hydrogen
Nitrogen-7
Carbon-6
Oxygen-8
Elements are the new building
blocks
Hydrogen
Nitrogen-7
Carbon-6
Oxygen-8
Hydrogen
Carbon-6
Hydrogen
Hydrogen
Hydrogen
Elements are the new building
blocks
H
H
H
O
N
C
H
H
C
H
H
O
C
Hydrocarbons
H
Methane
H
H
C
Propane
H
H
H
H
H
H
C
C
C
H
H
H
Butane
H
H
H
H
H
C
C
C
C
H
H
H
H
H
H
O
H
C
Hydrocarbons
Gasoline
O
H
H
H
H
H
H
H
C OH C C C C C C C
H
H
H
H
H
H
H
O
H
H
H
H
H
H
H
C OH C C C C C C C
H
H
H
O
H
H
H
H
H
H
H
H
H
H
H
C OH C C C C C C C
H
H
H
H
H
H
H
H
H
H
C
Carbohydrate
H
H
O
Glucose
Glycerin
Ribose
H
H
H
H
H
C O
C O
H
C O
H
H
H
H
H
H
C O
H
H
H
H
C O
C O
C O
C O
H
H
H
H
H
H
H
H
H
H
H
C O
C O
H
C O
C O
C O
C O
H
H
H
H
H
H
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A photon (packet) of light energy has an energy, E (Joules), proportional to
its frequency, f (sec^-1). The constant of proportionality is Planck's constant,
h (Joule-sec). So: E = h*f. The value of h = 6.63*10^-34 so you can see that
any single photon carries very little energy.
Anti-Proton annihilation 938 MeV
In order to create the anti-proton, protons were accelerated to very high
energy and then smashed into a target containing other protons.
Occasionally, the energy brought into the collision would produce a protonantiproton pair in addition to the original two protons. This result gave
credibility to the idea that for every particle there is a corresponding
antiparticle.
During the first four seconds of the universe, matter formed by pair
production.
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Two photons can collide to form a particle-antiparticle pair if the energy of each photon is greater
than the energy equivalent (E = mc2) of the particle or antiparticle. For instance, a proton has mc2
of 10-10 joules. Two photons, each an energy greater than this value, can collide to form a protonantiproton pair. This process is known as pair production. Conversely, a particle and antiparticle
can collide to form a pair of photons. For instance, a proton and antiproton colliding at a low
relative velocity will produce a pair of photons, each with an energy of 10-10 joules. (This is a high
energy for a photon, corresponding to an extremely energetic gamma-ray.) The process of
converting a particle-antiparticle pair to photons is known as annihilation.
When the universe was less than 0.0001 second old, the photons of the cosmic background were
so energetic, proton-antiproton pairs were continuously being formed by pair production. However,
the proton-antiproton pairs were also continuously being destroyed by annihilation.
At an age of 0.0001 seconds, the temperature of the universe dropped below 10 trillion degrees
Kelvin. At this temperature, the average photon energy is 10-10 joules, the energy equivalent of a
proton or antiproton. Pair production of protons stops (the photons have dropped below the
necessary energy), but the annihilation of protons continues.
Thanks to a subtle bias in the laws of physics, however, the production of protons is very slightly
favored over the production of antiprotons. For every billion antiprotons, there will be a billion and
one protons. So here's the situation after pair production stops:
1 billion and 1 protons + 1 billion antiprotons -> 2 billion photons + 1 proton
We now have a situation in which the universe contains lots of photons, a few protons, and no
antiprotons. We state that the protons have ``frozen out'', since they are no longer being produced
or annihilated.
Neutrons are about as massive as protons, so they freeze out at the same time as protons.
Electrons and positrons, however, since they are only 1/2000 as massive as a proton, are
produced and annihilated continuously until the universe drops to a much lower temperature.
• Protons are attracted to electrons. But
protons repel protons and electrons repel
electrons.
• This pulling and pushing accounts for all
compounds created from the elements.
• The element vs. atom
• Gold is the element that is yellow and
shiny.
• A gold atom is an atom that must have 79
protons. It also has 79 electrons. And 117
neutrons.
• Atoms are not stupid nor are the smart.
But they can do things that seem smart.
• The forming of crystals is just one. They
can form geometric shapes that can bend
light in many ways.
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What kinds of quarks are protons and neutrons made of? What was the old
name for the Top and Bottom quark?
Protons are made of two Up and one Down quark. The neutron is made of two Down
and one Up quark. The Up quarks have a 2/3 positive charge and the Down has a 1/3
negative charge. Fractional charges are a pretty funny concept, but remember we
(humans) made up the unit of charge that a proton has, so its very possible that there
could be a smaller division of charge. If you add those charges you will see that sum
is positive one for the proton and 0 for the neutron.
Truth and Beauty quarks were called T and B when originally proposed, to be Top
and Bottom in analogy with the nucleon quarks that had just been renamed the Up
and Down quarks. (Originally P and N had been used, but this led to confusion with
the nucleons.) Very soon after the proposal T and B was made, somebody, maybe
MGM, decided to call them Truth and Beauty. This nomenclature remained standard
for several years. The term Beauty is still often used for the B quark. The Cornell
accelerator was called a "Beauty factory" which sounds much nicer than a "Bottom
factory." After the B was discovered and years went by without the T, people started
to say "the quark model has no truth." This was true, but did not sound nice. This
incident caused the name Truth to be dropped and Top and Bottom again became
standard. Now that the T quark is well established, the name Truth can safely be
brought back, but I don't know if it will, since MGM does other things now.
A Theoretician, who formulates ideas or theories, suggests that to explain certain
natural phenomena, a certain particle must exist. Other scientists and
experimentalists do experiments to look for that particle. In the early 1960's a
theoretician, Murray Gell-Mann, proposed the quark theory. He named the quarks
then even though they had never been observed. It took experimentalists nearly 30
years to find proof of the existence of all six quarks. The Top was the last quark
discovered in two experiments called CDF and D0 at a sister lab to Jefferson Lab,
Fermilab, outside Chicago. They announced their discovery in April, 1994. Many
particles have been discovered by accident during an experiment looking at
something else. The experimenter then gets to name that particle, therefore a lot of
particles have awfully silly names.
• When a neutron undergoes beta decay, it becomes a set
of three particles: proton, electron, anti-neutrino. The
number of quarks is still the same: three. The number of
leptons is the same: zero. An electron has a lepton
number of +1. An anti-neutrino has a lepton number of 1. It is an anti-lepton.
• The neutron is about 0.2% more massive than a proton,
which translates to an energy difference of 1.29 MeV.
• Universe is mostly light (photons ) "...it was light that
then formed the dominant constituent of the universe,
and ordinary matter played only the role of a negligible
contaminant." Reminiscent of "Let there be light...".
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Pair Production : Pair production is the formation or materialization of two
electrons, one negative and the other positive (positron), from a pulse of
electromagnetic energy traveling through matter, usually in the vicinity of an
atomic nucleus. Pair production is a direct conversion of radiant energy to
matter. It is one of the principal ways in which high-energy gamma rays are
absorbed in matter. For pair production to occur, the electromagnetic
energy, in a discrete quantity called a photon, must be at least equivalent to
the mass of two electrons. The mass m of a single electron is equivalent to
0.51 million electron volts (MeV) of energy E as calculated from the
equation formulated by Albert Einstein, E = mc2, in which c is a constant
equal to the velocity of light. To produce two electrons, therefore, the photon
energy must be at least 1.02 MeV. Photon energy in excess of this amount,
when pair production occurs, is converted into motion of the electronpositron pair. If pair production occurs in a track detector, such as a cloud
chamber, to which a magnetic field is properly applied, the electron and the
positron curve away from the point of formation in opposite directions in
arcs of equal curvature. In this way pair production was first detected
(1933). The positron that is formed quickly disappears by reconversion into
photons in the process of annihilation with another electron in matter.
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Presto! Light Creates Matter
As nuclear bombs and many physics experiments show, turning matter into light, heat, and other
forms of energy is nothing new. Now a team of physicists has demonstrated the inverse process-turning light into matter. In the 1 September Physical Review Letters, the team describes how they
collided large crowds of photons together so violently that the interactions spawned particles of
matter and antimatter: electrons and positrons (antielectrons). Physicists have long known that
this kind of conjuring act is possible, but they have never observed it directly.
Working at the Stanford Linear Accelerator Center (SLAC), the 20-physicist collaboration focused
an extremely intense laser beam at a beam of high-energy electrons. When the laser photons
collided head-on with the electrons, they got a huge energy boost, much like ping-pong balls
hitting a speeding Mack truck, changing them from visible light to very high-energy gamma rays.
These high-energy photons then rebounded into the path of incoming laser photons, interacting
with them to produce positron-electron pairs.
Such particle pairs are often spawned in accelerator experiments that collide other particles at
high energies, and photons produced in the collision are the immediate source of the pairs . But in
those experiments, at least one of the photons involved is "virtual"--produced only for a brief
moment in the strong electric field near a charged particle of matter. The SLAC experiment marks
the first time matter has been created entirely from ordinary photons.
Princeton University physicist Kirk McDonald, a spokesman f or the multi-institution collaboration,
says the result, which was completely expected, is only the first step in using powerful lasers and
electron beams to explore the interactions of electrons and photons, described by the theory
known as quantum electrodynamics (QED). "We're exploring new regimes and trying to map out
the basic phenomena," he says. Physicist Tom Erber of the Illinois Institute of Technology is
pleased at the prospect of such experiments. "Hopefully, this will open the door to future
experiments which will approach [new] tests of QED."
• REAL PHOTONS CREATE MATTER. Einstein's equation E=mc2
formulates the idea that matter can be converted into light and vice
versa. The vice-versa part, though, hasn't been so easy to bring
about in the lab. But now physicists at SLAC have produced
electron-positron pairs from the scattering of two "real" photons (as
opposed to the "virtual" photons that mediate the electromagnetic
scattering of charged particles). To begin, light from a terawatt laser
is sent into SLAC's highly focused beam of 47-GeV electrons. Some
of the laser photons are scattered backwards, and in so doing
convert into high-energy gamma ray photons. Some of these, in
turn, scatter from other laser photons, affording the first ever
creation of matter from light-on- light scattering of real photons in a
lab. (D.L. Burke et al., Physical Review Letters, 1 September 1997.)
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LET THERE BE MATTER: IN THE BEGINNING, (SFX: FANRARE) THERE WAS E=MC2. A NEAT LITTLE
EQUATION BY EINSTEIN WHICH SAYS THAT ENERGY AND MASS ARE EQUIVALENT. SCIENTISTS
REALIZED IN THE 1930'S THAT MCDONALD: In principle any kind of mass could be transformed into energy and
vice versa. KIRK MCDONALD IS A PHYSICIST AT PRINCETON UNIVERSITY AND HE SAYS THAT MATTER
TURNS INTO LIGHT ALL THE TIME WHEN ATOMS COMBINE OR PULL APART. BUT TAKING A BIT OF LIGHT
AND TURNING IT INTO A PARTICLE--THAT'S TOUGH. AND IT CERTAINLY SOUNDS WEIRD TO MOST OF
US--THIS IDEA OF JUST CREATING SOMETHING OUT OF THIN AIR. OVER 60 YEARS SINCE SCIENTISTS
FIRST THOUGHT IT COULD BE DONE, MCDONALD IS ONE OF A GROUP OF SCIENTISTS THAT HAS
FINALLY SUCCEEDED. MCDONALD: "In some sense we are one of the slowest confirmations of an idea in
science this century." BUT THAT'S BECAUSE THE EXPERIMENT TOOK VERY MODERN TECHNOLOGY. IT
TAKES A HUGE AMOUNT OF ENERGY TO MAKE A TEENSY PIECE OF MATTER. TO MAKE AN ELECTRON,
MCDONALD NEEDED AS MUCH ENERGY AS IS IN ONE MILLION PHOTONS. AND THEN THE PHOTONS
HAVE TO SOMEHOW BE SQUASHED TOGETHER INTO ONE POINT. MCDONALD: "Ordinarily, . . . particles of
light. . .don't interact with one another. . . if light coalesced the sun wouldn't shine, it would never get here it would
all clump together into some other form of matter." GETTING PHOTONS WITH ENOUGH ENERGY REQUIRES
USING PARTICLE ACCELERATORS. AND GETTING THE PHOTONS ALTOGETHER INTO A SINGLE POINT
REQUIRES CRASHING THE PHOTONS INTO EACH OTHER WITH SOME PINPOINT LASER TECHNIQUES.
IT'S ALL COMPLICATED AND EXPENSIVE ENOUGH THAT YOU'RE NOT GOING TO SEE ANYONE
CREATING MATTER OUT OF THIN AIR ON A REGULAR BASIS ANY TIME SOON.
The Higgs boson, sometimes called the God particle, was first predicted in the 1960s by the British physicist
Peter Higgs. The Higgs mechanism for giving mass to particles was actually first proposed in the context of solid
state physics to explain how particle-like structures in metals can act as if they had an effective mass.
The Higgs boson itself has mass. Theory gives an upper limit for this mass of about 200 GeV (update: As of 10
June 2004, best estimate is 96—117, upper limit is 251 (95% confidence). As of 2002, particle accelerators have
probed energies up to 115 GeV. While a small number of events have been recorded that could be interpreted as
resulting from Higgs bosons, the evidence so far is inconclusive. It is expected that the Large Hadron Collider,
currently under construction at CERN, will be able to confirm the existence of Higgs bosons.
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Research supported by the Office of Science is making progress in the intense
search for the Higgs boson, which may be the force that finally explains why some
fundamental particles have mass, but others do not. Higgs is the last undiscovered
component of the Standard Model, physicists' current theory of matter and the forces
of nature. The model includes three families of particles called quarks and leptons;
bosons carry forces between other particles. The Standard Model predicts a
relationship between the masses of the Higgs boson, the W boson (which carries the
"weak force"), and a particle called the top quark. Precise measurements of the
properties of the top quark and W boson at Fermi National Accelerator Laboratory
and the Zo at the Stanford Linear Accelerator Center in the 1990s significantly
narrowed the predicted range for the mass of the Higgs boson. The SLAC
experiments obtained what remains the most precise prediction of the mass of the
Higgs, hinting that it should be light.
Scientific Impact: These experiments told scientists what mass range to seek in
direct measurements of the Higgs boson; when the Higgs is found, comparisons of
direct and indirect measurements will provide a strong test of the Standard Model.
The results also suggest that the Higgs might be within reach of existing accelerators.
SLD Event Display of a Z particle decaying to two quarks. An electron and positron
travelling in opposite directions (perpendicular to this page) collided at the center of
the detector and annihilated, creating a Z. The Z subsequently decayed to a quark
and anti-quark, which then hadronized to form two jets of particles traveling in
opposite directions. These are the two jets of green tracks seen in this projection