41 Early Theories of Matter amp Early Chemistry Alchemy and Related 42 Subatomic Particles amp Nuclear Atom 425 Ultimate Structure of Matter The Standard Model Not in Book Section 41 Early Ideas About Matter ID: 676899
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Slide1
Chapter 4 (Partial)Structure of the Atom
4.1 Early Theories of
Matter (& Early Chemistry – Alchemy and Related)
4.2 Subatomic Particles & Nuclear Atom
4.2.5 Ultimate Structure of Matter – The Standard Model (Not in Book)Slide2
Section 4.1 Early Ideas About Matter
Compare and contrast
the atomic models of Democritus, Aristotle, and Dalton
.Describe the activities related to the chemical sciences that occurred between the time of Aristotle and the early 19th century when Dalton’s theory was published.List the components of Dalton’s atomic theory.Explain how Dalton's theory explains the conservation of mass.
The ancient Greeks tried to explain matter, but the scientific study of the atom began with John Dalton in the early 1800's.Slide3
Section 4.1 Early Ideas About Matter
Identify
the components of Dalton’s theory that are not strictly correct and provide examples of why they aren’t
.
Name the two instruments that are routinely used to obtain images of atoms.Describe the basic operational principles of the Scanning Tunneling Microscope (STM).(Cont.)Slide4
Key Concepts
Democritus was the first person to propose the existence of atoms.
According to Democritus, atoms are solid, homogeneous, and indivisible.
Aristotle did not believe in the existence of atoms.
John Dalton’s atomic theory is based on numerous scientific experiments. The scanning tunneling microscope (STM) and the modified scanning transmission electron microscope (modified STEM) are instruments capable of atomic scale imaging.
Section 4.1 Early Ideas About MatterSlide5
Early Philosophers
Thought matter formed of:
Earth
Air
Fire WaterSlide6
History: Development of Atomic Model
Empedocles
Aristotle
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Atomic Theory Timeline
Democritus
Leucippus
Zeno
J. Dalton
J. Proust
A. Lavoisier
R. Boyle
R. Bacon
Democritus Aristotle Boyle Lavoisier DaltonSlide7
Democritus Greek, 460-370 BC
First to propose matter was not infinitely divisible =
concept of atomSlide8
Democritus, Greek Philosopher
(460-370 BC)
His theory: Matter could not be divided into smaller and smaller pieces forever, eventually the smallest possible piece would be obtained
This piece would be indivisible
Named the smallest piece of matter “atomos,” meaning “not to be cut”Slide9
Democritus – Atomic Theory
To him, atoms were small, hard particles that were all made of same material but were different shapes and sizes
Atoms were infinite in number, surrounded by empty space, and always moving and capable of joining togetherSlide10
Democritus’ Concept of Matter
Matter is
empty space
through which atoms move
Atoms are solid, homogeneous, indestructible, indivisibleDifferent kinds of atoms have different sizes and shapesDiffering properties of matter are due to atoms size, shape, & movementChanges in matter result from changes in groupings
of atoms and not changes in atoms themselvesSlide11
Aristotle
Greek Philosopher
(
384-322 BC)
14 years old when Democritus diedBelieved matter made of 4 basic elements (earth, air, fire and water)Disagreed with Democritus - believed matter was continuous (did not accept idea of the “void”)His ideas endured for 2000 yrsSlide12
Alchemy for 2000 years
Aristotle believed any substance could be
transmuted
(transformed) into any other substance simply by changing relative proportions of the 4 basic qualities
This mindset dominated quest for new substances done by the alchemists Slide13
Alchemy for 2000 years
Idea of
transmutation
laid foundation for alchemy
Alchemists were searching for evolution from ignorance to enlightenment by searching for: elixir of life (source of eternal life/youth)philosopher’s stone (substance to turn base metals into gold; also el. of life)aqua vitae (“water of life” – concentrated ethanol solution – whiskey etc)panacea (substance meant to cure all diseases)
During the search for ability to transmute matter (e.g., change lead into gold),
they did a lot of
good experimentation
that laid foundation for modern scienceSlide14
Alchemy
"The hopeless pursuit of the practical transmutation of metals was responsible for almost the whole of the development of chemical technique before the seventeenth century, and further led to the discovery of many important materials.”
http://www.levity.com/alchemy/Slide15
Alchemy
Popular belief is that Alchemists
made contributions to the "chemical" industries of the day
—ore testing and refining, metalworking, production of gunpowder, ink, dyes, paints, cosmetics, leather tanning, ceramics, glass manufacture, preparation of extracts, liquors, and so on
Alchemists contributed distillation to Western Europehttp://en.wikipedia.org/wiki/AlchemySlide16
Science During 1600’s to1800’s
Scientists were discovering concepts and relationships by doing large, basic experiments with stoves, pots, ovens, and basic glassware, much of which had been developed by alchemists
With observable properties came explanations!Slide17
Robert Boyle 1627-1691
Sometimes referred to as Father of Modern Chemistry
One of first to publish all experimental details of his work, including experiments that did not work
Boyle revived Democritus’ ideas by proposing that a substance was
not element if it were made of two or more componentsSlide18
Robert Boyle ~ 1660
Best known for his quantitative work with gases (Boyle’s Law)
Still believed in alchemy – that metals could be converted into gold
Was first to propose existence of elements in the modern sense
Boyle considered a substance to be an element unless it can be broken down into simpler substances Slide19
Marie-Anne and Antoine Lavoisier
1743-1794
Mother and father of modern chemistry?
Studied various types of reactions involving oxygen: respiration, burning, rustingSlide20
Antoine Lavoisier (France) ~1760
Studied chemical reactions quantitatively
Credited with being first to propose law of conservation of matterSlide21
Lavoisier
Was sure that air contained > one element
Was able to determine amount of “reacting component” in air - named this component oxygenSlide22
Lavoisier
Pictured experiment demonstrates Law of Conservation of MassSlide23
Lavoisier
Law of Conservation of Mass
There is no detectable change in total mass of materials when they react chemically to form new materials
Mass of products will equal mass of reactants in a chemical reaction
During chemical reaction, matter neither created nor destroyedSlide24
Joseph Proust (France, 1754-1826)
~1794 Studied chemical composition of compound copper carbonate (CuCO
3
)
Found all samples of CuCO3 had same relative composition of elements by mass: 5.3 parts Copper: 4 parts Oxygen: 1 part CarbonThis finding led to law of definite proportionSlide25
John Dalton
(1766-1844)
A schoolteacher!
Devised Law of Multiple Proportions “when two elements form more than one compound, they come together in whole number ratios”Slide26
John Dalton (1766-1844)
Used work of Lavoisier, Proust, and Gay-Lussac to revive Democritus’ idea that matter was made of atoms
Based much of his theory on
Law of Conservation of Mass
Law of Constant Composition Slide27
John Dalton’s Atomic Theory
Matter made up of atoms. Atoms of given element identical.
Atoms can’t be created, destroyed or divided.
Atoms may combine in the ratio of small, whole numbers to form compounds. In chemical reactions, atoms are separated, combined, or rearranged.
All atoms of one element have the same mass. Atoms of two different elements have different masses.Slide28
John Dalton’s Atomic Theory
Matter composed of extremely small atoms
Atoms of given element are identical
Atoms of different elements are different
Can’t be created, divided, or destroyedDifferent atoms combine in whole number ratios to form compounds
In chemical reactions, atoms are separated, combined or rearrangedSlide29
Dalton’s Atomic Theory
Experimental evidence
looked at mass ratios of compounds
Theory explained conservation of mass
Element A
Element B
Compound AB
2
mass = m
A
mass =
m
A
+ m
B
mass = m
BSlide30
Dalton’s Atomic Theory
Slightly wrong about
Indivisibility of atoms (
subatomic particles
) All atoms of same element having identical properties (isotopes) Although atoms themselves not created or destroyed, slight changes in mass occur as energy absorbed/released (thanks to James Kong & A Einstein)“Exotic” matter (neutron stars, plasmas, dark matter, etc)
not composed of atoms as such (thanks to Adam Sorrentino)Slide31
Atom Definition
Smallest particle of an element that
retains the property of the element
This simple definition does not deal with the reality uncovered by modern nanotechnology research – individual atoms or small clusters of atoms of an element do not always behave in the same way as a bulk sample of the elementSlide32
Imaging Atoms
Atom diameters ~ 0.1 to 0.5 nm (water molecule diameter ~0.3 nm)
Techniques exist to “image” atoms (not really “seeing” them in the conventional sense of the word)
Not readily available until STM commercialized (see following)
http://en.wikipedia.org/wiki/Scanning_tunneling_microscopeSlide33
Schematic of STM
http://www.iap.tuwien.ac.at/www/surface/STM_Gallery/stm_schematic.htmlSlide34
Based
on “
tunneling current
”
Starts to flow when sharp tip approaches conducting surface at distance of ~ 1 nmCurrent extremely sensitive to distanceTip mounted on a piezoelectric tubeAllows tiny movements by applying a voltage at its electrodes
STM OperationSlide35
Electronics control tip position so tunneling current (tip-surface distance) is kept constant while scanning a small area of the sample
Movement recorded - displayed as an image of the surface topography
Under ideal circumstances
individual atoms
of a surface can be resolvedSTMSlide36
STM – Moving Atoms
Modified STM can be used as a tool for picking up, moving, and putting down
atomsSlide37
Imaging Atoms: Modified Scanning Transmission Electron Microscope
In 2002, IBM researchers and their collaborators
modified
an electron microscope; allowed
clear images at the atomic scale to be madeModified electron microscope is second major instrument to provide images of atomsCan’t be used to move atoms like STM type instrumentshttp://physicsworld.com/cws/article/print/23440Slide38
Practice
Early & current theories of matter
Problems 1- 5, page 91
Problems 29 – 33, page 112Slide39
Chapter 4 (Partial)Structure of the Atom
4.1 Early Theories of Matter
4.2 Subatomic Particles & Nuclear Atom
4.2.5 Ultimate Structure of Matter – The Standard Model (Not in Book)Slide40
Section 4.2 Defining the Atom
Define
atom
.
Distinguish between the subatomic particles in terms of relative charge and mass.Describe the structure of the atom, including the locations of the subatomic particles and the relative sizes of the atom and the nucleus.Identify the scientists that contributed to the discovery of the nature of the atom and be able to describe their specific contribution and the experiment on which their discovery was based.
An atom is made of a nucleus containing protons and neutrons; electrons move around the nucleus.Slide41
Key Concepts
An atom is the smallest particle of an element that maintains the properties of that element
.
Electrons have a 1– charge, protons have a 1+ charge, and neutrons have no charge.
An atom consists mostly of empty space surrounding the nucleus; the size of the atom relative to the size is the nucleus is about 10,000.
Section 4.2 Defining the AtomSlide42
Crookes (Cathode Ray) Tube
See page 92, Figure 4-7Slide43
Effect of Electric and/or Magnetic Fields on Electron TrajectorySlide44
Discovering the Electron
From
cathode ray tube
experiments, it was determined that rays:
Were actually stream of charged particles Carried negative charge
J J ThomsonSlide45
Discovering the Electron
Thomson (1856-1940)
Measured effect of electric and magnetic fields on cathode ray to determine
ratio of charge to mass
(q/m) for electronFrom comparison with known (q/m) values, concluded that electron mass much less than hydrogen atom must be a subatomic particleDid not
determine actual value of massSlide46
Discovering the Electron
Millikan (1868-1953)
Determined
charge
on electron from oil drop experiment (see following) From mass/charge ratio (previously determined by Thomson), calculated electron mass, me me = 1/1840 mass of hydrogen atomSlide47
Millikan’s Oil Drop Experiment
Ions
produced by energetic radiation
(X-rays)
Some ions attach to oil droplets, giving them a net chargeFall of droplet in electric field between the condenser plates is speeded up or slowed down, depending on the magnitude and sign of
charge on dropletSlide48
Millikan’s Oil Drop Experiment
Electrically charged condenser plates
Atom
izerSlide49
Millikan’s Oil Drop Experiment
Analyzed data from a large number of droplets
Concluded that the
magnitude
of charge (q) on a droplet is an integral multiple of electronic charge (e) q = n e
(where n = 1, 2, 3, . . . ).Slide50
AKA “chocolate chip cookie dough” model
Proposed by Thomson
Plum Pudding Atomic Model
Smeared out “pudding” of positive charge with negative electron “plums” imbedded in it
+
Electrons
(negative)
+
+Slide51
Nuclear Atom (Rutherford)
Rutherford devised test to distinguish between plum pudding and nuclear models
Plum pudding –
cloud
of positive charge Nuclear – concentrated positive chargePlum pudding model advantage: + charges can avoid each otherAlpha particle deflection from gold foil
Concluded that there must be nucleusSlide52
Rutherford’s Experiment
Lead Box
Radioactive
Sample
Gold
Foil
Fluorescent
Screen
Alpha Particles
Striking ScreenSlide53
Rutherford Scattering Experiment
Most go straight
through
Some deflected
Some bounced back!Slide54
Rutherford Scattering Experiment
Over 98% of alpha particles went straight through
About 2% of alpha particles went through but were deflected by large angles
About 0.01% of alpha particles bounced off gold foil
“...as if you fired a 15” canon shell at a piece of tissue paper and it came back and hit you.”Slide55
Rutherford Scattering Experiment
Alpha particles should pass right through the atoms with minimum deflection
Expected Result
(plum pudding)Slide56
Rutherford Scattering Experiment
Expected Result
(plum pudding)
Actual Result
(nuclear model)Slide57
Rutherford Conclusions
Atoms contain a positively charged, small core, called
nucleus
Note: structure of nucleus (as protons) not yet known
Most of atom is empty spaceSlide58
Discovery of Protons
Protons
(discovered 1920 – Rutherford)
Nucleus contained positively charged particles called protons Charge equal and opposite to that of electronSlide59
Missing Anything?
Shouldn’t protons repel each other?
Since electrons weigh nothing compared to protons…
If beryllium atom has 4 protons, mass should be ~ 4
amuActual mass 9.01 amu! Where is extra mass coming from?Need more experiments!Slide60
Discovery of Neutron
Neutron
(discovered 1932 – James Chadwick)
Nucleus contained subatomic particles called neutrons
No chargeMass nearly equal to that of protonSlide61
General Features of the AtomSlide62
Nuclear Atom – Relative Sizes
If entire atom were represented by a room, 5 m x 5 m x 5 m, the nucleus would be about the size of a period in the textbook
Nucleus diameter is ~ 1/10,000 diameter of an atomSlide63
Atom Components
See table page 97, table 4-1
Particle Symbol Relative mass
Electron e
- 1/1840 Proton p+ 1.000 Neutron n0 1.001Slide64
Summary: key events in discovery of nature of matter for chemists
~400 BC
Democritus’ Atomic Theory (not accepted)
~350 BC
Aristotle elements: earth, air, fire, & water
1803
John Dalton’s Atomic theory began forming
1897
J. J. Thompson discovers electron
1910
Robert Millikan determines charge on electron
1911
Ernest Rutherford discovers positive nucleus
1919
Ernest Rutherford discovers proton - evidence for proton as a constituent of nucleus
1932
James Chadwick discovers neutronSlide65
Practice
Subatomic particles & nuclear atom
Problems 6 - 9, page 97
Problems 34 - 46, page 112Slide66
Chapter 4 (Partial) - Structure of the Atom
4.1 Early Theories of Matter
4.2 Subatomic Particles & Nuclear Atom
4.2.5 Ultimate Structure of Matter – The Standard Model (Not in Book)Slide67
Section
4.2.5 Ultimate Structure of Matter – The Standard Model
List
and describe the fundamental particles of nature.
List the four fundamental forces and their relative strengths; know that bosons are the carriers of force.Describe hadrons, baryons, mesons, quarks and leptons and be able to identify their component particles (if they are not themselves fundamental).
The Standard Model describes the fundamental particles of nature and the forces that act between particles.Slide68
Section
4.2.5 Ultimate Structure of Matter – The Standard Model
List
the 6 kinds of quarks and the 6 kinds of leptons.
Describe how the proton, the neutron and the electron fit into the classification of matter under the Standard Model.Describe the nature of antimatter and the method by which is was both predicted and experimentally verified.Describe the role that large particle accelerators such as the Large
Hadron Collider (LHC) play in discovering new information about the nature of matter.Slide69
4.2.5 Ultimate Structure of Matter – The Standard Model (Not in Book)
Standard Model Intro – Particles & Forces
The Emptiness of Matter
Fundamental Forces
Sub-structure of particlesMatter and Anti-MatterTracing Development of Ideas via Nobel PrizesTools of the Trade – Fermilab and CERN (LHC)Slide70
Beyond proton/neutron/electron Picture
Textbook, page 114
“... scientists have determined that protons and neutrons have their own structures. They are composed of subatomic particles called quarks. These particles will not be covered in this textbook because scientists do not yet understand if or how they affect chemical behavior. As you will learn in later chapters, chemical behavior can be explained by considering only an atom’s electrons .”Slide71
Beyond proton/neutron/electron Picture (not in book)
To understand nucleus and how some nuclear radiation processes occur, need to examine both
structure of nucleons
(proton, neutron) and
forces acting at nuclear distancesThe standard model of physics attempts to describe all known forces and elementary particlesSlide72
What Is Matter ?
Matter is all the “stuff” around you!
Big picture (from standard model):
Hadrons
Matter
Leptons
Baryons
Mesons
Charged
Neutrinos
Forces
Weak
EM
Strong
Gravity
Quarks
Anti-Quarks
Elementary ParticlesSlide73
Standard Model Summary
The
Standard Model
(
SM) is our current best description of the particles of which matter is made and the forces which govern these particlesSM describes 4 fundamental forces SM describes 12 elementary particles: 6 kinds of quarks and 6 kinds of leptons (not counting anti-particles)Particles come in two major categories: hadrons and leptonsSlide74
HadronsSlide75
Particles Built from Quarks - Hadrons
Hundreds of hadrons have been observed
Except for proton & neutron, they are unstable - half lives < 0.1
sFree neutron (outside nucleus) is unstable – half life 10.2 minSlide76
Particles in Standard Model
Six
leptons
are all
elementary particles – includes the electronAll other particles (hadrons) are composed of combinations of quarks (6 kinds) – isolated quarks are not permittedClass of hadrons called
baryons composed of 3 quarks – includes proton & neutron
Class of hadrons called
mesons
composed of 2 quarks (quark + anti-quark)
“Ordinary” matterSlide77
Dimensions of Subatomic ParticlesSlide78
If protons and neutrons were 10 cm across, then quarks and electrons would be < 0.1 mm in size and entire atom would be ~ 10 km across
Structure Within the AtomSlide79
Space
is mostly “empty space”Slide80
Atoms > 99.999% empty space
Electron
NucleusSlide81
Protons & Neutrons are > 99.999% empty space
g
u
d
u
Quarks make up negligible
fraction of protons volume !!
ProtonSlide82
The Universe
The universe and all the
matter in it is almost all
empty space !
(YIKES)Slide83
Why does matter appear
to be so rigid ?
Forces, forces, forces !!!!
Primarily strong and electromagnetic forces which give matter its solid structure
Strong force defines nuclear sizeElectromagnetic force defines atomic sizeSlide84
Standard Model
Four Fundamental Forces
In order of decreasing strength:
Strong – binds nucleons Electromagnetic – “opposites attract”Weak – involved in radioactive decay (beta decay)Gravity
Forces arise through exchange of a mediating field particle (a boson)Slide85
Four Fundamental Forces
?Slide86
Forces and Particles
Gravity and electromagnetic force act between all particles with mass and charge, respectively
Leptons not composed of quarks, so aren’t subject to strong force, but are subject to weak force
Quarks subject to all four forces
Attractive force between nucleons (protons, neutrons) is byproduct of strong force, since nucleons are composed of quarksSlide87
The Nucleus
Concentrated positive charge in nucleus
Nucleus should repel and blow apart
But nucleons have a deeper structure
Proton
NeutronSlide88
Standard Model - Forces
Neutrons and protons in nucleus held together by
strong force,
which has a short range
Strong force able to overcome strong electric repulsion of + charged protonsElectromagnetic (EM) force between charged particles (electrons attracted to nucleus) Weak force involved in neutron decay – involves changing one type of quark into 2nd
type with electron emission Matter mostly empty space; forces, especially EM forces, make it seem like it isn’tSlide89
Forces In The Atom
Electrons held in place by
electromagnetic force
Nucleons held together by
strong force
Force
Carrier Particles (Bosons)
Strong
Gluons
Electromagnetic
Photons
Gravity
Gravitons?
Getting weakerSlide90
Standard Model
Fundamental
Particles and Force Carriers
All 6 quarks and 6 leptons have corresponding
antiparticles with opposite chargeSome particles are their own antiparticlesSlide91
Standard Model - Generations
EM
Strong
Higgs Boson (gravitron) ??
WeakSlide92
Standard Model Summary
Up
&
down quarks
(in the form of neutrons and protons) and electrons are constituents of ordinary matterIndividual quarks cannot be isolatedOther leptons and particles containing quarks can be produced in cosmic ray showers or in high energy particle accelerators; these particles are all short-livedEach particle has corresponding antiparticleSlide93
Matter & Forces from Standard Model
Hadrons
Matter
Leptons
Baryons
Mesons
Charged
Neutrinos
Forces
Weak
EM
Strong
Gravity
Quarks
Anti-Quarks
Proton & neutron in this group
Electron in this groupSlide94
Gen
I
II
III
Each generation is more massive – takes higher energy to createSlide95
Gen
I
II
IIISlide96
Proton made of three
quarks
One
Down
Quark
Two Up Quarks
Up quark has charge +
2/3
and mass of (approximately)
1/3
Down quark has charge –
1/3
and mass of (approximately)
1/3
Mass =
1/3
+
1/3
+
1/3
= 1
Charge =
2/3
+
2/3
–
1/3
= +1
The Proton – Not ElementarySlide97
The Neutron – Not Elementary
Neutron also made of three
quarks
Two Down Quarks
One Up Quark
Mass =
1/3
+
1/3
+
1/3
= 1
Charge =
2/3
–
1/3
–
1/3
= 0
Neutrons can decaySlide98
Matter - Elementary Particles
Proton & neutron are both baryons
Proton: 2 up quarks and 1 down quark
Neutron: 1 up quark and 2 down quarks
The three elementary particles that make up ordinary matter (atoms) are the up quark, the down quark, and the electronPhysicist’s perspective: ordinary matter is composed of 2 kinds of baryons and one type of leptonSlide99
neutron
proton
Beta Decay In Neutron
electron
neutrino
W
–
boson
Example of
weak force
, of which W
–
is the bosonSlide100
Antimatter – Paul Dirac
In 1928, wrote down equation which combined
quantum theory
(developed in 1920s by Schrodinger and Heisenberg) and
special relativity (1900s, Einstein), to describe behavior of electronEquation could have two solutions, one for electron with positive energy, and one for electron with negative energyBut in classical physics (and common sense!), energy of particle must always be a positive number!http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history01.htmlSlide101
Antimatter – Paul Dirac
Dirac interpreted this to mean that
for every particle that exists there is a corresponding antiparticle
, exactly matching the particle but with opposite charge
For electron, for instance, there should be an "antielectron" identical in every way but with a positive electric chargeIn Nobel Lecture, Dirac speculated on existence of completely new Universe made out of antimatter!http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history01.htmlSlide102
Antimatter – Carl Anderson
1932, young professor at Caltech, studied showers of cosmic particles in cloud chamber; saw track left by "something positively charged, and with the same mass as an electron"
After nearly 1 year of effort and observation, decided tracks were actually
antielectrons
, each produced alongside an electron from impact of cosmic rays in cloud chamberCalled antielectron "positron", for its positive charge. discovery gave Anderson the Nobel Prize in 1936 and proved existence of antiparticles as predicted by Dirachttp://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history01-a.htmlSlide103
Anderson's cloud chamber picture of cosmic radiation from 1932 showing for first time the existence of anti-electron
Particle enters from bottom, strikes lead plate in middle and loses energy as can be seen from greater curvature of upper part of track
http://www.aps.org/publications/apsnews/200408/history.cfm
http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history01-a.html
Antimatter – Carl AndersonSlide104
Standard Model Development
Developed
and verified by
careful analysis of high energy physics experiments (particle accelerators and colliders) along with further development and refinement of quantum mechanics
Also requires improved experimental equipment, methods, analysis techniquesSlide105
Current Work
Large accelerator experiments at
Fermilab
(Illinois) [stopped operation Oct 2011] and at CERN (Switzerland/France)
in the Large Hadron Collider (LHC) done to search for new particles and test Standard Model predictionsSlide106
LHC
Technology Review (MIT) May/June 2008 By Jerome Friedman
The recently completed
Large Hadron Collider, the world's most powerful particle accelerator and most ambitious scientific instrument, is being readied to address some of the deepest questions in physics. Hundreds of feet below the surface of the earth, straddling the Swiss-French border near Geneva, it will smash counter-rotating, seventrillion-electron-volt beams of protons against one another in a 27-kilometer ring of superconducting magnets.Slide107
LHC
With this immense energy, the LHC will be capable of producing new types of particles that are thousands of times heavier than the proton. And it will enable physicists to study phenomena at one-ten-billionth the scale of the atom.
The science will be carried out with
five multisystem particle detectors
, the most massive of which are Atlas and CMS. Atlas is comparable in size to a seven-story building, 135 feet long and 75 feet wide; CMS, a somewhat smaller but heavier detector, weighs more than one and a half times as much as the Eiffel Tower. Slide108
Compact Muon Solenoid
CMS (high energy particle physics detector) at CERN lab (Geneva
)
An example of one of the LHC particle detectorsSlide109
END