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Understanding A Quantum Universe(one

contemporary model of reality based on Quantum

Mechanics)

- By Dr. M.B. Debowski

Contents

- Slide 03 Outcomes
- Slide 04 Introduction
- Slide 05 Required Prior Knowledge
- Slide 06 Defining Quantum Mechanics
- Slide 07 Viewing Reality
- Slide 08 The Nature Of Models
- Slide 09 Development Of The Model
- Slide 10 Spectroscopy
- Slide 11 Need For A New Theory
- Slide 12 The Origins Of Quantum Theory
- Slide 13 Electromagnetic Waves From Atoms
- Slide 14-17 Essential Components Of The Quantum

Mechanical Model - Slide 18-20 Detailing The Quantum Mechanical

Model - Slide 21 Science Fiction Becomes Science Fact
- Slide 22 The Phenomenon Of Life
- Slide 23 Conclusion
- Slide 24 Review Questions

Outcomes

- By the end of this presentation participants will

be able to - define quantum mechanics
- list the historical development of this model
- clarify the meanings of the key terms in this

model - explain the workings of the model
- write down some of the consequences of this model

including its strengths, limitations and

practical uses.

Introduction

- Have you ever marvelled at the pretty colours we

see in a soap bubble. It is this very feature

which has rocked the world, turned science

upside down and made science fantasy into science

reality. We call the model that explains this and

many other phenomena Quantum Mechanics.

Required Prior Knowledge

- Sir Isaac Newton appears to have been the first

noted scientist to believe that light consisted

of particles. He called them corpuscles.

Everything discovered up to 1888 suggested that

Newton had been entirely wrong to regard light as

corpuscular. Then it was discovered that when

light strikes an electrical conductor it causes

electrons to move away from their original

positions. That phenomenon could only be

explained if the light delivered energy in

definite packets. In a photoelectric device

intensity of light controls the current produced,

but frequency of light controls the voltage

produced. This appeared to raise a contradiction

when compared to sound waves and ocean waves,

where only intensity was needed to predict the

energy of the wave. In the case of light,

frequency appeared to predict energy. Something

was needed to explain this phenomenon and also to

reconcile experiments that had shown light to

have a particle nature with experiments that had

shown it to have a wave nature.

Defining Quantum Mechanics

- Quantum mechanics is, at least in part, a

mathematical machine or model for predicting the

behaviors of microscopic particles and a basis

for measuring instruments we use to explore and

predict those behaviors. In that capacity, it is

spectacularly successful in terms of power and

precision, head and shoulders above any theory we

have - ever had.

Viewing Reality

- Quantum mechanics enables us to understand the

dynamics of electrons, protons and other

fundamental particles. This model only holds true

for inanimate objects as the dynamics we see

are the product of the disordered motion of

billions of particles In other words what we

observe in these inanimate objects are a kind of

average dynamics. At the macroscopic level then,

we see patterns and order, while at the molecular

level there is only chaos.

The Nature Of Models

- Make sure you dont confuse reality with models.

The quantum mechanics model of reality is simply

that a model that seems to be able to explain

and predict features of our universe. Just as in

a toy battle ship model it is not meant to be

real but simply be a tool to help us understand

and predict phenomena.

Development Of The Model

- Founding experiments
- (1805) Thomas Young's double-slit experiment

demonstrates the wave nature of light - (1896) Henri Becquerel discover radioactivity
- (1897) Joseph John Thomson's cathode ray tube

experiments discover the electron and its

negative charge. - The study of black body radiation between 1850

and 1900, which could not be explained. - (1909) The photoelectric effect Einstein

explained this using the concept of photons,

particles of light with quantized energy. - (1911) Robert Millikan's oil-drop experiment,

which showed that electric charge occurs as

quanta (whole units), Ernest Rutherford's gold

foil experiment disproved the plum pudding model

of the atom which suggested that the mass and

positive charge of the atom are almost uniformly

distributed. - Professor Walter Ernhart-Plank's Proton Collapse

experiment disproved the Rutherford model and

temporarily cast doubt on the distribution of

protons throughout an atom. - (1920) Otto Stern and Walter Gerlach conduct the

Stern-Gerlach experiment, which demonstrates the

quantized nature of particle spin - (1927) Clinton Davisson and Lester Germer

demonstrate the wave nature of the electron 1 in

the Electron diffraction experiment - (1955) Clyde L. Cowan and Frederick Reines

confirm the existence of the neutrino in the

neutrino experiment - (1961) Claus Jönssons double-slit experiment

with electrons.

Spectroscopy

- It is fairly easy to see a spectrum produced by

sunlight (white light) when it passes through the

curved surface of a bubble of soapy water, a

prism, the beveled edge of a mirror, a special

pane of glass, or through drops of rain to form a

rainbow. This was displayed and explained by

Young in 1805. - When samples of single elements are energised

they emit light. They emit light at several

characteristic frequencies. The frequency profile

produced is characteristic of that element. NASA

photo of the bright-line spectrum of hydrogen. - How are both emission and absorbtion spectra

explained?

Need For A New Theory

- The interference that produces colored bands on

bubbles cannot be explained by a model that

depicts light only as a particle. It can only be

explained by a model that depicts light as a

wave. The drawing here shows sine waves that

resemble waves on the surface of bubble being

reflected from two surfaces produced by the curve

of a film and consequently producing different

wavelength and hence colours.

The Origins Of Quantum Theory

- Quantum mechanics developed from the study of

electromagnetic waves through spectroscopy which

includes visible light seen in the colors of the

rainbow, but also other waves including the more

energetic waves like ultraviolet light, x-rays,

and gamma rays plus the waves with longer

wavelengths including infrared waves, microwaves

and radio waves. Relation between a cycle and a

wave half of a circle describes half of the

cycle of a wave

Electromagnetic Waves From Atoms

- The characteristic emissions of elements suggest

a specific atomic structure. At an atomic level

the wavefunctions of an electron in a hydrogen

atom possessing definite energy (increasing

downward n1,2,3,...) and angular momentum

(increasing across s, p, d,...). Brighter areas

correspond to higher probability density for a

position measurement. Wavefunctions like these

possess a sharp energy and thus a sharp

frequency. The angular momentum, energy and

consequent wavelength are exact figures.

Essential Components Of The Quantum Mechanical

Model 1

- Uncertainty principle
- In 1927, Heisenberg stated
- "You can say, well, this orbit is really not a

complete orbit. Actually at every moment the

electron has only an inactual position and an

inactual velocity and between these two

inaccuracies there is an inverse correlation."The

consequences of the uncertainty principle were

that the electron could no longer be considered

as being in an exact location in its orbital.

Rather the electron had to be described by every

point where the electron could possibly inhabit.

This is called a probability distribution. - Classical physics since Newton assumed that if

you know the position of stars and planets and

details about their motions that you could

predict where they will be in the future. For

subatomic particles, Heisenberg denied this

notion showing that due to the uncertainty

principle - one cannot know the precise position and momentum

of a - particle at a given instant, so its future motion

cannot be - determined, but only a range of possibilities for

the future - motion of the particle can be described.

Essential Components Of The Quantum Mechanical

Model 2

- In 1925 Heisenberg published a paper entitled

"Quantum-mechanical re-interpretation of

kinematic and mechanical relations. This began

the age of quantum mechanics. The consequence of

this article was for scientists to "discard all

hope of observing hitherto unobservable

quantities, such as the position and period of

the electron," and restricted research to actual

observable quantities. - Heisenberg approached quantum mechanics from the

perspective that an electron was an oscillating

charged particle. Amplitudes of position and

momentum that have a period of 2 p like a cycle

in a wave. Heisenberg described the particle-like

properties of the electron in a wave as having

position and momentum in his matrix mechanics.

Matrix mechanics was the first complete

definition of quantum mechanics, its laws, and

properties that described fully the behavior of

the electron. It was later extended to apply to

all subatomic particles. - Schrödinger wave equation
- Having established that particles could be

described - as waves in 1925 Erwin Schrödinger analyzed what

an - electron would look like as a wave around the

nucleus of - the atom. Using this model, he formulated his

equation - for particle waves.

Essential Components Of The Quantum Mechanical

Model 3

- Wavefunction collapse
- The measurement of the position of the particle

nullifies the wave-like properties and

Schrödinger's equation then fails. Because the

electron can no longer be described by its

wavefunction when measured due to it becoming

particle-like, this is called wavefunction

collapse. - Eigenstates and eigenvalues
- The word eigenstate is descriptive of the

measured state of some object that possesses

quantifiable characteristics such as position,

momentum, etc. Quantum mechanics affirms that it

is impossible to pinpoint exact values for the

momentum of a certain particle like an electron

in a given location at a particular moment in

time, or, alternatively, that it is impossible to

give an exact location for such an object when

the momentum has been measured. Due to the

uncertainty principle, statements regarding both

the position and momentum of particles can only

be given in terms of a range of probabilities, - A definite value, such as the position of an

electron that has been successfully located, is

called the eigenvalue of the eigenstate position.

Essential Components Of The Quantum Mechanical

Model 4

- The Pauli exclusion principle
- The Pauli Exclusion Principle states that no

electron (or other fermion) can be in the same

quantum state as another within an atom. This

principle has an effect on the probability for

the distribution of electrons. - Dirac wave equation
- In 1930, Paul Dirac combined Heisenberg's matrix

mechanics with Schrödinger's wave mechanics into

a single quantum mechanical representation in his

Principles of Quantum Mechanics. The quantum

picture of the electron was now complete. - Quantum entanglement
- Quantum entanglement means that when there is a

change in one particle at a distance from another

particle then the other particle instantaneously

changes to counter-balance the system. In quantum

entanglement, the act of measuring one entangled

particle defines its properties and seems to

influence the properties of its partner or

partners instantaneously, no matter how far apart

they are. Because the two particles are in an

entangled state, changes to the one cause

instantaneous effects on the other.

Detailing The Quantum Mechanical Model 1

- In quantum systems, fundamental particles exist

as ghostly "super-positions" where they can be in

a billion different places at once or in a

billion different states at once. - Physicists certainly don't fully understand

quantum mechanics but this model is

unquestionably accurate in its ability to predict

properties and behaviours. Nobody can agree on

what it really means for our view of reality. In

some interpretations, observations by conscious

beings make the world "real." In - others, signals travel backward in time
- to connect every particle in the universe.

Detailing The Quantum Mechanical Model 2

- One interpretation is that there exists a

multi-verse (as opposed to a universe) in which

everything that can happen really does happen --

but in parallel universes. Although our conscious

self inhabits only our own universe --

fundamental particles inhabit the entire

multi-verse. This property allows them to occupy

multiple places or states simultaneously Each

place or state is in a parallel universe. - But what makes an object drop out of the

quantum world? Most physicists agree that systems

enter quantum states when they become isolated

from their environment and pop out of the

multi-verse when they exchange significant

amounts of energy with their environment, an

interaction that is termed "quantum measurement."

Detailing The Quantum Mechanical Model 3

- It has come as a surprise to many scientists that

Quantum Mechanics rules behaviour over bigger

systems also. German scientists have recently

demonstrated that a single fullerene molecule (

which is composed of a sphere of 60 carbon atoms

and is often called the "bucky ball"), can be in

two places at once.

Science Fiction Becomes Science Fact

- Many people are familiar with Einsteins theory

of relativity. It involves the bending of time

and space. Much less well known is that he also

helped to found quantum mechanics. - Quantum mechanics is so alien to Newtonian

(conventional) reality models that even Einstein

couldnt accept many of its implications. In

quantum mechanics, for instance, every option

that can happen in a system does happen,

simultaneously. When an electron or proton is

placed at a crossroads where it can travel to the

right or to the left, it goes both ways.

The Phenomenon Of Life

- It is important to note that properties of

materials we define as alive seem to

diametrically oppose those predicted by quantum

mechanics. These property variations are

explained because the fundamental structure of

living materials is ordered rather than random as

in inanimate objects. Inside living cells, there

is order right down to the level of the single

molecule that determines the form of every

creature that lives or has ever lived. Living

dynamics consequently are not a product of

inanimate chaos, but rather the product of highly

structured actions directed by the molecular

ringmaster DNA. I shall address modifications

and consequences of this model for life systems

in a subsequent presentation.

Conclusion

- Our Creator has made existence so incredible that

the more we learn, the more Creation constantly

stretches our understanding of His power. - The secrets of existence are hidden all around us

and may be unlocked by answering questions as

simple as Why are there colours in a bubble? - So, welcome to a new Reality, one bounded by the

Quantum Mechanical model a multi-verse of

surreal objects both there and not there - at any instant.

Review Questions

- In one sentence define quantum mechanics.
- List the major historical development stages of

this model. - Clarify the meanings of five key concepts in

this model. - In one paragraph explain the workings of the

model. - Write down two strengths of this model.
- Write down two limitations of this model.
- Write down two practical uses (or understandings)

from this model.