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Understanding A Quantum Universe one contemporary model of reality based on Quantum Mechanics

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Title: Understanding A Quantum Universe one contemporary model of reality based on Quantum Mechanics


1
Understanding A Quantum Universe(one
contemporary model of reality based on Quantum
Mechanics)
  • By Dr. M.B. Debowski

2
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

3
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.

4
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.

5
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.

6
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.

7
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.

8
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.

9
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.

10
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?

11
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.

12
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

13
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.

14
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.

15
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.

16
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.

17
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.

18
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.

19
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."

20
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.

21
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.

22
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.

23
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.

24
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.
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