How I learned to stop worrying and love physics

flinkexistenceMechanics

Oct 27, 2013 (3 years and 10 months ago)

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How I learned to stop worrying
and love physics

The Course So Far…


Introduction to the debates



General Epistemology



Epistemology of Science



Epistemology of Religion


From here on ……


The big debates


Physics


Quantum Mechanics, Thermodynamics &
Relativity


Astronomy & Cosmology


Evolution, Creationism and Intelligent Design


Mind and Cognition


Morality, Ethics and Sociobiology


Process thought


Physics


The Beginnings


Assyrians, Babylonians, Egyptians


Astronomy (Agrarian Societies)


Astrology


Mayans, Aztecs


Greeks


Systematized Scientific Thought


Democritus vs. Aristotle (Two World Views)


Astronomy, Mechanics, Optics…….


Ptolemy vs. Aristarchus

9

14

16

28

30

Q/M

Physics

Q/M

Philosophical
Issues

Implications

Discussion

Quiz

Relativity

Thermodynamics

Implications

Discussion

4

6

9

11

13

18

20

Astronomy/
Cosmology

Religious
Cosmologies

Implications

Discussion

Quiz

Evolution

The Science

Creationism

Intelligent

Design

Implications

Discussion

Summary

Discussion

Quiz

Essay Due

Greek Physics


Aristotle


Four Elements (earth, Water, Air,
fire)



Democritus


Atomistic View



Ptolemy


Geo
-
centric Universe



Aristarchus of Samos


Heliocentric Universe

Ideas that prevailed in
antiquity….


Infinitely divisible matter, geocentric
universe, ‘natural state’ of objects


Aristotle and Ptolemy


Dominated thought through the middle
ages


Completely incorrect astronomy and
mechanics


Alternate views present


Why did they not prevail?

The Middle Ages


Rise of the
I
slamic empire



Translations from Greek



Developments in Astronomy, Optics,
Mechanics




Did the ‘scientific method’ develop?

The Scientific Revolution


Astronomy


Copernicus


Heliocentric Universe


Explains rotation of stars etc. in terms of earth’s
movement around the sun


Galileo


Observations

using telescope


Laws of motion


Kepler’s Laws


Tycho

Brahe carefully collected data


Formulated mathematical laws


The Scientific Revolution


Huygens


Wave theory of light


Astronomical observations


Boyle

-
Boyle’s Law

-
Steps towards Atomic Theory


Pascal


Fluid flows


Pascal’s Law





The Scientific Revolution


Newton


Laws of Motion


Law of Gravitation


Kepler’s Laws follow from these general
principles


Corpuscular Theory of Light


Development of Calculus to aid in
understanding physics

Philosophical Underpinnings


Realism


Theories describe the world as it is in itself



Determinism


Present state predicts future state



Reductionism


Whole is the sum of its parts


Demise of Classical Physics


Ultraviolet Catastrophe


Quantization of energy



Nature of Light (Newton or Huygens)


Photoelectric Effect





Nature of Electrons


Double Slit Experiment

The Ultraviolet Catastrophe

Classical physics can describe the shape of the
blackbody spectrum only at long wavelengths.
At short wavelengths there is complete
disagreement.


This disagreement
between observations
and the classical theory
is known as the
ultraviolet catastrophe.

Planck’s Solution

In 1900, Max Planck was able to explain the
observed blackbody spectrum by assuming that
it originated from oscillators on the surface of
the object and that the energies associated with
the oscillators were
discrete
or
quantized:

E
n

= nhf n =
0, 1, 2, 3…

n

is an integer called the
quantum number

h

is
Planck’s constant: 6.62


10
-
34

J

s

f

is the frequency

The PhotoElectric Effect

Around the turn of the century, observations of the
photoelectric effect were in disagreement with the
predictions of classical wave theory.

When light is incident on
a surface (usually a
metal), electrons can be
ejected. This is known
as the
photoelectric
effect.

Photoelectric Effect

Observations of the Photoelectric Effect


No electrons are emitted if the frequency of the
incident photons is below some cutoff value,
independent of intensity.


The maximum kinetic energy of the emitted
electrons does not depend on the light
intensity.


The maximum kinetic energy of the emitted
electrons
does

depend on the photon
frequency.


Electrons are emitted almost instantaneously
from the surface.

The Photoelectric Effect Explained


The photoelectric effect can be understood as follows:



Electrons
are emitted by absorbing a
single photon.



A
certain amount of
energy is
required to remove the
electron from the material.



The
maximum observed kinetic energy is the
difference between the photon energy and
this
energy.

Double Slit Experiment



Electrons through a single slit act as
particle


If we now have two slits close by a
diffraction pattern is observed
i.e

wave
like behavior


If we try and detect which slit the
electron goes through the diffraction
pattern disappears



Double Slit Experiment

The Strange Quantum World


Wave Particle Duality



How to describe systems?



Wave Function describes the state of a
system in a probabilistic sense



Systems exist a superposition of states



Observation collapses to a particular state


Schrodinger’s Cat

Philosophical Underpinnings


Classical Realism


Physical theories describe nature as it is in itself


Instrumentalism


Theories a human constructs for correlating
observations and making predictions


Critical Realism


Physical theories are a partial representation of
limited aspects of the world as it interacts with us


EPR Paradox


Two particles separate with zero initial
momentum


Measure component of momentum of one


Automatically component of momentum of
second is determined !!!!


Action at a distance?


Hidden Variables?



Holistic World?

Two Views


Complementarity (Critical Realism?)


Must consider interaction between subject
and object in an experiment


Conceptual limitation of understanding



Realism


Theories are description of nature in itself


Hidden Variables to explain away apparent
indeterminacy?


Points to Ponder


Does Complementarity imply
instrumentalism?


Complementarity a good paradigm for
science and religion?


Indeterminacy



temporary ignorance?



measurement or conceptual issue?



inherent to nature?


Parts and Wholes


A new paradigm for
understanding the world?