Quantum Theory

Black Body Radiation Temperature determines the wavelength of emitted light. “Red hot”: mostly red light - 3,000 o C. “White hot”: all colors – 6,000 o C. my/blackbody/bbody.html my/blackbody/bbody.html

It was assumed light could have any energy. The math of the theory did not match the distribution of wavelengths observed:

Max Planck solved the black body radiation dilemma He created an equation that fit the observed distribution of radiation. To do so, he had to assume that energy came in packets, called quantum.

Planck’s Constant Frequency/energy = Planck’s constant Planck’s constant (h) is one of the most important constants in nature. (h) = x joule seconds

Photoelectric Effect Certain light beams can knock electrons off of some metals. This was independent of the intensity of the light beam. (total energy) It WAS dependent on the wavelength of the light.

Short wavelengths have larger quanta (packets of energy) to knock off electrons.

Light – particle or wave? Light followed the wave equation defined by James Clark Maxwell. Light also seemed to exist as packets, like particles. The particle/wave designation seems invalid for the subatomic world.

Particles are also Waves 1923: Louise de Broglie found that matter had both particle and wavelike properties. If E = hc/wavelength (from Planck) and E = mc 2 (from Einstein), than wavelength = h/(mass x velocity).

Very small particles exhibit the same wave addition and cancellation characteristics as waves do.

Niels Bohr Planetary Atom Electrons orbit the nucleus in specific circular orbits. Problem: a charged particle in acceleration emits light. Changing direction is a type of acceleration, yet orbiting electrons emitted no light.

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Schrodinger’s Solution The orbit of an electron can only be a whole number multiple of the electron’s wavelength. The orbital is a standing wave of an electron. There is no “changing direction” of the electron.

The electron simply exists in these locations, without actually moving from one point to another.

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Schrodinger wave equations Any system can be treated as a wave equation in quantum mechanics. The orbitals of chemistry are solutions to Schrodinger wave equations.

Electrons materialize from one location to another without passing a plane of zero probability existence. This is just quantum weirdness.

Paul Dirac’s improvements of Schrodinger’s wave equations He generalized the equations to relativistic theory. He mathematically explained electron spin with angular momentum. He postulated the existence of antimatter based on the negative square root of E=mc 2.

Quantum Mechanics gives probabilities 1926, Max Born: the square of the wave equation gave the probability of finding the particle in a given location. Many (Einstein) felt that probability was not good enough.

If we really understood something, we should know what will happen and what is really going on “behind the scenes”.

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Heisenberg Uncertainty Principle We cannot know both the velocity and location of an electron. The more we know about one, the less we know about the other. High energy light gives a better location, but disrupts the velocity.

Low energy light disturbs the velocity less, but gives high uncertainty of location. Lower energy light gives worse resolution. The uncertainty of position times the uncertainty of momentum is greater or equal to Planck’s constant divided by 4p.

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Uncertainty vs. Determinism Uncertainty was not just a result of the crudeness of the instruments, it was a fundamental law of nature. Determinism – the idea that you can state the future if you know everything about the present. Einstein favored determinism, but uncertainty was found to rule.

Double slit experiment The same results are obtained with light, electrons, or any other type of “wave”. ?v=DfPeprQ7oGc ?v=DfPeprQ7oGc How does the particle going through the slit “know” that the other slit exists?

Since the electron, like all matter, has wave characteristics, its final location is defined by the probability given by the square of the wave equation for the given system it is in.

Bell’s Theorem John Bell used a thought experiment and logic to prove that reality is non-local. Non-local means objects are affected by distant objects and events that cannot reach them with a force, because they are outside of the light cone.

Outside the light cone, signals or forces from one object must travel faster than the speed of light to create the observed behavior.

Quantum Entanglement When two particles or events affect each other without any signal or force. Determinism, and our common sense, says that this is totally impossible.

Quantum mechanics predicts when it will or will not happen, and what the probability of the outcome will be. ?v=Jh8uZUzuRhk&feature=rel ated ?v=Jh8uZUzuRhk&feature=rel ated

Collapsing Probability Waves Quantum mechanics says that the measurement of a particle, such as an electron, collapses the probability wave to a single event.

With entangled particles, the measurement of one collapses both of their probability waves simultaneously. Any interaction, human or not, collapses probability waves.

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Quantum Theory and the Universe Cause and effect gives way to probability. The things you do can instantaneously affect things far away (non-local).

Events can happen without a force or signal to cause it to happen - the fabric of space allows, or even causes it to happen. Objects do not always have specific properties until they are interacted with; the properties hang in some sort of limbo.

The Standard Model This is the current quantum theory. Many new subatomic particles have been discovered. There are three families of particles.

Each family contains two of the quarks, an electron (or one of its cousins), and one of the neutrinos. These are the building blocks of all matter.

Four Force Particles Strong force – The gluon holds the nucleus together. Weak force – The W and Z bosons cause radioactivity. Electromagnetism – The photon causes light.

Gravity – The graviton is the cause. Experiments have established all force particles except the graviton. Gravitons are expected to be discovered soon.

Standard Model Equation It uses an input of 19 pieces of information, which are properties of the force and mass particles. It has been flawless at predicting experimental outcomes as probabilities.

Everything that happens in the universe, besides gravity, can be predicted by the Standard Model. Newton’s equations fall out of Standard Model for normal conditions.

Particle Behavior The uncertainty principle allows for extreme particle behavior on the subatomic level.

There is a trade off between the energy a particle has and the time it takes to measure this energy, which allows the energy of a particle to fluctuate wildly over a very short duration of time, called the quantum jitters. “Tunneling” is allowed. 6LKjJT7gh9s&feature=related 6LKjJT7gh9s&feature=related

More Unification Steven Weinberg and his colleagues unified the weak and the electromagnetic forces. They won a Nobel Prize for this work.

Weaknesses of Standard Model It explains how nature behaves, but not why it behaves in the way it does. It does not include gravity; therefore, it cannot be a complete theory of the universe. Its use is primarily for the subatomic level.

A few good web-pages uantum.html uantum.html and.ac.uk/~history/HistTopics/The_Quantu m_age_begins.html and.ac.uk/~history/HistTopics/The_Quantu m_age_begins.html q4ZkM&feature=related q4ZkM&feature=related yt8Kc&feature=related yt8Kc&feature=related

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????? Wild possibilities or psudoscience? 4KLc 4KLc