Category Archives: Physics

Schrödinger’s Cat

Now let’s look at another thought experiment, that of Schrödinger’s Cat. This thought experiment is supposed to confound the micro and macro worlds of quantum physics and ordinary, human-size physics. A cruel device is built consisting of a closed box which contains a sample of radioactive material, a mechanism to release poison into the box if an atom of the radioactive material decays, a living cat, and a door that must be opened to reveal the condition of the cat to an external observer.

The story of the experiment goes that if the observer waits to open the box until there is a 50% probability that an atom decays, the state of the cat (hidden in the unopened box) to the observer will be both alive and dead. The cat’s so-called wave-function will be a superposition of the wave-function of a live cat and that of a dead cat, which will collapse into one or the other only by the opening of the door and the observation of the actual condition of the cat. This is called the Copenhagen Interpretation.

Some say that the detector of the poison release mechanism will be the true observer in this experiment, and before the external observer opens the door the cat will be definitely alive or dead because of the action of the mechanism. This might be considered the objective collapse theory. Others say that the world splits in two between a world where the cat is alive and one where the cat is dead. This is called a many-worlds interpretation.

There seems to me a similarity between Maxwell’s Demon and Schrödinger’s Cat. The fourfold elements of the experiment are shown above, but now consider these elements in a system in terms of Aristotles’s Four Causes. The material causes are the discreet constituents of the experiment, everything from box to atoms to cat to observer. The efficient cause is the decay or non-decay of a radioactive atom. The final cause is action of the observer in opening the box. The formal cause is the poor cat in its ambiguous state, simultaneously both dead or alive.

It doesn’t make too much common sense to say that the opening of the box and the observing of the cat “causes” the atom to have really decayed or not, and so concretize the past and the cat into a certain way of being, but that is mostly what the Copenhagen Interpretation is saying. Indeed, Linear Logic, which has been described many times on this blog, has been used to describe aspects of quantum physics for decades.

References:

http://en.wikipedia.org/wiki/Schr%C3%B6dinger%27s_Cat

http://en.wikipedia.org/wiki/Copenhagen_interpretation

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Maxwell’s Demon

I am currently reading Tor Norretranders “The User Illusion”, and he opens the book with chapters on information theory and thermodynamics. His description of the thought experiment “Maxwell’s Demon” made me realize that this system has all the ingredients of a fourfold: the two chambers, the demon, the door between the two chambers that the demon operates, and the molecules that the demon allows to or prevents from passing through the door from one chamber to another. The only way between the two chambers is through the door. The molecules are in a gaseous state, with a distribution of velocities, so some are moving faster than others.

The major physical action that the demon can perform is to open or close the door. If the demon did this randomly, it would accomplish nothing, and the system would ultimately evolve the same as one without door or demon. Instead the demon is able to open and close the door so as to allow faster molecules to collect in one chamber and slower molecules to collect in the other. The demon doesn’t touch the molecules, but he is somehow able to tell whether a molecule is fast or slow so he can decide whether to open or close the door.

The purpose of the thought experiment is to suggest that this system could violate the second law of thermodynamics by increasing order. By letting faster molecules move to one chamber, the system would then be able to do work by, for example, powering an engine. Perhaps the temperature differential is also able to power the demon itself. We would then have a perpetual motion machine, one that could give us unlimited energy, as long as there was a surplus of energy after the needs of the demon.

However, the modern analysis of the thought experiment shows that entropy does indeed increase within this system because the demon would eventually have to forget information about the molecules, and his forgetting would increase entropy. The demon would have to be an irreversible process.

References:

http://en.wikipedia.org/wiki/Maxwell%27s_demon

Tor Norretranders / The User Illusion: Cutting Consciousness Down to Size

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The Physical Force Carriers

The probable discovery of the Higgs Boson was announced recently. I was initially confused about the difference between the Higgs and the yet to be discovered Graviton. After some reading on the internet, I’m still confused, but they are theorized to be two different particles, since the Graviton is the quantum manifestation of the force of gravity, and the Higgs is the quantum manifestation of the field that gives certain particles mass. Since the Graviton can effect Photons, and the Higgs can’t, they must be different.

You would think that since particles have to have mass to be effected by gravity, they would have to be related. I guess there are some theories out there that do that, but none have been validated. Additionally, the Higgs Boson is part of the Standard Model, and the Graviton isn’t, even though the Higgs doesn’t seem to fit nicely into those 4 x 4 matrices.

The above fourfold is patterned after the Four Fundamental Forces of Physics.

http://en.wikipedia.org/wiki/Quantum_gravity

http://en.wikipedia.org/wiki/Higgs_boson

http://en.wikipedia.org/wiki/Standard_model

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Attraction and Repulsion

Gravity is Love.

 — Brian Swimme

The principle of attraction and its opposite repulsion is pervasive throughout the conceptualization of modern physics. Even ancient Empedocles, of the four elements fame, thought that in all nature the force of attraction and combination was Love or Philia, and that the force of repulsion and separation was Strife or Neikos. These forces have now been depersonalized and mathematized, but still inhabit natural laws which must be obeyed. (See the Four Fundamental Forces of Physics.)

At all levels of matter and energy, from the lowest atomic interactions to the highest cosmic forces, the duality of attraction and repulsion are everywhere. In atoms, there is the strong force and the weak force that respectively pull nuclei together or push them apart. In and between atoms and molecules, covalent bonds, magnetic polarities, electric charges, hydrogen bonds, salt bridges, and hydrophobic effects gather and scatter and even make life possible. In the large-scale macro world, electromagnetism and gravity extend their influence. And in the cosmic arena, the mysterious effects of dark matter and dark energy perform without our current understanding.

In the biological world, attraction and repulsion are seen in the action of plants and animals. The plant is attracted to light and moisture, and repulsed by darkness and dryness. The animal is attracted to food and safety, and repulsed by lack and danger. Plants and animals are also attracted to their kin, and repulsed by their non-kin, because there is strength in commonality. However, too much sameness becomes toxic. It is the dynamic between attraction and repulsion that creates much of the living world and its richness.

In the human world, culture and language enable the forces of attraction and repulsion. Known culture and language is attractive; unknown culture and language is repulsive. But the human mind also craves newness. Interactions between the same and the different have been a great source of the creative drive which fuels the human spirit.

Note:

The sums of attractions are combinations. The sums of repulsions are separations.

References:

http://en.wikipedia.org/wiki/Empedocles

http://www.npr.org/blogs/13.7/2010/10/21/130724690/gravity-is-love

http://biocracy.info/blog/blog5.php/2008/06/08/attraction-repulsion

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