IRC-Galleria

Thirty-one years ago [1949], Richard Feynman told me about his "sum
over histories" version of quantum mechanics. "The electron does
anything it likes," he said. "It just goes in any direction at any
speed, forward or backward in time, however it likes, and then you add
up the amplitudes and it gives you the wave-function." I said to him,
"You're crazy." But he wasn't.

* Freeman J. Dyson, 1983

http://user.web.cern.ch/user/news/2009/091106b.html

"On Tuesday 3 November, a bird carrying a baguette bread caused a short circuit in an electrical outdoor installation that serves sectors 7-8 and 8-1 of the LHC. The knock-on effects included an interruption to the operation of the LHC cryogenics system. The bird escaped unharmed but lost its bread."

http://www.digitoday.fi/tiede-ja-teknologia/2009/11/06/linnun-pudottama-leivanpala-pysaytti-hadronitormayttimen/200923334/66

"Aiemmin tällä viikolla CERN:n Suuri Hadronitörmäytin eli Large Hadron Collider (LHC) ylikuumeni osittain. Syyksi on epäilty leipäpalaa, jonka luultavasti pikkulintu on pudottanut laitteen hiukkaskiihdyttimen ulko-oven koneiston väliin."

Experiment to simulate conditions in an exploding star slowed down millions of times.

The world's most powerful laser (covering the area of an American football field) is focused onto a sample of calcium, sulfur, carbon and iron the size of a pinhead. These materials are thought to be the same as a star's nucleus. At the instant of ignition the laser runs at a power output (wattage) twenty times larger than the electrical consumption of the USA.

Shock wave tears the atoms apart, and the superheated gas plasma explodes outwards coalescing into fractal tendrils reminiscent of an astronomical photo of a nebula.

Music is Portishead - Wandering Star (1994)



More about the Super Laser at the National Ignition Facility
http://www.kqed.org/quest/television/super-laser-at-the-national-ignition-facility

Feynman checkerboard with two paths contributing to the sum for the propagator
from (x / εc, t / ε) = (0, 0) to (3, 7).


The Feynman Checkerboard or Relativistic Chessboard model was Richard Feynman’s sum-over-paths formulation of the kernel for a free spin ½ particle moving in one spatial dimension. It provides a representation of solutions of the Dirac equation in (1+1)-dimensional spacetime as discrete sums.

It can be puzzling as to why a rotation of 720 degrees or two turns is necessary to return to the original state. This comes about because in quantum theory the state of a particle or system is represented by a complex probability amplitude and then when a measurement is made on the system the probability of it coming out some way is given by the square of absolute value of the appropriate amplitude.

Say you send a particle into a system with a detector that can be rotated where the probabilities of it detecting some state are affected by the rotation. When the system is rotated through 360 degrees the observed output and physics are the same as at the start but the amplitudes are changed for a spin ½ particle by a factor of -1 or a phase shift of half of 360 degrees. When the probabilities are calculated the -1 is squared and equals a factor of one so the predicted physics is same as in the starting position. Also in a spin 1/2 particle there are only two spin stated and the amplitudes for both change by the same -1 factor so the interference effects are identical unlike the case for higher spins. The complex probability amplitudes are something of a theoretical construct and cannot be directly observed.

If the probability amplitudes changed by the same amount as the rotation of the equipment then they would have changed by a factor of -1 when the equipment was rotated by 180 degrees which when squared would predict the same output as at the start but this is wrong experimentally. If you rotate the detector 180 degrees the output with spin ½ particles can be different to what it would be if you did not hence the factor of a half is necessary to make the predictions of the theory match reality.

The Checkerboard model is important because it connects aspects of spin and chirality with propagation in spacetime and is the only sum-over-path formulation in which quantum phase is discrete at the level of the paths, taking only values corresponding to the 4th roots of unity.

Paul Davies's book The Goldilocks Enigma (2006) reviews the current state of the fine tuning debate in detail, and concludes by enumerating the following responses to that debate:

1. The absurd universe

Our universe just happens to be the way it is.

2. The unique universe

There is a deep underlying unity in physics which necessitates the universe being the way it is. Some Theory of Everything will explain why the various features of the Universe must have exactly the values that we see.

3. The multiverse

Multiple Universes exist, having all possible combinations of characteristics, and we inevitably find ourselves within a Universe that allows us to exist.

4. Creationism

A creator designed the Universe with the purpose of supporting complexity and the emergence of Intelligence.

5. The life principle

There is an underlying principle that constrains the universe to evolve towards life and mind.

6. The self-explaining universe

A closed explanatory or causal loop: "perhaps only universes with a capacity for consciousness can exist." This is Wheeler's Participatory Anthropic Principle (PAP).

7. The fake universe

We live inside a virtual reality simulation.