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Author Topic:   Reaching the practical end of physics?
AnswersInGenitals
Member (Idle past 150 days)
Posts: 673
Joined: 07-20-2006


Message 12 of 68 (437334)
11-29-2007 6:10 PM
Reply to: Message 9 by Silent H
11-29-2007 5:03 PM


Been there, done that.
I think your questions, particularly as rephrased by frgab, could equally well have been asked right after Newton published his theories of mechanics and gravitation. These theories enabled one to predict the motions of the planets, but not significantly better (at that time) then the existing techniques. They gave a better description of what happens when you hurl a rock or shoot an arrow, but doing so with accuracy relied far more on the subconscious skills of the warrior than upon any calculations. They greatly increased our understanding of the workings of nature, but for a long time did not contribute to our control of nature.
This reminds me of a famous (and probably apocryphal) exchange between Queen Victoria and Michael Faraday when the queen visited Faradays lab for a demonstration of his brand new invention, the electric dynamo. Queen Victoria asked Faraday; "So Mr. Faraday, that's all very nice and interesting, but of what the fuck use is the damned thing?" Faraday replied; "Madam, of what use is a baby?"
Another important aspect that has not been mentioned is that while elementary particle physics, cosmology, and the physics of the solid state (now usually referred to as condensed matter physics and includes our understanding of the semiconductors used in our computers, etc.) seem to deal with quite different components of nature, in fact there is a great deal of commonality in the mathematics and models of these topics. A key part of the current theory of elementary particles, the standard model, is a mathematical description called spontaneous symmetry breaking. This concept and its development originated in solid state physics.
I am currently reading and highly recommend a very nice popularization (very easy read and no equations) of the current state of fundamental physics: "The Trouble with Physics", by Lee Smolin. It will give you a good idea of what is currently taking place in the field, and as the title implies, its current impasses. If you read this book, keep in mind the extremely sophisticated and powerful mathematical and modeling techniques that are being developed to tackle these problems.

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 Message 9 by Silent H, posted 11-29-2007 5:03 PM Silent H has not replied

  
AnswersInGenitals
Member (Idle past 150 days)
Posts: 673
Joined: 07-20-2006


Message 23 of 68 (437431)
11-30-2007 1:40 AM
Reply to: Message 18 by Hyroglyphx
11-29-2007 8:03 PM


A cut above (the speed of light).
NJ: You can get some idea of what is going on by taking a scissors and slowly closing them by moving the handle parts together. The point where the two blades intersect will move much faster than the handles or the blades themselves. But that intersection point is not a real 'thing'. If you unscrew the two halves of the scissors so that the blades aren't even touching you can still get the intersection to move a much greater speed than the blades themselves. If the blades are very nearly parallel you might actually get the intersection to move faster than the speed of light. But that intersection cannot carry any information or push any matter along with it without imposing a great deal of force on the blades. If you get the blades nearly parallel and try to squeeze any object along the intersection, as the intersection approaches the speed of light the forces imposed by that object will approach infinity.
What the quoted researchers did was to take a medium in which light of different frequencies travel at different speeds (referred to as a dispersive medium because in the shape of a prism it will disperse the light of different frequencies in different directions and spread them out) and send in a few light beams of different frequencies. Now, think of these light beams in the shape of undulatory waves with their slightly different wave lengths moving at slightly different speeds. The point where they intersect and add up can, with proper adjustment of parameters, move much faster than the individual waves themselves, just like the blades of the scissors. This is called the phase velocity of the group of waves. No matter or information can be pushed along at this intersection at the phase velocity. It is really, more than anything else, just a mathematical apparition. As has been said, nothing in these experiments violates Einstein's theory of relativity. In fact, there has been no repeatable experiment to date that violates Einsteinian relativity. By the way, the principles and mathematics involved in these experiments is pretty much college freshman level. It is the experimental details of creating the dispersive medium and the various light wave packets that makes these experiments so challenging.

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AnswersInGenitals
Member (Idle past 150 days)
Posts: 673
Joined: 07-20-2006


Message 47 of 68 (437933)
12-02-2007 1:40 AM
Reply to: Message 43 by molbiogirl
12-01-2007 3:49 PM


Grandpatricide revisited.
I have a particular problem with time travel, especially time travel into the past. Lets say I travel back to the year 1900. In my pocket I'm carrying a snub nose 38 caliber handgun loaded with hollow point copper jacketed bullets. I hunt down my paternal grandfather and shoot him dead. Since my father was conceived in early 1903 and born in late 1903, who killed my grandfather? Now, I don't actually have a problem with the death of my paternal grandfather - in 1915 he fled Russia to America and abandoned his wife and children, including my father. My problem is with that gun and the bullets. They were manufactured in 2002 from ores mined in the US in 2001.
So when I arrive back in the year 1900 with my gun, every atom in that gun (and the bullets) is in two places at the same time - refined and cast into the various parts of the gun in my pocket in Russia and as various oxide ores in the hills of Wisconsin (iron). Chile (copper), and Belgian Congo (chromium). However, those laws of general relativity that supposedly allow for time travel are based on what physicists call 'well behaved functions'. These functions are continuous, smooth, and most important, single valued - without these properties, one cannot do calculus to analyze GR results.. The time lines for those various elementary particles in my gun thus cannot allow those particles to be in two places at the same time.
Unfortunately, the gun is the least of my problems. The atoms making up my body as it exists here in 2007 in the US, and presumably back in Russia in 1900 also had already existed all over the damn planet - in various animals, plants, the air and who knows what else - in 1900 so my atoms are now (i. e., in 1900) in two distant places at the same time. I know that GR allows for the single valuedness of timeline functions to fail at certain unique points, i. e., singularities, but traveling back in time has to avoid passing through such singularities if objects are to retain any cohesion. And anyway, me, my gun and my grandfather would not be locked into a singularity at the time I carried out my act of revenge.
Any thoughts or resolution to this conundrum?

This message is a reply to:
 Message 43 by molbiogirl, posted 12-01-2007 3:49 PM molbiogirl has not replied

Replies to this message:
 Message 48 by cavediver, posted 12-02-2007 6:16 AM AnswersInGenitals has not replied
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