The science threads - Physics

I haven't done much with this in recent years, but I have a buried fascination with quantum physics. I actually gave a speech on it my freshman year of high school, much to the boredom of just about everybody. ;)
 
Quantum phyiscs is far from boring... if you explain it correctly... look at Feynman's lectures ! Fantastic.
 
Wow.
I really like the idea of having an escape velocity FASTER than the speed of light. *The idea of black holes.

But that doesn't make sense to me, if a black hole had a escape velocity that large then how does it exist? Wouldn't it pull its self into its self? Wow...negative space is the result I guess.

Strange. I never really understood any of this before.

Meh, I'll read more whenever I get the time.
 
Why would an esacpe velocity faster than the speed of light be a problem ? It just means that nothing can reach this escape velocity, so nothing escaped from the black hole.
The escape velocity does not really "exists", it's a definition, like the equator... it's perfectly defined but does not include any energy, material or information. So it can be as fast as one wants.
 
This past week on PBS I saw two of the three part series detailing String Theory. It was hosted by Brian Greene. Interesting stuff, but so far a lot of what these physicists are working on has not been able to be observed or tested in the laboratory. With that fundamental problem of a lack of real world testing, many of these physicists admit that this indeed is not science YET, but rather philosophy. I read the article in Scientific American at the local library yesterday, and I tried to check-out the book but someone else had it. It sounds interesting, but I don't think that most people are going to understand it without the mathematical background that the physicists are using to work through these theories. I recall from the conversation in Scientific American that the coordinates that they are using to describe the position of a particle in space are not the same cartesian coordinates that we all used to working with, i.e. x, y, z. Rather, they are using these coordinates in a matrix with probablilites, and the problem with matricies is that multiplication is not commutative, A*B does NOT equal B*A UNLESS the matrix is diagonal. While I know this from taking one semester of Linear Algebra, I do not know why this is so; there is probably some deep mathematical theories or proofs that explain that. The math these guys use is intense and trying to explain Super String Theory to the general public without it may be a tough sell. I also recall that the model uses 11 dimensions and that the physicists posit that an currently unobserved but supposedly existent particle, the graviton, leaves the surface of our dimension and goes to another dimension. The physicists say that this is purhaps why the universe will continue to expand indefinitely since gravity in our universe will get weaker with time.

This theory may appear to explain a lot, but until we can observe some facts that correlate with the theory, or rather hypothesis, I think this will remain a very elaborate mathematical description that possibly explains the universe. If something can't be observed or measured, then it doesn't exist, scientifically speaking.
 
I don't agree with you. Theories are never observed or emasured. They are verified by experimentation and when possible by predictions.

The string theory is in its infancy and has still a long path to go before being as verified as the relativity or the quantum theories are. Nevertheless is seems very promizing. And the work of Brian Greene is also to make it easier to understand like Einstein work was also to explain the relativity theory so that others can understand it and test it.
 
Most of my studies in physics tend towards the study of fields rather than particles/strings. I enjoyed General Relativity and the large scale structure of the universe quite a lot (I was never one for calculating out solutions or individual paths, I always wanted to see the large global views of things), and also spend some time looking into things like Quantum Field Theory and Gauge Theory. I had a professor who did some work in String Theory, but I never took much time to look very closely at it.

In Gauge Theory you have something very much like extra dimensions but they are not physical in nature. What I mean by that is that they do not act in the same way that the three physical dimensions work, these are degrees of freedom that take on group structure (Lie Groups actually). There is a full range of 6 additional degrees of freedom associated with every point in space-time. Looking at all these extra degrees of freedom as fibers you can studies them over given paths producing fiber bundles... which starts getting into the type of mathematics I was doing.

Things like the path of an electron threw a magnetic field (which is usually done via probabilities in Quantum Mechanics) can be thought of as connections over these fiber bundles (the bundles take on a manifold structure). These connections are very much like the connection defined by Levi-Civita to help study General Relativity. The first Gauge Theory (though it wasn't originally thought of as such) was Maxwell's Equations. Gauge Theory was "out of fashion" until Yang-Mills Fields was introduced in the mid 50's.

As for the idea of proving theories, the time honored tradition has always been to create a theory that models what we know about nature, then when the model predicts what we know is there point it to something which we didn't know and see if the model holds up. Repeat until the model breaks then fix it. It really shouldn't be that hard to get String Theory to predict something that is within observation that other theories fail to produce.

The problem with physics is that it is very expensive and has some major egos, both of those put together mean it is slow to recognize when the wrong path has been taken or to try out a number of different paths instead of just a few.
 
With that fundamental problem of a lack of real world testing, many of these physicists admit that this indeed is not science YET, but rather philosophy.
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Init.flamewar: are you implying that philosophy would not be science ... ?
 
chemistry... said:
With that fundamental problem of a lack of real world testing, many of these physicists admit that this indeed is not science YET, but rather philosophy.
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Cat said:
Init.flamewar: are you implying that philosophy would not be science ... ?
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Philosophy can be scientific, it does not have to. What chemistry is proposing is that this theory cannot be accepted as science as it is not yet demonstrated. It does not imply that philosophy cannot be made with a scientific approach.
 
If philosophy can lead to physics, physic can also lead to philosophy, mostly when it changes our view of the world.

http://superstringtheory.com/blackh/blackh4.html said:
"perhaps spacetime geometry is not something fundamental in string theory, but something that emerges in the theory at large distance scales or weak coupling. This is an idea with enormous philosophical implications"
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chevy said:
What chemistry is proposing is that this theory cannot be accepted as science as it is not yet demonstrated.
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I hope not, because it throws out a ton of real science.

Newtonian physics (which is the heart of our space program) has been shown not to work as a realistic model of gravitation, and yet we still rely on it for a great deal of science today (because for most things the results of Newtonian physics aren't different enough from General Relativity to make using the harder calculations a requirement).

Many things have been disproven or replaced with better models that are still in use as tools in science today. And just because some things prove to be a dead end (like the Steady State Theory) doesn't mean that they have been removed from science or wasn't science before a better model was proposed.

In the area of String Theory we have a model of nature. This is a mathematical model based mainly on our current physical understanding of nature. It is science. It is the most pure form of science. It is science in the process.

Real science is dealing with unknowns. Real science is the process, not the end results. Asking questions about what you don't know, not resting on what you do know. Theory is the heart of science.

Any one who is preaching theory cannot be accepted as science is teaching science in a junior high school.

:rolleyes:

On the other hand, what I was doing was philosophy. My main area of study was mathematics and I didn't care if any of what I did was ever applied to anything. It wasn't the point. My work on tight immersions and embeddings of both polyhedral and smooth manifolds had no application to any science I know of. The technique I developed for studying regular homotopy of orientable manifolds (using contour diagrams) is about as philosophical in nature as you can get.

Philosophy can be safe and clean. Science is often dangerous and dirty.

I never got into science enough to get dirty, I just enjoyed playing with the mathematical models. I surely wouldn't have the guts to stake my career on any of the "physics" I was ever doing. And I would never have tried to publish any results I came up with in anything other than mathematics journals.

I have great respect for those who base their careers on the cutting edge of science, because that is where the real science is.
 
Chevy, I knew you liked physics the first time I saw one of your posts from your title. ;)

Which raises another interesting issue. The way they describe the issue with Schrodinger's cat, etc., it makes it sound like the result hasn't happened until you look at it, at which point it is determined if the particle is here or there, or the cat is dead or not, etc. But to me it seems like it has happened for sure, and you don't know it until looking at it... it's all very confusing.

I also haven't researched anything in this issue for about 4 years... I will be taking a course in physics at some point during my 2 years at junior college, and I might read about it before then just to satisfy my curiosity.

Anybody read Greggory Benford's Cosm? Not exactly feasible in practice, but a good read nonetheless.
 
arden said:
Chevy, I knew you liked physics the first time I saw one of your posts from your title. ;)

Which raises another interesting issue. The way they describe the issue with Schrodinger's cat, etc., it makes it sound like the result hasn't happened until you look at it, at which point it is determined if the particle is here or there, or the cat is dead or not, etc. But to me it seems like it has happened for sure, and you don't know it until looking at it... it's all very confusing.
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Indeed it is confusing. This is a mental experiment. If you take the theory to its ultimate meaning it means that "it happens in the past at the moment you open the box". Which of course is nonsense.

The current theory is more complex and has a lot to do with all interaction between degrees of freedom that reduce the probability of one or the other event making that thing "happens" really, and not only potentialy at macroscopic level.
 
In the PBS television special, the physicists themselves said that unless there is "real world testing of this theory, it is philosophy, not science, YET". Please note, I'm not making that statement, but someone else in the television special did.
 
Back to the theme of the thread. I was not so much discussing philosophy against science, but more about the implications and significations of the string theory.
 
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