# Tagged Questions

Pertains to any question concerning the ideas that are formulated, whether mathematically or not, to explain or describe physical phenomena.

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### How is the apparent significance of (length) scales in physics explained?

From what I understand, especially from reading arguments on Physics.SE, different (length) scales of a system are extremely important. It's clear that if there are two scales $\delta,d,D,\Delta$ with ...
445 views

### Why does iteratively solving the Hartree-Fock equations result in convergence?

[ Cross-posted to the Computational Science Stack Exchange: http://scicomp.stackexchange.com/questions/1297/why-does-iteratively-solving-the-hartree-fock-equations-result-in-convergence ] In the ...
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### Style in Physics vs Mathematics [closed]

I'm a mathematics major who has taken a few physics courses and the presentation in physics texts bothers me. In mathematics, the standard format is a theorem-proof repetition with some discussion. ...
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### Compatibility of economics and physics?

This is an open-ended and broad and multi-part question; but I would be willing to accept an answer that simply corrects my misconceptions. I am sorry if it is inappropriate or too soft for this ...
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### What fundamental principles or theories are required by modern physics?

We have been taught that speed of light is insurmountable but as we know an experiment recently tried to show otherwise. If the experiment did turn out to be correct and confirmed by others, would ...
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### Proof Human Designs for Fusion Could Work

Are there convincing proofs on paper that fusion is possible the various ways humans are trying to design machines to do it or is the only way absolutely proven to work in theory also the only way ...
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### In astronomy what phenomena have theory predicted before observations?

As far as I know, astronomy is generally an observational science. We see something and then try to explain why it is happening. The one exception that I know of is black holes: first it was thought ...
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### What theory is the person in this song talking about?

What he is talking about sounds interesting to me, and I would like to know more. But I need to know the name first. http://www.youtube.com/watch?v=Ogn5FrVGtAg&hd=1
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### What are the facts that allow accepting the Oort cloud theory?

I admit without any fact that the Oort cloud (comet reservoir) should exist, and it seems to be accepted by far by the large majority of astronomers. But it is still a theory without any direct ...
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### What are the implications of the speed of light broken? [duplicate]

Possible Duplicate: What would be the effects on theoretical physics if neutrinos go faster than light? I don't know if it's been asked before, but I couldn't find a thread about it. I ...
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### Why *should* the mass of elementary particles theoretically be of the magnitude of the Planck mass?

Why should the mass of elementary particles be theoretically of the magnitude of the Planck mass? I've read that already a few times but I don't understand why it should be that way. For example: ...
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### Non-computable numbers in Physics

It is known that there are real numbers that can't be calculated (non-computable numbers). Quite probably that some physical phenomena (it is possible still undetected) depend on this numbers. Whether ...
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### What does transport equation represent in terms of physical quantities?

In my math course we're taught to solve PDE (partial derivative equations) like transport equation: $$c\frac{\delta u}{\delta x} +\frac{\delta u}{\delta t}=0$$ If $u(x,t)$ is the quantity ...
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### Is instantaneous velocity an abstraction?

In introductory analysis, the discussion the derivative emphasizes that while average rates of change are measurable, instantaneous rates of change are a "limiting abstraction". While this makes ...
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### Critics of Mannheim's Conformal Gravity Theory?

I'm looking for more articles/reactions/critiques/support for Philip Mannheim's recent conformal gravity theory. See here: http://arxiv.org/abs/1101.2186v1 Any ideas on where to start?
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### Can the universe be described by a Markov chain?

This may be a fairly basic question as I don't have a strong background in physics. I intuitively thought that the universe must be able to be described by a Markov chain. That is, I thought you ...
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### Why Is String Theory Called A Theory [duplicate]

Possible Duplicate: Laws of Atomic Theory - how is this possible? Generally in science, a theory is effectively a fact. The theory of evolution is not a guess, or a hypothesis. It's ...
332 views

### Laws of Atomic Theory - how is this possible?

Not sure if this is the right place to post, but how is it possible to have laws of a theory? A theory is not able to be a law, since it's just an explanation that can always be disproven. So how is ...
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### Models of neutrinos consistent with OPERA's results

I guess by now most people have heard about the new paper (arXiv:1109.4897) by the OPERA collaboration which claims to have observed superluminal neutrinos with 6$\sigma$ significance. Obviously this ...
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### How is the “negative dispersion” derived?

I'm looking at Kopfermann H., Ladenburg R., Nature, 122, 338-339 (1928) and it appears Ladenburg in Ladenburg R., Z.Physik, 4, 451-468 (1921) was the first to discover the phenomenon of "negative ...
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### Lev Landau's “Theoretical Minimum”

The great russian physicist Lev Landau developed a famous entry exam to test his students. This "Theoretical Minimum" contained everything he considered elementary for a young theoretical physicist. ...
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### what is the difference between a blackhole and a point particle

Theoretically, What is the difference between a black hole and a point particle of certain nonzero mass. Of-course the former exists while its not clear whether the later exists or not, but both have ...
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### How exactly does time slow down near a black hole?

How exactly does time slow down near a black hole? I have heard this as a possible way of time traveling, and I do understand that it is due in some way to the massive gravity around a black hole, but ...
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### Spinning X-Rays [closed]

X-Ray jets emit from galaxies as a result of spinning mass. I'm thinking about the ties between electricity and magnetism here, and how Gauss law ties all this stuff together. OK, so is there a way ...
777 views

### Do the laws of physics evolve?

Hubble's constant $a(t)$ appears to be changing over time. The fine stucture constant $\alpha$, like many others in QFT, is a running constant that varies, proportional to energy being used to measure ...
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### How to invent a theory? [closed]

Is it possible to write down step-by-step instructions for inventing a new theory? I've been wondering if there exists some 'recipe' or proceedure for inventing a new theory. Presumably some ...
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### Electric field at a point being an $n^{th}$ derivative of electric (or magnetic) field at some other point

This is a theoretical question for which i would like to know an answer with an example. I'd like to know if its possible to create a setup where the electric field at a point $P$ is $n^{th}$ ...
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### Lawrence Krauss' Theory of Origin

I don't understand how a vacuum, the absence of matter, can hold energy. How can it hold energy when Einstein proved that matter is energy? And a second related question; how does the energy in a ...
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### what is meant by “crossover phenomena”?

In many articles I read the term "crossover phenomena" and a lot of methodology discussed according to it, with little or no description about what is meant by it. Sometimes there is a connection to ...
1k views

### Is it really Impossible for Bumblebees to fly?

According to some source or other (I forget which now) it is theoretically impossible for bumblebees to fly by virtue of their size/bulk/aerodynamic properties. Is this old adage apocraphyal or true? ...
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### How does the curvature of spacetime induce gravitational attraction?

I don't know how to ask this more clearly than in the title.
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### How to validate a new physics theory and keep the credit for it [closed]

For the last few years, My friend worked on figuring out the "theory of everything". She is afraid of sharing her theory with well known physicists, because she doesn't want other people to take ...
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### Alternative theories to the big bang?

Hey all, are there any theories out there on the origins (or infinite existence of) the universe beside the big bang that actually adhere to current scientific knowledge and fact?
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### Can the study of the quantum information structure in QFT with holographic duals be relevant to string theory?

I'm interested in characterizing the behaviour of measures of quantum information in strongly correlated quantum field theories which admit a gravity dual description, e.g through AdS/CFT duality. In ...
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### Matter-Antimatter Asymmetry in Experiments?

As I hope is obvious to everyone reading this, the universe contains more matter than antimatter, presumably because of some slight asymmetry in the amounts of the two generated during the Big Bang. ...
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### laws and theories

What is a physics law, a theory, and what is the relationship among them? I know this is a very basic question, so any reference to epistemology will be greatly appreciated :)
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### How did these guys get the masses from Heim Theory?

I won't even bother to ask about validity as I read the other post on this. So I know how we all feel about that. I hadn't even heard of it till today when I stumbled across it searching for something ...
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### What does the Many-Body Problem say about mathematical physics?

I was interested to read the answers to the other Many-Body Problem questions on this site and was left with one nagging question of my own. What does the Many-Body Problem reveal about reality and ...
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### Does String Theory disagree with General Relativity?

I would like to expand on what I mean by the title of this question to focus the answers. Normally whenever a theory (e.g. General Relativity) replaces another (e.g. Newtonian Gravity) there is a ...
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### Why does my body accumulate charge?

If I wander outside in cold weather for 10-20 minutes my body accumulates charges. I get electric shock if I touch metal, e.g., door knob, car door etc. Now I've two questions: Why does human body ...
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### List of theories supporting origin of universe [closed]

Big Bang theory is widely accepted theory when it comes to origin of universe. What other really compelling theories are out there explaining/supporting the origin of universe. I know many people ...
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### Does the positive mass conjecture indicate a necessity of interactions in our universe?

The positive mass conjecture was proved by Schoen and Yau and later reproved by Witten. Total mass in a gravitating system must be positive except in the case of flat minkowski space, where energy is ...
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### Existence and uniqueness of solutions for Einstein equations

Now that an equivalence of Navier Stokes and Einstein equations has been established, and it is known solutions to Einstein-Maxwell-Boltzmann exist and are unique, and it is known that Einstein ...
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### Besides Field and Gauge theories what other types of theories are there? [taxonomy ] [duplicate]

Possible Duplicate: What are the most common theories and their categorization/motivation? Besides Field and Gauge theories what other types of theories are there? Found the answer at ...
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### What is information?

We're all familiar with basic tenants such as "information cannot be transmitted faster than light" and ideas such as information conservation in scenarios like Hawking radiation (and in general, ...
1k views

### What Do We Get From Having Higher Generations of Particles?

Background: I have written a pop-science book explaining quantum mechanics through imaginary conversations with my dog-- the dog serves as a sort of reader surrogate, popping in occasionally to ask ...
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### Tesla's theory of gravity

I was reading up on Tesla's Wikipedia page last night, and I came across this: When he was 81, Tesla stated he had completed a "dynamic theory of gravity". He stated that it was "worked out ...
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### Interaction ranges in the Standard Model - Electrodynamics vs QCD

as you might know, the Standard Model of physics can be seen as a $U(1)\times SU(2)\times SU(3)$ gauge theory where each symmetry group accounts for different force fields. The behaviour for the ...