Pertains to any question concerning the ideas that are formulated, whether mathematically or not, to explain or describe physical phenomena.
41
votes
33answers
5k views
Great unsolved physics problems [closed]
We all know that some theoretical ideas lack experimental evidence while in other cases there's a lack of a suitable theory for known phenomena and established facts and concepts.
But what problem in ...
31
votes
5answers
147 views
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 ...
22
votes
4answers
956 views
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, ...
15
votes
2answers
5k views
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. ...
14
votes
7answers
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 ...
12
votes
9answers
169 views
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 ...
12
votes
7answers
355 views
Macroscopic laws which haven't been derived from microscopic laws
Can you think of examples where a macroscopic law coexists with a fully known microscopic law, but the former hasn't been derived from the latter (yet)? Or maybe a rule of thumb, which works but ...
10
votes
5answers
6k views
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 ...
10
votes
2answers
518 views
Is the G2 Lie algebra useful for anything?
Seems like all the simpler Lie algebras have a use in one or another branch of theoretical physics. Even the exceptional E8 comes up in string theory. But G2? I've always wondered about that one. ...
10
votes
7answers
3k views
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 ...
10
votes
3answers
481 views
Can physics get rid of the continuum?
Almost every physical equation I can think of (even though I don't actually feel comfortable beyond the scope of classical mechanics and macroscopic thermodynamics, as that's enough for dealing with ...
8
votes
4answers
231 views
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 ...
7
votes
6answers
447 views
Why are the physical sciences described perfectly by mathematics?
Why are the physical sciences described perfectly by mathematics?
7
votes
1answer
497 views
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 ...
6
votes
4answers
352 views
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. ...
6
votes
5answers
420 views
Is physics rigorous in the mathematical sense?
I am a student studying Mathematics with no prior knowledge of Physics whatsoever except for very simple equations. I would like to ask, due to my experience with Mathematics:
Is there a set of ...
6
votes
4answers
1k views
What are the challenges to achieving cold fusion?
I am an absolute neophyte regarding physics. What are the challenges to achieving cold fusion?
I'm not sure this is a duplicate of Why is cold fusion considered bogus?, because that question is ...
6
votes
2answers
149 views
Is the step of analytic continuation unavoidable or can you model around it?
One sometimes considers the analytic continuation of certain quantities in physics and take them seriously. More so than the direct or actual values actually. For example if you use the procedure for ...
6
votes
2answers
449 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 ...
6
votes
1answer
449 views
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?
6
votes
1answer
197 views
Naturalness and experiments
Is there an example where model building that is motivated only by Naturalness, has led to experimentally verified observations?
If the question is unclear, or if the reader wants more elaboration, ...
6
votes
3answers
233 views
What categorical mathematical structure(s) best describe the space of “localized events” in “relational quantum mechanics”?
In a recent (and to me, very enlightening) paper, entitled "Relational EPR", Smerlak and Rovelli present a way of thinking about EPR which relies upon Rovelli's previously published work on relational ...
6
votes
1answer
139 views
What is the origin of flavor? [duplicate]
Possible Duplicate:
Origin of lepton/quark generations?
In the standard model (and in nature), Fermions appear in different generations, or flavors. Besides up and down quarks and ...
5
votes
6answers
526 views
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 ...
5
votes
2answers
252 views
Does the mathematics of physics require impure set theory?
Suppose for the sake of this question that all mathematics is ultimately reducible to set theory in such a way that the only mathematical objects there really are, are sets.
Now, there is a common ...
4
votes
2answers
847 views
What does a Field Theory mean?
What exactly is a field theory?
How do we classify theories as field theories and non field theories?
EDIT:
After reading the answers I am under the impression that almost every theory is a ...
4
votes
5answers
699 views
Can a scientific theory ever be absolutely proven?
I personally cringe when people talk about scientific theories in the same way we talk about everyday theories.
I was under the impression a scientific theory is similar to a mathematical proof; ...
4
votes
2answers
361 views
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 ...
4
votes
4answers
472 views
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 ...
4
votes
2answers
782 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 ...
4
votes
2answers
232 views
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 ...
4
votes
1answer
105 views
Would it be possible to have an electron-less solid?
We can create plasmas quite easily, indeed you can buy a plasma cutter and generate it all day long for less than $500. Would it be possible to trap a plasma, say magnetically, and cool it so much ...
4
votes
2answers
119 views
What equations govern the formation of droplets on a surface?
When some smooth surface (like that of a steel or glass plate) is brought in contact with steam (over e.g. boiling milk) then water is usually seen to condense on that surface not uniformly but as ...
4
votes
4answers
404 views
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 ...
4
votes
2answers
459 views
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?
4
votes
2answers
429 views
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 ...
4
votes
0answers
235 views
Relating the variance of the current operator to measurements
(EDIT: Thanks to Nathaniel's comments, I have altered the question to reflect the bits that I am still confused about.)
This is a general conceptual question, but for definiteness' sake, imagine a ...
3
votes
4answers
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? ...
3
votes
5answers
780 views
How does the curvature of spacetime induce gravitational attraction?
I don't know how to ask this more clearly than in the title.
3
votes
2answers
200 views
Has anyone else thought about gravity in this way?
Picture yourself standing on a ball that is expanding at such a rate that it makes you stick to the ball.
Everything in the universe is expanding at this same rate.
To escape the earths gravitational ...
3
votes
2answers
772 views
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 ...
3
votes
1answer
126 views
Straightforward questions about calculating SUSY F-terms
So in the Lagrangian for a SUSY theory we have the F-terms, which I have seen written (e.g., in Stephen Martin's SUSY primer) as
$F^*_i F^i$
where
$F^i = \frac{\partial W}{\partial \phi^i}$.
I ...
3
votes
3answers
180 views
Does the second law of thermodynamics tell me how the entropy changes?
In thermodynamics I can e.g. compute the properties of ideal gases with certain energies $U_1,U_2$ in boxes with certain volumes $V_1$ and $V_2$. Say I have two such boxes and they have some specific ...
3
votes
1answer
292 views
The possibility of free electrical energy?
Please excuse my lack of knowledge/understanding.
Question: Why Nikola Tesla's Free Energy concept was never worked upon? Even today.
Context: Now that we know Nikola Tesla was a genius and did ...
3
votes
3answers
317 views
shifting from mathematics to physics
I am a postgraduate in mathematics. I studied physics during my B.Sc.studies.I want to go for further studies in physics particularly in theoretical physics. I am in a job and cant afford regular ...
3
votes
1answer
192 views
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 ...
3
votes
1answer
89 views
Are there microscopic theories, which work, but which wrongly predict macroscopic behaviour?
Motivated by this question (and the P. W. Anderson article linked in that question, which I came across here somewhere today and just read) I wonder about something, which is somewhat bordering an ...
2
votes
8answers
563 views
What are the frameworks of physics?
Are there physical theories in use, which don't fit into the frameworks of either Thermodynamics, Classical Mechanics (including General Relativity and the notion of classical fields) or Quantum ...
2
votes
6answers
473 views
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 :)
2
votes
2answers
146 views
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 ...
