@ACuriousMind I've had a hard time figuring out where Socrates is making meaningful distinctions between de jure persuasion and de facto persuasion in his Apology, and where he's being overly pedantic. I'm not sure there's a line.
@ACuriousMind Was there anything in particular that inspired the change, or just a love of philosophy (which I can totally understand, by the way - I don't mean to diss philosophers)? Also, your clapping makes me picture the dungeon guy at 0:51 here.
@HDE226868 At one point, I decided (or realized?) that searching for a truly sound epistemology is kind of like searching for a theory of everything - we probably won't ever truly find one, but that's doesn't stop the ones we have to be useful approximations.
The treatment of electrons as waves has combined with spherical harmonics (below image) to form the foundation for a modern understanding of how electrons "orbit."
Tweaks to the spherical harmonic differential equations yields the Schrodinger equation (below image), which is the accepted model...
The treatment of electrons as waves has combined with spherical harmonics (below image) to form the foundation for a modern understanding of how electrons "orbit."
Tweaks to the spherical harmonic differential equations yields the Schrödinger equation(below image), which is the accepted model ...
Well, pointing it out (as you have done) is a partial solution. Making it non-rewarding (including getting answers) would be ideal, but isn't going to happen.
@ACuriousMind Understood, take a good rest. In the meantime I will try to improve my communication skills further so that I won't end up draining you. I am very sorry the confusing chats have put too much toll on you
Fun realization: The fact that the magnetic field does no work is the same as the fact that $\vec{B}$ is associated with the three non-time components of the field tensor $F_{ab}$. (Since the time component of 4-vectors are generally energies)
@Secret it looks an interesting subject, though I confess I know little about it. My PhD was on solid state photochemistry. A friend of mine worked on transition metal clusters, with a relation to catalysis, but I never really understood what he was doing.
This week's NewScientists are touching upon many big issues, such as measures to keep data giants such as google and facebook from going rogue in the future with our data, and a heightened need of educating the general public the worth of our data and how we should handle it and the long term implications
Other issues include AI help in sorting through disease data to have diagnose a disease, while the doctor talks to the patient and provide directives
The chat's are usually a bit disorganised. We've been experimenting with using the chat for someone to make a presentation, like Secret's talk yesterday, but this is just an experiment.
@DavidZ well, you've tended to post agenda when you've wanted to talk about a particular subject. But I'm not trying to push you into the scheduled chat organiser role - I suspect that's a thankless task :-)
@JohnRennie Yeah, in the few cases where there is something I think really needs to be discussed, I'll put that on the agenda.
The intent is more that people suggest topics to constitute the agenda for a chat session. But typically nobody has anything to suggest, which is why I wind up deciding most of the time.
I'm yet to find a testable prediction by string theory
I heard Imperial College used string theory calculations for some QMs. Couldn't find anything detailed on it though, in fact I didn't even find what in QM
@SpaceOtter the stuff you read about string theory in the popular science media is a charicature of it. The reality is far more complicated than the simple summaries suggest.
String theory isn't a single theory that can be proved or dispoved.
It's more like a huge motley collection of maths, and various bits of it shine a new and interesting light on more conventional fields like quantum field theory.
@SpaceOtter Which bit of It's more like a huge motley collection of maths, and various bits of it shine a new and interesting light on more conventional fields like quantum field theory was I not clear about?
You can't prove or disprove string theory because it isn't a single object. Bits of it may prove not to be useful while other bits of it turn out to be useful.
The point is that the popular media simplifies and sometimes misrepresents the reality. Someone whose only knowledge of string theory comes from pop science simply isn't ina position to judge.
@SpaceOtter the second string revolution in 1995 discovered links between the five different perturbative formulations of string theory that suggested they were different descriptions of the same theory. That's all.
https://en.wikipedia.org/wiki/Quantum_suicide_and_immortality [Musing inspired from this week's NewScientist] We don't really have an analogue of attaching consciousness to an electron, that is, a property that has some feature of consciousness that can allow us to actually carry out the quantum suicide and then determine whether the consciousness analogue property sruvive through all n rounds, hence testing whether we are in a multiverse?
We all know that fiber optics are very small, but my question is, why are they small? Does it give them some advantage in transmission of data? If yes then how? What would happen if we make the fiber optics larger in size, or even smaller?
I know nothing on the subject so I'm in no position to take part in the discussion that's not what I was suggesting.
So the theory that at the fundamental level matter and energy are made of tiny vibrating strings is an aspect of the theory but it's actually just a collection of equations that appear to be describing that and a new take on old news like QFT?
So the predictions that the tiny vibrating strings would entail can be completely disregarded as another part of the "motley collection"
https://www.newscientist.com/article/mg23130890-900-metaphysics-special-is-time-an-illusion/ I think the key to this question is not whether time is emergent or fundamental, but how exactly at the smallest and largest scale, things are being imposed an ordered relation. That is answering how causality arise in all scales might help us to work out why there is this concept called "time"
@SpaceOtter A 1D object traces a line called a world line as it travels through spacetime. You can calculate what trajectory it follows simply by finding the function that minimises the length of this world line. In fact all of GR follows from this simple principle given you define the length of the line in the right way.
A 2D object traces out a surface rather than a line, and this surface is called the world sheet. If you minimise the area of the worldsheet, and also quantise it, then this is the principle on which string theory is based.
But the maths is so hard that even now no-one really understands what the theory means. As a result, instead of the single unifying idea that we have in GR there is a huge array of related mathematical ideas.
Although it all stems from consideration of the trajectory of the 2D object it's a gross oversimplification to say it's a theory of vibrating strings.
Suppose you have a document explaining something. Suppose that document uses \section, as LaTeX documents are wont to do.
Now suppose that document happens to be something you want to include as a sub-part in your thesis, or a book, or whatever.
So naturally you're going to split the content of your original document into the preamble in one file, and the content in another.
However...
you still have the problem that you have these \section commands. When you include your little document into the larger one, it's likely that \section is no longer correct; perhaps everything needs to "move down a level" so the sections should now be subsections.
What do we do? Do we give up? Do we use LuaTeX? Do we use MS Word?
Even if I renew my mathematica subscription via my uni license now, it would take at least 2 days before the matheamtica office sent me the license code
@DanielSank Since build 2016a, matlab has a symbolic toolbox that allow to do limited symbolic manipulation. Let's see if your integral is one of the luck ones
Yeah, I have just replaced y and s by 7 and 23 respectively, All numerical values bubbled out, but the integral remains unevaluated, so sometign else has to be done about the domain of that integration
1. direct integrate->refuse to do 2. sub y=7 s=23->get NaN 3. hack positve valued square roots by using absolute value->diverges (or might be overflow)
Dammit! I keep getting notifications of upvotes, which is good, but they're all on the SciFi SE where I've answered a couple of story identification questions.
That happens, I have many ancient questions that were answered which get upvotes ever now an then, I just click away the notation as they pop, after all ,they don't make noise unlike facbeook notifications
I'm refreshing my mechanics knowledge and have a question.
Say we have an object moving with a constant acceleration $a$ moving in one dimension. Furthermore, $v_0 =0$, $s_0 = 0$ and $t_0 = 0$ (with $s$ being the traveled distance).
Then the speed $v$ of the object at time $t$ is given by $$v(t...
@yuggib Perhaps it is trivial for you. You are a PhD mathematician and PhD level set theory is accessible to you. But for me, it's impossibly difficult.
@0celo7 : IMHO when you understand the wave nature of matter, you understand that string theory kind of missed a trick: "string theory is a theoretical framework in which the point-like particles of particle physics are replaced by one-dimensional objects called strings". The electron is not a point particle.
@0celo7 : I don't "trust" Crowell per se. But I've seen some of his educational material, and I know that many of the things he says are correct. How can I put this diplomatically? JR tends to give answers which attract a lot of upvotes, but as I've said before, science is not a democracy. IMHO one of the problems at PSE s that the popscience answer gets the upvotes, and the right answer doesn't. Hence a lot of expert posters are ex posters.
First, I'll state some background that lead me to the question.
I was thinking about quantization of space-time on and off for a long time but I never really looked into it any deeper (mainly because I am not yet quite fluent in string theory). But the recent discussion about propagation of info...
@SpaceOtter When you use quantum field theory to quantise a field you end up with a characteristic sequence of field modes, and these field modes correspond to particles with different momenta. This is how the concept of a particle emerges from quantum field theory.
So the things we call gluons emerge when we use quantum field theory to describe the strong force.
When we quantise a string we get a much more complicated set of modes, but if looked at in the right way it looks like a combination of QFT field modes. In other words the quantised string behaves like a combination of particles.
Relating the modes of the string to the field modes we observe around us, like electrons, gluons, etc, truns out to be so hard that no-one has managed to do it - at least not in a convincing way. Nevertheless, in principle the strings have excitations that look like the particles around us.
This is one of the problems with string theory. It predicts particles exist, but not which particles exist. Depending on various adjustable parameters there could be lots of different types of particles that the strings produce.
That's part of the reason you hear people saying that string theory doesn't predict anything.
First, relating string theory modes to ordinary particle modes is perfectly well understood: It can be shown that the tree-level string interactions always correspond exactly to the amplitudes of a quantum field theory. This QFT is called the "effective QFT" associated to a particular string model.
Second, the "problem" you refer to also exists in QFT - no one tells you which fields to put into the theory, there's nothing unique about the Standard Model in any sense - but is much worse there since there are much more possible QFTs than there are possible effective QFT resulting from a string theory model. The space of non-stringy QFTs is called the "swampland" and there's a famous paper by Vafa about it.
@0celo7 my professor claimed that when adding and subtracting measured quantities, the amount of significant figures do not matter and one is only concerned with the amount of digits to the right of the decimal point
Indeed, string theory so heavily constrains the possible models that there is only a finite number of them (how many there are depends on the counting, but 10^500 is a number commonly cited), while there is no such finiteness for possible QFT models.
i.e you have 1000g of a substance measured by crude measuring equipment (only measures 1 sig. digit) then add 131.342g of the same substance with which you measured 6 sig. digits) @0celo7
@ACuriousMind: I agree with all of this. If you interpreted anything I said as being critical of string theory then I gave the wrong impression. Maybe I gave the wrong impression to SpaceOtter too ...
@0celo7 I could have tested out of this intro course and gone into a more difficult chem class but honestly i'm lazy and this fulfills requirements so yolo
@0celo7 You count stable solutions to the "string equations of motion", which are essentially the requirement that there's no conformal anomaly. The notion of "stable" is indeed related to something called the KKLT mechanism that John mentions.
However, it should be noted that I think those countings only count CY-like compactifications. It might be possible that there are other compactifications not captured by the counting.
These parameters are in principle continuous, but the KKLT mechanism means they can take only discrete values, and the number of possible combinations gives the 10^500 estimate.
The discrete values correspond to wrapping of branes round the compact dimensions in some fashion that I completely fail to understand.
@JohnRennie I read your last three messages up there as "We don't really know how to relate string modes to particles, and it's a problem with string theory that it doesn't predict exactly which modes will occur". If that's not what you wanted to say, either I fail at reading comprehension or it's phrased rather badly.
I am looking for an explanation about the idea of "operator mixing" and its associated concept about when anomalous dimension has to be thought of as a matrix.
For example this idea is slightly touched upon in this article though the link to anomalous dimension doesn't lead anywhere. Here they ...
@0celo7 What John said - it is desirable to not fully break the extended supersymmetry of superstring theory, and the compactifications which preserve at least a minimal amount of SUSY are exactly CY. The residual supersymmetry is then broken at another, lower scale to yield the Standard Model. This is one of the reasons string theorist are rather dismayed that the LHC hasn't found any hints of SUSY so far - the closer that scale lies to the string scale, the less "natural" it becomes.
@JohnRennie Ah, yes, that is correct - we have to do it the other way around: Build the string theory and examine what QFT is gives.
Really, the main trouble is that evidence for supersymmetry isn't forthcoming, and the non-supersymmetric models are far less understood.
You're assuming because the three rightmost digits are zero that they aren't known so the weight is 500 - 1499g. And maybe that's right - I wasn't there so I can't say. However the obvious interpretation is that the instructor meant 999.5 - 1000.49g.
I'm just saying that I think in this case the error is in the rightmost digit. The point being that when you add your 131.342g you first round it to 131g.
@SpaceOtter : it's all very hypothetical. See stuff like this: "A feature of gravitons in string theory is that, as closed strings without endpoints, they would not be bound to branes and could move freely between them. If we live on a brane (as hypothesized by brane theories) this "leakage" of gravitons from the brane into higher-dimensional space could explain why gravitation is such a weak force". There's no evidence for branes or higher dimensions.
Besides, IMHO plain-vanilla physics tells you why gravity is so weak.
No, I'm not going to explain the rather rudimentary error analysis used by some random chemistry instructor. What I am willing to explain, and have done, is how not to get zero marks in the test sheet set by that instructor.
@0celo7 : but when you contrive your charged particles as the current-in-the-wire the strong forces nearly balance, but not quite. So the residual force is weak. Again see Rod Nave's most excellent hyperphysics. OK? Are you happy with that?
The treatment of electrons as waves has combined with spherical harmonics (below image) to form the foundation for a modern understanding of how electrons "orbit."
Tweaks to the spherical harmonic differential equations yields the Schrodinger equation (below image), which is the accepted model...
We all know that fiber optics are very small, but my question is, why are they small? Does it give them some advantage in transmission of data? If yes then how? What would happen if we make the fiber optics larger in size, or even smaller?
I'm refreshing my mechanics knowledge and have a question.
Say we have an object moving with a constant acceleration $a$ moving in one dimension. Furthermore, $v_0 =0$, $s_0 = 0$ and $t_0 = 0$ (with $s$ being the traveled distance).
Then the speed $v$ of the object at time $t$ is given by $$v(t...
I am looking for an explanation about the idea of "operator mixing" and its associated concept about when anomalous dimension has to be thought of as a matrix.
For example this idea is slightly touched upon in this article though the link to anomalous dimension doesn't lead anywhere. Here they ...
