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Posts posted by imatfaal

  1. The popular press do like to lionize (or sometimes demonize) those that are extraordinary - this means you will very rarely get a balanced and honest view of those in the public eye. This combined with the fact that in the recent past people like to down play their own talents and work ("I was just lucky..." "It happend that I was the guy on the spot..." "Really it was a team victory" etc. ) means that both the natural ability and the hours of grind are hidden. I have spent time around world class track cyclists and they will talk about the amazing support and coaching, the team morale and camaraderie, and the expert sports nutritionists, psychologists, and physiotherapists; very rarely will they mention that multiple times a day they will be curled up in pain in a foetal position on the floor cramping up and vomiting from lactic acidosis nor that they were given this opportunity because of the exceptional talent and inherent physiology they displayed as an untrained child.


    It is the modern day humility

  2. !

    Moderator Note


    OK Mandlbaur. Last chance to get this thread back on the tracks. Your next post MUST include an equation (with proper naming of symbols) which you believe defines the conservation of angular momentum.


    FYG [latex] \textbf{L} = \textbf{r} \times \boldsymbol{\rho}[/latex] says nothing about conservation - it merely relates the linear momentum of a particle to the angular momentum of that particle around a specific axis at a perpendicular distance with the magnitude the same as r


  3. ...

    As in, does the velocity cause any length contraction/time dilation?


    Any length contraction is in the direction of motion and can be dealt with in components (if you think in the frame of the pellet then there is no time dilation and all frames must give same answer) - in the y direction / vertical axis the velocity at every moment is similar for the dropped pellet and fired pellet; so no matter how small the relativistic correction might be it would still be the same for both.


    And for those who quibbled that this post should not be in "Relativity" - surely this is galilean / newtonian relativity? :P Although forum subtitle does say it is for SR and GR


    Studiot, I have attempted your modification of the question my methodology is shown below:


    In triangle CBO:


    θ = tan^-1(0.6)

    θ = 30.96375653...



    tan(θ) = h/y

    y = h/tan(θ)

    y = 7.8/tan(30.96375653...)

    y = 13



    In triangle AOB:


    alpha = 23.57818 degrees

    beta = 29.55192 degrees

    gamma = 126.86990 degrees


    a/sin(a) = b/sin(b) = c/sin© [sine rule]


    sin(alpha)/y = sin(gamma)/d


    d/sin(126.86990) = 13/sin(23.57818)


    d = (13/sin(23.57818))*sin(126.86990)


    d = 25.99999762


    d = 26 (nearest whole number)

    Imatfaal, Your proposal matches the answer in the back of the book. Though I'm not familiar with using pi in this topic.



    @Ruairi I tend to work in radians rather than degrees. The total internal angle of a triangle is pi radians. If you have not covered radians yet then just substitute 180 degrees for Pi and 90 degrees for Pi/2 and it will all make sense.


    You will also note that you do not need to use a calculator - nor work out any trigonometrical values; all the values needed are given and you can do this with a pencil and paper. It is massively important to learn when you can do this - you are likely to be asked exactly this sort of question in exams in which you are not allowed a calculator!


    @studiot OK so that's exactly how I proceeded above. Your post started with the injunction to ignore right angles so I just could not see what you were doing. thanks

  5. It doesn't need to exist. As far as we know, they don't exist. But IF space-time can be described by quantum field theory then the quanta would be what we call gravitons.



    That is my understanding too. I would add that quantum field theory for the other 3 fundamental forces has turned out to be one of the most accurate and explanatory models in human history - so the search for a theory of quantum gravity (and thenceforward unification) is a path worth following.


    Maybe one of the experts can weigh in on this further question - with the data from experiments such as LIGO, BICEP2, Gravity Probe B etc. has anything cropped up that was a prediction based on solely the existence and current understanding of the graviton from qft rather than based on the understanding of GR (or on both classical and quantum theory). I know the sort of gravitational radiation fits with spin2 massless particle - but that was predicted by GR and graviton made to fit rather than other way around. Is there anything upon which GR is silent but qft might have got right?


    I think you have to assume that this a problem in 3d. You are looking into a right-angled corner

    y is along the floor and h is up the corner of two walls etc. This would allow three right angles in the corner


    1. Establish length of y

    Tan(theta) = opposite/adjacent = h/y = 7.8/y

    0.6 = 7.8/y

    y= 7.8/0.6 = 13


    2. Use sine rule

    y/sin(alpha) = d / sin(90) = d/1

    d= y/sin(alpha) = 13/ sin(alpha)

    d= 13/(0.4) = 32.5





    actually upon further inspection (ie sin(alpha+beta) =.08) I realise I made an improper assumption. Correction follows





    Whilst this is a 3d problem one must not assume that this is a right angled corner - in fact the point that sin(alpha+beta) is not 1 means that angle opposite d cannot be right angle. To visualise image two walls with an angle not equal to 90 degrees between them - h is the vertical join of theses walls, y is a horizontal, the plane in which d is scribed is the floor


    1. Establish length of y

    Tan(theta) = opposite/adjacent = h/y = 7.8/y

    0.6 = 7.8/y

    y= 7.8/0.6 = 13


    2. Use sine rule (gamma is angle opposite d)

    y/sin(alpha) = d / sin(gamma)

    d= sin(gamma)*y/sin(alpha)


    2a. determine sin(gamma)

    Note Sine( Pi - Angle) = Sine (Angle) as sine curve is symmetric around pi/2

    But gamma + alpha + beta = Pi

    gamma = Pi - (alpha + beta)


    Sin(gamma) = Sin (Pi - (alpha+beta))

    per above equality

    Sin(gamma) = Sin (alpha +beta)


    3. continue sine rule

    d= sin(gamma)*y/sin(alph)

    d= sin(alpha+beta)*y/sin(alpha)

    d= .8*(13/.4)

    d= 26





    @studiot - I concur with your answers for the angles. Yet I still fail to see how you can solve the upper right hand triangle - you only know one angle and a side; that can create any number of triangles, all with different length y. Could you specify for me how you do this without assuming that the angle between y and h is a right angle?


    Hello pavel, good to see you back again, you often add something useful to threads.




    With regard to part (b) of your question the answer is not so simple.


    It depends upon what you are sampling.


    Here are two examples.


    1) You have divided a cornfield into squares for testing yield. Placing all the tests sequentially in one corner may hit fertile or stony ground.


    2) You are a buyer checking a box of apples for % rotten apples. A rotten apple is much more likely to infect neighbours than remote apples.


    In both of these sampleing sequentially may well produce different resutls from a proper spread of testing.


    Sampling theory developed from real life situations like these and it is obviously important to ensure that the sample is as representative as possible of the whole sampled population.

    This is why sampling theory is a huge area in its own right.



    "2) You are a buyer checking a box of apples for % rotten apples. A rotten apple is much more likely to infect neighbours than remote apples."


    I find this very intriguing. You are right of course, but the upshot is so complicated. A corner apple has only three neighbours which might have been able to turn it rotten - a centre apple has eight etc.; assuming a rectangular array. Assuming different number of generations of infection possible then the odds of a centre apple remaining fresh with a rotten in the box is contrasted with the odds of a corner apple remaining fresh - as the number of generations grows this comparison moves from same, to centre more likely rotten, and back to the same again.


    I know it will have been does before - but when I have a decent pc in front of me I think a little analysis and some monte carlo or bust is called for

  8. In the video, they meantioned that the series was was used in 26 dimensional String Theory as well, which is why I speculated that Infinity could be realized in reality but requires extra dimensions.


    FWIW, certain aspects of infinity are included in my own interpretation of GR which involves falling through the EH of BHs at the SoL.


    QFT is predictive and has been tested to phenomenal precision. String Theory has not once been tested to any level of prediction; basically almost all complex maths will find itself bound up in string theory in some way.


    Whether string theory turns out to be empirically predictive or theoretically useful in physics, one thing is for certain - it is mathematics and modelling of the highest possible order; perhaps mankind's greatest abstract achievement.

  9. ...

    Apply the above for the standard model of particles including the Higgs field under action via

    [latex] \stackrel{Action}{\overbrace{\mathcal{L}}} \sim \stackrel{relativity}{\overbrace{\mathbb{R}}}- \stackrel{Maxwell}{\overbrace{1/4F_{\mu\nu}F^{\mu\nu}}}+\stackrel{Dirac}{\overbrace{i \overline{\psi}\gamma_\mu\psi}}+\stackrel{Higg's}{\overbrace{\mid D_\mu h\mid-V\mid h\mid}} +\stackrel{Yugawa-coupling}{\overbrace{h\overline{\psi}\psi}} [/latex]

    and voila you just incorporated every SM field into your spacetime curvature using action. Every field contributes in some fashion.


    Excellent post as always Mordred. And because I could never contradict you on physics, I will take this opportunity to take a mild shot at your nomenclature >:D


    It's Yukawa coupling and Higgs (no apostrophe; named after him not his possessive - which would mean anyway that the apostrophe would be after the s )


    Now awaiting the Skitt's Law moment... :P

  10. Today I learned that forensic investigations have been in use since the 13th Century.




    I have learnt that Forensic no longer means what it used to mean. Forensic means to me "pertaining to the courts of law" and "suitable to being part of the factual pleadings in court" - it seems that through the use of forensic as an adjective in front of words like science and medicine has morphed the meaning such that Forensic now means Forensic Science.*


    So regarding the discovery magazine article - that may well be the first forensic science but definitely not the first forensic investigation; just off the top of my head Cicero details some forensic investigations (often forensic accountancy) and that would be 1400 years earlier



    * I also blame CSI and its ilk

  11. Exactly, it can't be. Which means that you'd need to pin down the additional information that is conveyed by understanding the context and include that in any string meant to encode the meaning of the work.


    Best case scenario, sentences would need the "index number"-equivalent of heavy footnotes in order to fully capture the meaning of anything written that way.


    Agreed. My point was that one form of additional information was a belief (in the mind of L) in the level of credence (in the mind of T) of the words of C; thus one of the "heavy footnotes" would need to be a set of P(x1,x2,...,xn). In summary a recursive reference - and we all know what recursive references can do in a scenario of transcribing one set of language into a series of numbers (!)

    At the 400 year anniversary of Shakespeare's death, they had 10 actors (9 plus Prince Charles) who each said the lines "To be or not to be, that is the question" in sequence. Each one gave a stress on a different word in the sentence, so you had the sensation that they were saying 10 different things, which they probably were.



    Entertaining, if nothing else



    Lovely - really fun. Liked Sir Ian's very quiet aside "Hello Eddie"

  12. Talking of Shakespeare - there is the famous line from Two Gentlemen


    Who is Silvia? what is she,
    That all our swains commend her?
    Holy, fair, and wise is she;
    The heaven such grace did lend her,

    That she might admirèd be.


    The first line was once read by an angry and vindictive actor as

    Who is? Silvia? What! Is She?? [imagine vicious gossip talking about a third party]


    But, obvious punctuation errors aside, reading the glorious poem by WS it is hard to believe that this can be shorn of context and survive.

  13. Imatfaal, it appears that you want to bring in a third party into this "communication"! That brings in an assumption which you have apparently not considered. I start with one individual and then discuss information being presented (what I call communication) to that individual without making any assumptions as to where that communication comes from. That is, I have defined the individual who is trying to comprehend (think "learn the language") the meanings of the communications he is attempting to understand). I have made no definition of the source of that communication. It could be a party similar to himself (of course, before he learns anything, he can have no concept of what he actual is as he has learned no concepts) or that source could consist of a number of different entities. If you don't leave the issue open, you are making unjustified assumptions...


    Then you are not discussing language - divorcing language from source is not possible; even if we do not know the source we will create a placeholder for that source, moreover even in the extreme example in which we believe there is no source that information will colour a listeners perception. And everything we do in the process of comprehension is contextualized by the source.


    I would say you are the one making an unjustified, and unnatural assumption; that language can be separated from speaker, situation, and listener. You must reduce in order to simplify for an experiment or model - but the removal of an intrinsic factor cannot be ignored.

  14. I think that first sum is related to the Riemann Hypothesis, or at least the zeta function, and i believe uses a different summation method - i don't know nearly enough to comment further though.



    The second case is just a manifestation of it being possible that probability zero events can occur. This is uncontroversial, if somewhat clumsy language.



    I'd go further and say that without infinity, particularly the idea of limits, statistics would be unable to progress beyond it's state several centuries ago. The Law of Large Numbers and the Central Limit Theorem are absolutely fundamental to probability theory and both rely on asymptotic results. Are you saying these theorems are incorrect and we should throw away the last few centuries of statistical knowledge reliant on them?


    It is the Ramanujan Summation - which gives an answer to the value of an infinite divergent series; in normal use there is no sum to an infinite divergent series - this is a special version which bears passing resemblance to the sum and allows further study of the concept. You are also correct in that it is used in zeta function methodologies


    I have read that Ramanujan summation is also used in normalization of certain quantum field theories - which in turn give positive predictions in terms of real world results. So it is weird and a bit unwholesome but there is definitely very important maths there



    It's early and my brain is still waking up, but I don't see how it wouldn't. You will have E = pc and p = h/lambda (those are QM equations which do not apply just to photons) and any wave has lambda*f = v, which in this case is c since the particles are massless. So lambda = c/f = hc/E E = hf


    "(those are QM equations which do not apply just to photons)" - OK so this was the bit I was unsure of; thanks.


    ...The graviton - as the boson of a gravitational radiation (ie not as the virtual boson of gravity) - can hold any frequency and will reflect the period of the quadrapole which generated it just as the real photon does (obs not quadrapole etc) . I also think that Energy will still be proportional to frequency although I do not know if it is still as straight forward as E=hf


    Thinking more - I guess the frequency of the graviton, just like that of the gravitation radiation, will be twice the of frequency of the varying mass system (eg twice the frequency of rotation in the LIGO event); it's quadrapole - two peaks for each complete cycle of driver

  16. ...

    The second step of my argument is fact that "understanding" a communication can be seen as a phenomena which occurs between two communicating individuals which can be defined by the probability the the "listening" individual knows the "truth" the other individual places on the specific thoughts being communicated.



    Are there not multiple scenarios in which the listener's and communicator's credence levels are identical but the presence of a third party and more importantly the third party's knowledge/expected credence (ie expected by Listener & Communicator) are the crucial factor?


    Thus the [latex] Message^{\ Communicator}_{\ Listener}(x_1, x_2, P_{third\ party}\left(x_1,x_2,...\ x_n\right) , \cdots,x_i , \cdots , x_n) [/latex] is actually contingent on a probability.


    There is nothing in the communication (ie that would be represented by x1,x2 etc) which deals with the third party's expected credence but it may completely alter the import of the message.


    To give a real world example: C makes a statement which L knows to be false and which C already knows L knows to be false. In the presence of a third party T this statement whilst not changing in any form can mean multiple things; the meanings are all contingent on the shared and expected shared credence of T ie if T also knows the falsehood then it is a shared falsity, but if it is expected that T is unaware of the falsehood then it is a shibboleth between C and L excluding and differentiating T.


    If you are happy that probabilities of third party credence can form the message then I agree - but otherwise no.



    IF the field (space-time) could be quantised, then the interaction (curvature of space-time) could also be described in terms of the exchange of virtual photons.



    I am not aware that it does.



    None. It can't.



    As the graviton would be massless, it would travel in straight lines at the speed of light.


    "What does it look like" doesn't make much sense. Any "image" of a fundamental particle is a poor analogy.



    It would be a real particle, a boson. Its interactions (gravity) would be mediated by virtual particles (i.e. not particles).



    I don't think it can accumulate energy. (I think the photon is unique in coming in a range of wavelengths/energies. Although, obviously, massive particles can gain kinetic energy by being accelerated.)






    As others have said, this is just nonsense.


    Great answer - would quibble only this


    "I don't think it can accumulate energy. (I think the photon is unique in coming in a range of wavelengths/energies."


    The graviton - as the boson of a gravitational radiation (ie not as the virtual boson of gravity) - can hold any frequency and will reflect the period of the quadrapole which generated it just as the real photon does (obs not quadrapole etc) . I also think that Energy will still be proportional to frequency although I do not know if it is still as straight forward as E=hf

  18. You have heard McDonald's food is so unpalatable that even flies avoid it?


    No that surely cannot be true (and flies can be connoisseurs of fine food :) )

    That sounds based on a little experiment run by Morgan Spurlock - he of "Supersize Me" - a selection of McDonalds "food" was put in bell jars and watched over a period of months. Lots of the food remained fairly intact and was not colonised by mould or other microorganisms - flies, I think, were excluded


  19. !

    Moderator Note


    Bimbo36 for your guidance; proselyting quotes from your holy book of choice are NEVER acceptable. I have trashed the religious follow up in the biology forum. Even the religion forum is for discussion of religion - not for conversion, nor for proclamations of faith. In a rational investigation an injunction from a holy book has no place and will nearly always be met with scorn and often with modnotes and warnings.


  20. I was used to eating it everyday.’ in OP, edited to ' I used to eating it everyday.'

    a grammar mistake. sorry.


    Is it true McDonald can be left there for months or even years without any fly near to it ? it is unbelievable !


    Just for your guidance


    "I was used to doing something" is an acceptable usage; it means you have become accustomed to a practice


    "I used to doing something" is incorrect. A little better is "I used to eat it everyday" - I would prefer "In the past I ate it everyday"

  21. Just to check is your food bought by your parents/parent most of the time; cos in most of the world junk food is not cheap, it just seems that way if you don't know how to prepare food.


    And we can control ourselves - it is a matter of will-power. Some people have greater self-control than others - this is just human nature; we vary hugely even though we are so similar in many other ways. There are quite a few threads on here with journals of people stopping smoking, my cycling forum has literally hundreds of threads of people losing weight (it makes those hills so much easier), and you will find every day tales of human fortitude and will-power all over the internet.

  22. ...

    America is so polarized, republicans will always be Republicans and democrats will always be Democrats no matter what policies 'their' party implements, that republicans consider this a good thing, and anything Democrats do a bad thing ( even if good ). The same holds true with good Republican policy. M Romney's health care plan was a 'bad thing' to democrats. Until it was co-opted by B Obama's Democrats.



    This old chesnut of they are both as bad is just plain wrong. I think in your country and in mine it is closer to be correct - but in the USA it is simply not true. BTW I think Romneycare was statute which was created by a Democrat legislature under a Republican Governor (he vetoed the left wing dirty socialist stuff). The fact that Romney had worked with Dems was a major negative against him for many of the tea-party faithful that were the ideological core of the modern GOP

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