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Posts posted by Royston


    The energy in a comet impact is bugger all compared to a GRB, the last 2/3's of your paragraph is nonsense. GRB's are not really comparable, the energies and the subsequent processes are boring.


    Oh dear, I don't even recall writing this, it doesn't make sense. Going by the date I was celebrating a friends birthday that day...(IOW I was mentally incapacitated). Sorry about that.


    By way of redemption, neutron stars have exceptionally strong gravitational fields, so anything travelling towards one (be it a comet or asteroid) has the potential to accelerate to a very high velocity (up to a large percent of the speed of light). Energy is conserved, so the kinetic energy of the body impacting the neutron star (which will be huge at those speeds) is balanced by thermal energy et.c on impact, and hence a very high energy explosion.


    A body in orbit around a star that tips over it's Roche limit will be broken up by tidal forces, and will (for the most part) join the accretion disk. Comets have a low tensile strength, so for the bulk of the debris to crash into the neutron star and not join the accretion disk, would probably require some unique initial conditions.


    Finding yourself stopping a high-velocity snowball might be no less painful than being struck by a slow-moving pebble. Yes? No?



    This seems to be along the right lines.


    EDIT: I don't find GRB's boring, quite the opposite...I have no idea where that came from redface.gif .

  2. Mathematic - many thanks for the comment. Yes, I'm inclined to agree with you there. However, as so often seems to be the case whenever I post a question in forums such as these, it didn't take me all that long afterwards to find myself stumbling upon answers of sorts while hunting around elsewhere on the net. Here, I refer to the so-called 'Christmas Burst' of 2010. Back then two explanations were offered up for the cause of this extraordinarily lengthy gamma ray outburst. For me, the most telling of these two explanations pointed to a cometary impact upon an otherwise quiescent neutron star located within our own galaxy. Since then this notion has given way to the other explanation, then doing the rounds: namely that the cause for this GRB was due to a considerably more distant supernova explosion. Even so, the fact that the astrophysicists were willing to entertain a (large) cometary impact as a possible cause for this GRB does leave me wondering whether such strikes are as benign as is so often thought. Unfortunately, I simply don't have the necessary number-crunching abilities to sweat the answer out for myself - at least not yet! In the meantime, I offer the link below as supporting evidence for my query.




    The energy in a comet impact is bugger all compared to a GRB, the last 2/3's of your paragraph is nonsense. GRB's are not really comparable, the energies and the subsequent processes are boring.

  3. I thought my posts were reasonably popular.


    approx 30,000 views.


    Logical fallacy. Besides, it is usually the case, (and this is not directly aimed at you), that the worst threads get the most traffic. For example, members who simply won't take advice and keep arguing their case, despite being hopelessly wrong. Other members watching the thread, see this is as a form of entertainment, the thread gets lots of hits...it's harsh, but that's the internet.



    I am a visual person, I think in pictures, I have a pencil and notebook and piece of paper in my top shirt pocket. I,go to bed with a notebook beside the bed. I taught in pictures, I draw and paint pictures, If any body asks me a question , I reach for my notebook and doodle the solution.


    Unfortunately, this is the problem. You shouldn't treat the speculation forum as your personal note book. Collate your notes in private, then produce a coherent, well structured report to present to the community. Bearing in mind, that it should adopt the same rigour you would expect from a scientific paper, albeit a stripped down version. Diagrams are essential for mathematical models, but art is probably more at home in general discussion, or an art forum.


    Looking back on this thread, would you, in all seriousness, present that to the department of transport ? I don't mean to sound over critical, but I've seen better work boshed together at the last minute for a GCSE project.


    You cant teach old dogs new tricks.



    That maybe true to an extent, but I've worked with people your age, who have just started studying physics. Their views and appreciation of science and nature has changed, so I really don't see that as an excuse. You used to teach physics, so I find your methodology a bit baffling.


    I hope this is sound advice, because surely you want to avoid the kind of responses DH has posted.

  4. Hmm. How about eating ourselves? MyMeat yuck.


    If the technology became commercially available, I think it would be inevitable somebody would attempt a McMe burger. There's also the possibility of cultivating the cells of endangered species, e.g Snow Leopard sausages, rasher of Rhino, and so on. Needless to say, anything with flesh would be game (no pun intended).

  5. I think the word incompatible is misleading. QM describes very small scale things, and GR and SR describe very large scale things. They do not describe the same things differently. Thus, they are not incompatible.


    Except that you can make predictions in the macroscopic domain using QM (see Ehrenfest theorem) to a suitable classical limit. Besides, it's GR and QM that are incompatible. Quantum electrodynamics combines SR and QM.


    EDIT: Cross posted with xyzt

  6. Just a question on the general trend of % of of mass in galaxies being DM relative to there size.


    Do the larger galaxies tend to have more (as a percentage) than smaller galaxies?


    I tried a search but, at least with the keywords I used, I found no answer.


    This probably won't help too much, but on the larger scale (i.e dark matter halos in which numerous evolving galaxies can be contained) dark matter evolution can be approximated using the Press-Schechter model and N-body simulations. N-body simulations can be used to track the behaviour of DM halos. Combining N-body simulations with numerical models you can predict certain properties of galaxies, and these are called semi-analytic models. This is more for galaxy evolution, but clearly there's a link to DM distribution and the subsequent properties of a galaxy. This is very new work, and different models require different assumptions. This may give you a starting point to investigate though. Note, that I studied cosmology some time ago, so I'm not sure on the current consensus.


    There was work carried out by Eduardo Battaner and his team, http://www.alphagalileo.org/ViewItem.aspx?ItemId=58466&CultureCode=en which attempts to resolve what you're asking, but I'm pretty certain it's not accessible (meaning I'm not going to pay for it). But, if you dig around you may find something.


    I read that dwarf galaxies actually contain higher proportions of dark matter than larger galaxies, (It is important to remember that proportion is not the same as amount). From that, it can be said that smaller galaxies would contain a higher percentage of dark matter than larger galaxies, but this observation could be flawed, and is open to interpretation.




    Do you have a link ?

  7. I really hope the name "schmeat" doesn't stick. I think that would stop many people who might otherwise think this is a pretty fantastic idea.


    It is slightly off putting. It's impossible to use a name that distinguishes it from regular meat, without reminding the consumer that it's produced differently. But Schmeat is a bad choice. Maybe something like 'morally modified meat' or Mmmeat.

  8. As CaptainPanic stated earlier...


    It's probably Google, Bing and a bunch of other search engines. They visit everything online frequently.



    Out of interest, what do you hope to gain by tracking the number of (human) visitors to your profile ?



    EDIT: That was in response to krash661


    I have seen my own mother in a wheelchair, bloated around the face, obviously weak do to stress lines about her eyes and neck. She is in a hospital, her eyes are somewhat glazed over from their natural color(I don't know what that means yet) and she's in a gown.


    It is far more likely you saw subtle signs of your Mum's health deteriorating, and this would conjure worst case scenarios in your mind. I can sympathize with this, as I've had to endure the same thing, but a different condition.



    Unfortunately though (and it sounds a bit cold), trying to convince your audience that you have predictive prowess doesn't cut it. You've suggested an idea, and you need to back it up with the same rigor as any other scientific theory or 'theory' in this case ;). The glaring error, is that your idea is very vague, so it's almost impossible to draw any conclusions from it. There have been a few proposals linking antimatter with dark energy, but not too sure on their validity, that's about as close to your idea that I can think of.



    We are expanding through each of these NOBLE/ALKALI expansions, sodium/neon is the one that we are now expanding through, each of these overlap, it is why we have trace elements of previous expansions within us, it is a continious cycle,

    You will notice there are 11 expansions which is predicted in M theory/string theory, which predict 11 dimensions,

    Each of these expansions is a dimension/universe.


    They radiate out from radon/francium, as i have tried to show,


    First view in smallest magnification.




    It's clear from this post that you're making the same mistake a good 90% of posters in the speculations forum make. You can't make improvements on a theory or model (although I don't have the slightest idea what you're trying to improve upon) unless you have a thorough understanding of the subject.


    As an analogy, suppose a musician (say a pianist) wanted to add something to a classical masterpiece. In order to do this, they would have to be able to play this masterpiece to the same precision as the original, before they can start manipulating the notes and timing et.c. You're basically donning a pair of boxing gloves, and randomly hitting the keys, and trying to convince us you have improved upon a masterpiece.


    Do you, in all honesty, have a thorough understanding of string theory, chemistry and big bang cosmology ?


    AFAICS, you've sporadically grabbed information off the internet, and lumped it into an incoherent mess.

  11. You have replied to my question of: How are they different? by giving yet another example confirming that they are different.


    My example was to show that charge has inherent properties (displayed by the dynamics of the electron / positron). For instance, if they curve in opposite directions this implies symmetry, no ?

    Thanks, but I already know that they are different: I would like to what it is that makes them different?



    Saying that the difference is charge, is just a statement, it is not adding anything as an explanation.


    Not really, charge is well defined in physics, so it's certainly more than 'just a statement' http://en.wikipedia.org/wiki/Charge_(physics)

  12. If they are point like particles, fair enough, but then how is the electron different from the positron, how is their physical form different from each other?


    If you say that they have no physical differences, then that is the same as saying that they are identical particles.


    You seem to be caught up with the word 'form'. If you mean attributes like spin, mass et.c they're identical. However, it shows on the diagram they have opposite charge, so that's the difference.

    In which case, how do you explain their different behaviour?


    Well, a demonstration of this difference would be to fire them through a magnetic field. The electron will curve in an opposite direction to a positron, which shows they have opposite charge.


    EDIT: swansont replied while I was posting.

  13. Not sure yet how this differs from previous observation of decay of orbit fitting with general relativity's prediction of energy being radiated through gravitational wave - but will update if/when I realise what the new bit is.



    It states the distinction in the abstract...


    'However, the most massive NSs known today reside in long-period binaries or other systems unsuitable for GW (gravitational wave) radiation tests. Identifying a massive NS in a compact, relativistic binary is thus of key importance for understanding gravity-matter coupling under extreme conditions'

    From the discussion...
    'The orbital period of PSR J0348+0432 is only 15 seconds longer than that of the double pulsar system, but it has 2 times more fractional gravitational binding energy than each of the double pulsar NSs. This places it far outside the presently tested binding energy range [see Fig. 4a & (8)].Because the magnitude of strong-field effects generally depends non-linearly on the binding energy, the measurement of orbital decay transforms the system into a gravitational laboratory for a previously untested regime, qualitatively very different from what was accessible in the past.'

    It goes on to explain that if GR becomes invalid at these extreme conditions, there would be a violation of the strong equivalence principle i.e the gravitational field is independent of an objects position and velocity. Such a violation would lead to GW emission deviating from the predictions of GR. I assume this rules out Brans-Dicke theory, not sure on the details though.
    EDIT: On further reading it doesn't rule out Brans-Dicke theory. mellow.png
  14. Surely these terms are defined prior to the question ?


    In any case, all you need to do is check your units. For instance, p and v are in imperial units for pressure and specific volume respectively, so check the imperial units for work, and see what happens when you multiply p and v.


    As for the 728 and small k. Given that the equation for specific kinetic energy is [math]K=\frac{u^2}{2}[/math] where u is *velocity, this points to either a proportionality constant or a conversion factor, so work through your units.


    Hint: look up conversion factors for 1 Btu/lbm


    I'll leave it to you to suss out k.


    *In your question velocity is given as v1 measured in fps (feet per second).

  15. Thanks Royston. Your mention of the term "Pure Velocity" gets at what I was thinking of earlier. "Velocity" isn't a physical thing, it's just a fancy word for "speed"".


    Velocity is described by a vector (speed isn't), as for the rest of your post, it's not really chemistry based. If you want to discuss cosmology, then start another thread.

  16. There are also reports that this interpretation was "mathematically" proven...


    It depends what you mean by that. A physical theory should be mathematically consistent, it's a basic requirement. However it needs to hold up to experiment and be provable / falsifiable. It's the latter where MWI doesn't really hold. In this case, a massive assumption is required to explain the results.


    other say that that these "worlds" were observed


    Do you have a link or citation for this ?

  17. But I'm a bit confused by your claim that energy is a "property".


    In the same way that velocity or momentum is a property.


    It's hardly surprising that energy is confusing, when you hear terms such as 'pure energy' on Discovery and Horizon et.c (it's not a substance). I think this term arises because it is quite an abstract way of book keeping in physics. Have you ever heard the term 'pure velocity' ?


    Couldn't we just stay with Newton, and tweak the equations a bit?


    Why ? Quantum theory is without doubt the most successful theory in physics to date, in any case, in certain circumstances it reduces down to Newtonian mechanics.

  18. I think this is an issue of courtesy that posters must think about when posting videos, but I'm unsure any rule changes are in order.


    There shouldn't be any rule changes due to the fact that posting a video is no different to posting a body of text i.e it is a discussion (and funnily enough a Science) forum, you should read/watch then come up with your own conclusions to present an argument.


    I happen to agree with this...http://www2011.mpe.mpg.de/ir/irretreat2011/read/2009_schawinski_b.pdf. But so what...unless I narrow down the specifics, then it muddies the discussion.

  19. I'm not convinced of the usefulness for an undergrad.

    1) You (or at least "I") learn much more from attending talks, seminars, workshops, and conferences (or any other form of human-human interaction) than you do from reading papers.


    True, but that's clearly beside the point...the context of the thread is finding information that is (for the most part) trustworthy.


    2) If you're citing a paper in your work based only on (a) being on a topic somewhat related to your work, and (b) being published in a "list of reputable journals" then you should perhaps not cite it at all. If you're citing something because you rely in the information therein, then "I use it because it is listed in an okay journal" is not sufficient. If you cite a randomly-found paper solely based on being published in Nature and having 150+ citations because you have to fill the "overview over the field" section of your thesis, then you clearly have no overview over the field (which in many fields would actually be a lame thing to expects of someone below lecturer level, anyways).


    I can't see that I even argued that, or more to the point, why you assumed that I was arguing that. As much as it's reassuring that my citations are not based solely on the source, or a tentative link to the subject, I still can't see why (from an undergrad perspective) that a name and shame of certain journals would not be useful. IOW, I simply don't have the technical ability to differentiate nonsense from legitimate. Sticking to reputable journals, at least, increases the probability that the information is more trustworthy than a free-for-all journal.


    3) I do admit that one can feel very helpless when trying to find suitable interesting, readable, and helpful research papers about a topic, and fully understand why one would ask for assistance in this task. I do, however, believe that it is the duty of the research group (and in particularly the supervisor) to provide this help. Not in the sense of "here, read these papers I printed out for you", but at least in the sense of "Yin&Yan did something on this in the late nineties".


    I guess, but one of the main learning outcomes of my dissertation, is that you have the ability to use and facilitate checkable and credible sources. So it is (to a certain degree) up to the student.


    4) Let's face it: Already as of today Google scholar is probably more efficient at telling useful papers from useless ones than a compilation of "reputable journals" could ever be.


    That really depends on the search term.


    Besides, the only reason I've devoted 12 hours of my time each day to investigate complicated AGN feedback that agrees with cosmological timescales, is to say, hey look, I study astrofizzics....aren't I clever.

  20. Hi,

    i have been reading about iraq wars since my childhood. And there have been also many hollywood movies made about gulf war. But i just came to know that iraq which gets mention as bethlehem is infact a population of white skin african race muslims. So on tv and in media they show iraqis as good english and urdu speaking country, but infact is a african language speaking country but white in color. So their habitual lifestyle living is very much similar to africans, algiers, tunisia, algeria..etc.

    So does americans have an affinity towards african like countries like nigeria, iraq etc???


    Hi eric,


    Muslims are a highly evolved alien race who descended from the planet, Klackshudrrrr. They were transported to Earth through a collimated proton beam.


    I found one the other night, disguised as a used tissue. Luckily I managed to fend it off, before it's huge throbbing proboscis entered my face and forced me to write unintelligible shite on a science forum.

  21. I've been buried in research, so sorry for the late response...but thanks all for the replies.


    Who decides? How do they decide? This list of yours would be elitism, no doubt, and who would make it? The publishers of the "good" journals? There are de-facto lists of what's good and what's bad, but it's generally word of mouth.


    I guess from my perspective, it's grabbing information that is 'to the best of my knowledge' (and therefore) less likely to be littered with poor papers. It's not so much elitism, more, it's the best I can go on (at my level). I can see why it would be considered elitism, but I'm perfectly aware that the peer review process is far from water tight.


    Cha-ching! There's lots of money to be made by publishing hokey journals, particularly if you just pretend that you have a peer review process and don't have technical editors.


    I overlooked the money aspect...so all I need is a web designer and a Baez filter :P


    I think the people mainly interested in such a list are people not active in the respective fields of research, who happen not to be the target audience for research journals.


    I'm not sure how broad a statement that is, i.e whether that's applicable to other fields of science (over physics). But again, from an undergrad point of view, would such a list not be useful ?


    Nobody would believe that papers published in "reputable journals" are automatically legitimate, whereas those are not published therein are automatically crap.


    Of course not, I gave the Lancet example for a reason. However, I agree with your other points, except that Perelman had reached notoriety in the mid nineties, long before his work on the Poincare conjecture. ;)

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