Royston

Here's an update on the progress at the LHC, from physicsworld... http://physicsworld.com/cws/article/news/36769

Gauss ?

Yes, that was the reasoning behind the de Broglie formula, it starts with considering a photon, so zero rest mass, and (as Neon Black has posted) uses the relationship from SR i.e [math]E^2 = p^2c^2 + m^2c^4[/math] which clearly simplifies to [math]E = pc[/math] the energy of a photon. Then using the Planck relationship, [math]E = hf = \frac{hc}{\lambda}[/math] and where [math]p = \frac{h}{\lambda}[/math]...giving [math]\lambda = \frac{h}{p}[/math]. I realize this has already been shown, but there's clearly a leap, it's derived from a particle with no mass, and then plugs mass back into the final formula, as [math]p = mv[/math] which is a bit silly (i.e the Newtonian approximation of momentum is used), but as Klaynos has pointed out, experimentally it works just fine. Maybe I'm missing something, but it does seem like a guess (as you said) that the relationship will hold for particles with mass. Obviously with something like a golf ball, the wavelength will be tiny, and so observing diffraction effects with large objects is clearly impossible.

Oranphil, there are more than enough threads on the subject...if you have anything new to add to the current debate/s I suggest you join the discussions there. Try to make sure your arguments against GW havn't already been covered....and ummmm, good luck. I gave up long ago, anthropogenic causes to GW seem pretty obvious to me, even with a rudimentary understanding of science it becomes clear, if you've studied the subject (at a basic level) it becomes even clearer. And no, I'm not going to discuss the subject, I'll leave that to others, it's getting tiresome.

How odd, not only did I read the New Scientist article earlier, when looking for a different article concerning a recent thread, but I was actually reading about the fluctuations in a vacuum as per 'The Lightness of Being' this morning, on the way to work (Gluons and the Grid)...I stopped on the sub-chapter 'Grid Weighs' (incredibly good book BTW) The more I read about QCD, I've only covered the absolute basics so far, the more fascinating it becomes. I was ignorant in thinking that QCD solely dealt with the strong nuclear force, but it seems far more reaching than that.

EDIT: Oops, this was in response to Arch (below), Martin posted at the same time. Thanks for the links, after posting I found this article (New Scientist) where I can see now that dark matter annihilation is being considered in this instance (as well as what you've provided, Arch)...for some reason I thought the ideas behind the source of positrons (from the centre of the Milky Way) et.c was very much divided, but clearly I was wrong...obviously the source from my OP, is more local. The article gives some historical background, and future developments of discovering the nature of dark matter, so is worth a read as a summary if nothing else... http://www.newscientist.com/article/mg19926702.600-has-dark-matters-telltale-signature-been-spotted.html

I've been on the RSS feed for Universe Today for some time now, but this article in particular caught my eye. Partly because it affects Earth directly, but I found the possible cause of these cosmic rays due to dark matter annihilation more interesting... http://www.universetoday.com/2008/11/19/cosmic-rays-from-mysterious-source-bombarding-earth/ From the article... I realize it's a 'wait and see', to eliminate the latter if such an object is found near our solar system, however although not being an expert on dark matter and how it interacts, I was surprised that this was considered. Are they jumping the gun with putting this explanation forward, or are the models that describe dark matter annihilation (or at least these particular dark matter candidates) sound enough for this to be a serious candidate for these cosmic rays ? In any case, it's certainly a discovery that's worth following.

Well these 'people' are being silly by making sweeping statements about a subject and the level of difficulty. It depends which branch, what level and of course individual ability. Even if you're naturally gifted in a certain subject, e.g maths, it can easily be thrown away by not practicing. By the same token, if you're quite poor at a subject, but work hard and practice (practice being the key to mastering maths) then there's no reason why you can't be good at it, or at least be comfortable with the subject. You'll soon find out what your strengths and interests are, and that's the subject/s you should pursue.

Wasn't sure whether to put this under general chemistry but seems more appropriate here, however an art student in London has transformed a delapodated bed-sit into a crystalline grotto using copper sulphate. Every square inch of the bed sit is covered in blue crystals. More here, including a brief description on how he did it... http://entertainment.timesonline.co.uk/tol/arts_and_entertainment/visual_arts/article5097449.ece

Hmmm, I just reread this, and it wasn't really what I meant. As mentioned earlier, you could blindly accept a theory (which is close minded), or you could attempt to come to terms, and give serious consideration to the implications, which is where a leap of intuition comes into play. There are plenty of examples in physics that turn our intuitive versions of reality on it's head. It's perfectly acceptable to question current theories, but not on an intuitive basis, but on a purely scientific basis i.e proposing an alternative which may, or may not be even more bizarre. Didn't mean to flog a dead horse, I just wasn't happy with my previous statement.

Expansion is only observed on massive distances, roughly 100Mpc and up. On shorter scales gravity takes hold, which keeps bodies in orbit et.c and local galaxies pulling towards each other e.g Andromeda and the Milky Way. With objects themselves we have much stronger forces at play e.g the electrostatic force. So the answer's no.

Which is good, and besides this entire discussion is daft, relativity has been tested again and again, we've even based technology on it's predictions, so to speculate on a Universe without it, is pointless. This is really a reply to apologize for my crankiness yesterday, it's not really a good idea to be posting on a forum if I'm upset over other stuff, and venting leads to poor discussion.

Well yes, I'm more than happy that a change in frequency won't mean 'super-potent destroyers', whatever the crap that means. Considering I'm bombarded with much higher frequency radiation, I'd like to see you prove your argument...go ahead.

Pete, what's your idea of an 'open minded' physicist. Personally I think it's a loaded question, however, I tend to think being 'open minded' is accepting what logic and experiment dishes out, regardless of how counter intuitive it is.

That is only true to an extent, for large distances red shift will be observed whichever angle you care to pick...that's standard cosmology. Besides, I think the source of the confusion is that lightsword isn't using the correct terminology, and his argument is b*llocks anyway. Yuk, you mean absolute space...in any case, the frequency of light due to your position is hardly going to make a system unstable. After reading your post I stupidly thought the Unruh effect would cause instability, but that only holds if the frame of reference is accelerating...and at such large distances there's no problem if what you said is correct, which it isn't. It gets worse, a static or steady state Universe works fine with relativity, despite it being claimed as Einsteins biggest blunder, there's nothing to assume that relativity can't hold if the Universe is static, relativity works because it's dependant on a frame of reference, that's all.

True, but only in a system in equilibrium (i.e it has no direction...though it's not a vector like you said), with two bodies where heat flows between them, temperature determines a direction of heat...I should of been more specific.

Temperature is merely the direction of heat, and so can't be applied to the properties of an individual particle, such as a photon.

Ah right, I see what you mean. Well, the event happens in the Universe (yes I realize that's stating the obvious, but you'll see why I brought this up) and the Universe, as it is, follows the conservation laws...energy, momentum, charge et.c So really it's a given, the collapse of the wave function deals with measurement, we're not interested in what's conserved, just the outcome of the experiment...with my example the position of the electron. It's like saying, when I use my ruler, am I breaking conservation laws...well, no...of course not. Conservation laws don't come into it. You could argue I'm using energy to use my ruler, and energy is conserved, but that's a separate argument entirely, does that make sense ? I could bolt on energy conservation to my use of the ruler, but there's no need, because that's not what I'm interested in. Put it this way, (frantically trying to think of an example) suppose I'm trying to calculate time dilation with a relativity problem, so with this problem I'm only concerned with moving clocks run slow i.e t' is always less than t, and c is constant in all inertial frames, so I use the following equation... [math]t' = t\sqrt{1 - \frac{V^2}{c^2}}[/math] There's no mention of conservation laws in that equation, because that's not what I'm interested in. That's an incredibly long winded way of saying, conservation laws hold, but calculating something that doesn't include them, clearly won't break them Foodchain, sorry if I came across as abrupt in my last post, that wasn't my intention...I've had a sh*tty last few weeks, putting it mildly.

I'm intrigued to know, why on Earth you think it would. In a nutshell, there's a probability of a certain outcome before we make a measurement, so supposing I fired an electron through a double slit, there's a probability of where it will end up on the screen. Once it hits that screen, we have an exact position, so the probability is reduced to one value (an eigenvalue.) So why would that violate, or have anything to do with a conservation law ? Here's another example, have a look at my sig. This assumes that some deluded numty thinks Elvis is probably still alive. So if said numty thinks they observed Elvis buying some brylcream in Walmart, the wavefunction collapses to Elvis being alive i.e [math]\Psi_{Elvis}(t) = \Psi_{Alive}(t)[/math]. Well, according to them. I'm not sure I follow iNow's reasoning in answer to your question. But the wavefunction describes and is used to predict a physical system, I wouldn't class it as solely a mathematical concept. In any case, not meaning to sound rude, that doesn't really address the question. What measurement problem, and what does that have to do with conservation laws ? EDIT: I don't have my textbooks for reference, but I can go into more detail later, if you wish.

Little Big Planet arrived at our door last week, and it is, as you said, amazing. We've already created a bog standard platform game, and are now working on an arcade classic, that so far, doesn't appear to have been tackled yet. The style, intuitiveness plus narration from Stephen Fry, all works really well together, and the potential for future upgrades / downloads for LBP is huge.

I'm sure 'The Sun and Moon Corrupted' will be enjoyed by many on here, especially anyone who peruses the Speculations forum with a critical eye. My housemate bought me this book for my birthday, the uncorrected bound proof, so I'm lucky enough to have a rare copy. The author Philip Ball is a writer and consultant editor for Nature, and his experience with fringe science becomes abundantly clear in just the first few chapters. The book follows a journalist Lena, who is trying to track the elusive and notorious Karl Neder (the star crackpot), for an article on his ideas, and life. I won't give too much away, but Karl Neder is a special case within the fringe science fraternity, and his story becomes all the more intriguing as you progress through the book. I'm not sure if anyone has read this yet, so I'll leave you with an extract from chapter 4, which shows some examples of articles submitted for publication through the journal 'Natural Science'... 'Dear Natural-Science-friends,' Dr Rudiger Vogt of Hamburg began 'I was a Computer-Man in lots of stations. I am in the Possibility to resolv every Computer-Problem. Nobody knows - but you.' Dr Vogt added in brackets, '(I have to go in a Hotel in Munich, where the Conditions for Analysis are better for me, concerning Problems of Atom and Relativity.)' There followed three sections, titled 'Astrophysics'. 'Atomphysics' and 'Space Fligt'. It was all handwritten on the back of old flyer's for a piano recital at the Hamburg Konzertsaal. K.S Venkatasubramanan from Jodhpur had his mind on another matter: LENGTH OF THE SKY Introduce Alhpabets A to Z and then give the numbers one, two, three and so on from A to Z. By adding 1 + 2 = 3, 2 + 3 = 5, 3 + 5 = 8 and likewise up to Z then we will get 294. Then multiply the Number that is 1 x 2 = 2, 2 x 3 = 6, 6 x 4 = 24 likewise upto Z. Then we will have 92901102606070746780000. By adding both we will have 929011026060707467800294. Introduce [math]\pi r^2[/math]. Then [math]\pi = \frac{22}{7}\times r^2[/math] then we have [math]\frac {22}{7}\times (929011026060707467800294)^2[/math] By concluding it we will get the figure. It is the length in Kilometers of the sky. But things got even stranger. The delicate hand of M.Sato of Hokkaido Medical University told the tale of 'Alice-God in Wonder-universe.' It was like a poem, beautiful and airy as Oriental silk, filled with a sense of yearning... (it gets funnier from then on) Hopefully that's given you a taster, I'm literally ten pages from the end, but I've really enjoyed this book, especially due to some of the posts I've read on SFN. If anybody wishes to discuss (after reading it of course) this rather unique book, I'll look forward to any future posts. EDIT: Ewww. I'm sure the font wasn't that large when I posted last night...sorry for shouting.

Thanks pioneer, what would we do without you ?

You can calculate the intensity for any value of [math]\theta[/math], and from there you'll know the maximum...no offense, but I'm not sure where to start with the math i.e I'm not willing to spend several hours on a post explaining it. I'm confident you can look this up yourself. As an afterthought, this phenomena is not constrained to a lab...far from it. Any crystalline structure where there's regular spacings will display such effects, in fact it was this discovery that lead to the use of X-rays in medicine (as one example.) TBH I get very niggled when QM is represented as something that's solely reproducible in a lab, when it's effects are predicted and observed outside a laboratory...Yay, thanks to QM my mobile phone has better resolution <sigh>

OK, I'm bought...I've just ordered a copy from amazon. Despite I'm now trying to avoid popularizations like the plague now (most I've read are a culmination of analogies trying to describe important milestones in physics), I guess that comes from learning the subject properly ? It should arrive in a few days, and for under £10 no less. Now I really should go out, otherwise I'll have a stack of books arriving at my door.

Depends what you mean by weaker...intensity ? Maybe I'm misreading your question, because (not meaning to sound rude) surely you know this ? In any case, I'm killing time before going out... Constructive interference will cause high intensity, where the path difference between the two waves is [math]d\ sin\theta[/math]. d being the distance between the two slits. Compare two waves, and the path difference would mean constructive interference at any given point is a positive integer of wavelengths i.e [math]n\lambda[/math]. Destructive is therefore [math]n + \frac{1}{2}[/math], so... [math]d\ sin\theta = n\lambda[/math] Now it's just a case of plugging in some numbers, however you'll find that as the distance between the slits increases (providing the wavelength is constant) then [math]\theta[/math] must decrease causing the interference fringes to be closer together. So the intensity decreases, as the angle of maximum intensity has decreased...i.e less constructive interference, if that's what you meant by 'weaker' ? But again, I may have misread your question.