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Everything posted by Griffon

  1. Is that a question of surprise that such is possible? It certainly is possible because such stars are thought to be first generation stars formed at the earliest times. They are very low in atoms of higher atomic mass because they were formed before supernovae generated such elements.
  2. Science makes progress through anomolies like this. It could mean nothing more than a slight problem in our understanding of the age of stars, the universe or both. After all the error on the estimated age of the star means its lower value lies within the accepted age of the universe. On the other hand this discrepancy could point to a major problem with our understanding of cosmology. It's impossible to say with certainty where the problem lies . My hunch is that the problem lies in our understanding of how to estimate the age of stars. Whereas the time since the Big Bang has not only been studied more thoroughly but is estimated by several different methods I understand. .... though as we saw recently, the age of the universe isn't set in stone, having got 60 million years older due to the recently published new cosmic microwave background data.
  3. Quark - I've not heard of what you describe. But a planet won't deviate from its normal orbit unless perturbed by another massive body. If that perturbation ceases then the planet will resume its normal albeit modified orbit. I wonder if you have in mind orbital resonances in which bodies have a periodic influence on one another which affect their orbits?
  4. Is there an original manufacturer's mark or model number on the laser by any chance? Just to confuse matters I see there's a vanadate laser using neodymium lutetium vanadate (Nd:LuVO4) crystals which has two lasing wavelengths at 1066nm and 1076nm which double to 533nm and 538nm - not far from your measured wavelengths. That might be a long shot though.
  5. "The theory in which the properties of macroscopic systems are predicted by the statistical behaviour of their constituent particles." The Penguin dictionary of Physics. I just recall how many years ago I and most of my fellow students looked a bit gloomy before a statistical mechanics lecture.
  6. Maybe you could check the manufacturer's website to find out exactly what sort of laser you've got there. By the way, I've just discovered that "In addition to the common 1,064 nm wavelength, Nd:YAG has over a dozen other weaker lasing transitions between 1,052 nm and 1,444 nm". http://www.repairfaq.org/sam/laserssl.htm#sslclm I had a vague recollection there are other lines near 1064 nm in YAG lasers.
  7. Green laser pointers are more commonly frequency doubled Nd vanadate lasers I believe. I agree Nd:YLF is a possibility. The two lasing transitions have orthogonal polarisations. Just a guess, but may be the laser is flipping between the two wavelengths if there's poor polarisation selection.
  8. It's difficult to envisage this without seeing it. A photograph of the shadow, window and pipe would help. What colour is the ground? Have you tried placing a piece of plain white paper on the ground to eliminate the colour of the ground affecting what you see? Secondly are the colours you see within the shadow due to light coming from somewhere else? Light refracted in the window glass perhaps, another source reflecting light within the room or outside the window? Thirdly, are the colours very near the edge of the shadow or more diffuse across a wider area of the shadow?
  9. If I were in your situation I would go see my local family doctor, and that is what I recommend you do. I expect your doctor will refer you to a specialist who will investigate your problem, provide you with reassurance and provide appropriate treatment.
  10. Griffon

    Yay, GUNS!

    Just a general observation. If one lives in a society in which gun ownership is low it makes sense to keep it that way by having very restrictive laws on gun ownership. This I feel is the situation in Britain. Very few people here own guns or indeed ever come across them in ordinary life. We do not have a 'gun culture' and it would be very unwise to encourage widespread ownership of such an unnecessary and dangerous hazard into our society. One might take the opposite view in a society where there is widespread gun ownership.
  11. That results in g going through two maxima and minima per day as the earth rotates - much as there are two tides per day. So g is a minimum when the moon is both above our heads and beneath our feet if I understand this correctly. Not much though - ±1.5 × 10^−6 m/s^2 or so. http://www.trin.cam.ac.uk/clock/theory/rcl_report.pdf
  12. But it's not "just" an interface problem. It's a problem of how sense is made of the information that's stored and retrieved. One can imagine an electronic retrieval system for the brain which provided answers to concepts you understand like what is the capital of France or how do I make a cheesecake. But if my brain had access to complex information like a full description of advanced quantum physics this would be no use to me unless I fully understood the concepts. What we really need is an ap for the brain that adds intelligence and comprehension!
  13. Interesting. I've just tried experimentingg with that comparing relative tuning of guitar strings using beats with tuning by electronic tuner. I found the electronic tuner more accurate than the beat method. In fact even my ear is better than the beat method. I find beats are quite difficult to distinguish once they get down to 1 or 2 Hz. But my tuner and my ear can still tell the two strings are not in tune. Beats are easier to hear with the lower strings than higher ones though.
  14. Nice idea! I'd love a direct mental interface to Google. Isn't part of the problem that it's not just about information storage and retrieval? Yes we could short cut the time required to learn information. But there's no short cut to learning how to understand it is there? Also no short cut to learning how to judge whether information is valid or not.
  15. OK. Thanks. Just to clarify - are you saying that the primary changes in scale weight caused by the moon are due to tidal forces?
  16. One hears beat frequencies frequently when tuning a guitar by using the relative tuning method in which adjacent strings are tuned to one another. It's quite a nice way to demonstrate a simple bit of physics.
  17. Raleigh scattering is elastic scattering of light by particles smaller than the wavelength of the incident light. "Elastic" because the scattered light has the same frequency as the incident light. The scattered photons have the same energy as the incident photons in other words. One can think of the incident oscillating EM radiation perturbing the electron distribution within the scattering molecules. The induced oscillation of charge within the molecules radiates light at the incident frequency into all directions not just the forward direction of the incident light. I don't know much about Mie scattering except to say that I think it's a more general formulation of light scattering by particles of all sizes. So it includes Raleigh scattering which as I said concerns scattering by particles smaller than the wavelength of the incident light.
  18. Yes, I am thinking of scale weight I believe. The weight you can measure, or feel if you like. Aren't the moon and earth in free fall with respect to one another? I can see that the force due to the moon on any point on the earth is going to be a function of the distance from that point to the moon's centre of mass. That distance varies of course, as will the force. But why isn't that force offset by an equal and opposite force due to orbital acceleration - at least to first approximation? After all, the moon is not in orbit of the earth. The earth and moon are in orbit of one another - specifically their barycentre.
  19. OK. That's interesting. I'd never come across Loomis. So the moon does have an influence on g, which in turn affects weight. I'm still intrigued though because ... Suppose you were in a spacecraft in an eccentric orbit about a planet. You would be weightless (not massless) irrespective of how near or far you were from the planet. What is the difference between this and being on the earth? I can't see how the moon being nearer or further away makes any difference to our weight, unless of course it's a higher order effect.
  20. Not at all .... or at least that's what I argued during a a discussion in the pub yesterday. Am I right? The lunar distance varies by about +/- 6.5% between apogee and perigee. It was speculated during the pub discussion that weight should vary because gravitational force is inversely proportional to distance squared. In other words, if the moon were directly overhead one should be lighter, and even more so if the moon were closer. I argued to the contrary that the earth and moon are in orbit about one another and in a state of 'free fall' relative to one another. With respect to the other body we are weightless regardless how near or far it is. Is this right? Or are there higher order effects? PS I assume tidal forces, which depend on gravitational differential, will vary with lunar distance, but this (I think) is a different matter.
  21. Broadly speaking I agree with you. But, reading the experts' explanations of the "anomaly" read to me, as a non-expert in this field, like perfectly reasonable explanations as long as you accept the "old earth" explanation. If you don't, such dismissive arguments as 'the extra C14 could be due to uranium decay' leave enough wriggle room (uncertainty) for the creationist to thrive in. You're right though, I'm probably being naive in thnking they will be convinced. Even so, it is always good when creationists have been casting doubt in some area to be able to completely explode their reasoning.
  22. Science has several very reasonable explanations for levels of modern carbon in very old samples. Although this satisfies the scientist, who for all sorts of other reasons quite reasonably assumes that these samples are truly old, it leaves enormous scope for the creationists to reinforce their followers' faith that the earth is young. I still feel that some definitive experiments in this area would be useful to test the various rational explanations for the c14 anomaly. I can see though that science has problems taking on creationists because of the perceived risk of lending credibility to their ideas. Bit of a dilemma there. Also as soon as one creationist idea is exploded, they just move on to another area where uncertainty in the science offers them the opportunity to mislead.
  23. Thanks for your responses and the links to various sources. Much appreciated. I am working my way through Kirk Bertsche's 9 page essay on the subject. Thanks DH for this link. Excellent. This article does a good job at explaining the technical complexities of measuring the very small amounts of C14 present in these ancient samples and why non-zero amounts are measured. I'm a complete non-expert in this field of radiometric dating, but it strikes me reading this how contamination by modern carbon introduced during sample preparation seems to be a severe issue. I'm wonder whether they've extracted samples under an inert atmosphere and then used laser ablation to ionize samples in their mass spectrometers? I'm probably teaching grandmother to suck eggs, as the old saying goes. Getting back to my OP - I feel that some definitive work needs to be done in this area. It's easy to see that the sceptical creationist is simply going to see the scientific response as making excuses for the data instead of holding up some hard data that either explains or explodes the anomaly.
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