Natski

So we've had 20 years of high temperature superconductors and I cannot help but ask myself why isn't my power cord made out it? In all this time you would expect some kind of applications to be coming through (excepting the odd industrial application). I assume the main prolem is with the engineering side of superconductors. What are the main problems in this field preventing superconductors appearing more often in our lives? Natski

Does light have a temperature? Often in photography they discuss color temperature, but does this mean light has a measureable, real temperature? DOES LIGHT ITSELF HAVE A TEMPERATURE?

Hi everyone, I'm doing a project on the magnetic moments of some lanthanide ions. Specifically Ce III Nitrate, Pr III Nitrate, Dy III Nitrate and Er III Nitrate. I calculated the magnetic moments for the ions using their term symbols. I think I may have bodged them up though and I wanted to check with someone whether this was the case. Term symols for the level lying lowest in energy: Ce+3: 2F5/2 Pr+3: 1S0 (J=0 clearly not good) Dy+3: 8S1/2 (gives a huge magnetic moment) Er+3: 6H5/2 Thanks for any help, Natski

how would one calculate the entropy change of the universe when a block of mass m, heat capacity C, at temperature T is dropped from a height h into a lake (resevoir) of temperature T also? thanks natski

Although, some things can travel faster than c, [for example, action at a distance (the entanglement), phase velocity of waveguides and quantum tunnelling] no information or energy can be transferred faster than c. That is Einstein's first postulate of SR- which is, to date, yet to be shown otherwise experimentally or theoretically. Natski

Thanks for the info on that one. It is interesting though. I remember reading that Dirac (I *think* it was him, not sure) noticed that the relativistic energy-momentum equation... E^2 = m^2c^4 + p^2c^2 that for zero momentum obviously... E^2 = m^2c^4 and therefore... E = +/- mc^2 (note the +/-) The -ve was always just thrown away as something that had no physical meaning, but when Dirac took the -ve sign seriously he theorised the existence of anti-matter. I seem to remember in optics (Fresnel diffraction I think) another case where the -ve root had an important consequence. My point is I think -ve roots shouldn't be discarded so easily. The math describes the physical world, no matter how strange it may seem. Natski

Hmm, I think some or all of dark energy may be due to quantum fluctuations, which is consistent with my argument. http://physicsweb.org/articles/news/8/6/17 http://arXiv.org/abs/astro-ph/0406504 I think the problem is that most of the energy produced by quantum fluctuations must not be contributing to the dark energy because quantum fluctuations would produce 10^120 times more dark energy than observed; but it still would certainly seem a strong candidate to be the source of it. Thoughts? Natski

Dark energy, which also goes under many different names in various fields (such as quantum fluctuations, the cosmic force), is the name given to the force that is causing the universe to accelerate. No understanding of this force really exists, just a series of theories currently untested, and mostly untestable. However, this force could be described as an anti-gravity force since it exists where mass does not. Infact, this zero-point energy is stronger the greater the vacuum, so I have read. The reports on this swing in and out so the real thruth is yet to be unveiled, but it does seem to at least *counter-act* gravity is regions where there is no mass. In other words, it creates a force of the opposite sign in areas of the opposite conditions. Surely that description could put it as a candidate for anti-gravity? Does any force we know of truly cancel another? Surely they all just counteract one another until the net force is zero? Natski

Before I start, I must warn you I am a chemist/physicist not a biologist. However, this problem has been in my mind for some time and I want to know if anyone can help. I have heard that our perception of time changes with temperature. If I recall correctly, in the cold time seems to pass slower and in the heat in seems to pass faster. During a recent ski holiday, whilst using the sauna facilities, I played some music through the speakers, I couldn't help but notice the beat of the music was slower. Infact it seemed significantly slower. This was at the point where I was about to leave because I was feeling so overheated and exhausted, I stopped as long as I could and I believe this effect was real (in my mind). So what is going on? Does the brain create some chemical which can affects our perception of time? If so, what chemical? And how does temperature affect this phenomenon? Thanks, Natski