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Thread ID: 55052	2005-03-01 10:10:00	Teleportation / Time travelling...	Renmoo (66)	PC World Chat

Post ID	Timestamp	Content	User
329535	2005-03-12 01:59:00	Terry, we're old fashioned, but some of the new-fashioned stuff dates from 1948 or so. ;) I've just been reading Richard Feynman's "Six Easy Pieces", and "Six Not-so-easy Pieces" (edited up version of lectures he gave -- he tried out one set of lectures when he came to NZ, on the basis that if they didn't go down well, NZ was far enough away not to hurt his reputation). Quantum ElectroDynamics (QED :) ) eliminates the wave/particle duality, by integrating the probabilities of all possible paths of a particle. It accounts for refraction, the two slot "problem" ... etc. Feynman Schwinger (and a Japanese) got the Nobel for this, and Freeman Dyson actually understands it. Of course as Feynman says, no-one understands quantum stuff --- if you say you can understand it, you don't understand it. ;) But it gets the right answers.	Graham L (2)
329536	2005-03-12 02:48:00	Thanks Terry The words "enough effective mass" is about the point where my head implodes. :dogeye: I had less trouble reading Stephen Hawkings' books.:( I can't get past the concept that mass is mass is mass, so I shall go and have a lie down and a cold compress I think. Cheers Billy 8-{) :stare: Quite simple really B. Very similar to a rose is a rose is a rose.Only different. ;)	Cicero (40)
329537	2005-03-12 02:53:00	In that case,why does some copper go black in the air,whilst other goes green? This can be observed at the ch ch town hall,where it is black,where as my weather cock has gone green. Oh dear my chemistry ended at"A" level at school. I think that black copper is copper oxide, and that green copper is copper chloride???? Verdigris. Must depend on what is in the atmosphere. I know the copper roofed dome at school was green, but I thought that may have been due to Black Country polution, specifically the dreadful Albright and Wilson chemical works that caused the rain to be acid, and burn holes in leaves. But this is nothing to do with fluid mechanics, hydraulics, etc there must be chemists on PF1 who can answer this one? :help: Too old, Graham, to start learning QED I'll stick with my 1951 edition of Ditchburns 'Light'. :thumbs:	Terry Porritt (14)
329538	2005-03-12 04:25:00	Thanks Terry The words "enough effective mass" is about the point where my head implodes. :dogeye: I had less trouble reading Stephen Hawkings' books.:( I can't get past the concept that mass is mass is mass, .... We have to thank Mr Einsteins Theory for suggesting that energy has mass, as in e=m.c². For light energy e=h.v, Planks constant times frequency of the radiation., hence the (effective, my word) mass of a light photon is h.v/c² Verdigris and patinas: www.medpovrly.cz	Terry Porritt (14)
329539	2005-03-12 04:57:00	Space is curved . The easiest way to think of this is to imagine the Universe as being the surface of a giant globe . All journeys away from Earth in a straight line lead back to Earth - just like they do here in the real world . Bugger you Winston! I had just got my brain repacked inside its shell and then I noticed this little gem . :groan: So if the universe is a globe, contained within a space-time continuum, what lies outside the boundaries of that curved (warped?) monstrosity? Answer me that then, if you can . I have struggled mightily with the concept of the big bang theory, which I undertand to have occurred far back in the future when Darth Vader stole the Dilithium crystals from Scotty while he was busy at the other end of the engine room, and for the first and cruelly fatal time Kirk was unable to reach warp speed fast enough to save his ship and the rest of the civilised universe as he knew it . So, when the big bang occurred, what did it expand into? Apart from the Dilithium crystals, what else was there to explode in the first place, and what silly clot was playing with the matches? It's all too much for me, I'm off for a liberal libation of Speights' finest, and another lie down . Cheers Billy 8-{) :confused: Didn't somebody once say that nature abhors a vacuum, or was that 'women can't tolerate silence'?	Billy T (70)
329540	2005-03-12 05:23:00	Fascinating stuff . I hadn't realised Feynman had solved or at least explained the wave/particle duality problem . Gravitational Lensing: this occurs when a galaxy or massive object between us and a more distant galaxy, bends the light of the further away galaxy . The result is that we see two galaxies (well, three really including the one in the middle) - one above and one below the galaxy we can see in the middle . Thus this middle, and nearer galaxy creates a gravitational lens . If you think of gravity as the bending of space like the walls of a funnel, whatever enters the funnel runs around the sides in a downward direction . However if it is going fast enough it spirals out of the funnel but with its direction changed . Thus light is bent by gravity . Spaceships use this as free energy to "slingshot" around planets, or moons . There are two benefits: a change of direction, and incresed speed . Thus the fastest path to Mars is a slingshot around Venus . Not the shortest but the most efficent . Orbital mechanics is the subject .	Winston001 (3612)
329541	2005-03-12 08:14:00	Hang about Winston . . . . >> Thus light is bent by gravity . Spaceships use this as free energy to "slingshot" around planets, or moons . There are two benefits: a change of direction, and incresed speed . << Spaceships use classical Newtonian orbital mechanics as you say later, to link this in the same breath as light being bent by a large gravitational force as predicted by General Relativity is likely to lead to misunderstandings and confusion amongs the gullible on this forum :nerd: You know we haven't yet discussed the expanding universe which followed the big bang, doppler effect, and the red shift . This thread could go on for ever :eek:	Terry Porritt (14)
329542	2005-03-12 08:29:00	So if the universe is a globe, contained within a space-time continuum, what lies outside the boundaries of that curved (warped?) monstrosity? Answer me that then, if you can. Outside? Uh......there is no outside. The surface of the globe is the total universe - there is nothing beyond it. But within it, lie potential pathways linking vast distances. Remember, this is a mind exercise to help us visualise what is otherwise nonsense. :) The universe is expanding at every moment. Thus the globe grows bigger. But outside that - non-space. There are elegant mathematical theories for this but it is all Greek to me. :@@:	Winston001 (3612)
329543	2005-03-12 09:01:00	You know there is a very much simpler way of visualising space, which I'll get to in a second. I dont really like all these descriptions/analogies of space. They can be confusing and taken literally, when all they are doing is using words imperfectly to try to describe complex maths, which let's face it, very few are competent enough to comprehend. The simple model I like is this: We all know what cartesian axes are, 3 axes at right angles to define euclidean geometry, each axis divided into say units of metres, and that works well for us on earth for defining a point in space. Now imagine a similar set of axes with the origin conveniently on the earths surface. The axes comprise metre long measuring rods with a clock at each junction, and the rods stretch out into the infinite universe. The rods are going to be distorted by the gravitational fields they pass through, pulled, lengthened, shortened, bent etc, and the clocks will all be running at different rates because of gravity, the original 90 degrees between axes will be distorted. That is how I can imagine curvature and distortion of the 'space-time continuum' due to gravity. The red shift, 'Hubbles Law',named after Hubble who from astronomical observations discovered that the wavlengths of spectral lines of distant nebulae was moved towards the red end of the spectrum compared to similar lines in the solar spectrum. The further away the nebulae, the greater the shift. It leads to the expression v=50d, where v is the recession velocity in centimetres per second, and d is the distance of the body in parsecs. A parsec is 3 x 10 to 18th power centimetres. ( As quoted in my Ditchburn when units were cgs and not metre kilogram sec) This led to the idea of the expanding universe, and eventually to the big bang theory.	Terry Porritt (14)
329544	2005-03-12 09:46:00	Sorry Terry, I was getting a bit carried away . I cheerfully admit that I confuse Newtonian space with Einsteinian space . 4-space is not intuitive . But hopefully the general concept of space being curved, particularly in the presence of masive objects, gets across . So, when the big bang occurred, what did it expand into? Apart from the Dilithium crystals, what else was there to explode in the first place, and what silly clot was playing with the matches? [/I] The first question is - where did the Big Bang come from? There are various theories, but no known answers . God is one . The collapsed Omega Point of a previous universe which had fallen in on itself, is another . There are esoteric theories that the beginning just "popped" into existence, on a probability wave . Or that our universe curved around on itself in the early stages and created itself . And other universes - or they created ours, just like flowers unfurling . This is drawn from quantum theory involving positive and negative vacuum . As Terry noted earlier, empty vacuum has energy . :@@: Once the Big Bang was underway, lots of exciting things happened . A German chap with a very large brain, Professor Max Planck, gave it some thought . His contribution - apart from inventing quantum mechanics, was to calculate Planck Time . This is the earliest point that current physics can model particle and electro-magnetic behaviour . Specifically Planck Time is the moment (10)-43 of a second after the start of the Big Bang . Fairly early on in the piece . This is also known as the Planck Length for the distance traveled by a photon in that time . At this moment the four forces came into being - gravity, electromagnetism, and the weak, and strong nuclear forces . Today scientists are looking for the Grand Unified Theory which will describe the single rule which explains all the forces - and describes the force that existed earlier than Planck Time . Anyway there was lots of interesting particle interaction from this moment on and a very fast expansion of the early universe . Extremely hot but no light as such . That came about 300 years later when the photon decoupled and went off to have a look aound . This is the Inflationary Theory of the universe . As a matter of interest, the closest scientists can get so far to Planck Time, using a large accelerator, is (10)-10 . The big question today is whether the universe is open or closed . Will it continue to expand forever, or falter and then collapse .	Winston001 (3612)
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