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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
329495	2005-03-05 10:55:00	Originally posted by Terry Porritt The rotation of the earth has no effect on time at all, except in so far as the magnitude of what we call a day would be different. Other authorities don’t necessarily agree with this claim. For example the New International Version of the Bible notes (Joshua ch10, vs13-14): “So the sun stood still, and the moon stopped, till the nation avenged itself on its enemies. The sun stopped in the middle of the sky and delayed going down about a full day. There has never been a day like it before or since…” If the sun stopped in the sky the earth must have stopped rotating (any other theories?), and stayed stopped for a full day, the length of this full day, contrary to the quote above, seems to have been independent of whether the earth was rotating or not.	Abdul~Alhazred (6966)
329496	2005-03-05 11:45:00	Originally posted by Terry Porritt They contain terms like sq rt (1-v^2/c^2) in the denominator, so if v>c we have root of a negative number. Then time dilation becomes imaginary , it does not run backwards . This seems a strange claim. “Imaginary” numbers were also called “impossible” numbers by as great a mathematician as Leonhard Euler. However, just as ordinary (or “real”) numbers can be used to describe physical entities (with whatever degree of accuracy), so likewise can complex and imaginary numbers. Did you ever try analysing alternating current without an Argand diagram? Can be done, but …. An “imaginary” number can certainly describe a real situation. Just because a number describing time dilation is imaginary, this provides no implication of any kind that the time dilatation thus described is itself imaginary, any more than does the use of a real number. So how do you know, much less how are you able to prove, that time dilatation does not run backwards? Gottfried Leibniz referred to complex numbers as a "sublime outlet of the divine spirit”. What better reference to their applicability do you need?	Abdul~Alhazred (6966)
329497	2005-03-05 19:01:00	This seems a strange claim. “Imaginary” numbers were also called “impossible” numbers by as great a mathematician as Leonhard Euler. However, just as ordinary (or “real”) numbers can be used to describe physical entities (with whatever degree of accuracy), so likewise can complex and imaginary numbers. Did you ever try analysing alternating current without an Argand diagram? Can be done, but …. An “imaginary” number can certainly describe a real situation. Just because a number describing time dilation is imaginary, this provides no implication of any kind that the time dilatation thus described is itself imaginary, any more than does the use of a real number. So how do you know, much less how are you able to prove, that time dilatation does not run backwards? Gottfried Leibniz referred to complex numbers as a "sublime outlet of the divine spirit”. What better reference to their applicability do you need? You didn't realise I was writing tongue in cheek, you are being too literal. Mathematics is the best tool we have to try to describe the physics of the real world. Imaginary numbers are one tool as you described. I said if v>c; but it is not possible with our present state of knowledge for the velocity of light to be exceeded or even equalled by something possessing mass. So the relativistic eqations we use to describe time dilation and other effects, will not apply if v=c. Accelerating electrons in a cyclotron was probably one of the first experiments to show relativistic effects as a particle approached near to the speed of light. As regards your other post, what you choose to believe as part of your religion is your affair, and I will not comment.	Terry Porritt (14)
329498	2005-03-05 19:25:00	Just adding to my comment about mathematics being the best tool we have to describe the physical universe, bear in mind that the rules of mathematics and the real world dont necessarily coincide. The physical principles always have to be kept in mind. It is easy for pure mathematicians to get carried away with the beauty of their maths, and try to apply something to the real world that doesn't conform with physical observations. That is not to say that such exercises should not be done, because physical observations may well subsequently catch up with the maths.	Terry Porritt (14)
329499	2005-03-06 01:11:00	jameskan: People won't fly off the Earth (as long as it decelerates at less than 1G) as long as we have gravity. The force of gravity working on you is F= m1.m2.G/r^2 , where your mass is m1, the Earth's is m2 and the gravitational constant is G. r is the distance between your centre of mass ("Centre of Gravity"!) and the earth's. Worry if the rotation rate increases. When a calculable rotation rate (thus radial acceleration) is reached, people will become weighless and start floating off. Those climbing Everest will go first, divers in the Dead Sea will be last. Those in mines or tunnels, or the bunkers built to protect precious items like politicians, money, and bombs, will be the survivors. :groan: It's not influenced by rotation around the sun ... though of course it is affected by the mass of the sun. The "r^2" divisor makes that effect fairly small. The moon has more effect, because it's much closer (tides).	Graham L (2)
329500	2005-03-06 01:57:00	Well, switch to another scenario. Let's say the earth start to deccelerate until it comes to and stand still and start to rotate the other way round. That means the sun will rise from the west. And add some spice to it, the earth start to go around the sun the other way round. Will the time goes reverse or what?	Renmoo (66)
329501	2005-03-06 02:10:00	Well, switch to another scenario. Let's say the earth start to deccelerate until it comes to and stand still and start to rotate the other way round. That means the sun will rise from the west. And add some spice to it, the earth start to go around the sun the other way round. Will the time goes reverse or what? I am now convinced you are trying to "have me on" :thumbs:	Terry Porritt (14)
329502	2005-03-06 02:15:00	No problems . You will need to exchange your sundial for one from the same latitude in the the Northern hemisphere . But that's the same "reversal of time" we've got now . Change hemispheres, and sundials go the other way . Have you ever wondered why "clockwise" is called that when our sundials are "counterclockwise"? Your candle clock will keep the same (bad) time . Your Clepsidometer will keep the same time . Your digital watch will keep the same time . Your pendulum grandfather clock will keep the same time (if the gravitational constant stays the same) . The high precision atomic clocks in the GPS satellites will keep the same time . Direction of the heliocentric rotation doesn't matter; it's the geocentric rotation which (loosely these days) determines the mean solar day of 24 hours . All the divisons are arbitrary . The French revolutionary assembly ordered a metric time system . 10 hours per day, 10 days per week . . . It didn't last .	Graham L (2)
329503	2005-03-06 02:15:00	When the Vogons destroyed the Earth to make way for a hyperspace bypass, time didn't stop for Arthur Dent or Ford Prefect, instead they hitched a ride.	Terry Porritt (14)
329504	2005-03-06 03:11:00	As originally posted by Terry Porritt As regards your other post, what you choose to believe as part of your religion is your affair, and I will not comment. Not my religion, I just think Josh is as entitled to have his views considered as you or I, coz ignoring the views of others enables a very selective perspective The quote was given merely to consider the interesting question of whether there exist unique definitions of the length of day. Perhaps someone like Neil Armstrong’s activities might be closer to your comfort zone. Now what portion of a day was it that he spent on the moon? I never did quite figure that one out. Would your definition resolve it for me? Cheers, Ab	Abdul~Alhazred (6966)
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