Ballistic Theory, Progress report...Suitable for 5yo Kids
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From: Henri Wilson on 9 Aug 2005 16:58 On 8 Aug 2005 15:57:20 -0700, "Jeff Root" <jeff5(a)freemars.org> wrote: >Jim Greenfield replied to Jeff Root: > >> Jeff Root wrote: >Your car has only one axle? Assuming that you are referring >to the axles on which the wheels turn, a car with four wheels >has four axles so each can turn at a different speed. >See http://auto.howstuffworks.com/differential.htm > >I'd think a simpler example would be better. Though I don't >know why you needed an example at all. An axle is an axle, and >an axle by itself is an extremely simple thing. All it is in >this case is a single, solid rotating body. > >> A clock driven at each end mechanically will read the same >> for eternity > >That is what you need to show. You haven't shown it, merely >asserted it. It seems obvious that the two clocks would read >the same, but what seems obvious isn't always true. GR predicts >that in certain circumstances, the two clocks would not read the >same. If you think that is wrong, you need to show why. There is no need for clocks. The ends of the shaft ARE the clocks. An observer at the bottom end will count N revs of the shaft per Earth day. One at the top will also count N revs per day. So one Earth day has a duration of N, irrespective of any gravity difference. HW. www.users.bigpond.com/hewn/index.htm Sometimes I feel like a complete failure. The most useful thing I have ever done is prove Einstein wrong.
From: Henri Wilson on 9 Aug 2005 17:00 On Sun, 07 Aug 2005 19:43:03 -0700, the softrat <softrat(a)pobox.com> wrote: >On Sun, 07 Aug 2005 23:46:41 GMT, H@..(Henri Wilson) wrote: > >>My theory says there is a threshold matter density, below which 'different >>things' happen. > >That theory would apply to the inside of many of the sci.physics >posters heads. > >(Too many 's'es for you, Bucky? Look in a mirror.) You aren't the first idiot to drop briefly into this NG. Go away fool! > > >the softrat >Sometimes I get so tired of the taste of my own toes. >mailto:softrat(a)pobox.com HW. www.users.bigpond.com/hewn/index.htm Sometimes I feel like a complete failure. The most useful thing I have ever done is prove Einstein wrong.
From: Jeff Root on 9 Aug 2005 18:10 Henri Wilson replied to Jeff Root: >> I'd think a simpler example would be better. Though I don't >> know why you needed an example at all. An axle is an axle, and >> an axle by itself is an extremely simple thing. All it is in >> this case is a single, solid rotating body. >> >>> A clock driven at each end mechanically will read the same >>> for eternity >> >> That is what you need to show. You haven't shown it, merely >> asserted it. It seems obvious that the two clocks would read >> the same, but what seems obvious isn't always true. GR predicts >> that in certain circumstances, the two clocks would not read the >> same. If you think that is wrong, you need to show why. > > There is no need for clocks. The ends of the shaft ARE the clocks. Jim said that there is a clock at each end, so I responded to that. However, I agree that your description works at least as well, if not better. I now think Jim just introduced an unnecessary complication in the description. I should have realized that and responded to what he probably meant, rather than to what he actually said. > An observer at the bottom end will count N revs of the shaft per > Earth day. One at the top will also count N revs per day. > > So one Earth day has a duration of N, irrespective of any gravity > difference. Yes. I agree with that completely. It also agrees with what Paul said. -- Jeff, in Minneapolis
From: Jeff Root on 9 Aug 2005 18:21 George replied to Jeff via Bob: > >> I'm not sure it makes sense to talk about the frequency of a > >> single photon, either. Any photon has a particular, measurable > >> energy which is associated with a particular frequency, but > >> there is no way to measure that frequency. > > I disagree Jeff, we can take a single photon and > fire it at a diffraction grating and measure the > wavelength hence the frequency. (I'm not sure if > single photons have had their frequency measured > by the heterodyne method yet.) If you measure > many photons, you can determine the bandwidth or > the uncertainty of the energy. Okay, I missed something extremely basic and obvious. Can it be done with a prism? Suppose I measure the wavelengths of a thousand photons, one at a time, and they are all the same, within my ability to measure. What would that say about the bandwidth or uncertainty of the energy? >> The question is 'how big'[long] is a photon. >> >> I can't see any reason that it should be more than one cycle in length. > > The reason I have offered several times is that > interference effects occur with path length > differences of many wavelengths even in single > photon experiments. If you don't want to treat > a photon as a point particle, you have to address > that aspect in some way. Interference occurs as if the light consisted of waves something like surface waves on a liquid, even though only a single photon is in the apparatus at any given time. QM doesn't provide any "explanation" of that, does it? Only a way to calculate the effects? Is the length of a photon involved in the calculation? Does the result of the calculation depend on photon length? Can the length be calculated from other givens? -- Jeff, in Minneapolis
From: George Dishman on 9 Aug 2005 18:49
"Jeff Root" <jeff5(a)freemars.org> wrote in message news:1123626106.863061.321220(a)g43g2000cwa.googlegroups.com... > George replied to Jeff via Bob: > >> >> I'm not sure it makes sense to talk about the frequency of a >> >> single photon, either. Any photon has a particular, measurable >> >> energy which is associated with a particular frequency, but >> >> there is no way to measure that frequency. >> >> I disagree Jeff, we can take a single photon and >> fire it at a diffraction grating and measure the >> wavelength hence the frequency. (I'm not sure if >> single photons have had their frequency measured >> by the heterodyne method yet.) If you measure >> many photons, you can determine the bandwidth or >> the uncertainty of the energy. > > Okay, I missed something extremely basic and obvious. > > Can it be done with a prism? Sure, fire a stream of individual photons at a prism and then on to a photomultiplier. > Suppose I measure the wavelengths of a thousand photons, > one at a time, and they are all the same, within my ability > to measure. What would that say about the bandwidth or > uncertainty of the energy? Simply that the bandwidth of thesource is less than the resolution of your instrument. >>> The question is 'how big'[long] is a photon. >>> >>> I can't see any reason that it should be more than one cycle in length. >> >> The reason I have offered several times is that >> interference effects occur with path length >> differences of many wavelengths even in single >> photon experiments. If you don't want to treat >> a photon as a point particle, you have to address >> that aspect in some way. > > Interference occurs as if the light consisted of waves > something like surface waves on a liquid, even though only > a single photon is in the apparatus at any given time. Correct, and importantly even if the difference between the path lengths is many wavelengths. > QM doesn't provide any "explanation" of that, does it? > Only a way to calculate the effects? Scientifically speaking, what is the difference between an "explanation" and "a way to calculate the effects"? > Is the length of a > photon involved in the calculation? Does the result of > the calculation depend on photon length? Can the length > be calculated from other givens? The most accurate theory is QED although a simpler classical analysis can give similar results in many cases. QED treats photons as point particles of exactly zero size so photons don't have a length at all. That's why I usually put it in quotes in this context, it isn't really a length as we normally consider the word but a measure of the maximum path difference over which interference effects can be detected. To do that, you need to fire several photons at say a pair of slits and see if there is a fringe pattern, you cannot get a pattern from one photon. But as soon as you do that, you are not measuring a single photon but rather the spread of the group, i.e. the uncertainty in the energies. Another consideration is more hand-waving, the proper time experienced by a photon is always zero so both paths are of zero length to the particle and the difference we see doesn't exist as far as it is concerned. IMHO, this question really shows how closely related the particle and wave views are, photons aren't really one or the other, they are somewhere between and it is our limited imaginations that try to insist on choosing. best regards George |