On Sat, Mar 5, 2016 at 12:36 PM, Gene Heskett <ghesk...@wdtv.com> wrote: > On Saturday 05 March 2016 10:46:04 Thomas 'PointedEars' Lahn wrote: > >> Gene Heskett wrote: >> > I've never heard of a massless photon, >> >> That is unfortunate as it should be common knowledge by now. >> >> > and they do exert a push on the surface they are reflected from, […] >> >> Photons exert a force on surfaces because they carry *momentum* or, as >> it had been understood in terminology that is obsolete now, a non-zero >> “*relativistic* mass” (that had been distinguished from “rest mass”). >> > To have "momentum" imply's mass in the real, we can measure it world. > > However with my lack of education, I have a hard time reconciling that > they travel at C speed, when the classical math says that anything with > mass traveling at C speed will have aborbed enough energy in getting to > C speed, that its mass is then infinite. But its obviously not. > > I once used relativity to explain to a degree'd FCC engineer exactly why > a UHF transmitter that used klystrons for amnplifiers, alway had a > backgound audio buzz. At the moment this was taking place, the station > was crippled as we'd had a circuit breaker failure, single phasing and > stopping the cooling water pump, which in turn destroyed the klystron > used as a visual amplifier (one circuit breaker boom as the building > went dark when the tube filled with steam, byby $120,000 USD), so just > to stay on the air, I had moved a weak & about used up klystron from the > aural cabinet to the visual cabinet, and tee connected the aural drive > into the visual drive. > > When the engineer came in the door, one of the first things he had > noticed when he monitored the station from about 15 miles away the > previous evening, was that we were a UHF, but didn't have that annoying > background buzz in the sound. So I had to explain it. > > What we were observing was that by combining the two carrier signals into > one tube, meant that both signals were being treated equally to the > phenomenon they had called incidental carrier phase modulation, and its > created in the amplitude modulated signal because the 4 foot long > electron beam is traveling at a speed where speed vs mass is beginning > to make itself measureable. Said simply, the tube amplifies the signal > by nominally 30db, by introducing an electrical field across the input > cavities gap that alternately speeds up, or slows down, an electron > traverseing that gap with a 20 kilovolt induced speed. 4 feet and 3 > more cavities later, those electrons are now bunched up, the ones in > front slowing to fall into the bunch, and the ones behind being pushed > to catch up with the bunch. That induces, because the beam is something > north of 5 amps, a considerable amount of power in the last cavity which > can be coupled back out and sent to the antenna, typically about 30 kw. > > However, because this beam of electrons is traveling fast enough for > relativity to come into play, the energy applied to speed the beam up > encounters an electron with higher mass as it accelerates, whereas the > energy applied to slow it encounters an electron with lower mass, so the > deceleration is fractionally greater. IOW, its not perfectly > symetrical, the net effect being that the average speed of the beam is > instantaneous power level dependent, the tube being effectively, > physically longer, with a longer transit time as the power level rises. > This is efffectively a frequency modulation, and an unwanted effect. > > Some circuits, once the cause of the phenom was known, were designed to > predistort this by intruducing an opposing FM and cancel it, but by then > the heyday of the klysron amplifier was coming to an end because of its > horrible efficiency, that 30 kw of output came at a cost of a few hairs > over 100kw in the beam supply, making a UHF transmitter the local power > companies largest customer by a fairly wide margin. That tramsitter used > nearly 200 kw for every hour it was on the air, and multi-thousand > dollar power bills were getting the bean counters attention. > > But when both signals, visual and aural, are subjected to the same > effect, AND the sound detection is based on the FM of the 4.5 megahertz > difference, it cancels out in the receiver. Later, while still operating > crippled, I made some aural signal to noise measurements, finding truely > amazing figures of nearly 80 db with video still applied, where when > operating with 2 klystrons as intended, it was hard put to make a bit > over 50 db. It was such a problem that the FCC allowed us to make those > measurements with the baseband video cable unplugged when doing a proof > of performance, required for license renewal every 5 years back in those > days. > > So in that scenario, I have first hand knowledge about relativity despite > my offical 8th grade education.
Gene, your massive and varied experiences trump my formal education any day. >Photons not having a mass but can exert > a push isn't something this 81 yo wet ram can quite figure out. In my > mind, when the ball bounces, its mass exerts a push on the wall it was > bounced off of. For a photon to do that, requires it have a mass, > however miniscule it might be, possibly just the mass of the light > energy its carrying. Can that be quantified to a known value, probably > color dependent? -- https://mail.python.org/mailman/listinfo/python-list
