A constant speed of light in all reference frames? Surely you can't be serious.
in [Relativity]
|
From: Ste on 21 Feb 2010 19:53 On 21 Feb, 22:37, mpalenik <markpale...(a)gmail.com> wrote: > On Feb 21, 4:57 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > and the authority of this group is > > implicitly invoked on yet another occasion. > > This group has no "authority" on anything whatsoever. The "group" to which I was referring, and you snipped the qualifying clause, was "physicists as a group of people", not "this newsgroup". > I have no idea why most of the people who post here do so. Indeed. I've asked myself the question why I post here. ;) > I even > asked PD about this a while back. For me, it's kind of theraputic, > after grading dozens of papers where freshman students have written > "no polarization" and then drawn a picture of polarized atoms, or > listed "the force the boy exherts on the mother is smaller than the > force the mother exherts on the boy" as a reason for why a mother who > pushes a boy on ice-skates doesn't move, while the boy does. I dare say the answer to that question (although I know you weren't asking the question) is that the movement of each depends predominantly on their relative mass and the friction with the ground. I certainly hope these students to which you refer were high-school students, not university students. > You can't call them stupid, although here, there is no such rule when > someone says something so mind-bogglingly sputid. On the other hand, > at least, freshman physics students are capable of learning, whereas > for some miraculous reason, 90% of the people here seem to be stuck in > perpetual, unwavering ignorance. Perhaps part of the reason is that students in a formal setting are pre-weeded for susceptibility to your teaching?
From: Ste on 21 Feb 2010 20:01 On 21 Feb, 23:10, mpalenik <markpale...(a)gmail.com> wrote: > On Feb 21, 4:57 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > If we were to extrapolate a trend from history, then physics has not > > yet given us a single equation which describes how the universe > > functions. It has given us some rules of thumb and some cumbersome > > approximations. > > This just further illustrates that you don't understand how physics > actually works. The history of physics isn't a series of blunders > that we've thrown out as we get better and better equations, hampered > by our belief in the old equations. Rather, physics at just about > every point in time since the renaissance has been a journey from very > specific to more general rules--criteria by which any new physics must > be constrained. Rubbish. > For example, Kepler, while not really a physicist per-se, devised > descriptions of the elliptical orbits that planets must follow. A description which in fact they don't follow, hence the need for GR. > Newton, then, discovered that this is a special case of the > conservation of angular momentum, which is a much more general > principle--however, conservation of angular momentum MUST be able to > reproduce the elliptical orbits of planets, or else it is wrong. > Kepler's rules constrained Newton's theories. > > Special relativity then changed Newton's laws, a bit. The basic > principles, like F = dp/dt remained, but Special relativity says that > space and time must transform differently than they do in Newtonian > mechanics. However, Newtonian mechanics is still a special case of > special relativity--as the speed of an object approaches zero, the > laws begin to reproduce Newton's laws. In other words "Newtonian mechanics are valid, as long as nothing is moving". Which somewhat defeats the purpose of mechanics, which is to describe movement, no? I think you're rewriting history Mark. > Newton's laws, in this way, > constrain Special Relativity. Because if it did *NOT* reproduce > Newton's laws at low speeds, it would be wrong. > > General relativity came along and it turns out that special relativity > only works as a limiting case of general relativity, specifically, > when there is no mass or energy present. As the amount of mass and > energy present goes to zero, general relativity reproduces special > relativity. If it could not do this, it would be wrong. In other words, SR is correct until it is applied to anything real. Again, given that science is supposed to describe reality... > Any new physics must be able to reproduce the old physics in the > regimes in which it has been tested. Any new theory that cannot do so > is necessarily wrong because it has already been ruled out by > experiment. > > There's no way to know whether at some higher energy or smaller > distance than we've observed the laws of physics actually are > different than what we believe. But even so, these new laws must > reduce to the old ones at lower energies and larger distances. I don't think there is any necessity that new laws encompass the old, so long as the new law is consistent with data.
From: mpalenik on 21 Feb 2010 20:04 On Feb 21, 7:53 pm, Ste <ste_ro...(a)hotmail.com> wrote: > On 21 Feb, 22:37, mpalenik <markpale...(a)gmail.com> wrote: > > > On Feb 21, 4:57 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > and the authority of this group is > > > implicitly invoked on yet another occasion. > > > This group has no "authority" on anything whatsoever. > > The "group" to which I was referring, and you snipped the qualifying > clause, was "physicists as a group of people", not "this newsgroup". Physicists have the authority to interpret their own equations because 1) they came up with them, so they know the principles that the equations are derived from (whereas you have repeatedly said that relativity is a form of correction for propagation delays which was, first of all, not how it was derived, and second of all gives very different predictions from what you get when you actually account for propagation delays. The two give different predictions, therefore they cannot be the same thing). 2) Have demonstrated that their models predict actual, measured phenomena 3) Have spend more than a month thinking about the issues that you are asking about > > > I have no idea why most of the people who post here do so. > > Indeed. I've asked myself the question why I post here. ;) > > > I even > > asked PD about this a while back. For me, it's kind of theraputic, > > after grading dozens of papers where freshman students have written > > "no polarization" and then drawn a picture of polarized atoms, or > > listed "the force the boy exherts on the mother is smaller than the > > force the mother exherts on the boy" as a reason for why a mother who > > pushes a boy on ice-skates doesn't move, while the boy does. > > I dare say the answer to that question (although I know you weren't > asking the question) is that the movement of each depends > predominantly on their relative mass and the friction with the ground. > I certainly hope these students to which you refer were high-school > students, not university students. Nope, first year college freshmen. Several students, on the last test that I graded, said that the force the mother exerts on the boy is much greater than the force that he exerts on her. Most of them didn't, but several did. > > > You can't call them stupid, although here, there is no such rule when > > someone says something so mind-bogglingly sputid. On the other hand, > > at least, freshman physics students are capable of learning, whereas > > for some miraculous reason, 90% of the people here seem to be stuck in > > perpetual, unwavering ignorance. > > Perhaps part of the reason is that students in a formal setting are > pre-weeded for susceptibility to your teaching? The people taking physics 172 are from physics, chemistry (sometimes), and engineering classes. The people taking physics 220 (physics without calculus) are from life science courses and other non-hard- science fields. They even have a physics without "math" for elementary education majors. All of these people seem to be able to learn something to varying degrees. All of them become unconfused about at least part of the course material faster than the people in this group. Do most of the people here seem to you like a random selection of sane, well adjusted, normal people? mpc755? BURT? Androcles?
From: mpc755 on 21 Feb 2010 20:06 On Feb 21, 12:25 pm, Bruce Richmond <bsr3...(a)my-deja.com> wrote: > On Feb 21, 11:34 am, mpc755 <mpc...(a)gmail.com> wrote: > > > > > On Feb 21, 9:18 am, "Peter Webb" > > > <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > > > "mpc755" <mpc...(a)gmail.com> wrote in message > > > >news:dba2b7ab-670a-473f-a7f3-5447e3f01e53(a)b7g2000yqd.googlegroups.com.... > > > On Feb 21, 12:27 am, "Peter Webb" > > > > <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > > > > "mpc755" <mpc...(a)gmail.com> wrote in message > > > > >news:1c9cf786-36cc-4fce-8b57-7f45f5b88ddd(a)v1g2000yqk.googlegroups.com... > > > > On Feb 20, 11:21 pm, "Peter Webb" > > > > > <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > > > > > > And if conducted in a laboratory in low earth orbit, with a relative > > > > > > speed > > > > > > of 25,000 kph relative to the ether - what will be the measured speed > > > > > > of > > > > > > light then? > > > > > > The light will be 'measured' to be 'c'. If the Observers in the > > > > > laboratory in low Earth orbit know how they are moving with respect to > > > > > the aether they will be able to determine the speed of light to be 'c' > > > > > with respect to the aether. > > > > > > ______________________________________ > > > > > So, according to you, in every inertial reference frame, the measured > > > > > speed > > > > > of light is "c", completely independent of how the observer is moving > > > > > relative to the ether? > > > > > Measured, yes. > > > > > ____________________________________ > > > > OK, is the speed of light measured as 'c' in every inertial reference > > > > frame? > > > > Measured, yes. > > > > _______________________________ > > > How about the rest of the predictions of SR? Will lengths and times measure > > > according to SR? You have no problem with the 80 foot ladder fitting inside > > > the 40 foot barn, or the twins "paradox" ? > > > I have already explained to you probably twenty times now the atomic > > clocks 'tick' based upon the aether pressure in which the exist. There > > may be length contraction at speeds near 'c'. > > > What you fail to be able to understand is the rate at which a clock > > 'ticks' is based upon the aether pressure in which it exists. For > > example, we have a clock on the embankment and a clock on a train and > > both the train and the embankment exist in the same three dimensional > > space. Since the state of the aether is determined by its connections > > with the matter the state of the aether is that it can be considered > > to be at rest with respect to the embankment. Since the train is > > moving relative to the embankment the train is not at rest with > > respect to the train. The clocks on the train will 'tick' slower than > > the clocks on the embankment. > > > This nonsense of the Observer on the train seeing the clock on the > > embankment 'tick' slower and the Observer on the embankment seeing the > > clock on the train 'tick' slower is exactly that, complete nonsense. > > You have progressed a long way from where you were. It's time to take > another step. From you previous posts I see you agree that the clocks > on the train are out of sync with the clocks on the embankment. Now > consider how the train observers measure the tick rate of a clock on > the embankment. Viewed from the train the clock at A on the > embankment passes along the length of the train. No single train > observer can deterimine the tick rate of A because he only sees A for > one instant. So the tick rate at A is determined by having multiple > observers record the reading on clock A and the time of that reading > *according to their own clock*. > > The clocks at A and A' are compared when they pass and the difference > in their readings noted. Next the clocks at A and B' are compared and > their difference in reading noted. If that difference has increased > the train observers must conclude that the clock at A is running slow > because it has lost time compared to the clock at B' *which is in sync > with the clock at A'*. > > The track observers see what the train observers are doing and realize > the train observers got a different result because *the clocks at A' > and B' are out of sync*. > > So now maybe you can see that the train observers can *measure* the > tick rate of the embankment clocks to be slower, even if it is in fact > faster. > > Bruce > When the clocks are moved on the train they wind up at A' and B' and read 12:00:01 and 12:00:00, respectively. Since the embankment is at rest with respect to the aether when the clocks are moved to A and B they both read 12:00:00. If the train is moving fast enough the clocks on the train should be ticking slow enough that the difference in the times at A' and B' should be outweighed by the slowness of the ticking. For example, let's say B' and A are co-located at 12:00:00. It takes 3 seconds, as determined by the clock at B', to go from A to B. It takes 5 seconds as determined by the clock at A to go from B' to A'. When B' and B are co-located their clocks will read 12:00:03 and 12:00:05, respectively. When A' and A are co-located their clocks will read 12:00:04 and 12:00:05, respectively. All of the Observers conclude the clocks on the train 'tick' slower than the clocks on the embankment. > > If the Observer on the embankment can see the clock on the train the > > Observer on the embankment will determine the clock on the train to be > > 'ticking' slower than the clock on the embankment. If the Observer on > > the train can see the clock on the embankment the Observer on the > > train will determine the clock on the embankment to be 'ticking' > > faster than the clock on the train. > > > If the Observers one the embankment and on the train have this > > information the Observers will conclude the embankment is more at rest > > with respect to the aether than the train is. > > > > But it is the reason why it it measure to be 'c' which > > > is the important part when discussing what occurs physically in > > > nature. The 'reference frame' is moving with respect to the aether. > > > When Observers synchronize clocks and then move to their respective > > > destinations they are not moving the same with respect to the aether. > > > As in the train example, the Observer moving towards B' is moving > > > against the 'flow' of the aether and their clock 'ticks' slower than > > > the clock at M'. The Observer moving towards A' is moving with the > > > 'flow' of aether and their clock 'ticks' faster than the clock at M'. > > > This unsynching of the clocks offsets the fact the light propagates at > > > 'c' with respect to the aether. A flash of light at M' will reach A' > > > and then B' but the clocks at A' and B' will read the same due to > > > their not be synchronized. The light will be reflected by mirrors and > > > now travel in the exact opposite direction in terms of the 'flow' from > > > A' back to M' and from B' back to M' so the light waves reach M' > > > simultaneously. > > > > Flash of light occurs at M'. Light waves propagate with the 'flow' of > > > aether towards A' and propagate against the 'flow' of aether towards > > > B'. The light waves arrive at A' prior to arriving at B', in nature. > > > But the time on each clock will read the same when the light arrives. > > > The light waves then reflect off a mirror at A' and propagate against > > > the 'flow' of aether towards M' and the light waves then reflect off a > > > mirror at B' and propagate with the 'flow' of aether towards M'. The > > > light from A' and B' arrives back at M' simultaneously. The Observers > > > measure the speed of light to be 'c' while at the same time the light > > > waves have propagated at 'c' with respect to the aether.- Hide quoted text - > > > - Show quoted text -- Hide quoted text - > > > - Show quoted text - > >
From: mpalenik on 21 Feb 2010 20:09
On Feb 21, 8:01 pm, Ste <ste_ro...(a)hotmail.com> wrote: > On 21 Feb, 23:10, mpalenik <markpale...(a)gmail.com> wrote: > > > > > On Feb 21, 4:57 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > If we were to extrapolate a trend from history, then physics has not > > > yet given us a single equation which describes how the universe > > > functions. It has given us some rules of thumb and some cumbersome > > > approximations. > > > This just further illustrates that you don't understand how physics > > actually works. The history of physics isn't a series of blunders > > that we've thrown out as we get better and better equations, hampered > > by our belief in the old equations. Rather, physics at just about > > every point in time since the renaissance has been a journey from very > > specific to more general rules--criteria by which any new physics must > > be constrained. > > Rubbish. Absolutely not rubbish. Thank you for showing your ignorance. > > > For example, Kepler, while not really a physicist per-se, devised > > descriptions of the elliptical orbits that planets must follow. > > A description which in fact they don't follow, hence the need for GR. As a matter of fact, the point here was that in a system where angular momentum is conserved, on a conformally flat manifold, you will get elliptical orbits. The only reason GR affects the perihelion of mercury is because spacetime is not flat near the sun. However, replace the sun with a charged body, instead of a massive one, or move farther out from the sun, and you have conserved angular momentum on a flat manifold--and it reproduces Kelper's orbits. If GR weren't capable of reproducing Kelper's orbits in some limit, it would be wrong. Thank you for ignoring the rest of my post where I explain this, though. |