madmac

Lord Antares. Do u mean that Einstein would say an infinite force tween two infinite plates?? (I reckoned he would say zero force, based on zero bending of space-time). But your comment re an infinite universe reminds me of the elephant in the room. No, not the BigBang question. No, i mean the speed of gravity question. Gravity takes time, depending on distance. I reckon that the speed is Van Flandern's more than 20 billion c. Some say the speed of light, c (eg LIGO's Gravitational Waves). Some say instantaneous at all distances, ie even at infinity. Some say instantaneous, but only locally, not at infinity. This all affects or can affect my infinite plate thought-experiment, but i am not looking for this complication, & it would rightly need its own thread (has the speed of gravity ever had a thread here??).

Strange. Nice video. But, Maxwell never saw them 4 equations. He i think had 8 (or 20), & they were variant. But re my OP re a man standing on an infinite plate. I would like to introduce a variant. This is an infinite plate near an infinite plate (i guess that the "near" is redundant). What would the gravity force be, in each of the three theories. This is i think simpler that my original OP of an infinite plate & a man (or a test mass). No equations needed this time i think. I am thinking that Newton would say an infinite force. And Einstein would i reckon say zero force. But i expect others here will say an infinite force. Mistermack. That there plate of mine is infinite in extent, not infinite thinness. I don't think i mentioned a thickness, but i suppose that in my thought-experiment it shouldn't make any difference whether the plate had zero thickness (as long as it had mass), or had a sensible thickness, or had infinite thickness. And it goes without saying that the plate needs to have infinite stiffness, or be perfectly stiff (not sure which term offends least).

Strange. Wiki says ....... "As measured in any inertial frame of reference..." etc.......... which is similar. Yes, the velocity c must depend on the method of measuring (determining). If one uses a special method of measuring based on a special model then that might be ok for some applications. But if it doesn't give true c then eventually a problem will arise, in which case science will investigate & discover new knowledge (benefiting mankind) , or, science will fudge & the fudge will be rewarded with a Nobel (benefiting one man).

Tim88 post#50. Thanx for the link to Tom Roberts' & Siegmar Schleif's website re What Is The Experimental Basis of Special Relativity. I refer to their wording in their Section 3 re Einstein's second postulate......... Any speed of light moves in the "stationary" system of coordinates with determined velocity c, whether the ray be emitted by a stationary or by a moving body. I like this wording (compared to other wordings that i have seen). It is of course itself made up of two postulates, hencely we should talk of three postulates not two, the third being that the velocity of the emitter does not affect the determined velocity c. But i want to mention the second postulate -- which now becomes simply....... Any speed of light moves in the "stationary" system of coordinates with determined velocity c. Here it is clear to me that Einstein doesn't say that light moves with velocity c -- he says that light moves with determined velocity c. That makes sense to me. SR & GR are models, & in these models u have rules for determining the velocity of c (& other things). Then u continue to follow the rules & u determine other numbers. And u relate these numbers to numbers determined by others using the same model. And everyone lives happily ever after. Re the real velocity of c -- who cares?? It is unlikely to worry anyone unless they have a very accurate clock.

Strange. Yes, i have read that Maxwell was the key to Einstein's foray into the STR. I have also read -- Maxwell's Original Equations -- by Tombe -- 2011 -- especially page 5. Yes, Newton believed that light was corpuscular, ie that it wasn't a wave. But his beliefs re light had nothing to do with his beliefs re gravity, quite the contrary.

zztop. What is the news on Reg Cahill?? I see that he is now Emeritus. He must have retired (70yrs). But he still has a phone & office it seems. I wonder what a free-range Reg Cahill will do. Lots of youtube, lots of seminars.

Strange & zztop. Yes that was one of the pages i googled (after starting this thread). Re-reading it i see that i missed a couple of things. It seems that an infinite wall (plate) presents difficulties for Einsteinians (even compared to an infinite sphere). I wouldn't hold this against SR & GR, an infinite wall is a silly notion anyhow. They seem to say that an infinite sphere produces zero curvature (of space-time i presume), & that an infinite wall would do likewise, giving a... "perfectly uniform and constant acceleration field. Such a field in the context of relativity, had no intrinsic curvature....... ". So here i return to my original guess of zero g. I don't see how zero curvature can equate to a uniform field -- it equates to zero field in my opinion. And i see that they worry re clocks. It seems that clocks (& frequencies) will vary if we have velocity, despite their uniform field. And they would vary if we have (my) zero field too i guess. But that is probably all irrelevant here. Most of this refers to test masses. But in my 3 cases i have a man. This wasn't intentional, but i suspect that replacing a test mass with a man makes things more difficult. And, madmac Einstein & Newton are (were) all aetherists, but perhaps they spelt it differently (aether, field & ether).

Strange. Yes of course they will all feel the same thing, but my meaning was what do the 3 theories say. I am happy to mention my guesses. This is before i googled. But even after googling i am still not sure re Einstein. Re Newton my guess was good. At first i thought an infinite g. Then i reasoned that as g reduced per square of distance then there might be some sort of finite limit (& of course google says that there is a limit, & as u say the equation includes the mass per square meter etc). And even better, i guessed that Newton's g might not depend on how far clear he stood. I don't know why i even thought of this, but i was pleased to see that google indeed says that a test mass will show the same g for all clearances (ie the equation for the attractive force or g does not include distance). Just a lucky guess by me here. A side issue. I am thinking that the g felt by Newton here is equivalent to inertial g, not (common) gravitational g. On Earth gravitational g would be stronger near his feet (nearer Earth) & weaker near his head (further from Earth). On the plate the g forces would be the same in every part of Newton's body, ie as per inertial g. I think that the above refers to Newtonian theory, & perhaps not to Einsteinian. Google doesn't make this clear. Re Einstein, my guess was that he feels zero g. I reckoned that bending of space-time would cancel along the length & breadth of the plate, giving zero bending, giving zero g. I found at least one Einsteinian analysis on google. I couldn't understand it. If i remember aright the explanation even mentioned clocks at different distances. And in the end their equation included a term for distance (unlike the Newtonian equation). Einstein is standing still (on that plate), he isn't running along (at a uniform speed)(nor non-uniform speed), hencely, some might reckon that Newton & Einstein should agree here re g. But i still prefer my zero g answer. But google says that both are wrong.

We have an infinite (thin)(flat) plate. 1. Newton is standing on the plate. Does he feel a g-force? 2. Einstein is standing on the plate. Does he feel a g-force? 3. madmac is standing on the plate. Does he feel a g-force (madmac is an aetherist). And, are these three g-forces (a) zero, or (b) mansized, or (c ) very large, or (d) infinite? I have my own ideas re the theoretical answers. But i am interested in other's ideas.

Re measuring or estimating fringe shifts. M&M used a yellow sodium light for alignment etc, but then a white acetylene light for the tests. Acetylene gave a nice big sharp black central main fringe, which they reckoned allowed measurements of 1/100th of a fringe. They even mentioned the possibility of 1/1000th of a fringe. But Pearce & Grusenick's green HeNe laser often gives fuzzy fringes (at least on the youtube video). This would make green M&Ms more difficult. Which reminds me, i think it was Hicks who pointed out that eyeballing the fringe shifts would give different results to photographic measurements (believe it or not).

zztop. When i read Hammar's short note & description i thought that it looked ok, & i didn't give it a lot of thought because after all no aetherist today believes in aether-drag, so the whole matter is of only historic interest. Although i do know of one or two who believe in a fixed aether, rather than a free-range aether wind, but even for them i suspect that they have the same disinterest. But if any further info is available showing that Hammar did indeed do rotation tests, then that would need further looking into. But his statement that he did tests at all azimuths doesn't mean that he did rotation tests. However, now that i have re-read the note, i realise that Hammar cannot see a fringe shift by just by peering in the direction of his gizmo. A fringe shift will only happen if something moves or rotates, or if something changes. Otherwise all u have is some nice looking fringes, & no shift. So what did Hammar do to try to get a fringe shift?? He had to do something, which should result in a fringe shift (eg rotate the gizmo), & having seen no shift, he proves his point. But Sfarti's equations etc need a good looking at in their own right. Perhaps tomorrow. DanMP. I had a look at your link for the Pearce vertical M&M on youtube. Very interesting. I measured the fringe shifts for all 6 of his rotations, 1 horizontal, 3 vertical (2 one way, 1 the reverse way), & 2 more vertical rotations examining Grusenick's finding that the fringe shifts change direction when the half-mirror is horizontal (ie when the arm is at 45dg). And i measured the fringe shifts in the Grusenick video, i horizontal rotation & 2 vertical. My measurements were mostly at 0.5sec intervals, measuring (estimating) to 1/20th of a fringe. I now have more respect for M&M and Co. Re the horizontal mirror business during vertical rotation, Pearce's rotations appear to give the same result as Grusenick's. Although Pearce says that the gizmo is pointing to 8 o'clock & 2 o'clock. I think he actually meant 7:30 o'clock & 1:30 o'clock (ie 45dg, ie what Grusenick found). This is interesting. Earlier i suggested that the 45dg happens because of a fluke, when the bending flex-shift equals the compression-tension-strain-shift. But Pearce's gizmo uses a 1" thick granite tile for a base, whilst Grusenick's uses Aluminium. And Pearce's axle passes centrally through the mirror complex, Grusenick's passes well outside the mirrors. Pearce made his gizmo only to show that Grusenick's 11 fringe fringe-shift (in the vertical plane) was due to strain, & wasn't a valid M&M result. He didn't know that Grusenick had already improved his gizmo, & Mark#2 gave a shift of 2 fringes, & Mark#3 gave 1.5 fringes. Pearce's gizmo gave 3 fringes & 2 fringes & 1.9 fringes (for 3 vertical rotations)(my measurements). Any M&M gizmo can detect an aether-wind (assuming it exists), but it wont be measureable unless the gizmo is well designed. The Grusenick & Pearce gizmos have a light path of i think less than 1m, much less than the 10m to 64m used by Michelson & by Miller. A calibration analysis might show that they need to detect shifts of less than 1/20th of a fringe (perhaps 1/200th). The approx. 2.0 shifts of noise in their vertical M&Ms give them no hope. And their horizontal M&Ms have about shifts of 0.9 (Pearce) & 0.5 (Grusenick) of noise (my measurements), still no good. If anyone wants to carry out their own measurements, u will need to measure & allow for the floppy targets, & the floppy cameras. I found that i had to add or subtract up to 0.4 shifts (Grusenick) & 0.27 shifts (Pearce). And despite their small sizes, neither gizmo returned to zero at the end of a rotation, this refers to both the horizontal tests & the vertical tests. Pearce's horizontal test finished at 0.25 fringes right (after 360dg)(should have finished at 0.00). His vertical rotations finished at 0.40 right, then 0.30 left, then 0.15 left (instead of 0.00). Grusenick's horizontal turn finished at 0.30 left, & the vert turns at 2.00 right, & 2.00 right (instead of 0.00). At the end of Pearce's 3 vertical rotations, if u keep watching, the fringes slowly drift 0.45 right over the next 26 seconds, while the gizmo is standing still, while Pearce is talking about something else.

zztop. No i am correct. Hammar merely showed that there is not entrainment by aether. Extending this to supposedly proving that there is no aether & no aether-wind is Sfarti's silly idea. Most of the wordage & equations & ideas in that article in that link are Sfarti's, not Hammar's. Sfarti says that he has resurrected Hammar's paper from 1935. No he hasn't, there was no paper, the figures & equations are all Sfarti''s. I will have a closer look at what Sfarti wrote, to see exactly where he is wrong, & i will report back. But it will take a little while.

zztop. I looked into Hammar a couple of weeks ago after u or someone else here referred to his test. His test was simply to find any evidence of aether-drag -- one leg of a sort of M&M gizmo was inside a thick steel tube, the other leg was out in the air. He found no evidence to support drag. This proved that Michelson's & Miller's ideas about aether-drag were wrong. In other words, aether, if it exists, suffers or enjoys little or zero drag. I don't remember seeing anything wrong with Hammar's test & logic etc. However i only read what was little more than a super-long abstract, less than one page. I suppose that he did write a multi-page paper, which i wouldn't mind reading. swansont. Yes points taken. But lets not forget that the OP concerns Einstein's forked-lighting-&-train imaginary experiment. I wonder what sort of reception he would have gotten had he posted his idea on a forum under the name madAlby. Bearing in mind also that his wordage doesn't include maybe or perhaps.

Strange. The math is common sense. Beryllium results in approx. 6 times less compression strain & tension strain than Aluminium. This would lower Grusenick's 2 fringe-shifts to 1/3rd of a fringe-shift. Not bad, but still more than the desired say 1/10th of a fringe-shift (because we don't want strain fringe-shift to be bigger than M&M fringe-shift). Now here comes the clever thing. He designs the gizmo so that the axle is central between the mirrors. This might need a big re-design of the gizmo. And if the axle is central, then the compression strain above the axle will be negated by the tension strain below the axle, & the nett strain fringe-shift will in theory be zero. Remember here that Grusenick's 2 fringe-shifts in his improved gizmo are due to the critical length of the arm being in compression, & later in tension. Here the critical part of the arm is the part of the arm between the mirrors. Hencely the fringe-shift due to the compression is a half of that-there 2, ie it is 1 fringe-shift. And the fringe-shift due to the tension is 1 fringe-shift also. And 1 plus 1 makes Grusenick's 2. If these are reduced by 1/6th by using Beryllium (assuming that Grusenick used Aluminium), we have 1/6 plus 1/6 makes 2/6ths. But if we put the axle in the center of the mirror complex, we have half of the critical length of the arm of the gizmo suffering compression strain, & a half suffering tension strain. A very simplified analysis suggests that in the half suffering compression the strain (if beryllium) is minus 1/12th of a fringe-shift (ie a half of 1/6th), & at the same instant in the half suffering tension the strain is plus 1/12th of a fringe-shift, & the plus & minus negate to give zero fringe-shift. And this negation would be found at all declinations (due to symmetry). And if the strain fringe-shift in the gizmo when in the vertical plane iz zero, then any measured fringe-shift would be due to M&M effect, & temperature effect. U might point out that if Grusenick does a good job of putting his axle centrally tween the mirrors then it doesn't matter whether he uses Beryllium or sticks to the cheaper Aluminium. That is true. But Beryllium is "safer".

zztop. I don't know why Grusenick did (tried) a vertical M&M. M&Ms are i suppose of no use unless u are looking for aether-wind. And if u do a vertical M&M then i suppose that u must reckon that the aether-wind is vertical (either going down or up). The idea being that u should get a maximum result in the plane of the aether-wind. And a null result if perpendicular to the aether-wind. I wouldn't say that a vertical M&M is silly. U could make a gizmo of say Beryllium, half again as stiff as steel, & only a quarter the weight. I daresay that Grusenick used Aluminium, which is less than a quarter as stiff as Beryllium, & is 46% heavier. Beryllium would give approx. 6 times less trouble from compression strain & tension strain. And his gizmo could be better designed to resist strain. He needs a bottom plate & a top plate, with small low-wt mirrors in between. And the axle should go through the middle of the mirror complex, so that the half under compression (the higher half) would be negated by the half under tension (the lower half). In addition the gizmo could be calibrated for strain. In the horizontal position u could apply compression to one side & tension to the other, to mimic the forces due to self wt found when in the vertical plane, & the fringe-shift due to the application of the compression & tension could then be deducted from the test readings. One problem is that few locations would be suitable for a vertical M&M. What i mean is that most locations would need the test to be carried out on some angle in between horizontal & vertical. An angled M&M would be a nightmare, the strain would be much worse than in a vertical M&M. But why not travel to the tropics, & do a horizontal M&M. In the tropics the aether-wind will be horizontal twice a day. No need for a vertical M&M. If ever Grusenick gets his M&M going properly i daresay that if he measures a valid M&M fringe-shift of say 1/10th of a fringe (four times per revolution), & if this is in the plane of the aether-wind, then this might equate to an aether-wind of say 444 km/sec, which is approx what us aetherists reckon. But i haven't done a proper calibration calculation. But these are the sorts of numbers needed. He would therefor need to get his strain "noise" down to no more than 1/10th of a fringe i reckon, else the noise will be bigger than the signal. The fact that the noise will be a half-turn thing, whilst the signal is a quarter-turn thing, might make things easier for Grusenick (not more difficult). Michelson & Morley & Miller & Co all thought that the Earth was orbiting & spinning through a fixed aether, & hencely that the apparent aether-wind was passing through Earth more or less parallel to the plane of the Equator (& perhaps it might be better to do tests near the north pole). But a 60dg angle off ideal must have seemed acceptable to them. 90dg off ideal would give a null result. It wasn't till later years that they realised that the aether-wind was almost perpendicular to the Equator, & that ideally they should be doing tests in the Tropics.

DanMP. Re your comment that -- the upward path becomes smaller than the downward path -- this is something about GR that i haven't seen before. But further to my above comments, re the new improved stiffer gizmo giving only say 2 fringe-shifts (when used in the vertical plane). No matter how stiff the gizmo, half of it will suffer compression when above the axle, & a half of it (below the axle) will suffer tension at the same time. Adding say 10 times the metal might give say 10 to 100 times the stiffness (depending on how well u do it), & thusly 1/10th to 1/100th the flexing (bending), but, it will do zero to help the compression & extension (axial strains). They will most likely be exactly the same, no matter how much stiffer re bending. Thusly, after making the gizmo stiffer, eventually getting the fringe-shifts down to only 2, Gusnik will then meet a wall, & no matter how much stiffer he makes the gizmo he will still find 2 fringe-shifts (which is perhaps why he gave up & made a fixed vertical gizmo, (Mark#4 i guess)). A solution would be to design the gizmo such that the axle is in the center of its guts. Here the compression in the top half might negate the tension in the bottom half. Notice that Grusenick has all of the guts of his gizmo on the same side of the axle. A part of it, the long arm leading to the plywood target, is on the opposite side to the guts, but i suspect that this is not good enough, i suspect that the axle should be in the center of the guts part (ie inside all of the mirrors). Re Grusenick's green light, i like it. Green is a genuine colour. Whereas M&M's white acetylene light always disturbed me, white is not a colour. Finally i found a reference that said that M&M saw colour in their fringes, which is what i suspected should happen. Anyhow, i am still suspicious of using white. And i said that Grusenick might need to measure fringe-shifts to 1/300th of a fringe, to keep on par with M&M who measured to 1/10th. But the calibration for an M&M gizmo depends on wave-length so my 1/300th is an oversimplification. The calibration i am talking about here is the one equating fringe-shift with speed of the aether (or in M&M's case, speed through the aether). I had another look at the video, i was correct, the fringe-shifts are not M&M shifts, an M&M shift is a quarter turn thing, not half turn. The first video rotation starts at 3:24, shifting stops & reverses at 3:38, & the camera returns to the start point at 3:50 (here shifting stops & reverses). Continuing, the next rotation has times 3:50 (shifting stops & reverses) , 4:00 (shifting stops & reverses), 4:10 (shifting stops & reverses)(now back at the start again, ie same position as 3:24 & 3:50). The question remaining is why do the reversals occur when at 45dg, ie when the semi-mirror is horizontal?? This 45dg business is an M&M signature (or would be, if there was an aether-wind, & if it were vertical). But M&M would find reversal 4 times per turn (not Grusenick's 2). Hencely, Grusenick's 45dg mystery must have a mechanical solution. If the fringe shifting due to axial compression (& tension) is equal to the fringe-shifting due to flexing, then we have our 45dg solution. Because axial strain is at a max when vertical, & bending strain (flexing) is at a max when horizontal, & the 45dg tells us that both are equal. The problem now changes a little. Grusenick reports the same 45dg angle for all 3 versions of his gizmo. This computes ok if the equality of the ratio of the axial & bending strains is exactly the same for all 3, which is possible, though unlikely.

zztop. Thanks for that wiki link. It mentions & demolishes a claim by Anderson re a supposed periodic change in G, but i hadn't heard of Anderson & his claim. It appears that Anderson's stuff is indeed rubbish, but i doubt that Anderson's rubbish has any bearing on the Russian's 0.7%. And i see in that wiki article that G*m is indeed used in orbital work, & is considered accurate to many more places than G itself (which is what i said in an earlier posting, was it on this thread or another, i mentioned it because i had read about G*m (for Earth) many years ago). U mention Cahill. This reminds me that Cahill says something about Cavendish & G, i don't understand it, but i think it might mean that a G deduced from a spherical lead ball cant be used for a spiral galaxy (hencely dark matter). This ties in with my earlier posting re a similar claim on this forum, that goes one stop further (i think) claiming in effect that a lead ball shouldn't be considered to be at a point, if at close range. I am not sure whether these are the same thing, or two separate problems.

studiot. Thanks for the equations linking delta G & delta g by a factor near 10 to the minus 12 (i haven't seen these, not recently). It did cross my mind that nonetheless my statement that a 1% change in G possibly equals a 1% change in g is ok, because G is itself down near 10 to the minus 11 (& later i read swansont's posting saying as much). And i suspect that there is much chicken & egg involved in G & M & m & g, apart from the simpler worry of using an accurate R etc. If G is 6.674 08 (by 10^-11), & if the standard uncertainty is 0.000 31, then that is 1 in 21,529. Whereas plus 0.7% (New Zealand team i think) is 1 in 142.86, which is 150.7 times larger than 21,529. For sure this needs a closer look at the tests, & for sure i will try, if nobody beats me to it. Thanks for the link to Kim's paper explaining errors leading to the borehole anomaly. I did manage to find a free copy. However i notice that this is dated 1989, & i feel sure that some of the anomalies have come up since. If so, & if the teams were aware of Kim's explanation, then we still have a problem. I will look into this, it might take a while, there is almost nothing in Google about any of this.

Strange. That business about Cavendish tests & assuming that wts can be considered to act at a point (ie the central point) is interesting. But all of this still leaves us no closer to understanding why..... ...... tests for G are on the one hand claimed to be accurate to umpteen places, ...... yet on the other hand some teams cannot get within much better than plus 0.7% or minus 0.3%, ...... & some variations in G are 10 times larger than the estimated errors, & up to 40 times even, ...... & we have a serious borehole anomaly, ...... & the Russians measure changes over time at one site (i think). Strange. Unicorns are rhinoceros. But the old reports were stretched & altered. Couldn't happen nowadays. A change of 1% in G equates i think to a 1% change in g. I will certainly be looking into all of this. Should any of this throw doubt on the equivalence of inertial mass & gravitational mass?? I wonder. I daresay that some tests are inertial, & others are not. Has anyone ever done a comparison along those lines?? I wonder.

hoola. Yes what could possibly change measurements of G?? Here are some candidates, not including the crankiest. 1. Gravitational Waves. The type found by LIGO. Due to stars orbiting each other, in extreme cases merging. 2. Gravitational Waves. Due to loss of mass by stars. Possibly due to an explosion. 3. Gravitational Surge. Due to reverberation of gravitational attraction forces to & from planets & stars. This lends itself moreso to aether theory, but might also be found in Eiinsteinian space-time, & even in a Newtonian world. Might be a cause of the Shnoll Effect. 4. Gravitational Turbulence. Found by Prof Reg Cahill (see posting #4). This too is probably a cause of the Shnoll Effect. 5. Tidal Changes in Gravity. Due to orbits, of Moon mainly. 6. Tidal Changes to Gravity. Due to the change in position of ocean water, & the atmosphere. Gravity Waves are ocean waves, which are good for surfing, but would have little effect on G. 7. Centrifugal forces due to Earth's spin. This pseudo-gravity effect needs to be allowed for, if not, calculations of G might be understated. I suppose that this refers to drop tests, not Cavendish tests. 8. Bad apparatus, & bad logic, & bad equations, & bad errors. Which show a false change in G. 9. A mistake in the simple Newtonian inverse square equation of gravitational attraction. Apart from the known mistake of not being correct at high speeds. There are three possible types of change in G i think. A. Where G at one site appears to change over time. Perhaps periodically. The Russians say they have measured a change. B. Where G has a constant value at one site, & at another site, but the values are different. Probably involving two different teams. C. Where G at one site has different values on the same day, due perhaps to a team using a number of different types of apparatus, or due to a number of teams using the same or different apparatus etc. (i don't know of any such cases). D. I will add one more, it belongs in B, but i think it deserves its own mention. It is the borehole-anomaly. Underground, g is less than expected. Everyone blames Newton's equation, but if the equation is ok then it means that G is different underground (this wording is bad, but it will have to do for now).

swansont. My comment about having a balance-clock next to the Grandfather clock wasn't to do with the accuracy of the Grandfather. The Grandfather feels any change in G, good, that is what we were originally talking about, & my idea of having a balance-clock next to the Grandfather was because the balance-clock is immune from the effects of G, & hencely makes it easy to use the Grandfather to find-measure changes in G (if any, which i doubt, despite the Russians). Such use of a balance-clock would give a bunch of numbers that would be easier to crunch than the case of having the Grandfather on its own (which would then require ultra accurate measurements of mass & L etc of the Grandfather, not needed if one has the help of the balance-clock, all of which is just my personal observation, i didn't read it anywhere). The Shortt pendulum is very interesting. I am thinking that the next step in improving that concept would be to have 2 identical pendulums in that partial vacuum chamber, each swinging towards & away from the other in unison (ie for vibrational reasons). I think that the modern pendulum tests of G look like that (not sure). Strange. Thanx for that link to Harrison's pendulum. i remember seeing the sad saga of his treatment by the Royal Society on TV. One of the first cases of censorship i guess. But, everyone is still missing one of my points -- no matter how accurate your timepiece or test for G, the Russian advice that their G varied by 0.7% was meant to be a statement about G, & while it is fair enough to start off by questioning their apparatus, u can bet that their apparatus was state of the art. All the same, something stinks. Either G stinks, or their ultra accurate apparatus has a source of error. I will look into it. Wait a minute. I remember a sister-thread from a few months ago where a poster advised that he had calculated that a Cavendish Test that treated the wts as point-wts can lead to an error of perhaps 0.3%. Weights (& planets) should only be treated as points if at long range (it seems). I will look into it. This might partly explain the 1% range of values found for G. But it wouldn't explain the Russian finding about their variation of G. I will look into it.

DanMP. I had another look at the video, & i read the story of the 2 new gizmos, & i read the many comments. Going from 11 fringe shifts to 2 fringe shifts by making a stiffer gizmo is a worry. It all smells like flexing. Except that the 45dg declination doesn't fit. The best comment was that M&M requires a shift each quarter turn, not each half turn. I should have spotted this straight away. So, an M&M effect is unlikely here. Except that with a path length of say 2m u would only get 1/30th the fringe shift of the 60m or so path lengths of say Miller. And even so, M&M and Miller and Co measured fringe shifts to 1/10th of a fringe mostly. Grusnick would have to measure say 1/300th of a shift to keep up. And as u say we have the extra complication of the different g at a different (say 1m) elevation during a turn. Here GR & aether-theory might give a similar (size) of effect that needs to be taken into account. The daytime shift of 0.5 fringes would i suppose be a temp thing. But i will need to read the exact wording (i have an urgent appointment right now). I'll be back.

swansont. I plead innocent to the charge that i cant see how a pendulum can be used to measure changes in G. I have always said that it could. But, i might have raised the question of accuracy. And not forgetting that it would need a balance-clock (or a modern clock) sitting near the pendulum clock to tell true time. At least i would if we are talking about a Grandfather clock. And yes i have found references to a pendulum being used to measure G. I can see how this is possible, using Newton's inverse square gravity equation. But, this appears to be a very modern thing, using a super accurate pendulum, with amazingly accurate measurement apparatus, supposedly giving G to umpteen places. I wonder what the error estimates might be for a Grandfather clock. John Cuthber inferred that they would be much better than the 1% (or 0.7%) that i was alluding to. Re two different effects, it might be a problem. One that comes to mind is what if Einstein simply used pendulum clocks for all of his SR & GR imaginings & equations. When he got to his rotating-disc-thought-experiment, the outer clock would be ticking faster than the inner clock at the axis, & i hate to think where things would go after that.

Strange. The equations (that i see on Google) for a pendulum suggest that the period will halve if g increases by 4. And the equations don't allow for GR, nor SR. I guess that they accept that pendulums are never going to go to the Moon.

zztop. I couldn't follow Cahill's derivation of his M&M calibration equation, however as usual i simply used some simple equations in an Excel table to calculate time difference in the 2 M&M arms & i got his answers, which convinced me he is correct. A good article re all this is -- "Review of Experiments that Contradict Special Relativity and Support Neo-Lorentz Relativity: Latest Technique to Detect Dynamical Space Using Quantum Detection (2015) -- Baltimore Conference.