oz93666 wrote: Because the effort required exercises your intellect...
So does solving real problems with real physics, instead of just honing my edge studying Zeno's Paradoxes, or Einstein's Relativity. But when I read stuff, and I have questions (like how Eddington ruled out the mirage effect in his proof of gravitational lensing, or how field splitting was ruled out in the Pound-Rebka experiment), I don't get straight answers. I just get told to read more books, and sometimes it just isn't going to make sense, because it's counter-intuitive. Well, I can handle theories that are counter-intuitive, as long as the predictions of the theory actually match the observations, and as long as good experimental methods were used. As best as I can tell in relativity, this is not the case. And somewhere in all of the confusion and the evasive non-answers, I come upon the opinion that relativity isn't a science — it's a religion. It's full of mysteries, and you just have to accept that you'll never truly understand it, but if you keep studying, eventually you'll be like the other people. Well, as religions go, relativity sucks. Go convert somebody else. I'm using a classical method, and it's all starting to make sense. I might not understand particle physics, and I might not understand the Big Bang, and I might not understand what's happening at the edge of the known Universe, where things are moving away from us faster than the speed of light. But I can explain the Sun and the Earth without resorting to QM or GR. And I can demonstrate that good scientific method requires that all known forces be ruled out before concluding that something strange is going on. So I'm using a good method, and I'm getting good results. And that's good enough for me.
Sain84
Re: Relativity
CharlesChandler wrote: how Eddington ruled out the mirage effect in his proof of gravitational lensing, or how field splitting was ruled out in the Pound-Rebka experiment
Eddington used multiple stars near the Sun to measure the light deflection all taken in the same image. They all had different distances from the Sun so would have different deflections. Atmospheric refraction which causes mirages would depend on angle above the ground, so stars would be shifted depending on altitude not distance from the Sun. Atmospheric refraction does have to be removed in such observations as it is in many others. Eddington's original experiment however is not the prime example because few now believe it's results are reliable.
However now there is no shortage of these sorts of measurements which can now be done with much more precise measurements. Hipparcos the ESA mission was capable of detecting the deflection at all angles from the Sun, and from some planets.
GAIA, it's successor will be capable of detecting the deflection from major moons. Deflection experiments can also be done with great precision with VLBI in radio as long as they are sufficiently far from the Sun to ovoid refraction.
On Pound and Rebka their original paper is sparse on details but the reason I think they ruled out splitting is likely because they were more familiar with the experiment than us. In more recent papers you can see that the width of the line is actually greater than the shift and the width is not changing. On the assumption this is the same for the different materials in Pound Rebka a split of less than the with of the line could therefore not cause a mistaken shift, but a wider line. This is not observed and I suspect this is the reason it was not in the paper.
A more recent paper includes a spectrum of both positive and negative velocities showing it is indeed a shift. They also include a simultaneous measurement from a reference instrument at the bottom of the tower. I can't find a free link to this paper unfortunately but for anyone who has access it is a much better paper than Pound Rebka.
Now that Sain has answered the questions plausibly, I'll repost Mathis' explanation of length contraction from another thread. And let's see if Sain or anyone agrees with it.
The following is from Mathis' paper, Relativity Demystified, at http://milesmathis.com/rel4.html and it seems that he does a rather good job of demystifying it.
. . . Einstein, the high priest, understood Relativity in large part, but his explanations only confused the rest of the world. And even Einstein did not understand Relativity in full. That is why he was not able to simplify it. Relativity is much more transparent than we have been led to believe.
. . . The reason the receding train looks shorter [length contraction] is that the length of the train is determined by a single image. Unlike the wave [lightwave?], which is built of a series of images, the length is determined by one image only. In other words, we could take a picture with a real camera, and using that one image, we could determine the apparent length of the train. (And, yes, that one image would be distorted by Relativity. That real picture, taken by a real camera, would be distorted by Relativity.) Now, that one image is made up of all the light reaching us at the same instant, from all the points on the train. Since all the light is moving the same speed, the light from more distant points on the train must be earlier light. To say it another way, all the light is reaching US at the same time, to make the image, so it can't have left all points on the train at the same time. If we work backwards from our eye, and go the speed of light for x seconds, we can reach some points on the train, but not others. This means that our image is made up of older and newer light. For instance, if the light from the nearest parts of the train was emitted at t = .0002s, then the light from the farthest parts of the train might have been emitted at t = .0001s. The light has farther to go, so to reach us at the same time, it had to be emitted earlier. If it was emitted earlier, then it was emitted when the object was not quite as far away. Therefore, the far end of the object will appear closer than it is. Therefore, the object will appear smaller or shorter than it really is. - That was a bit difficult, I realize. It is probably the most difficult thing to understand about Relativity, and it has been misunderstood and misinterpreted millions of times. If you can make sense of that paragraph, you can make sense of any of the subtleties of Relativity. - As one more aid to understanding, I will point out that this length contraction is exactly the opposite of the contraction of sound. . . .
By the way, I believe stars at various distances would be similar enough to various train cars on a long train in the above example. I'm not clear though on what velocities the stars would need to have and what directions of motion.
Sain84
Re: Relativity
Hi Lloyd, I'm afraid I don't agree with that. That is the classical expectation of applying a finite speed of light, relativity however adds another component. Even if your train was perpendicular to your line of sight with both ends at equal distances there would still be relativistic length contraction.
If we consider this delay as described neatly by Mathis a train receding from us would look longer, and yet the relativity says the length contracts, in fact it's invariant of direction. That's because the realistically factor does not include this geometric effect caused by the finite speed of light. The relativistic factor is a separate term. In order to properly calculate the length of the train realistically you would first apply length contraction and then you would go about considering the simultaneity as described by Mathis, or the other way round, it wouldn't matter which way.
CharlesChandler
Re: Relativity
Sain84 wrote: Eddington used multiple stars near the Sun to measure the light deflection all taken in the same image. They all had different distances from the Sun so would have different deflections. Atmospheric refraction which causes mirages would depend on angle above the ground, so stars would be shifted depending on altitude not distance from the Sun. Atmospheric refraction does have to be removed in such observations as it is in many others. Eddington's original experiment however is not the prime example because few now believe it's results are reliable.
I don't understand why the deflection would be a function of distance from the Sun, and not altitude. If a spacecraft flies past the Sun, is the gravitational attraction a function of how close it gets to the Sun, or is it a function of how long the craft traveled before the encounter? Does the so-called gravitational lensing follow the inverse square law?
I'm sooooooo confused!!!!!!
Please recommend that I enroll in the nearest university, so I can find the error in my ways as soon as possible!!!!
Sain84 wrote: However now there is no shortage of these sorts of measurements which can now be done with much more precise measurements. Hipparcos the ESA mission was capable of detecting the deflection at all angles from the Sun, and from some planets.
Sounds really fancy. Now, for me to be convinced, they would have to go out to the desert, and predict the deflection of light due to a mirage to that degree of accuracy, before claiming that their deep-space measurements were that accurate. Mirages can deflect photons several degrees in just a couple of kilometers. Anticipating the deflection to within a few arc-seconds requires measurements of the density gradient with even more precision than that, to get the experimental variance smaller than the assertions. Good luck.
JeffreyW
Re: Realativity
JeffreyW wrote:
1. How much faster is 99.9% the speed of light versus 99% the speed of light?
a. .9% faster b. 9% faster c. 1000% faster (10 times as fast) d. twice as fast e. none of the above
2. How much faster is 99.99999% the speed of light versus 99% the speed of light?
a. 200 times faster b. 100 times faster c. 10,000 times faster d. 100,000 times faster e. none of the above
The answer to number 1 is C. 1000% faster (10 times as fast)
The answer to number 2 is D. 100,000 times faster
JeffreyW
Re: Realativity
Michael V wrote: JeffreyW,
JeffreyW wrote: If you know the answer to the question then you will realize super-luminal velocities are unnecessary! As you approach light speed the velocity increases exponentially based on your frame of reference, thus things getting shorter/longer or time slowing/stopping is an appearance, not reality! The stars in front will blueshift like a mofo, and the stars behind you will disappear into the radio frequencies. Thus in future navigation systems it will be necessary to adjust the coordinates in reference to the velocity you are travelling, because solid rock like worlds will appear to be gamma ray sources as you travel towards them!
I am curious, what would you say is the fastest atoms have been observed to travel?. Not electrons, not protons, not nuclei, atoms!!. What is the fastest that an atom has ever been observed to travel at?. Perhaps you can also say, what is the fastest that a molecular structure has been observed to travel at?.
I'd like to open those questions to anyone and everyone who might have an opinion.
Michael
An "atom" or "molecular structure" is something that can change. Let me explain:
For craft that are propelled by engines, for example the engine/propulsion, fuel and structure are all mutually exclusive in an engineering sense, the integrity of the craft as it approaches high G's diminishes considerable. Such as F-18's when executing wartime maneuvers.
Why would the integrity of the craft diminish? The strength of the molecular bonds inside the iron/nickel alloys in the engine weaken? The fiberglass resin starts to jitter and crack in the wings? The fuel get too hot and reach diminishing expansion ratios when combusting in the engine...
All of this is caused because the molecular structure is breaking down (as it has different properties given the stresses and heat involved). Thus, to achieve craft that do not "fall apart" so to speak and can sustain high G maneuvers, we must figure out how to literally BREAK the molecules down temporarily so that they do not break apart from the maneuvers themselves, thus sustaining the craft's integrity, and then bring the molecules and bonds back together when the craft is at lower speed maneuvers such as landing and surveying other star systems up close.
What I really mean is that an "atom" or "molecule" will change its structure when travelling at high speeds. Thus the craft that we will develop will be able to turn into what we observe as a "laser" only on a much larger, stable structure. Thus we have this:
1. The structure BECOMES the fuel and engine (propulsion method). (think silver/grey disks that execute 90 degree flanking maneuvers when intercepted).
Since there is no MEDIUM in outer space, the craft we will develop will be able to travel as if they ARE the vacuum itself, thus they will be able to travel through entire vast star fields with no chance of collision and at impossible velocities with current technology.
Sain84
Re: Relativity
CharlesChandler wrote: I don't understand why the deflection would be a function of distance from the Sun, and not altitude. If a spacecraft flies past the Sun, is the gravitational attraction a function of how close it gets to the Sun, or is it a function of how long the craft traveled before the encounter? Does the so-called gravitational lensing follow the inverse square law?
I'm sorry I should have been more specific. By altitude I mean in the astronomical context, height in degrees above the horizon. Just like shining light into a prism the amount of deflection depends on what angle you shine light in. Gravitational attraction of a mass depends on how close it is to the Sun, how long it's traveled wouldn't matter in GR as long as both mass, energy and momentum are the same. As far as I'm aware gravitational lensing approximates (in the case of small angles and relativity weak fields) to an inverse law, proportional to 1/r, where r is the closest approach of the light ray.
CharlesChandler wrote: Sounds really fancy. Now, for me to be convinced, they would have to go out to the desert, and predict the deflection of light due to a mirage to that degree of accuracy, before claiming that their deep-space measurements were that accurate. Mirages can deflect photons several degrees in just a couple of kilometers. Anticipating the deflection to within a few arc-seconds requires measurements of the density gradient with even more precision than that, to get the experimental variance smaller than the assertions. Good luck.
Note that paper in question was done in space, atmospheric refraction has nothing to do with those results.
You could predict the deflection of a mirage if you had all the information. The mathematics involved is quite different however. When dealing with things high in the sky the equations simplify. When doing precision measurements, where possible the observations are done as close to the top of the sky as possible which makes the reduction simpler. You can see in this paper people have calculates the distortion of the solar disk very close the horizon.
But again this is much more extreme than what is actually needed to deal with refraction in astronomy as small zenith distances are used. There are many papers on simulating mirage scenes but none are analysed rigorously.
CharlesChandler
Re: Relativity
Sain84 wrote: As far as I'm aware gravitational lensing approximates (in the case of small angles and relativity weak fields) to an inverse law, proportional to 1/r, where r is the closest approach of the light ray.
I thought that gravity obeyed the inverse square law. Was this predicted by GR, or was it an heuristic adjustment? And on what grounds does this prove the effect to be due to gravity, if it doesn't behave like gravity? It sounds like an effect was observed, and it didn't act like gravity, but they wanted it to be gravity, so they said that it was gravity, but in this special case, gravity acts differently. Ah, the power of the preformed conclusion.
Sain84 wrote: Note that paper in question was done in space, atmospheric refraction has nothing to do with those results.
So space physics is different from terrestrial physics? How was that determined? They acknowledged gravity, but not EM, and nothing made sense, so they concluded that gravity acts really funny out in space? Once again we observe the power of the preformed conclusion.
Sain84
Re: Relativity
CharlesChandler wrote: I thought that gravity obeyed the inverse square law. Was this predicted by GR, or was it an heuristic adjustment?
It is not a heuristic conclusion. Gravitational attraction in the limit of weak fields is an inverse square law, light deflection is not because it is the sum across a whole path, something very different. The inverse law is entirely derived from GR. Even in Newtonian dynamics if you give light a small but finite mass you can get an inverse law of light deflection, the magnitude of deflection is different however and does not match observation.
CharlesChandler wrote: So space physics is different from terrestrial physics? How was that determined?
No, that's not what I said. When you do an experiment you remove potential sources of error, in this case turbulence and refraction. Atmospheric refraction is not a potential source of error here so it is not the basis for criticism. The physics is not changing, you are just removing a source or error.
CharlesChandler
Re: Relativity
Sain84 wrote: Atmospheric refraction is not a potential source of error here so it is not the basis for criticism.
How is it that a robust gravitational source in space, sufficient for "gravitational lensing", doesn't have an atmosphere? Moons and small planets in our solar system, if sufficiently bathed in solar wind, are without atmospheres. But Mars, and everything bigger, have atmospheres. The Sun has an atmosphere. Where did they observe lensing in the absence of an atmosphere that would refract the light?
Siggy_G
Re: Realativity
JeffreyW wrote: 1. How much faster is 99.9% the speed of light versus 99% the speed of light?
(...) The answer to number 1 is C. 1000% faster (10 times as fast)
This is also evident when comparing the actual numbers:
1,0 c ____________ = 300.000.000 m/s 0,9999999 c ______ = 299.999.970 m/s 0,99 c ___________ = 297.000.000 m/s 1% of 0,99 c ______ = _ 2.970.000 m/s
However, the reason Special Relativity gets immense increases in energy requirement is because the formula is constructed that way, with (1 - v/c) in the denominator e.g. the Lorentz factor. This means the denominator will approach (1 - 1) i.e. dividing by zero as v approaches c. The "evidence" for why endless energy is needed for these increased steps, is the formula, which in turn is a "logical consequence of the stated assumptions" i.e. that the upper limit for any object's velocity within one reference frame must be c. The formula is constructed to make mass at c an impossibility, and calculations using this formula are used as evidence... In other words, the assumption is the evidence.
Sain84
Re: Relativity
CharlesChandler wrote: How is it that a robust gravitational source in space, sufficient for "gravitational lensing", doesn't have an atmosphere? Moons and small planets in our solar system, if sufficiently bathed in solar wind, are without atmospheres. But Mars, and everything bigger, have atmospheres. The Sun has an atmosphere. Where did they observe lensing in the absence of an atmosphere that would refract the light?
The gravitational lensing effects extend much beyond the atmosphere of a body. For example the Sun's lensing effects can be observed across the entire sky. In optical you cannot take data too close to any major body because it will saturate the detectors. If this was due to refraction in the heilosphere it would not be frequency independent and thus the radio VLBI measurements would differ from the optical ones significantly, this is not observed as they agree on the gamma parameter along with other measurements.
CharlesChandler
Re: Relativity
Sain84 wrote: For example the Sun's lensing effects can be observed across the entire sky.
What is the deflection of a photon arriving at Earth along a tangent to the Earth's rotation (i.e., perpendicular to a line from the Earth to the Sun), such that the photon never got nearer to the Sun than the Earth?
marengo
Re: Relativity
Sain84 wrote: The gravitational lensing effects extend much beyond the atmosphere of a body. For example the Sun's lensing effects can be observed across the entire sky.
It is perhaps confusing to talk too much of the Sun's lensing effect. Surely one needs to recognise the basic effect here. That is that the gravitational potential is the propagation velocity of the Aether (or Space if you don't like Aether). As the grav. pot. diminishes as one approaches a mass, eg. the Sun, so the speed of light diminishes. This the basic effect of gravity. This effect is observed by the bending of a tangential light ray which occurs as that side of the ray nearest the mass is slower than on the opposite side. This bending is what leads to the 'lensing' effect. It is analogous to light bent by passing through a glass lens.
The bending of a tangential light ray can equally be seen as an acceleration towards the Sun. If you calculate the effect you find it to be TWICE the rate of the acceleration of matter. So the acceleration of light is in direct proportion to that of matter. Thus it seems correct to state, as I did at the beginning, that the propagation velocity of the Aether is the gravitational potential. But the exact mechanism within a mass particle can only be conjectured. Nevertheless we know the cause and we know the effect--the acceleration of mass.
