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Then accept the premise and move on. The premise is that you measure the amount of time it takes for light to traverse a ruler, measure this time a year later, and find that this latter measurement is greater than the initial measurement. This is a given condition for this thought experiment. Stop arguing against it.

You are quibbling with a supposition, and that is preventing you from moving on. Stop that! There was no change if there is no change in what is measured, including everything that can be measured (i.e, the dimensionless fundamental constants). Arguing otherwise is akin to philosophers arguing about how many angels can dance on a pin.

You are misreading the article and you are quibbling with a proposition. The article says " Suppose that we calibrate marks on a ruler using this definition one year, then next year find that light takes longer than 3 ns to travel the length of the ruler." That light "takes longer than 3 ns to travel the length of the ruler" is a given condition in this (thought) experiment. Quibbling with this will get you nowhere other than confused. You are throwing too many thoughts into the mix at once and all you are managing to do is to confuse yourself. Take it one step at a time. You are not taking your own advice. munion, you are the one who asked "what if the speed of light changed". At least, I think that is your question. You used phrases such as the "4D speed". That doesn't quite make sense, so I reinterpreted your question to something that does make a bit more sense. The question "what if the speed of light changed" doesn't quite make sense either, for the simple reason that the speed of light is currently defined to be a constant. The speed of light cannot change by definition. This question is implying is that our definition of distance is not quite right, that distance has some deeper meaning than the one provided by our current definition of a meter. A better rendition of this question is "What if the speed of light changed (assuming some better definition of distance exists)". Suppose our calibrated ruler has not truly changed in length. What has changed is the speed of light itself. The ruler will appear to have changed in length because we are using a faulty definition of distance.

The truth is out there, and Trent Franks (R-AZ) likes it a *lot*, more than three times as much as does Chris Dodd (D-CT). Franks also likes innocent unborn children, whereas Dodd likes health care as the top issue of the day. Politicians in general like the truth a whole lot better than lies. That of course is because politicians never lie.

No! You are not reading the article. Units! Always carry units in your calculations: 1 m / (299792458 m/s) = 3.33564095 nanoseconds. The thought experiment to which you take objection starts with this as a basis. One step at a time: Setup: You have some device that enables you to measure the time it takes a light pulse to traverse the distance from a transmitter to a receiver. This is a "real" experiment; you cannot measure 3.33564095 nanoseconds. You can however measure down to the tenth of a picosecond, 3.336 nanoseconds, for example. You have a ruler that you want to calibrate with this device. [*]Make a mark on the ruler corresponding to the location of the transmitter. [*]Move the receiver along the ruler, measuring the transmission time as you do so. [*]Stop moving the receiver when the transmission time is 3.3356 nanoseconds. [*]Make a mark on the ruler corresponding to the location of the receiver. You now have a calibrated ruler. You missed the next part of the experiment. Suppose next year you use the device to measure the length between the calibrated scratch marks, but now you measure 3.3381 nanoseconds (for example). What does this new measurement mean? (Your turn.)

Correct. That means the speed of light is 299,792,458 m/s and can not change -- at least using the current definition of a meter.

Light speed does not and can not change per the current definition of distance. You need to understand this before this discussion can move forward.

You are correct about time but not about length. As I said earlier, a meter is "the distance travelled by light in free space in 1⁄299,792,458 of a second." This means that The speed of light is constant by definition. By this definition of length, the only conclusion one can come to is that the ruler has gotten slightly longer. You need to understand this before we can move on.

The article is not erroneous. You objected to this: What would it mean to say that c varied with time? Would it actually mean anything? In conventional units, the metre is defined as the distance that light travels in about 3 nanoseconds. (This is not quite the same thing as saying that the metre is the distance travelled in 1/c seconds.) Suppose that we calibrate marks on a ruler using this definition one year, then next year find that light takes longer than 3 ns to travel the length of the ruler. According to the definition, we wouldn't say that the speed of light had fallen, but that the ruler had lengthened. How could that be? What would that mean? That is exactly correct. Our current definition of the meter is "the distance travelled by light in free space in 1⁄299,792,458 of a second." This means the speed of light is constant by definition. If one conducted the experiment described by the author of that site, the only conclusion one could come to using our current definitions of time and distance is that the stick has gotten longer. You are assuming that length is defined by marks on a stick. That is exactly how the meter used to be defined. There are a lot of problems with such a definition. In 1983 the standards committee dropped the old standard and adopted the definition quoted above. The standards committee made this change for good reason. The speed of light is constant per accepted scientific theory and every measurement of the speed of light bears that assumption out. Suppose someone did conduct the above experiment and found that the time it takes light to traverse the stick is increasing over time. The experimenters are going to try to find whether there are some hidden problems in their experiment. Suppose they find none. Are they going to assume the stick has grown longer just because it has per the current definitions of our units? No. They are going to poke, and poke and poke and poke, into this mystery. A result like that might well be worth a Nobel prize. Ultimately it will come down to a change in one or more of the supposedly constant dimensionless constants, which is why we have been harruanging on those dimensionless constants. What would such a change mean? We don't know. Science cannot answer that question because it assumes the speed of light is constant. It will stick to this assumption until some experiment shows the assumption to be wrong.

What do you think? We are not here to do your homework for you. That said, Some hints: What are the entities in this system? What are the relationships between them? The given information will help answer these questions.

You apparently missed the point of the article, munion. The section marked Is the speed of light constant? is a lead-in to the rest of the article. That question at the end of this little section, "How would we know which," is a rhetorical question. The author proceeds to answer that vert question in the remainder of the article. Your question, "What would happen if the speed of light changed," is a science fiction question. Physics cannot answer that question because the laws of physics assume the speed of light is constant. In the sense of what physics can describe, this is a non sequitur kind of question. It simply does not compute. There is a very good reason why physics assumes the speed of light is constant. First there is direct observation. The speed of light is constant, as far as we can tell experimentally. Second, the speed of light is in a sense just an artifact of our definition of units. A better question is to poke at the dimensionless constants such as the fine structure constant. These are not artifacts of how we measure things. They are more fundamental than the speed of light. And as far as we can tell, constant.

Yes. Lack of evidence is not evidence of lack. However, continued lack of evidence does correlate rather highly with lack of funding. Thirty years ago schools, including several prestigious ones, proved that the science could be subverted given adequate sources of money. Paranormal studies departments sprang up all over the place. The drying up of funding coupled with lack of success coupled with the utter intellectual embarrassment of the whole concept later led most schools to close these paranormal studies departments. Good riddance.

Let's back up a bit. I think what you are really asking is "are the physical constants really constant with respect to time?" Physicists assume that the key physical constants are indeed constant in the theories they develop. Our current understanding of the universe cannot answer your question because it is a nonsense question in terms of that understanding: The constancy of the key physical constants is built-in to that understanding. One obvious consequence, however: Energy would not be conserved if the physical constants varied with time. Energy is conserved because the laws of physics are invariant with respect to time. Get rid of that invariance and you get rid of conservation of energy. Because physicists do not like unwarranted assumptions, they test the heck out of these assumptions of the physical constants being constant. There are ways of looking back in time, a long ways back in time. For example, telescopes essentially see back in time. Another example are the Oklo deposits in Africa. Two billion years ago these formed a natural nuclear reactor. The decay products we see now from these two billion year old reactions demonstrate that the laws of physics have not changed over the last two billion years. Here is one web site that tries to answer your question: http://www.phys.unsw.edu.au/einsteinlight/jw/module6_constant.htm. It starts with this personal preamble (emphasis mine): As a child, I asked my parents "What if everything in the world had shrunk to half size overnight. How would we know? I'd be half as tall, but the ruler would be only half as long, so I couldn't tell." But this invited further questions: how long would it take to walk to school? If my half-length legs propelled me at half the speed, I wouldn't notice the change in the distance. Or perhaps shrinking all the molecules in my leg muscles would make the electrical forces stronger so I'd walk faster. Or maybe all the clocks would be sped up by a factor. Pendulums and planetary orbits would be shorter, and crystals would be stiffer (per unit area). Both gravitational and electric clocks would run fast. At the time, I didn't know about inverse square laws or quantum mechanics, but it seemed reasonable that the (electrical) muscular forces and gravitational forces should be changed, too. Conclusion in retrospect? Starting from this point makes the question more complicated and confusing than it need be - one ends up going around in circles. It's easier to start logically and work up from the basics. I think this same confusion is part of your problem. Read this article, see if it answers some questions.

munion, insane_alien did the best he could to interpret what you asked in terms of 4D speed. "Speed" means magnitude of a velocity vector, so what else could 4D speed mean other than the magnitude of the 4-velocity? The magnitude of the 4-velocity is indeed always constant. I think you meant something else, but I do not know what that something else is. Your question doesn't quite make sense, munion. That is why I asked what you meant by "Suddenly the 4D speed is changing for all with the same rate; your device will show something different?" Try asking without using the term "4D speed".

vacuodynamic, you seem to be missing the main point of Einstein's ether. Yes, Einstein did return to the concept of an "ether". From http://physicsworldarchive.iop.org/index.cfm?action=summary&doc=14%2F6%2Fphwv14i6a33%40pwa%2Dxml&qt= (emphasis mine): Most physics students learn from their text books that in 1905 Einstein banished the ether from physics as part of the revolution initiated by his special theory of relativity. What they generally do not learn is that in 1916 he reintroduced the concept as part of the revolution initiated by his general theory of relativity. The catch is, of course, that the ether he reintroduced differed fundamentally from the ether he had banished. So what is Einstein's ether? Another name for it: curved spacetime. Until you produce some sort of plausible argument and preferably evidence for this idea of yours, this idea of yours is speculation or pseudoscience. Thread moved to Pseudoscience and Speculation.[/red]

I was being a bit obscure, I guess. The following referred to Widdekind's pretty posting style, not the infrared issue. Back to the topic at hand: Just to reiterate, so nobody gets me wrong: I completely agree with iNow. We don't have pit organs, so unlike put vipers and constrictors, we cannot see in the infrared. The premise is bogus.

I knew there was something else bugging me about one of your posts. This one: I search the net for quotes by and commentaries on Einstein in which even a small part of the quoted phrase was attributed to Einstein. Nothing -- except for a bunch of anti-Semetic / nutjob / both web sites. Here's the neat thing: The above quoted phrase can be found verbatim on those wacko sites. That nobody but those wacko sites had anything like this and that the wacko sites are word-for-word identical makes my BS alarm ping off-scale high. Particularly troubling is the phrase "In his 1907 paper ... " Which 1907 paper? Einstein published several papers in 1907. My suspicion is that one of those authors simply invented this quote and that the others copied this invented work without attribution. (Hmmm. Fudged quotes in articles that accuse Einstein of fudging the data, plagiarizing content in articles that accuse Einstein of plagiarizing relativity. My irony meter just joined my BS meter at off-scale high.) You can allay my suspicions and you will get an apology out of me if you can perform but one little task regarding that troublesome piece of text: Tell me the paper in which the statement was made and a page number. A 'net reference to the paper is preferable.

Oh joy. Yet another crackpot site. "3) he suggested that mass depends on speed". Yep. He, with Lorentz, derived [math]E=3/4mc^2[/math]. " 5)...he derived the Lorentz transformations." Nope. In his work with Lorentz, the Lorentz transformations are axiomatic. That was about as much of that nonsense as I can stand. Besides, the crackpot font hurts my eyes. (Aside: Why do crackpots revel in making their sites painful to read, in both the literal and figurative sense?) I'll finish with this amazingly rich piece of nonsense from the article: "A Timeline of Western Philosophers, by Garth Kemerling in an Internet article dated 1997, 1998, 1999. He is only 1 of 500 philosophers featured on that timeline in the past 2600 years. In math, he is one of the top 26 mathematicians in the past 2600 years (see: Famous Mathematicians on the Internet). Even Einstein recognized Poincares superiority as thinker and author." So far, so good. Poincare ranks right up there amongst the most brilliant minds of all time. So what makes it too rich? The very next sentence: "For Poincare to fade into obscurity requires the cooperation of thousands of physicists." Where is the :rotfl: smiley when you need it? Did the author read what he wrote right before that? Has he read any physics texts? Math texts? Engineering texts? The fact is, Poincare did not make that final step. Physics and math are games for young minds. Poincare was doing what old scientists do at the end of their careers: He was mentoring, in this case, Lorentz. While he did develop a theory of relativity, but it was not Einstein's. It was not nearly as elegant and simple. He still had the Lorentz transformations as axiomatic and he still had an absolute reference frame. To make mattes worse, this absolute reference frame was completely undetectable. It was issues of aesthetics rather than a conspiracy of thousands of physicists (to what end??) that made physicists adapt special relativity over Lorentz Ether Theory. Let's go back in time 300 years before Einstein and Poincare. Tycho Brahe was the mentor to Johannes Kepler. Brahe, like Poincare, went halfway to the new point of view. Brahe developed a mixed model of the solar system, with the planets orbiting the Sun but the Moon and Sun orbiting Earth. He could not make that last step. Kepler could, and he one-upped Copernicus by throwing out the sacred cow of uniform circular motion. Even though Brahe was the mentor, it was his student that earned a big place in history. Brahe's place in history is diminished because couldn't let go of his sacred cows. What is it with the broken record garbage?

We've been over Preston and DePretto. DePretto deserves no claim. He made several errors that just happened to cancel. He got the right answer by pure dumb luck. When students make mistakes that luckily happen to cancel they might get partial credit. When scientists make mistakes that luckily happen to cancel, the only credit is negative. They certainly are not credited with the discovery. Preston did not use relativistic arguments. He instead based his argument on a rather dubious interpretation of a model that, by Einstein's time, was utterly falsified. Pure luck once again (just not dumb luck this time), and once again, no credit.

Why? How did Poincare's work help Einstein at all? Was Einstein aware of it? Do you even read the papers, or do you just read hate sites?

Web sites aren't peer reviewed. The burden of proof is on you Bombus, to show that the material on this web site comes from a peer-reviewed source. Good luck with that. A google search for "James Maxlow CV" yields nothing. "James Maxlow Curriculum Vitae": Nothing. "James Maxlow publications": A self-published E-book.

No, he is not. He is a professional crackpot, and he is quite serious about it.

Nonsense, even nonsense all dressed up in pretty colors, is still nonsense.

One problem with that line of reasoning: You, and others like you, are not physicists. You have the credibility of any other crackpot: Zip. Preston (not Oliver, get your facts straight) came to [math]E=mc^2[/math] via some ad hoc reasoning that is demonstrably false. He based his argument on a luminiferous aether that takes the form of ether particles. There is no luminiferous aether, and there certainly are no ether particles. At least Preston had an excuse for assuming the existence of an ether: In 1875, every physicist assumed such. The ether particle bit is, well, a bit cranky. DePretto based his derivation on the incorrect formula for kinetic energy and he assumed a luminiferous aether. DePretto had no such excuse as the Michelson-Morley experiment predated him by a couple decades, and he most certainly had no excuse for using [math]KE=mv^2[/math]. DePretto was'nt just cranky. In the words of http://www.crank.net, he was crankiest. No credible physicist came up with [math]E=mc^2[/math] before Einstein. That is his, and his alone. With this last post you have shown your true spots. You did not make the original post as an innocent query. Rather, you made it appear innocent in an attempt to hide your spots.

What do you mean by this?