Well, I’m not really a physicist, but my guess is that large variations in the speed of light over time would’ve provided evidence against GR long before now. So that’s the reason I’m inclined to believe that if it has changed, it changed very little.
[MontyPython]It got better.[/Monty Python]
Hear! Hear! We should remember, however, that our understanding of the universe is not complete and will likely never be complete. Many of the things we take for granted now will be laughed at in fifty years. While it would certainly complicate the math, there is no fundamental reason, really, why the electron charge can’t vary over time. We don’t even understand why an electron, or any fundamental particle should exist at all. You could certainly construct a reasonable theory that what we see as an electron is actually a much more complicated multidimensional object governed by very complex laws. (That is, essentially, what string theory does say though I’m certainly nowhere close to up to speed on it.)
When you think about it, there’s not even anything sacred about the laws of thermodynamics. While they do strictly conform to what we observe, there is nothing, in principle, that says they can never be violated. (Of course, an observed violation would have profound implications.) In any case, the first one, in fact, has either obviously been broken or is vastly more complicated than it appears – which is one reason why no one can really explain the Big Bang yet.
Toss in things like the wonderfully weird Casimir effect and it is apparent that we still have much to learn. There is more in heaven and earth than is dreamt of in our philosophy.
Lib,
What I could find from the original paper predicts a variation in the fine structure constant on the order of magnitude of 0.0001 percent or less over the period of time from a third to eighty five percent of the age of the universe. That is highly significant, but far short of the amount of change implicit in the YEC argument.
That ignores the fact that the YEC argument, when examined requires a distinctly non linear change in the speed of light, occurring very rapidly at first, and then stopping abruptly at the precise instant that the clock and telescope were introduced into scientific investigation.
It is also of note, in case YEC fanatics choose to use the argument anyway, the existence of the change depends entirely on the assumptions that the universe, including that portion of it which is local to ourselves is 12 or so billion years old. Not that that would stop them, of course.
Tris
Thanks, Tris. That was what I was looking for.
How’s that? The speed of light measured in meters depends upon the definition of the meter. The meter is defined as the distance that light travels in 1/229,792,548 seconds. This definition makes the speed of light constant and exactly equal to 229,792,548 meters per second.
The speed of light is constant by definition.
DrMatrix
Are you saying that, if the data bear out, that meters are changing length over time?
No. Our units of distance and time are matters of definition. In order to say that some distance has changed, it must be compared to our standard. The meter is the standard of comparison. It cannot change compared to itself.
DrMatrix: your quibble with the “defined” part of the statement made by Truth Seeker is understandable. The speed of light itself is defined independent of any measurement of the properties of electric and magnetic fields. However, if one were to ask, “how is the speed of the electromagnetic waves defined?” one would necessarily appeal to the two separate constants for the propagation of electric and magnetic fields through space.
Anyway, this is all simply sematics. The three “constant” are intimately related and are really just one. That is why we speak of the speed of light only and don’t worry ourselves with the other two.
It’s not necessarily obvious that tweaking the fine structure constant necessarily leads one to changing the speed of light. We could fiddle with all sorts of constants. Other than charge of the electron, I guess we could also fiddle with the mass of an electron (another seeming violation of the 2d Law of Thermodynamics). We could also fiddle with Planck’s constant.
Dr. Matrix
Maybe I have a mental block, but I don’t understand. Is this something akin to the whole universe and everything in it changing size overnight with the net effect that there was no change since measuring tools changed size also?
The National Institute of Standards and Technology maintains this web site giving information on the values of fundamental constants, and the definitions of units in which they are expressed.
The furor, if any, of the observations made is that the definition of units assumes the invariability of c and of the electron charge, among other things. Time itself is defined in terms dependent upon the fine structure constant. Distance is expressed as a derivative value of c. The reason that has been done is to avoid the need for prototypes, such as the venerable standard kilogram, which is an actual object.
If the constants are not constant, the entire model proves itself to be unusable for the scale for which the variation manifests. The butcher shop is not going to notice, and neither is the global positioning system. No new survey of Manhattan real estate will be needed. But the theoretical mathematics governing the interactions of elemental particles, and groups of galaxies, over femto-seconds, or billions of years will need to be examined.
And a new set of definitions will be needed, as well, to avoid the contradiction described by Dr. Matrix.
Tris
“What have you done to that cat? It looks half dead!” ~ Mrs. Erwin Schrodinger ~
This is merely further proof of the innate superiority of the English system of measurement. Good, solid dependable units – not like those wishy-washy meters. Today they’re one thing, 14 billion years from now they’ll be something else. I say we’ll never truly understand the universe until we jettison this artsy-fartsy “light years” nonsense and start measuring the volume of the universe in bushels and pecks.
**
This is certainly how most people think of them, however, I, at least, don’t know whether this is really true or whether it’s an artifact of only having one data point.
If, in fact, the speed of light is changing, then it may well be more than just semantics. I haven’t made any effort at all to work it out, but I suspect that tweaking permittivity alone could produce the observed effect.
Tweaking permittivity alone as opposed to what? Permeability is a defined unit, equal to 4 Pi * 10^-something (8 I think?). It’s a consequence of the choice of units. So a varying speed of light is exactly equivalent to a varying permittivity.
Lib,
Yes, in order to say that something has changed, you must have a standard of comparison. God didn’t leave his meter stick or wrist watch lying around. We defined the meter and the second. Our current definition of the meter depends upon the speed of light in such a way that the speed of light cannot change. Our previous definition used some wavelength as our standard. And before that two marks on some bar in Paris. With either of these definitions it would be meaningful to ask if the speed of light is constant, but not with our current definition. As long as we stick to one definition of the meter, asking if the meter has changed is like asking if one is still equal to one.
Thanks for the patient replies. Does the Planck distance change (in the context of the data holding)?
kitarak you are correct in saying it’s a choice of units, but there’s a bit more to it than that. The relationship between the electric constant and the magnetic constant are what define light speed in the solution of the electromagnetic wave equation. You can use a very convenient unit system where the speed of light is simply one and so are your other constants, but then you’ve just pushed back the definition into your units as opposed to your definitions of the fields produced by your electromagnetic sources.
Wasn’t the speed of light (and other EM waves) in vacuum defined in terms of unit electron and magnetic charges?
Or am I thinking of something completely different?
Urban Ranger there are no magnetic monopoles (charges). The EM waves’ speed in a vacuum is defined not by the “charges” themselves but by the permitivity and permeability (specifically the reciprocal of the square root of the product of the two) which are fundamental in describing how the fields drop off over distances.
Lib, I’d answer your question too, but I don’t understand what exactly you’re referring to in terms of whether the Planck distance changes. Do you mean in regards to this new quasar observation or in general? In general the Planck length is just as robustly defined as Planck time or Planck’s constant itself.
Is it possible that the “medium” itself (space / time) is changing? Ergo, a vacuum is not really a constant medium as is presupposed.
This is way over my head, physicists please tear me apart. But it seems to me that the very fabric of space / time may change in an expanding universe. Problem is, all I can think of is gravity, which…ah…I don’t really know.
LibThe Planck length is defined in the same units as any other length, specifically the meter. (1.6160 x 10[sup]-35[/sup] m)
The inconstancy of a constant creates difficulties with all the quantification systems used in modern physics. The change needed (if any) would depend heavily on the explanation of why and precisely how the electron/photon interactions observed in this experiment are not uniform. The changes would encompass both the new and old data.
Tris