c not a constant!

August 7, 2002 8:24 PM

c not a constant! Over a period of billions of years of course. If this theory is true, then E=mc² might not apply to a large period of time.
posted by riffola (29 comments total)

The way I see it, if light can bend due to gravity, I don't see why it can't speed up or slow down.
posted by riffola at 8:27 PM on August 7, 2002

There's a better article here, with a more in depth look and a less "golly gee, maybe Einstein wasn't so smart" take on the experiments.

One possibility [for the slowing] is that the structure of the vacuum in space has changed. This is where we get into the rather spooky world of quantum physics. When light travels through a medium other than a vacuum, such as glass or water, it slows down. A vacuum, far from being empty, is teeming with quantum "virtual" particles that flit in and out of existence.
posted by monju_bosatsu at 8:44 PM on August 7, 2002

Oh, and you can find what I'm sure is an insightful article in the August 8th issue of Nature.
posted by monju_bosatsu at 8:53 PM on August 7, 2002

The most interesting element of these observations, if true, is that they may make faster-than-light travel possible. The theory of relativity as it stands does not allow this, but the idea of the speed of light slowing down may change that.
posted by paradigm at 9:39 PM on August 7, 2002

Here's a link to the Nature article. Somewhat technical, but for those who want more detail than the above articles it's worth a look.

The discovery that the "constants" of the Universe have changed over time isn't altogether new (the first evidence of it was found a few years ago) -- the problem we only knew that a certain combination of the constants had changed, and we couldn't figure out which one of the constants (the electron charge or the speed of light) is responsible for the variation. What these physicists have done is to point out that if the electron charge changes, it might allow violations of the Second Law of Thermodynamics, which would be a Bad Thing (mb's article does a good job of explaining this.)

Personally, I've always been a little suspicious of the Second Law, since any proof I've ever seen of it boils down to a statement such as, "such events have a 1 in a googol chance of happening in the entire lifetime of the Universe" -- which is pretty damn slim as odds go, but not conclusive.

:::crosses fingers & hopes links work:::
posted by Johnny Assay at 9:51 PM on August 7, 2002

Hmmm.. I guess we'll have to wait a bit to see what consensus emerges on this. How cool would it be if we get to watch all of modern physics rebuild itself? Think I'll head to me university library to check out this out - although I probably won't understand more than the abstract.

The way I see it, if light can bend due to gravity, I don't see why it can't speed up or slow down.

Nope, that's jumping too far - they're definitely not claiming to have seen a gravitationally caused violation of c..
posted by slipperywhenwet at 9:55 PM on August 7, 2002

I didn't think riffola was saying that gravity could cause a change in the speed of light, but rather that if a physical property like gravity can bend light, why is it so hard to imagine that some other property might be able to affect its speed?
posted by mediareport at 11:29 PM on August 7, 2002

Btw, did anyone else go 'huh?' at this quote from the lead scientist in monju's link:

When I first heard about these observations...I thought it was horrible. The last thing we wanted in theoretical physics was to have something like this.

The last thing we wanted was a paradigm shift that better fits the data? Yow. Hope that was a mangled quote.
posted by mediareport at 11:37 PM on August 7, 2002

Heh, I was about to come in here and raise some hell because I read: "C was not a consonant".
posted by fooljay at 11:54 PM on August 7, 2002

I'm uncomfortable with the way Yahoo present this as a new idea.

Another resource that indicates otherwise. (With pop-up ad).
posted by nthdegx at 12:37 AM on August 8, 2002

Thanks mediareport for clarifying on my behalf, that's exactly what I meant, that it should not hard to imagine that light can slow down in the same medium, in this case vacuum.

Sorry about linking only to the Yahoo! news story, it's where I saw it first.
posted by riffola at 12:56 AM on August 8, 2002

This brings to mind the novel A Fire Upon the Deep, by Vernor Vinge.

In it there are diffrent zones in the Galaxy where diffrent levels of technology can function, due to changing physical constants.
posted by Iax at 1:19 AM on August 8, 2002

pardigm shifts are great, when you can look back fifty years from now and examine the implications of these observations without the stress of having to elucidate from the data, the data doesn't lie (normally) therefore trying to make sense of it, or to formulate a model to fit the observations is a real pain in the butt. It involves much head scratching and smoking of cigarettes, hence I think can relate to that miffed boffin.
posted by johnnyboy at 4:46 AM on August 8, 2002

Personally (having known him a little when he was just finishing his doctorate), I'd put money on the falibility of John Webb before questioning the constancy of the speed of light....
posted by andrew cooke at 5:06 AM on August 8, 2002

I didn't think riffola was saying that gravity could cause a change in the speed of light, but rather that if a physical property like gravity can bend light, why is it so hard to imagine that some other property might be able to affect its speed?

on an "innocent" level you can argue that if one thing can change, why not another. but if you're asking the same question from within the framework of modern physics then the speed and (apparent) trajectory of light are two very different things. in hand waving terms, it's taken as given that light travels in straight lines at constant speed. if you see something that "looks" like light bending due to gravity it's actually that space is curved (by gravity) - the light is following a straight line through curved space.

(now you can extend that to ask whether space "stretching" - as opposed to curving - can produce this change in speed. but that gives a different effect - redshift - which is already known (and, indeed, fundamental to the kind of observations that lie behind all this)).

i know, that doesn't really help ;-)

(this is all from distantly remembered astronomy phd - i'm no expert on the theory)
posted by andrew cooke at 5:15 AM on August 8, 2002

Einstein, Webb...whatever, right and wrong are all relative anyway...
posted by fooljay at 5:34 AM on August 8, 2002

I think this idea has been around for a while. I know of at least one book that goes in depth about the discovery. Too bad we have to wait until next year to read it.
posted by rodz at 6:17 AM on August 8, 2002

You know, I have a theory that God changes the laws of physics from time to time just to keep us human beings on our toes. Or, if there is no God, the universe runs on some corollary of the Heisenberg Uncertainty Principle -- it changes because we're getting close to figuring everything out. Thou Shalt Not Know Everything.
posted by Tin Man at 6:34 AM on August 8, 2002

Just like some Heisenbergian liberal to challenge God's fundamental(ist) Einsteinean Law. Sounds like a dicey proposition to me!
posted by nofundy at 8:04 AM on August 8, 2002

Thanks, Andrew, I'd forgotten that part about straight line/curved space.

in hand waving terms, it's taken as given that light travels in straight lines at constant speed.

Well, now, there's a convincing argument. :) Honestly, though, hasn't the constancy of c always been a provisional assumption? Given that, why is it such a shock that it may be wrong, unless large numbers of scientists forgot it was tentative and began believing it was a proven fact? I'll just be an "innocent" over here and remark that the idea of something -- anything -- in this wonderful fucked-up universe remaining constant forever has always struck me as wishful thinking at best.
posted by mediareport at 8:26 AM on August 8, 2002

i don't know if it helps, but it was assuming that the speed of light was constant (in all inertial frames) that leads to the special theory of relativity. so while this is "just" an assumption, it's one that has lead to one of the two big successes of modern physics.

if you assume something simple and it leads to predictions that fit with how the world works in so many odd and unexpected ways, then you tend to have some faith in that assumption.

scientists don't just "forget" about these assumptions, but the idea is to make do with as little "ok, so why don't we just say that XXX changes in some way so that we can explain YYY" as possible.

feynman´s (ecellent) book, the nature of physical law(s?), has some excellent comments about the "insight" of non-scientists...
posted by andrew cooke at 8:57 AM on August 8, 2002

I never said it was "just" an assumption. I said it was a provisional assumption and should be treated as such. That it's been extremely useful so far doesn't change the fact that it's never been more than, as you put it, simply "taken as given." The focus here shouldn't be on the failed "insights" of "non-scientists" but rather on the failure of scientists to keep their eye on the ball.

(I have a bachelor's in zoology/anthropology, btw).
posted by mediareport at 9:41 AM on August 8, 2002

Everything in physics is a provisional assumption. Who is shocked? The editors at Yahoo?

FWIW, Dirac had already theorized about changing constants back in 1937. He just didnt have any data to back him up.
posted by vacapinta at 9:52 AM on August 8, 2002

Everything in physics is a provisional assumption. Who is shocked?

My point exactly.

The editors at Yahoo?

And some high-level physicists, apparently.
posted by mediareport at 10:25 AM on August 8, 2002

if it's true that c varies it really is shocking news. it means a whole new area of physics will open up. it would be a momentous event.

you do any science within a hierarchy of assumptions. on a day-by-day basis the very smallest details change. the more fundamental aspects, however, are much more stable because they've been tested again and again.

i've personally worked on data similar to what is causing this latest hoo-hah. so have many many other people. the observations are of objects when the universe was a fraction (perhaps a tenth, iirc) of its current age. all those observations, until now, have been consistent with (and interpreted using) the assumption that the speed of light is constant. people have already looked for evidence that the speed of light changes and not found it. it´s not exactly a difficult hypothesis to dream up.

mediareport - you have a degree in zoology. presumably you would be at least a little surprised if they dug up, at the same level as a bunch of dinosaurs, the skeleton of a modern man? you'd be shocked not because you've taken your eye of the ball, but because there's so much evidence to support that particular hypothesis, because people have looked for that kind of thing and not found it. this is no different.
posted by andrew cooke at 11:35 AM on August 8, 2002

i've just thought of a better explanation (and my last word here): if this were true, it would be a once in a lifetime event for the people involved. more than that, it's the kind of thing that never happens in the careers of most scientists. if you can't understand why that is shocking then i don't think it's a question of good or bad science, but a lack of human empathy.
posted by andrew cooke at 11:42 AM on August 8, 2002

i miss out on all the best threads.

science isn't about answers.
posted by folktrash at 12:16 PM on August 8, 2002

presumably you would be at least a little surprised if they dug up, at the same level as a bunch of dinosaurs, the skeleton of a modern man?

Is that really a valid comparison? I mean, last I checked, no Nobel-winning evolutionary biologists were giving interviews in the early 1970s which discussed "...problems on the basis of our present theories, which are just, I believe, a transient phase of physics and will be superseded after maybe a few decades."

you'd be shocked not because you've taken your eye of the ball, but because there's so much evidence to support that particular hypothesis, because people have looked for that kind of thing and not found it.

Seems to me the textbook definition of a scientist taking his or her eye off the ball is not keeping in mind the likelihood of major paradigm shifts in the future. We have a lot to learn about evolutionary theory, no doubt, but the possible non-absoluteness of the constancy of the speed of light seems to have been predictable in a way that modern human remains showing up in dinosaur bone strata isn't.

The emotional shock question you raise is a different matter entirely, and I do empathize. But I have little sympathy for scientists who resist new thinking after the initial shock simply because it'll mean more work. As the lead scientist says in monju_bosatsu's first link says, "These are cherished laws and they don't really want to have to ditch them, because all of the favoured frontier stuff these days, with people working on string theory, M-theory and all these other sexy topics, would have to down tools and start with a completely different conceptual scheme."

Science is one of those harsh mistresses, you know? I expect it to throw us lots of curve balls for centuries to come.
posted by mediareport at 1:26 PM on August 8, 2002

[the "transient phase" quote came from vacapinta's link, btw]
posted by mediareport at 1:45 PM on August 8, 2002