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The Mutable Universe
September 1, 2010 12:53 PM   Subscribe

Ye cannae change the laws of physics. Or can you? (Single link Economist article)
posted by bearwife (91 comments total) 12 users marked this as a favorite

 
Don't tell me what I cannae do!

But seriously...

... one of physics’s greatest taboos, the assumption that physical laws are the same everywhere and everywhen

I thought it was commonly assumed that the laws were different in the first micro-instants of the Big Bang.
posted by Joe Beese at 1:08 PM on September 1, 2010


Does this mean Dirac was not crazy after all?
posted by vacapinta at 1:08 PM on September 1, 2010 [2 favorites]


You cannot. I can.
posted by Eideteker at 1:14 PM on September 1, 2010


Calculate alpha on google.

Calculate Googol on Alpha
posted by empath at 1:15 PM on September 1, 2010 [25 favorites]


Of course you can change the laws of physics. You just need an eraser or perhaps a bit of white-out.
posted by oddman at 1:16 PM on September 1, 2010 [2 favorites]


I would not be completely shocked by it, but I also know that physicists won't stop using 0137 for their four-digit PINs, to a surprisingly high probability.
posted by adipocere at 1:17 PM on September 1, 2010 [3 favorites]


I'm not reading anymore unless the article ends with "turns out you can and our newest Exploration Class vessel, Aurora One is now taking applications for a 2-year mission to Gilese and nearby systems. We have a pressing need for cartoonists and lively conservationists to provide entertainment and bonhomie."
posted by The Whelk at 1:17 PM on September 1, 2010 [19 favorites]


It seems I don't get to change anything, I just get, like, 1% of the rug pulled out from under me.
posted by StickyCarpet at 1:18 PM on September 1, 2010


Somewhere, there is a civilization of intelligent neutrino swarms amazed that alpha is just the right value for them to have evolved.
posted by benzenedream at 1:20 PM on September 1, 2010 [16 favorites]


Yes, but is it worse than that? Is he dead, Jim?
posted by TheWhiteSkull at 1:24 PM on September 1, 2010 [1 favorite]


Anathem by Stephenson springs to mind. He talked in that book about the fictional society being able to modify "twenty or so constants that defined the behavior of matter" to create what he called "newmatter".
posted by dblslash at 1:31 PM on September 1, 2010


This was the plot of a middle-of-the-rad scifi book I once read. The Earth leave a pocket of space where c was slower and suddenly everyone gets smarter because the chemicals in their brain react at a faster rate. Entering the pocket of slow c was what killed off the dinosaurs.

At any rate, we've seen so little of the universe that the experimentalist in me says this is basically a totally open question.
posted by GuyZero at 1:33 PM on September 1, 2010


Overall, not a bad piece of science journalism. But this is silly:

But if and when such confirmation comes, it will break one of physics’s greatest taboos, the assumption that physical laws are the same everywhere and everywhen.

If such a confirmation comes, it will just mean that some of the quantities we thought were constants are.....not constants. It doesn't mean the physical laws are different from place to place, it just means we don't know what the complete physical laws are yet.
posted by Salvor Hardin at 1:33 PM on September 1, 2010 [8 favorites]


I was reading a bit recently about whether the gravitational constant is actually constant. A recent paper posits that allowing Gc to vary at large scales can remove the need for dark matter...
posted by kaibutsu at 1:37 PM on September 1, 2010 [1 favorite]


e = mc^3.

There, I did it. Nae need to thank me.
posted by dances_with_sneetches at 1:41 PM on September 1, 2010


GuyZero, that's Poul Anderson's Brain Wave! It wasn't c but it was some unknown effect upon conductors, ever so slight. Everything (including animals) had their effective intellects quintupled. Vernor Vinge explored this again in A Fire Upon the Deep, wherein the galactic core had some subtle physical effects rendering it The Unthinking Depths, with regions further out allowing for greater depths and more interesting, nuanced technologies, such as FTL travel.
posted by adipocere at 1:49 PM on September 1, 2010 [1 favorite]


"So how would you move this moon, then?"

"Simple. Change the gravitational constant od the universe."

Q works in strange ways, friends.
posted by zoogleplex at 1:54 PM on September 1, 2010 [2 favorites]


It is difficult to imagine that physical "constants" could vary without there being some underlying conservation law or laws that such variation would, in turn, have to respect.

If I were writing sci-fi I'd say alpha proper has to be preserved -- some as-yet unknown mechanism would ensure that if in some region of space one of alpha's components varied then compensating variation(s) in the other component(s) would have to somehow be induced -- but that's clearly out if variation of alpha itself is being detected.

Which leaves me back where I started: if these constants can vary, do they do so freely? If not, what conservation laws are they (hypothesized to) obey, by what mechanisms do those laws act, and what is the nature of the coupling?
posted by hoople at 1:54 PM on September 1, 2010


Argh. "of."

iPad typing arks in storage ways, friends.

See what I mean?
posted by zoogleplex at 1:55 PM on September 1, 2010 [1 favorite]


oh, hey, thanks adipocere. I remember it as an interesting book with horribly awkward characters. I'll try to find it again though to see if I actually could identify awkward dialogue at age 15.
posted by GuyZero at 1:56 PM on September 1, 2010


Which leaves me back where I started: if these constants can vary, do they do so freely? If not, what conservation laws are they (hypothesized to) obey, by what mechanisms do those laws act, and what is the nature of the coupling?

FWIW (probably not much), this piece from the article suggests the change in Alpha is at least not totally random:

When they analysed the data from both telescopes in this way, they found a great arc across the sky. Along this arc, the value of alpha changes smoothly, being smaller in one direction and larger in the other. The researchers calculate that there is less than a 1% chance such an effect could arise at random.

This is very interesting. Anybody able to say what, if any, implications this finding might have for Big Bang Theory?
posted by saulgoodman at 2:09 PM on September 1, 2010


On the other hand, the small value of the change over a distance of 18 billion light-years suggests the whole universe is vastly bigger than had previously been suspected. A diameter of 18 billion light-years (9 billion in each direction) is a considerable percentage of observable reality. The universe being 13.7 billion years old, 13.7 billion light-years—duly stretched to allow for the expansion of the universe—is the maximum distance it is possible to see in any direction. If the variation Dr Webb and Mr King have found is real, and as gradual as their data suggest, you would have to go a very long way indeed to come to a bit of space where the fine-structure constant was more than 4% different from its value on Earth.

I don't get this. I must have missed the part where they had established any expectation of a large change in the constant, which seems necessary if they're conjecturing that this means that the universe is bigger than they thought.
posted by invitapriore at 2:10 PM on September 1, 2010


Q works in strange ways, friends.

"Redefine gravity. And how am I supposed to do that?"
"You just do it!"
posted by amethysts at 2:12 PM on September 1, 2010


saulgoodman wrote: "This is very interesting. Anybody able to say what, if any, implications this finding might have for Big Bang Theory?"

Sheldon's head will probably assplode.
posted by wierdo at 2:14 PM on September 1, 2010 [3 favorites]


I don't get this. I must have missed the part where they had established any expectation of a large change in the constant, which seems necessary if they're conjecturing that this means that the universe is bigger than they thought.
posted by invitapriore at 5:10 PM on September 1 [+] [!]


Yeah, you missed it because it's not there. I don't know what the author thinks they're talking about - sounds like they misinterpreted something the physicists said.
posted by Salvor Hardin at 2:22 PM on September 1, 2010


A recent paper posits that allowing Gc to vary at large scales can remove the need for dark matter...

Yes please. I am all for restoring both dark matter and dark energy to the realm of 'unknown variable' rather than 'here's this particular thing that is a real thing, and it's everywhere in the universe except where we look!'
posted by shakespeherian at 2:26 PM on September 1, 2010 [1 favorite]


So what would a difference in pi look like?
posted by dibblda at 2:30 PM on September 1, 2010


So what would a difference in pi look like?

A circle drawn on a sphere. Or a hyperboloid.
posted by kaibutsu at 2:34 PM on September 1, 2010 [1 favorite]


Sorry I can't provide the paper -- it doesn't look like Physical Review Letters has accepted it yet, perhaps because it was just submitted. This is a summary of work on the fine-structure constant . And here are some of Webb's more recent papers.
posted by bearwife at 2:35 PM on September 1, 2010


I don't get this. I must have missed the part where they had established any expectation of a large change in the constant, which seems necessary if they're conjecturing that this means that the universe is bigger than they thought.

kind of odd that the economist is publishing a blog entry on an unpublished astrophysics article: here is a preprint of the research on the arxive.
posted by ennui.bz at 2:36 PM on September 1, 2010


Thanks ennui.bz
posted by bearwife at 2:37 PM on September 1, 2010


I really don't get the logic behind statements like "Wow! These conditions just happened to be the exact ones we'd need to evolve and survive!"

Well... yeah. If that weren't the case we wouldn't be here to remark otherwise.
posted by Solon and Thanks at 2:38 PM on September 1, 2010 [3 favorites]


because pi is the ratio of diameter to circumference: a circle drawn on a sphere has a larger diameter for a given circumference. A hyperboloid has less diameter per circumference. A sphere is a surface of positive curvature; a hyperboloid has negative curvature, and a plane has zero curvature. Thus, variations in pi occur as the curvature of space varies. This is well-known to happen (the curving of space due to gravity), though space seems to be flat on average.
posted by kaibutsu at 2:38 PM on September 1, 2010 [1 favorite]


Woah...
posted by Splunge at 2:39 PM on September 1, 2010


The paper is right here.

Also, as I linked to above, in the Dirac article, theories of varying physical constants is old news. It is just that there is a lot of resistance to the idea. But many different theories for parametrizing the variations have been introduced over the years.
posted by vacapinta at 2:39 PM on September 1, 2010 [1 favorite]


Thanks vacapinta.
posted by bearwife at 2:51 PM on September 1, 2010


Also, as I linked to above, in the Dirac article, theories of varying physical constants is old news. It is just that there is a lot of resistance to the idea. But many different theories for parametrizing the variations have been introduced over the years.

Except that this is a purported variation in *space* rather than time. The fact that the variation is dipole suggests to me that it could be due to unaccounted for local motion of the milky way relative to the quasars. but that seems like a simple enough objection that they must have accounted for.

the bottom line is that this sort of measurement is enormously speculative given the raft of assumptions that go into doing experimental astrophysics and i have no idea why, theoretically, you would want the f.s.c. to vary in space...
posted by ennui.bz at 2:52 PM on September 1, 2010


Not that this has much bearing on the overall finding, which is fascinating, I think it's worth pointing out that here

The universe being 13.7 billion years old, 13.7 billion light-years—duly stretched to allow for the expansion of the universe—is the maximum distance it is possible to see in any direction.

the author of the article has fallen into a common misconception of big bang cosmology. See here for a good explanation. We can in fact see galaxies much farther than 14 billion light years, without any extra-weird physics.
posted by toutvabien at 3:03 PM on September 1, 2010 [1 favorite]


Oh, great. Once the word of this gets out, state legistlatures will go back to legislating the value of pi....
posted by GenjiandProust at 3:12 PM on September 1, 2010


... one of physics’s greatest taboos, the assumption that physical laws are the same everywhere and everywhen

My understanding is that it was not really taboo until Hume pointed out the assumption at work in all inductive reasoning, i.e., that the future will necessarily resemble the past in all relevant aspects.

But yeah, it is a taboo. Then again, induction is useful. So there is that.
posted by joe lisboa at 3:14 PM on September 1, 2010


Salvor Hardin: It doesn't mean the physical laws are different from place to place, it just means we don't know what the complete physical laws are yet.
Wasn't this sort of "hidden structure" idea Einstein's attitude about quantum theory? I'm under the impression that didn't work out so well.
posted by Western Infidels at 3:19 PM on September 1, 2010


e = mc^3

I c what you did there.
posted by Blazecock Pileon at 3:26 PM on September 1, 2010 [3 favorites]


This was the plot of a middle-of-the-rad scifi book I once read. The Earth leave a pocket of space where c was slower and suddenly everyone gets smarter because the chemicals in their brain react at a faster rate. Entering the pocket of slow c was what killed off the dinosaurs.

Wow, that's terrible sci-fi. Changing the speed of light wouldn't have any impact on the ionic chemical reactions that the brain uses. It certainly wouldn't just make you 'smarter'.
posted by delmoi at 4:22 PM on September 1, 2010


Thanks kaibutsu,

I guess I wonder what it would look like to an observer in that part of the universe. I suppose if you drew a circle on a sheet of paper in that kind of reference frame, it would look like a circle does on earth, but calculating pi from the measurement of the radius and circumference would come out to a different ratio?

Also, awesome that someone has an answer for a question like that here.
posted by dibblda at 4:33 PM on September 1, 2010


Western Infidels: Wasn't this sort of "hidden structure" idea Einstein's attitude about quantum theory? I'm under the impression that didn't work out so well.

The fact that Einstein didn't find the hidden structure doesn't mean there is no such hidden structure. Albert was specifically motivated by a hatred of the implicit unresolvable uncertainties implied by QM. You gotta remember this is a guy who once said he came up with Special Relativity partly because he didn't observe relativistic dilation effects at bicycle riding speed. So Albert was all about certain obsessions, some of which just happened to be right. Were the universe built just a little differently Einstein would be remembered today about the same way Time Cube Guy will be one day.

The big problem is that there surely seems to be a hidden structure necessary to explain QM if the universe behaves like any sort of machine we could ever hope to understand, but it may be that that hidden structure is worse than Albert's worst nightmare, a capricious lying trickster that is actively seeking to make itself out to be something it isn't. If that's the case, it's not a problem science is well equipped to explore.
posted by localroger at 4:39 PM on September 1, 2010


These "alpha is changing in the Nth decimal place" studies are always a little weird to me. I was in an observational astronomy group for awhile, and we just didn't have great energy resolution, didn't have a great description of how photon energies got turned into spectrum bins (hint, it isn't some simple 1-1 thing where you precisely know the energy of a given photon), and of course didn't have the exact redshift of all the glowing matter in one pixel of an image. I've been out of that field for like 10 years now, so maybe these guys have overcome those obstacles, but when I see weird results like this (minuscule delta-alpha dipole across the whole damn observable universe) I think, "this is what noise plus really small calibration errors looks like".

Also weird seeing the odd reaction people have to the fine structure constant. "If alpha is changing, what part of it is changing? c?" Alpha is a fundamental constant. Hyperintelligent mood-slime from the gamma quadrant will measure it and get the same value (or minor differences, if it's varying). c is what happens when a particular group of clever apes builds a really nice bar out of atoms and measures lengths with it, then builds a really nice clock out of atoms and measures time with that, and then describes c in terms of many times the atoms vibrate when light crosses over that bar. If alpha changes: your atoms change size, the ape-bar changes length, the ape-clock ticks at a different rate, causing an apparent shift in c, without altering the structure of spacetime even one bit. Eventually sensible apes (or sensible mood-slime) figure this out and choose units of time and distance where c = 1, which is about as constant as things get. Now I recognize that not everyone sees things this way, but I know a substantial number of physicists do, so it's weird that every time this stuff gets written up in the popular press, there's always speculation about which "part" of alpha is changing, and it's usually assumed to be c. I think it's just because people are really uncomfortable with special relativity.
posted by Humanzee at 4:39 PM on September 1, 2010 [2 favorites]


pi is the ratio of diameter to circumference

Pi is a mathematical constant. This is like claiming the value of 3 can change.
posted by 7-7 at 4:45 PM on September 1, 2010


localrodger:
You gotta remember this is a guy who once said he came up with Special Relativity partly because he didn't observe relativistic dilation effects at bicycle riding speed
I've never heard that explanation for how Einstein came up with special relativity. Einstein joked around a lot though, so I wouldn't put it past him to say that to some reporter. Certainly the dominant explanation is that he really believed in Maxwell's equations, and they pretty unambiguously predict that electromagnetic waves will travel at c, no matter who's doing the measuring. The standard explanation was that Maxwell's equations must only be right in a certain reference frame. Einstein postulated that they must be right in all reference frames. That alone gives you special relativity. Other people had already written down pretty much all the equations of special relativity before he did, so I think it was only a matter of time until someone put it all together. [Wiki on history of special relativity]

The big problem is that there surely seems to be a hidden structure necessary to explain QM
No. Who knows, maybe there is some "hidden structure" but it surely is not necessary. Quantum mechanics is internally consistent and matches experimental data quite well. The real "problem" with it is that there is a cottage industry in making it seem strange and outlandish, to sell pop-sci and/or new age books.
posted by Humanzee at 4:58 PM on September 1, 2010 [2 favorites]


I think its more likely that natural LAWS hold up than it is that a group of scientists have measured and assessed everything in a multivariable reach project 100% correctly.

Look for upcoming letters soon.
posted by hal_c_on at 5:26 PM on September 1, 2010


Wasn't this sort of "hidden structure" idea Einstein's attitude about quantum theory? I'm under the impression that didn't work out so well.
posted by Western Infidels at 6:19 PM on September 1 [+] [!]


Well, that didn't work out well because in fact there are no hidden variables determining the state of a particle - it really is a probability cloud. But that has absolutely nothing to do with this.

What I'm saying is that if it turns out that the fine structure constant is different in different places, that doesn't mean that the laws of physics are not constant, it means we don't know the complete laws of physics. Just like, if you see an apple on a table, and conclude that all tables have apples on them, then you see a table with no apple, you wouldn't conclude that the universe follows no consistent set of rules, you would conclude that you didn't fully understand the mechanics of the apple-table relationship, then modify your understanding accordingly.
posted by Salvor Hardin at 5:35 PM on September 1, 2010 [3 favorites]


Humanzee...

1. There is no D in my nick.

2. Einstein was very famously obsessional, and I've read quite a bit of him. I realize the math would have told him that he wouldn't see effects on his bicycle, but I also find it very believable that the experience of riding the bicycle and not seeing effects had a confirming influence with regard to his obsessional beliefs about the universe.

3. Do not forget that Einstein got his Nobel Prize not for relativity, but for the photoelectric effect, which is quantum work. This is one reason many people think his wife really did his Nobel work. (I'm not committed on this myself, I think AE might not have gotten the memo as to the implications at that point.)

4. You cut out the part of my hidden structure comment that said if the universe behaves like any sort of machine we could ever hope to understand. Yes it could just turn out that the universe is just plain weirder than makes any damn sense to our macroscopic sensibilities, but most people aren't very happy with that. Having a pretty good background in information theory, which allows for a lot of weirdness that macroscopic sensibilities don't, I find that QM doesn't make a lot of sense there either. So QM pretty much only makes sense in its own little self-contained world where we just say, okay, the equations say this implies that and it all works out,but nobody can describe an underlying mechanism of any sort that makes any sense that doesn't involve the equivalent of faeries and elves. If you find that satisfactory then more power to you, but we've come a long way from that universe full of nice understandable billiard balls that tug and push on one another in ways that kind of make sense except there's a lot of them and they're very small.
posted by localroger at 5:38 PM on September 1, 2010


It's possible to build deterministic machines that act randomly given a certain amount of computer analysis. There are actually theories about things like P-time random which means that any algorithm that can run in P time on a given input won't be able to predict the pattern. But a slower algorithm might be able too.
posted by delmoi at 6:09 PM on September 1, 2010


1. Sorry for the D
3. I'm familiar with Einstein's work, as well as the wife story. In addition to the photoelectric effect, Einstein did some groundbreaking work characterizing the statistics of cold matter, according to quantum mechanics. I think he always understood the implications, he just had philosophical intuition that led him to dislike them and suspect there was something deeper underneath. In this case, his intuition has proven to be a dead end so far.
4. I cut that part out because it's pure value judgement. I don't know what it means to say the universe behaves like a machine, but I do feel like I "understand" quantum mechanics quite well. I don't know what you mean by "underlying mechanism", especially when you talk about "faeries and elves". I think quantum field theory provides an intuitive (if complicated) non-elven framework for understanding the universe. You may be comfortable with billiard balls pushing on each other, but historically people weren't. What was the "mechanism" of the pulling? No one could say, but quantum field theory can explain that quite well: virtual particles.
posted by Humanzee at 6:14 PM on September 1, 2010 [1 favorite]


I think he always understood the implications, he just had philosophical intuition that led him to dislike them and suspect there was something deeper underneath. In this case, his intuition has proven to be a dead end so far.

In fact, his attempts to trip up quantum mechanics lead to him to author a few papers of the form: "If quantum mechanics is true and complete, then it must lead to this absurd outcome." And when tested in experiment, it invariably turned out that the absurd outcome was actually the reality. He understood quantum mechanics as well as anyone. He just didn't like it.
posted by empath at 7:18 PM on September 1, 2010 [1 favorite]


I think quantum field theory provides an intuitive (if complicated) non-elven framework for understanding the universe. You may be comfortable with billiard balls pushing on each other, but historically people weren't.

If we looked inside of billiard balls and only found tiny billiard balls inside them, then we haven't explained anything at all, only pushed the question further down the line. You can't explain mechanical physics with mechanical physics without begging the question.

Why are leaves green? Because they are made of green stuff. Why is the green stuff green? Because it's made of even smaller green stuff, and so on. Eventually, we get to a level where words like 'green' don't even make sense, and you're talking about photons being absorbed and emitted by electrons at particular frequencies, and you finally have an explanation of where green comes from which doesn't involve the word 'green', but of course now you have a new problem -- what is 'electromagnetism'.

And so we go deeper. I think the universe will continue yielding 'explanations' as long as we continue probing the fabric of reality with higher and higher energies. But there is no 'fundamental' particle.
posted by empath at 7:27 PM on September 1, 2010


If your model can't predict anything better than mine*, then it doesn't explain the world better than mine. If my model says that there are some things that can only be predicted probabilistically, and you don't have a better model that does works in an entirely deterministic fashion, and if that makes you uncomfortable, then tough noogies.

*There is some value to models that make less accurate predictions but do so with simpler, faster computations, but I don' t think that's the core issue.
posted by ErWenn at 8:09 PM on September 1, 2010


Anybody able to say what, if any, implications this finding might have for Big Bang Theory?

It's a big old boost to Brane Theory, which predicted uneven distributions of matter and energy, and even overlapping universes. The big bang happened when two branes collided, according to the theory, so lots of strange things happen along our infinite brane of spacetime in the aftermath.
posted by Slap*Happy at 8:37 PM on September 1, 2010


It's a big old boost to Brane Theory

Yay! That's one I'm rooting for. Any theory that makes the universe bigger, older and stranger gets my vote.
posted by saulgoodman at 9:02 PM on September 1, 2010


empath: Quarks are thought to be "fundamental"- as in non-divisible- right? Unless they're made of preons. Wikipedia says that if we find the Higgs, then most preon theories will probably be rendered invalid.
posted by BungaDunga at 9:34 PM on September 1, 2010


7-7

Alpha is made up of constants including pi, that's the point.

They don't know which constant or combination of constants is changing.

I'm not saying that it absolutely is pi but it would be interesting if it was.
posted by dibblda at 12:06 AM on September 2, 2010


You people just don't understand. There is only e, pi and i, eternally locked in a relationship of mutual definition, giving birth to all possible universes in their struggle to establish their own independent identity.

We are nothing, a vanishingly small manifestations of brownian motion in the random preturbation that is our observable universe; a side-effect, an immeasurable speck on the eternal abstract fabric that is Euler's identity.

They are your God. They simply exist, unchanged, unyielding. In open sight, yet unknowable. Creating all, governing all, yet oblivious of your hopes, your aspirations, your prayers.

We spend all this time searching for eternal truths and laws and meanings but it is all meaningless. Everything that we are - us, our universe, all possible universes - is encoded in the digits of these truths, somewhere in there, in a language that we will never decipher. We will never find out Why.

Despite our pitiful efforts it will all eventually collapse - their struggle spent, their conclusions reached, their relationship cemented - and there will be only 1.

PS Please visit my website, there are newsletters and also a gift shop
posted by vanar sena at 3:14 AM on September 2, 2010 [1 favorite]


Quarks are thought to be "fundamental"- as in non-divisible- right? Unless they're made of preons. Wikipedia says that if we find the Higgs, then most preon theories will probably be rendered invalid.

Well, they're all made of 'strings', supposedly... and the strings are made of...?
posted by empath at 4:44 AM on September 2, 2010


"They don't know which constant or combination of constants is changing."

Pi isn't. It can't.

It's plausible that other physical - not mathematical - constants might change.

Pi simply absolutely cannot.
posted by edd at 5:11 AM on September 2, 2010


I love stuff like this. I really wish I understood it so I could really appreciate it even more. But I really don't, so I just read articles like this and skim over the parts that get too technical for me. I guess that puts me in the position of relying on the writer to explain the implications at my level.
posted by Shohn at 5:42 AM on September 2, 2010


It's plausible that other physical - not mathematical - constants might change.

Well, pi, the mathematical constant cannot change but pi appears in the fine structure constant as the reduced Plank constant. And if you go back, you see that the reduced Plank constant is itself a physical not a mathematical quantity.

That is, it often first shows up as a conversion factor between classical and quantum variables, between the De Broglie wavelength of particles and their momentum. Then, we use that as the definition of the quantum momentum operator - the translation operator multiplied by h-bar.

So...could it be that we are seeing regions of space where h-bar actually changes value? Or, h-bar has different values for different types of matter. If this is so, its not that these regions obey different physical laws, its that they have different regimes for the transition from Classical to Quantum Physics. That is, h-bar is like a slider which makes the world we live in "more classical" or " more quantum"
posted by vacapinta at 6:50 AM on September 2, 2010


Here's a question -- if the value of pi changes in curved space, then wouldn't the value of e also change? how could the rate of compound interest vary with the curvature of space? That seems absurd on the face of it.
posted by empath at 7:01 AM on September 2, 2010


Alternatively, if pi changes value and e stays constant, then the value of 1 or i or 0 must change, which is even crazier.
posted by empath at 7:03 AM on September 2, 2010


Pi does not change in any space. It does not change.
posted by edd at 7:45 AM on September 2, 2010


kaibutsu: the analogy you're making I'd quibble with. Identifying pi with a particular appearance it makes in geometry (ratio of radius to circumference in flat space) seems a little misleading. I'd guess you don't really think that, say, sqrt(6 * zeta(2)) takes on a different numeric value when evaluated in a region of very curved space?

Humanzee, vacapinta: I wasn't that clear the first time through. Take Dirac and his LNH (as summarized in wiki): so Dirac speculates that M ~ t^2, which requires spontaneous generation of "new" mass to "make the bookkeeping work". Alright, but is then -- or is the real speculative theory he put forward -- just putting that out there as a quasi-empirical thing? Or is it more like more conventional theories, in that, eg, he worked through the implications on questions like: "So, matter can be generated spontaneously. Can it be destroyed deliberately? (EG: not just converted to energy or other forms of matter, but destroyed destroyed.) Would destroying matter slow down the passage of time (or reverse it)? Locally or globally?"

I've seen these kinds of theories come and go (and get popular press etc.) for a long time now, but have never known what to make of them (other than that most physicists consider them longshot speculation). When they are proposed, are they worked out at a level of detail to answer the kinds of questions above, or not? Are they more along the lines of "if we add these mechanisms we can fit some tighter curves to our empirical data" or "here's a fully-worked out theory not only fitting the data but explaining (eg) why or why not you're able to effect the passage of time by destroying matter (in Dirac's case)?
posted by hoople at 8:13 AM on September 2, 2010


I really don't get the logic behind statements like "Wow! These conditions just happened to be the exact ones we'd need to evolve and survive!"

Well... yeah. If that weren't the case we wouldn't be here to remark otherwise.

Welcome to the Anthropic Model, Solon and Thanks.
posted by IAmBroom at 8:28 AM on September 2, 2010


edd wrote: "Pi does not change in any space. It does not change."

And all this time I thought pi was just something some smart people have measured ever more accurately over the years. I don't know why it seems fundamentally impossible for the ratio of circumference to diameter of a circle to change if one moves into a region of space with a different topology.

You make the measurements and get a different result. What are you going to say but "that's weird"? I guess you could say that if you get a different result you weren't actually measuring a circle, even though you stuck a pin through a string into a piece of wood and tied the other end to a pencil and drew it yourself.

While I have no evidence to support it and am not strongly wedded to the idea, I suspect that the universe is far weirder than we expect in places far away from here. Beyond a certain point, we simply cannot say whether or not the same rules apply there as do here. (well, it's equally probable that the same rules apply, but we have yet to discover all of them)
posted by wierdo at 8:28 AM on September 2, 2010


Nonsense about pi changing aside, Planck's constant and the speed of light are both dependent on the units you measure them in. That means you can call them both 1. On the other hand, certain constants don't depend on the units we use - dimensionless constants. These mysterious numbers are the only parameters which could possibly change to give observable physical results. We have no idea why these numbers are the value that they are, and it's natural to speculate on whether they might change and what the consequences would be if they happened to be different.

(This means that if the speed of light were to change, there would be no way to notice it, because all the physical mechanisms we could use for measuring that speed are coupled to the speed of light - in other words the speed of light is irrelevant!)

It turns out there are at least 26 dimensionless constants. Most of them are related to particle masses.

This is a great introduction by a physicist:

http://math.ucr.edu/home/baez/constants.html
posted by 7-7 at 8:48 AM on September 2, 2010


BTW, the geometric definition of π as the ratio of circumference to diameter applies only in Euclidean (flat) space. Since no part of the universe is strictly flat, your circles are never going to give you strictly π (if you could measure lengths to ridiculous numbers of decimal places).

However, π can be calculated purely mathematically as the limit of an infinite series. For example:

π/4 = 1 - 1/3 + 1/5 - 1/7 + 1/9 - ...


That's why claiming π might change makes no sense. It's like claiming 2 can change.
posted by 7-7 at 8:59 AM on September 2, 2010


Pi has context.

I'm going to step back and talk about something entirely different for a second to illustrate context, namely, mass. Mass has context. What is mass? Well, where are you talking about it?

Are you talking about gravitational mass, the measurement of which determines gravitational pull? Are you talking about inertial mass, the measurement of which determines how much something resists being accelerated? Are you talking about mass to energy conversion, the special case of which is E=mc2? Einstein's achievement in General Relativity was that he tied the first two contexts together and say, "Those are the same thing." Measurement thus far suggests that those two are at least numerically equivalent.

Similarly, pi has a context.

Pi: the ratio of the circumference to the diameter.

Pi: what happens at the end of 4 * [1 - 1/3 + 1/5 - 1/7 + 1/9 - 1/11 + 1/13 ...]? Note, this converges slowly, don't try this at home.

Should you move into an area of spacetime that is very obviously Not Flat At All, pi in the first context would change, in a manner not unlike measuring a circle drawn on a globe rather than on a flat piece of paper.

Were pi in the second context to change, well ... math would probably asplodes.
posted by adipocere at 9:02 AM on September 2, 2010 [1 favorite]


(This means that if the speed of light were to change, there would be no way to notice it, because all the physical mechanisms we could use for measuring that speed are coupled to the speed of light - in other words the speed of light is irrelevant!)

Not if the dimensional constant varies across space-time. That is what I thought this discussion was about.
posted by vacapinta at 9:09 AM on September 2, 2010


vacapinta: Like I said, the speed of light is a dimensional constant. If you changed it, you'd change the length of the meter, and everything else in the universe. Nothing would change relative to anything else.

The only parameters that can change with observable results are dimensionless parameters. If you read the article, it's the fine structure constant they're talking about, which is 1/137ish (at least in this neck of the woods).
posted by 7-7 at 9:17 AM on September 2, 2010


This is a very interesting claim. It's true that the claim hasn't actually been published yet, but submission via the arxiv preprint server is standard procedure in this field and the group behind the submission is full of credible people.

One thing that's not made clear in the article is that the fine structure constant is already known to change, as a function of the distance between two charge particles. If you measure the charge of an electron from very far away, you are interacting both with the electron and with the cloud of virtual particle-antiparticle pairs that surrounds it. However as the distance between your probe and the electron gets smaller (which happens as you use probes with higher and higher energy), you get inside of this cloud and see the "unscreened" electron charge, which is a little bigger than the "screened" charge that an electron has inside an atom. This is called the "running" of the fine structure constant; from zero-energy probes to measurements taken at CERN the fine structure constant increases from 1/137 to maybe 1/125.

As for whether one or another bit of the fine structure constant is changing, that's kind of a moot point. If the fine structure constant is changing, the effect is that the strength of the electric charge changes: the fine structure constant is basically the ratio of how much calculational weight to give processes whose Feynman diagrams have no loops >---< compared to processes whose diagrams have one loop, like >--o--<. If you have some theory where the speed of light changes (those do exist) or where the size of a lump of spinning changes (haven't seen one of these) or where, say, the temperature of the microwave background affects the permittivity of the vacuum, then these theories will have some other effects. But in a very real way, you can't change the fine structure constant without changing the electric charge.
posted by fantabulous timewaster at 9:45 AM on September 2, 2010 [1 favorite]


hoople: the large number hypothesis that you're referencing is really just a bit of numerology. There's no particular reason to take it seriously. From the standpoint of general relativity, there's no meaningful way to calculate the mass of the universe, so my feeling is that M~t^2 is essentially a random equation that relates a garbage number to a highly uncertain number with no justification.

The "context" for pi in the fine structure constant is the number of radians per half-cycle. It's 3.14159...

fantabulous timewaster:
It's occurred to me that someone could have a theory with c changing; off-hand it seems like it would manifest itself in coordinated changes in many dimensionless constants. But it seemed like a weird and arbitrary thing to do, and I've never seen such a theory outside of pop-sci (admittedly, I'm out of the business now). Do you have a link to one?
posted by Humanzee at 10:49 AM on September 2, 2010


And all this time I thought pi was just something some smart people have measured ever more accurately over the years. I don't know why it seems fundamentally impossible for the ratio of circumference to diameter of a circle to change if one moves into a region of space with a different topology.
Well, I think the argument would be that pi is defined as the ratio of circumference and diameter of a circle in a particular (Euclidian, I guess) space. So if you change the space, you do change the ratio of the circumference and diameter, but not pi. Hmm.

It's not something you measure physically but rather something defined by a mathematical formula using an infinite series.
vacapinta: Like I said, the speed of light is a dimensional constant. If you changed it, you'd change the length of the meter, and everything else in the universe. Nothing would change relative to anything else.
What? If the speed of light changed, how would the length of the meter change? Obviously it wouldn't, and the fact that the speed of light had changed would be immediately observable.

First of all, there's e = mc2. So either the mass released in chemical reactions would go down to keep e constant, or the energy released by chemical reactions would go up or down. The second would probably be catastrophic for biological life. The second obvious change would be that the amount of time required to communicate with satellites and other things would go down (or up). Arguing that everything else would change along with it just makes no sense.
posted by delmoi at 11:55 AM on September 2, 2010


I think I didn't explain this very clearly.

Time and space are all defined in terms of the speed of light. A meter is defined as the distance light moves in 300 million cycles of a cesium atom. Let's say God cuts the speed of light in half. That means that everything in the universe can only move half as fast, including everything you're using as a reference for your units. From your perspective, it still takes 300 million cycles of a cesium atom for light to travel the length of your meter stick. From God's perspective, since he's a construct for the purpose of this argument, your meter stick is half as long as it was. (Or you might just be moving more slowly). You're measuring the speed of light in terms of how many cycles of the atom it takes to bounce a signal off of a mirror. Again, your measured speed of light won't change! It'll be the same thing for e=mc2, since energy is defined in units of distance and time.

Changing the speed of light would not be observable. The only truly meaningful parameters in physics are dimensionless numbers. Everything else is just a convenient system of units that we strange-looking apes imposed on the universe.
posted by 7-7 at 12:50 PM on September 2, 2010


From your perspective, it still takes 300 million cycles of a cesium atom for light to travel the length of your meter stick.

From my perspective, wouldn't the light now only travel half the distance of my meter stick? It sounds to me like you're wrongly equating the distance with our definition of it. If we found out about the change and made a bunch of new meter sticks that conformed to our definition of a meter they would be half as long as the old ones.
posted by invitapriore at 12:57 PM on September 2, 2010


Unless it's been established the speed of light and the dimensions of the universe are related in some hard-coded ratio; that we define space and time in terms of c in our equations seems like insufficient proof of that.
posted by invitapriore at 1:06 PM on September 2, 2010


invitapriore: But how would you find out about the change? Everything in the universe would simply be happening slower, including your own perceptions (since your thoughts are the result of brain chemistry, and chemical processes depend on particle interactions, which depend on the speed of light). Nothing changes relative to anything else, so nothing would have changed from your point of view. The only person who'd know would be God.

To quote another physicist: "The speed of light is about the relationship between the change in time and the change in space. In natural units, the amount of change in time is precisely equal to the amount of change in space. The speed of light _means_ the change in time equals the change in space."
posted by 7-7 at 1:11 PM on September 2, 2010


So let's say I turn my meter stick over and use the English system measurements on the other side-- inches and feet. These are not defined using c. Now do I notice that photon is only traveling half the distance?
posted by shakespeherian at 1:15 PM on September 2, 2010


Sorry to drop a bomb and run off like that.

Pi is a mathematical constant. This is like claiming the value of 3 can change.

Well, I suppose that depends on how we define three...

Pi, as a number, has a number of equivalent definitions, but I tend to think of 'ratio of diameter to circumference of a circle in Euclidean space' as the most fundamental. It's the first place it came up historically, and the first definition given in the wikipedia article on pi. It's worth noting that the 'in Euclidean space' caveat was clearly appended after the discovery of non-Euclidean geometries; in short, a context was found in which pi would vary, and then the variation was defined away. This is both expected and totally acceptable. So yes, pi varies if we drop the Euclidean hypothesis.

It also means that drawing really big circles to measure pi is ineffective, exactly because we live in curved space. Draw a circle around the solar system, measure the circumference and diameter, and you'll certainly get some error.

There are lots of other geometric ways to screw with the definition of pi. What's a circle? The set of points equidistant from a given point, right? It's pretty easy to dream up geometries where circles aren't remotely circular looking. For example, if we measure distance simply as difference in the x and y coordinates (the 'taxi-cab metric'), a 'circle' looks like a diamond. The taxi-cab pi is then 4*sqrt(2), for the unit circle. This notion of having different measures of distance and angles is the really fundamental concept.

Modern geometry (and, by extension, physics) works with the notion that at each point in space there is a local way to measure lengths and angles. Usually, these are assumed to vary smoothly, so that the measuring rules at one point are pretty much the same as the measuring rules at all points nearby. However, things might vary quite a bit if you move a larger distance. From these local measures, you can compute the curvature of a space at each point (so long as your space has more than one dimension). This is a fantastically important notion, because it means that curvature of a space depends only on how measurements _inside the space_ work. In particular, you can have curved spaces that aren't embedded in a higher dimensional space. Noticing space-time curvature doesn't necessarily mean that our universe is embedded in a twenty-dimensional space.
posted by kaibutsu at 1:33 PM on September 2, 2010


shakespeherian:

how would you be able to see the light reflected from your measuring stick used for your comparison quickly enough to discern the difference in the speed of the photon you're measuring if the light reflected from the measuring stick is also moving slower (which it would be)?
posted by saulgoodman at 1:35 PM on September 2, 2010


As far as we know, this is what the Universe Builder looks like. Those 26 dimensionless parameters control all the physics we know about.

Apologies to Neal Stephenson. Also, don't those neutrino masses look like the Creator just couldn't be bothered replacing the defaults?
posted by 7-7 at 4:14 PM on September 2, 2010


Humanzee, I think I was remembering an idea by Joao Magueijo, whose name comes up quickly if you search the arxiv for "VSL." But I don't have a single reference that says "here is the idea, here are the problems it solves, here are its weaknesses," etc.

Note that not everything scales trivially the same way if you assume a change the speed of light corresponding to a change in one other parameter. Consider the gravitational potential energy U = GMm/r between two masses. If your redefinition c' = c + δc means that the relativistic rest energy E = mc2 changes, then your U has four factors of c on top and δU/U = 4δc/c. If the masses stay the same but the length changes, your U has one correction on the bottom and δU/U = -δc/c. If mass and length stay the same but your clock ticks change, then regular old Newtonian physics gives you the wrong period t = 2π√(r3/GM) for an orbit.

More or less, that's the result which is being reported here. If you change the fine structure constant, the effect on an absorption spectrum is not simple: some transitions get redder, while others get bluer, in a way that's very different from the sorts of systematic overall shifts you would get from a miscalibrated detector. That's one of the things that makes this claim seem robust: it's not an observed variation in a single observable, but a plausible attribution to one parameter of a set of shifts across an entire spectrum.
posted by fantabulous timewaster at 4:50 PM on September 2, 2010 [1 favorite]


how would you be able to see the light reflected from your measuring stick used for your comparison quickly enough to discern the difference in the speed of the photon you're measuring if the light reflected from the measuring stick is also moving slower (which it would be)?

Presumably we're measuring with photon receptors rather than eyeballing it, aren't we?
posted by shakespeherian at 6:51 PM on September 2, 2010


Yep, that seems like it would work, intuitively. But it's out of my depth to say whether it would actually work.

I think everything is more interconnected than you're allowing. Since the speed of light is theoretically also the speed at which time effectively stands still (unless I'm misremembering my long ago reading of Relativity: The Special and the General Theory), I think changing the speed of light would also effectively change the rate at which time passes, and the units used to measure distance in space, to some related degree. But then, I ain't a physicist, so I could be mistaken here.
posted by saulgoodman at 8:10 PM on September 2, 2010


(I know the predicted change in the rate of time I alluded to above is all relative to an observer in a particular reference frame, but still, the theory to my mind suggests these phenomena--time, space, the speed of light--are fundamentally interrelated. But my previous caveats about my qualifications still apply.)
posted by saulgoodman at 8:14 PM on September 2, 2010


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