SLAC ceasing to exist?

Via Zapper Z comes the news that the DOE wants to rename SLAC! The DOE wants the names of the national labs to be trademarked, but Stanford won't let them trademark anything with "Stanford" in it (which is why, I believe,
I mentioned this to my Post Doc, whose husband works at SLAC, and apparently they're having some kind of naming contest (whether real or fake is unknown to me), and NLC, short for National Light Center (or something like that), because SLAC is starting to be used primarily as a light source, is leading the pack (NLC was the name for one of the precursors of the ILC, so it's supposed to be a joke).

Anyway, this is just silly, I think. Lots of bureaucratic silliness, which I find incredibly annoying. I hope this rename doesn't happen, but if it does the new name had better be good.

String Theory may be useful after all

Here's an interesting string theory article from Nature (subscription required, sadly). It's about how string theory may be an accurate description of the strong force, what it was originally invented to explain.

Over the summer I took some high schools kids to talk to Leonard Susskind, a Stanford Professor and one of the developers of string theory. He described its original formulation as a theory of the strong force. One of the rationales he gave for thinking like this is that it's impossible to spin apart a nucleon. By that he meant that if you take anything bigger than a nucleon (say, a basketball), and spin it fast enough, it will break into constituent pieces. This is true for everything from a planet down to an atom. But when you spin a nucleon (proton or neutron) it doesn't break apart, but it does stretch out and turn into something like a dumbbell shape (and presumably gains a noticeable dipole moment). So one of the things that could explain that phenomenon is a force acting like a super-strong rubber band holding the constituent parts of the nucleon (quarks) together.

Anyway, that's the story given by someone who was there for why it was developed. The article gives a different description:

So particle physicists started casting around for other ways of attacking the problem. In 1968, the Italian theoretician Gabriele Veneziano made a brilliant guess and wrote down a concrete mathematical expression, the Veneziano amplitude, that explained some important features of high-energy scattering. But his formula could not be understood in terms of point-like particles; instead, it required the existence of extended objects — strings. These strings are thin tubes of energy formed by force lines that bind quarks together, and, just like violin strings, they can oscillate in many modes. The numerous resonances of strong-interaction physics would then be nothing but the different oscillation modes of these strings.

Here's a large chunk of the meat of the article:

The new approach that revives the link to string theory first suggested itself in 1998, when Juan Martín Maldacena conjectured a link between a close relative of QCD and a 'superstring' living in a ten-dimensional curved space-time. Although the theory in question, known as supersymmetric N = 4 gauge theory, is sufficiently different from QCD to be of no direct interest to experiment, the link raised the prospect of a general connection to some form of compactified string theory. This equivalence is now commonly referred to as the AdS/CFT (Anti-de-Sitter/conformal field theory) correspondence. If true, it would mean that string theory was originally not so far off the mark after all — its ingredients just need to be interpreted in the correct way.

The Maldacena conjecture raised a lot of interest, but seemed for a long time to be quantitatively unverifiable. This was because it takes the form of a duality in which the strongly coupled string theory corresponds to weakly coupled QCD-like theory, and vice versa. But to verify the duality, one would need to find a quantity to compare in a regime of intermediate coupling strength, and calculate it starting from both sides. No such quantity was obvious.

Help came from an entirely unexpected direction. Following a prescient observation, the spectrum of the N = 4 theory has been found1, 2 to be equivalently described by a quantum-mechanical spin chain of a type discovered by Hans Bethe in 1931 when modelling certain metallic systems. There are not many quantum-mechanical systems that can be solved analytically — the hydrogen atom is the most prominent example — but Bethe's ansatz immediately applied in a much wider context, and constructed a bridge between condensed-matter physics and string theory (in this context, see the recent News & Views article by Jan Zaanen on the nascent connection to high-temperature superconductivity). Indeed, even though the mathematical description of the duality on the string-theory side is completely different from that on the condensed-matter side, a very similar, exactly solvable structure has been identified here as well.

Puzzling out the details of the exact solution is currently an active field of research. But in one instance, that idea had already been put to such a hard test that a complete solution now seems within reach. The context is a special observable entity, the 'cusp anomalous dimension', which was argued to be ideally suited as a device to test whether string and gauge theory really connect. Some of its structure at strong coupling was also worked out. Just recently, Beisert, Eden and Staudacher have extracted the analogue of this observable on the field-theory side, and have been able to write down an equation valid at any strength of the coupling. Since then, work has established that their 'BES equation' does indeed seem, for the first time, to offer a means of reformulating theories such as QCD as string theories.

Much still needs to be learned from this one exactly solvable case. There is justifiable hope that this solution will teach us how to go back to the physically relevant case of QCD and finally arrive at the long-sought dual description by a string theory. It may even take us closer to realizing the quantum-field theorist's ultimate dream, unfulfilled for more than 50 years: completely understanding an interacting relativistic quantum-field theory in the four space-time dimensions that we are familiar with. Progress towards this goal can be judged independently of loftier attempts to use strings in the construction of a theory of everything.

So there's something, even if string theory isn't a theory of everything, it may yet be useful.

2007 Nobel Prize in Physics

The 2007 Nobel Prize in Physics has been awarded to Albert Fert and Peter Grünberg for Giant Magnetoresistance, or GMR. This is one of those discoveries that really matters, given that it's how hard drive read heads work. I was kind of hoping for a Stanford win (Andre Linde is always one of the people on the short list

Axis of Evil in the universe?

Here's a cool article (subscription probably required) from Science about the so-called "axis of evil" in the universe. In case you've never heard of it, here's a picture:

Going my way? The CMB quadrupole (top left), octopole (top right), and the next two multipoles. The red dots mark their symmetry axes, which appear to line up.
CREDIT: NASA/WMAP SCIENCE TEAM

The multipole moments mentioned in the caption are just the way that the full map was broken down, as a sum of progressively finer undulations. The courses is the dipole, which splits the map in two, then the quadrupole (four), octopole (eight) and so on. The coincidence is that the largest moments have their symmetry axis lined up. The question is whether this is just a coincidence or something more meaningful, and it's really hard to say which. The problem is that we only have on universe to look at, and we can't really make the assumption that this isn't just a fluke. And so far the efforts to explain it are seriously flawed, not matching up with other data.

This might end up being a big deal because if it's more than just a coincidence one of the sacred assumptions of the universe, that there's no preferred direction, is totally wrong. That would have deep implications, some conservation laws (energy, momentum, and angular momentum) are the result of assumptions about space, which could end up being wrong!

I have to be honest, I think this is probably just a mirage. Adding a preferred direction to the universe would be quite revolutionary, and it just doesn't sit well with me. I know that's not a good reason to ignore new data, but this hasn't been proved yet. If the universe ends up having an axis, then so be it, but I doubt it does.

Old notion of the distribution of charge inside the neutron overturned

Apparently the old notion of the distribution of charge inside the neutron has been overturned:

For two generations of physicists, it has been a standard belief that the neutron, an electrically neutral elementary particle and a primary component of an atom, actually carries a positive charge at its center and an offsetting negative charge at its outer edge.

The notion was first put forth in 1947 by Enrico Fermi, a Nobel laureate noted for his role in developing the first nuclear reactor. But new research by a University of Washington physicist shows the neutron's charge is not quite as simple as Fermi believed.

Using precise data recently gathered at three different laboratories and some new theoretical tools, Gerald A. Miller, a UW physics professor, has found that the neutron has a negative charge both in its inner core and its outer edge, with a positive charge sandwiched in between to make the particle electrically neutral.

This is pretty cool, but I wanted to know how the quarks arrange themselves inside the neutron in order for this to happen. It would seem that the down quarks are at the center and outside and the up quark is in the middle, but that doesn't make much sense (since then the up would be in the middle). But then again I don't know much of anything about quantum chromodynamics, perhaps this does make sense.

One of the reasons I mentioned it here is because it's a good example of something we've believed for a while (in this case 60 years) being suddenly overturned. This was published in PRL, so I doubt it's junk, and it will probably be well-received by the Physics community (again, provided it does have good evidence going for it). It's always good to have examples of when a long-held belief is just overturned; it demonstrates the power, flexibility, and nondogmatic nature of science.

Magnetars, and example of cool science

I'm currently watching The Universe on the History Channel, and they're talking about "The most dangerous places in the universe". It's mostly about black holes, but they briefly mention things called magnetars, that I had never heard of before. They are fascinating little creatures.

A magnetar forms when a massive star that's spinning fast and has a strong magnetic field collapses, exploding in a supernova and eventually settling into a spinning neutron star. Unlike neutron stars, magnetars have ridiculously strong magnetic fields (caused by the dynamo mechanism). To give an idea of how powerful the magnetic field is, it's 1,000,000,000,000 times stronger than the earth's magnetic field, and 10,000,000,000 times stronger than a neodymium magnet. These fields are so strong that they have an energy density over 10,000 times as great as lead, and at 1000 km would actually be lethal, tearing flesh apart because of water's dipole moment.

We know they exist because the super-strong fields have weird effects on photons, and some rare phenomenon are best explained through this mechanism (there are less than 20 found so far).

This is an example of really cool science, and it fills me with a sense of wonder and awe that such magnificent and bizarre phenomenon actually exist in our universe.

Hints of a breakdown of special relativity

When I saw the article titled "Hints of a breakdown of special relativity" in a SciAm blog, my curiosity was piqued. I thought it was just going to be the old, debunked story, but it's not.

The team from the MAGIC gamma-ray telescope has some tantalizing evidence that, in fact, special relativity is incorrect. They found indications that high-energy gamma rays travel slower through vacuum than low-energy rays. Here's the meat of the observation:

The team studied two gamma-ray flares in mid-2005 from the black hole at the heart of the galaxy Markarian 501. They compared gammas in two energy ranges, from 1.2 to 10 tera-electron-volts (TeV) and from 0.25 to 0.6 TeV. The first group arrived on Earth four minutes later than the second. One team member, physicist John Ellis of CERN, says: "The significance of the time lag is above 95%, and the magnitude of the effect is beyond the sensitivity of previous experiments."

Now, why exactly this would happen is way beyond my understanding. According to SciAm, it could be that there's some kind lensing that occurs due to fluctuations in the fabric of space-time that happens at higher energies. (It sounds almost like increasing air resistance with speed, perhaps that's a good metaphor the proposed effect?) This kind of effect can happen in theories of Quantum Gravity, and if this result is real, it could help constrain the possible "theory of everything".

However, it needs to be said that this is a big claim, and it could be totally wrong. There need to be thorough checks done on the work, and it would be nice if a separate lab confirmed the result. But if it stands, this could well be one of those turning points in modern physics. I can't wait to hear more, new physics is very exciting! (Or at least it is when it's possibly a real result.)

Falling Physics

This Straight Dope article on surviving high falls is good, but I think it lacks one specific fact. One question involved blacking out during freefall, and I think it's important to mention that you black out because of acceleration, not speed. Your velocity could be anything and you'd be just fine, because any constant velocity is indistinguishable from another (and hence from rest). But accelerations will black you out, at something around 10 g's (that's acceleration due to gravity, 32 ft/s^2 or 9.8m/s^2). But during free fall you're experiencing less than one g (less than because of air resistance).

Well that's not quite true, when you hit the ground you're going to get quite a few g's, but up until then you're golden (it's not the fall that kills you...)

Speed of light still not broken, but now we really know why

I'm glad I read Physics blogs, because they always know more than me. Check that out if you want a very detailed backstory to yesterday's "Speed of light NOT broken" story. It turns out that the only person who thinks that SR was violated is someone who has a history of making more of these experiments than they deserve, and that the paper that's available is totally inadequate for the claims that are being made. So basically I was right (it happens from time to time).

So check that out if you care at all about the speed of light and superluminal information transfer.

We have NOT broken the speed of light

We have broken the speed of light, the article's headline boldly proclaims.

No, we haven't. I absolutely guarantee it. First, let's look at what they did:

The pair say they have conducted an experiment in which microwave photons - energetic packets of light - travelled "instantaneously" between a pair of prisms that had been moved up to 3ft apart.

Well there's not really anything here. My first guess was that this was some issue about Quantum Entanglement, but it might not be (and that doesn't offer FTL communication anyway, that's just a sloppy interpretation of what's happening). If this is about entanglement then it's not news, this has been done dozens of times, and it doesn't break SR.

But if it's not about entanglement it doesn't matter, because there's no way light traveled faster than light. It reminds me of someone who asked me if humidity can be above 100%. My response was, "No, because can't hold more water than it can possibly hold."

Light always travels at the speed of light, and the speed of light varies based on the medium the light is in. This comes straight from Maxwell's Laws (see here if you're interested in why), and it's what inspired Einstein to think about what light would look like if you ran alongside it (of course, he figured out that no matter how fast you were running it would still go at the speed of light). Special relativity comes straight from Maxwell's laws, and if something is found to violate SR, then Maxwell's laws aren't correct.

Now, it's always possible that our current knowledge of the universe isn't correct, even something as old and well-established as the fundamental theory of electricity and magnetism. But the more established and well-tested the theory, the less likely this becomes. It's like evolution, sure it could be wrong, but it almost certainly isn't. The same is true of Maxwell's Laws, they've been so thoroughly tested to such insane limits that if they're wrong it would shake physics to its core (given that those four little equation form an entire section of physics, and form the foundation for relativity, one of the two pillars of modern physics, the other being QM).

So while it's possible that these two researchers have broken the speed of light, I highly doubt it. Besides, if you look at their setup the have light traveling one meter, which happens in about 3 nanoseconds. I think it's more likely that they measured incorrectly (that there's some error in their experiment) than that half of modern physics is wrong. If I never hear about this monumental discovery again, I'll be pretty sure that I'm right.

Update: A different article has more information, this one attributes the FTL travel to quantum tunneling, which is a process by which a particle goes through an energy barrier that it classically shouldn't be able to go through. I'm not very experienced with this phenomenon, but my understanding is that this still doesn't violate SR since it's not actually moving that distance, the wavefunction has just spread over to the other detector. Since the wavefunction covered the whole distance anyway, the particle wasn't localized before measurement, so it can't be said to have traveled FTL in any real sense (keep in mind that could all be wrong). But it's so hard to say what's going on based on these news reports, they don't include reference information and I can't see it here anyway, so I can't check any actual paper for an idea of what's going on.

In any case, I still stand by my original assessment that this isn't revolutionary, but as always, I could be wrong.

UPDATE 2: Wow, I should have checked Eureka Alert a while ago. Here's a reasonable explanation of what happened. It was indeed tunneling, and it also does not violate SR. As is typical with science reporting, the reporter seized upon the most fantastic interpretation of the results, and not the sober analysis presented at the end. We did not break the speed of light, end of story.

Philosophia Naturalis #10

Welcome to the tenth edition of Philosophia Naturalis, the physical sciences blog carnival. We’ve got the month’s best physics and astronomy blogging here, for your reading pleasure!

First up is Scott Aaronson, who goes into great detail on how quantum computers can solve the factoring problem in Shor, I’ll do it. If you’re put off by math, worry not, for Scott has graciously substituted metaphors involving clocks for all advanced mathematics. If I understood it, you almost certainly will.

In our next entry, Matt Leifer asks, “why is many-worlds winning the foundations debate?” He dives in to a philosophical discussion about the nature of science and uses “Quine’s pudding bowl” to cast good doubt upon the many-worlds interpretation. If you’re up for some philosophy of science (and who isn’t?) give it a read.

Continuing the streak of Quantum-themed entries, Alejandro Satz attempts to explain Quantum Mechanics in words of one syllable. He manages to a pretty good job with a difficult task. I’m not sure I could write anything using only monosyllabic words.

For a change of pace, Joseph Polchinski, guest-blogging at Cosmic Variance, rebuts some of Lee Smolin’s anti-string rhetoric in Science or Sociology? Check it out whether you love or hate string theory (or even if you’re one of those rare people who is entirely neutral to the idea).

In a follow-up to Polchinski’s post titled String Theory: Not Dead Yet, Sean Carroll describes how it’s business as usual for String theorists despite the common misconception that it’s “dead and buried”. He also talks about some of the challenges they’re facing and why it’s still the leading candidate for a theory of quantum gravity.

Speaking of gravity (but without the quantum), Clifford Johnson implores you to Read a Gravity Essay Today. Apparently you can win $5,000 for writing an essay on gravity, who knew!

Now we slide into astronomy and cosmology with Rob Knop, who discusses how the universe is going to end in The Big Rip: an end to the universe without recollapse. According to Rob, there’s an alternative to heat death or recollapse, involving “Phantom Dark Energy”.

Charles Daney muses on NASA’s priorities, new planets, and future space missions (mostly European) in The $13,000 bottle of water. It certainly sounds like the Europeans are on top of their game when it comes to interesting experiments in space, us Americans can only hope that NASA gets its act together and starts doing more real science again sometime soon.

There seems to have been a flurry of news about extrasolar planets this month, and physics bloggers got in on the action. Steinn Sigurosson reports on the discovery of a planet around a metal-poor star in Mo’ Better Planets. Next, Greg Laughlin has the scoop on a Neptune-sized snowball 33 light-years away, and its implications for the study of extrasolar planets. Finally, Phil Plait tells us about the fist map of an extrasolar planet. It’s quite a crude map, but a very impressive feat.

Continuing our foray into the science of the stars, mollishka from a geocentric view discusses her work on the Lyman-alpha forest. There’s a little bit of atomic science and a whole lot of astronomy in this post, it’s a very worthwhile read (especially if you’re like me and quite deficient in astronomy knowledge).

In our final bit of astronomy, ZapperZ from asks Is Too Much Physics Bad For Astronomy?, and then asks it again in Follow Up To “Is Too Much Physics Bad For Astronomy?” His short answer is “no”, but for the full (and much more interesting one) click on the link!

I happen to enjoy a good bit of irreverence every now and then, and so we’ll end this month’s PN with some irreverent looks at physics.

Chad Orzel starts us off with Many Worlds, Many Treats, wherein he explains the many-worlds hypothesis to his dog, and why she shouldn’t be expecting any steaks to fall from his lap any time soon.

Next up, Steinn Sigurosson takes an irreverent look at Boltzmann brains and their implications in on the spontaneous appearance of minor deities.

And finally, we have a webcomic from PartiallyClips:



That does it for this month’s Philosophia Naturalis, tune in next month for more excellent physical sciences blogging!

Official Call for Entries

I'll be hosting the next issue of Philosophia Naturalis here in a little over a week, on May 24th. Guidelines for articles are here, but my interpretation is more or less "if it's about the natural sciences and it's good, it'll get in."

So you can leave a comment here (or anywhere on the blog) to suggest an entry, you can e-mail me, or you can contact the carnival's creator, Charles Daney, at the Philosophia Naturalis webpage. Just suggest good articles!

What's the deal with magnetic monopoles?

So what are magnetic monopoles, and why are they important?

A monopole is just something with only one pole (enlightening, I know). Normal permanent magnets (or the Earth) are dipoles, they have a North and a South pole. If you cut a magnet in half you don’t get one North and one South pole, you get two smaller and weaker dipole magnets.

Imagine an electron. You probably picture it as a point in space, and you probably picture its electric field as lines pointing radially outward. That’s a monopole, an electric monopole. Now if you switch from it having electric charge to having magnetic change, you’ll have a magnetic monopole.

You might be saying right now, “Well that’s all well and good, but I’ve never seen one of the magnetic monopoles, why should I think they exist?” If you are thinking that, then you’re on to something. No one ever has seen a magnetic monopole. If you look at Maxwell’s Equations, you won’t see any magnetic charge anywhere. But Maxwell noticed that it could easily be added, but the lack of evidence for them dissuaded him from including them.

I just said that no one has seen a magnetic monopole, and this is true, in a sense. Valentine’s Day 1984, Blas Cabrera, my advisor, saw a signature on a detector that is exactly what you’d expect if a monopole had passed through. However, further experiments made it vanishingly unlikely that this was an actual monopole, and Blas will tell you it almost certainly was not. (Personally I’d like to believe it was, and I’m impressed Blas can admit that it wasn’t.)

Now you’re probably thinking, “If we’ve never seen one, why do we care about them?” That’s also a good question. It turns out that if you take quantum mechanical principles and mix them with electrodynamics, you can prove that if there exists one magnetic monopole anywhere in the universe, then both electric and magnetic charge will be quantized. This is called Dirac’s quantization, and is a pretty stunning result. I’ve seen the calculation done and it’s quite beautiful (but too complicated and lengthy for a blog entry). There’s no real reason for the quantization of charge without this (at least that I know of), so the fact that charge is indeed quantized is a good indicator that there is a monopole somewhere out there (maybe it did go through Palo Alto in 1984). Unfortunately for any monopole lovers, there’s probably less than one per cosmic horizon, which means your odds of finding one are just about nil.

Besides that, Grand Unification Theories and other high-level theories, such as String Theory, demand their existence. For a while, theories demanded too damn many of them, and people were concerned about why there were so few. Alan Guth’s Inflationary Cosmology did a fantastic job of explaining the small level of monopoles, which is one of the many reasons it’s so widely accepted.

I hope that now you have a decent grasp of magnetic monopoles, what they are and why they matter.

Magnetic Fields Do No Work

Every time I head about a perpetual motion machine (or some other kind of free energy), I know immediately how it works. It’s one of a short list of well-known but poorly-understood (at least among the general population) physical principles. The two big ones are magnetic fields and the Casimir Effect. I’m going to be talking about magnetic fields today, and why they can never be used to make any kind of perpetual motion machine.

Everyone loves magnets, and if they don’t they should. I know I do, I have about 40 neodymium super-magnets on my desk. They’re fascinating, and with their invisible and seemingly magical attraction, they have mystified child and adult alike for generations. Surely there must be some way to harness this power and get free energy!

There’s just one problem with this: magnetic fields do no work.

Some physics background for those who don’t have it, work is basically force times distance. If you apply a force over a given distance you do work, any time you move an object you’re doing work (however, sitting at your computer and playing solitaire is not work). Work has the units of energy, and (ignoring friction) the work done moving an object is exactly equal to the change in its energy.

So if magnetic fields don’t do work, then we can’t get any energy out of them without dissipating the field itself.

But, you ask, how do I know that magnetic fields don’t do work? The answer to that requires some vector calculus (unfortunately, no one likes vector calculus), but it’s not too bad. Skip it if you don’t care, but I promise I’m not going to kill you with Math.

The magnetic field (B) is defined as:



That X in the middle does not mean “times”, it’s the cross product, which basically means that the force from a moving charge in a magnetic field is perpendicular to both the field and to the velocity of the charge.

Work, in the true mathematic form, is:



F is the force and ds is a bit of the path, “dotted” into the force. But we know that ds is equal to the velocity time a small bit of time, dt (because that’s the part of the path that the object moves in time dt).

Now recall that the force is equal to the field crossed with the velocity, and to get work we have to dot it with the velocity:



The cross and the dot products have a peculiar property that if this happens, the result is always zero. Geometrically this happens because the cross product creates a vector that is perpendicular to both the initial vectors, but the dot product evaluates the length that two vectors have in common. If they’re perpendicular, then the answer is always zero.

So magnetic fields do no work, and hence you can’t get any energy from them (without dissipating the field).

If you don’t like that argument (although it’s perfectly solid), I’ve got another one for you. The energy density of the magnetic field is:



If you integrate that over all space, you get the entire amount of energy contained in the field. Because every magnetic field falls to zero as the distance away increases, that integral is finite, and hence the total amount of energy one can extract from a field is finite. This is why I repeatedly added “without dissipating the field” to the end of “magnetic fields do no work.” This is also why objects (such as paper clips) will go flying towards magnets: they modify the field, changing how much energy is stored in it. You could conceivably extract energy from this, but only as much as you put into it (and actually less because of losses due to friction), just like every other physical system.

So, while magnets are fun and fascinating, anyone who claims that they’ve harnessed free energy from them is either mistaken or a liar, and they have an incomplete grasp of electromagnetism. Remember, magnetic fields do no work!

The bizarre and intriguing story of Oleg Jefimenko and the solutions to Maxwell's Equations

I recently heard the story of Oleg Jefimenko during a lecture on Electrodynamics, specifically the general solution to Maxwell’s Equations.

Jefimenko’s tiny bit of fame comes from Jefimenko’s Equations, which are the general solution to Maxwell’s equations expressed solely in terms of sources, that is charge and current distributions. The equations are messy and difficult to work with, and aren’t used much in practice. But they do reveal certain bits of physics (such as the applicability of the quasistatic approximation (the link goes to a thermodynamics page, but the idea is the same) and that fields must be created by sources), and it’s always nice to have the general solution to a problem available.

These equations weren’t written down until 1966, about a century after Maxwell’s Equations were known. Some people will claim (as the Wikipedia article cited does) that Jefimenko’s Equations were written down earlier, but those earlier versions are always slightly different and not quite complete. What’s really funny is that Jefimenko wrote them down in an attempt to formulate an alternative to Maxwell’s equations.

When my current Professor, David Griffiths, was in the process of writing a paper on the subject, he independently derived Jefimenko’s equations, and tried to figure out if anyone had done it before. Other than some slightly tricky and annoying math, they’re not hard to derive, so someone must have done it. He found that Jefimenko had written them in a book that was published by a company that had only published one other work, also by Jefimenko (apparently regular publishers wouldn’t take his books, so he went to a prestige press). He contacted Jefimenko, and Jefimenko didn’t believe that he had solved Maxwell’s equations, but that he had created an electromagnetic theory separate from (and doubtless better than) Maxwell’s. Of course he had done no such thing, his formulation is exactly equivalent to Maxwell’s, but he wasn’t buying it.

According to Griffiths, Jefimenko currently submits one or two papers a week to American journals, gets denied, then publishes them in Europe (where review is apparently not as stringent). I don’t know what they’re about, the Wikipedia article says he focuses on overthrowing Einstein’s General Relativity and Maxwell.

I found this story behind some esoteric equations to be pretty amusing, and thought others might agree. I hope you’ve enjoyed the convoluted and intriguing story behind Jefimenko’s equations.

[Most of my information comes from a lecture with Griffiths, and as such could not be found online. Anything that is available online has been referenced.]

Bad News From Switzerland

This is incredibly bad news.

Let me back up some. The LHC (Large Hadron Collider) in CERN is the next-generation particle accelerator. It will, at the very very least, tell us how correct the Standard Model is. It could show us the Higgs Boson (the so-called God Particle that I'll have to do a post on some time, the short version is that it gives all matter mass), and possibly even mini black holes. It could very well tear our knowledge a new one once it starts smashing protons together.

But in a stress test over the weekend the casing of one of a series of crucial magnets (in an accelerator magnetic fields accelerate and direct the particles) failed and broke (for more technical details see the link above). A press release from Fermi-lab (who designed the magnets) said it could delay the LHC up to three years. However, Scientific American link above cites CERN scientists as saying that it has yet to be determined how long the delay will be.

That is incredibly bad news. There are people working in every branch of physics, from String Theory to Cosmology, and especially particle physics, who have been waiting to see what will fly out when two protons hit at 7 Tera-electron-Volts. It will be a big blow for the LHC to be delayed, when it was so close to yielding the anticipated data. I'm sure that the entire physics community is hoping for some good news in the next few days (or weeks). I know I'll have my fingers crossed that this is only a minor problem. It would be devastating if it weren't.

Why do electrons stay in wires?

What keeps electrons in wires?

That’s a question I had never asked myself, and it’s one few people have considered. The answer isn’t as easy or obvious as you’d expect, but if you’re curious about it, read on.

The short answer is that the electron clouds and the nuclei of the atoms at the edge of the metal form a dipole. A dipole is essentially a set of two charges that form a mathematically unique field (see the Wikipedia article for a picture). The field from this dipole keeps the electrons in, as they’d need a kinetic energy of roughly 4 electron volts (eV) to get through the dipole field.

If you’re having trouble imagining it, an analogy is a water channel, where the dipole field is the walls and the electrons are the water. The water doesn’t have enough energy to get over the boundary (this case the potential barrier is gravitational rather than electrical), and so it flows along the path of the channel. The analogy is good for another reason too, water has to flow downhill (following the gravitational field), and so do the electrons (following an electrical field). (One difference is that the gravitational field is created by the Earth, whereas the electric field is created by the current.)

This effect has to do with the work function, the energy needed to pull an electron off of a metal into free space. Experiments around the turn of the century had discovered that when a metal was bombarded with light of the right frequency, electrons would fly off, creating a current. This is called the photoelectric effect. Physicists couldn’t quite explain it until Einstein realized that it meant that light is both a wave, with a frequency and wavelength, and a particle with quantized energy and momentum. One of his 1905 trio of amazing papers put forth this hypothesis, and it’s what won him his Nobel Prize (nope, Relativity never won him one, and the other two were on Brownian Motion and Special Relativity).

So that’s why electrons stay in wires (and metals in general).

Bubble Computers?

Everybody loves bubbles. How can you not? Some people might love bubbles so much that they want to make a computer that calculates with bubbles.

That might seem crazy, but thanks to Manu Prakash and his colleagues at MIT, it may soon be possible. They've built channels that control bubbles in fluid streams, and they can construct analogs of almost every electrical component, from transistors to oscillators. Eventually, they hope to build these up into bubble CPUs and bubble memory.

Well, what's the point? Bubbles are certainly slower than electrons, making a bubble computer much slower than a regular computer. But electrons can't carry payloads, and bubbles can. So the idea is that bubble computers would be much more versatile in analyzing and testing chemical and biological signals, only needing to be reprogrammed to change tasks, while nearly every chemical requires specialized chips today.

Will you be using a bubble computer in the near future? Almost certainly not. But the thought is cool nonetheless.

[Via Buzz Skyline]

Forget About Phi

For some reason, there have been a few “golden ratio” websites popping up for the past few days. I was going to let the first one go, but when the second one popped up I had to say something.

First, what is the golden ratio? It’s the ratio that you get if you divide up a line into two sections such that the ratio of the larger to the smaller is the same as the whole to the larger. This comes to about 1.618, and is often called phi. You can also approximate it by dividing two consecutive Fibonacci numbers.

What’s so important about this ratio? That’s the thing, there’s nothing special about it at all. Many claims are made about it (see the first link), but none are true. It’s not in the Parthenon, it’s not in any Renaissance paintings, it’s really not anywhere. It’s not even the most pleasing ratio to the eye, studies asking people to pick out the most pleasing rectangle (whatever that means) do not find ones involving phi to be the most pleasing.

Don’t believe me? Pick up The Golden Ratio: The Story of Phi, the World's Most Astonishing Number by Mario Livio. He discusses where phi does and does not show up, and it’s almost never anywhere sensational. It is found in certain places, such as plants and crystals. But phi was first defined because it appears in the pentagram, so it shouldn’t be entirely surprising that a geometric ratio appears in things constructed geometrically, like crystals.

As for plants, it most frequently appears in the ratios of the number of degrees between two leaves on a stalk. Livio hypothesizes that this is an evolutionary adaptation, that because phi is irrational it allows the most leaves to be exposed to the sun at once.

I can’t say so much about the second link, but since phi being pleasing optically is bunk, I’m skeptical that it’s pleasing musically as well.

Another thing to note is that nothing is ever “equal” to phi, just “close”. Often 1.6 is close enough for people to claim that phi is involved. When you think about how much wiggle room there is in measuring lengths (or times) and how many different places you can possibly measure, something “close” to phi is going to come up frequently. Don’t buy into it, it’s nothing special, just someone grasping for straws.

Besides, phi isn’t even fundamental. It’s not in any physics equation, or any equation at all (as far as I know). Marvel at pi or c or h or alpha or e or the other e, but not phi. Phi just doesn’t deserve it.

Quantum Mechanics Isn't Spiritual

I cannot stand it when people invoke Quantum Mechanics in the context of spirituality. Why? Because it’s stupid, and it shows that they don’t understand it at all.

Quantum mechanics isn’t spiritual. Why do I say that?



That’s why.

In case you’re unfamiliar, that’s the Schroedinger Equation, which is at the heart of quantum mechanics. Any waveform satisfies that equations, and from the waveform you can, in principle, determine the probability of the particle’s behavior.

Wow, second order partial differential equations, I feel such intense spirituality I might just break down and give up this whole materialism thing.

Even at the popular level, only someone with a highly distorted “understanding” (if you can call it that) of QM could possibly derive anything spiritual out of it. I suppose it would be understandable if the entirety of your knowledge came from What the Bleep do we Know?, which is widely regarded as the stupidest misinterpretation of QM ever.

Yes, QM is very weird. But it’s just equations that describe how particles behave in certain situations. It’s no more spiritual or special than Newton’s Laws or the equations of Special Relativity, or any mathematical construct. They may be beautiful in the sense that the contain vast amounts of information in such simple forms, and they have dramatic consequences for our understanding of the world, but they’re not spiritual. That’s just silly.