illuminating science

Interesting story over at Physical Review Focus on new superconducting wires that are light weight, incredibly strong and, being superconductors, carry current with no resistance.

There are two points of interest in this article. First, is the practical aspect. These wires can carry incredibly large currents, which in turn are capable of producing very high magnetic fields. They are also incredibly strong, potentially “stronger than steel”. This means if you want a superconducting device you can build it entirely from these wires, and you don’t need a heavy steel frame as well. Why is all this of interest? Among the probably many reasons is thatthese are all conditions that are needed “in several futuristic spacecraft propulsion systems”, i.e., being light and strong but capable of producing high magnetic fields. I’m not sure what these systems involve, though - have to get back to you on that one!

The second main point is of theoretical interest, namely, what makes materials superconduct? Superconductivity in simple materials, such as lead, is well understood. Materials have resistance because when electrons try and flow through the material, they collide with other atoms and lose energy (just like trying to run through a crowded room - you keep hitting people and having to start again.) When cooled to almost absolute zero, however, electrons in certain metals pair together in what’s known as Cooper pairs. These pairs of electrons are then able to move through the metal while dodging all the other atoms. There’s no good analogy for this, really - it’s a quantum mechanical effect and most of our usual intuition doesn’t apply. Just be impressed that this is quantum mechanics on the macro scale - working in every day life!

What we don’t understand is high temperature superconductors, which superconduct at around 100 degrees above aboslute zero (-173 degrees Celcius, give or take.) According to the original theory, the comparitively high temperatures would destroy the superconductivity. We don’t have a good theory yet to explain what’s going on, and many groups, including ours at the University of Queensland, are working to understand it. The material these wires are made out of is similar to these high-T superconductors (it can’t be explained by the original supercondtivity theory) but the material issimpler, which might mean researchers can use it to understand what’s going on in all the materials. A successful theory might mean we could build better and cheaper superconductors, perhaps even ones capable of working at room temperature!

For more info on superconductors, check out superconductors.org for a good general overview, or for a slightly more advanced treatment, there’s the ever-faithful Wikipedia. And, of course, Google searches turn up many links!

Okay, this is seriously cool. Flying cars may actually become a reality, and in the near future too (the next few years!). The big car companies Honda and Toyota “are developing prototypes of small flying devices.” Initially, these would be “air taxis”, ferrying people between small airports, say. But you can guarantee that personal cars won’t be far behind.

Why is this interesting for physics? Nanotechnology and microelectronics (basically, very small-scale constructions!) are probably going to play a big role in making these cars feasible both in size and in cost. Physicsists will certainly be involved in some capacity! Thanks to Slashdot for the tip off.

A trio of small, 10cm (4 in) telescopes have discovered a new extrasolar planet (i.e., one not in our solar system). These guys weren’t amateurs, though - they are members of TrES (Trans-Atlantic Exoplanet Survey), a wordwide group.

How do you detect a planet? Remember, it’s hundreds or thousands of light years away, and so dim that you couldn’t possibly see it directly beside its sun. The trick they use is to look for transits of the planet across the face of its sun - remember the recent Transit of Venus? Venus passed between us and the Sun (our Sun!), which we say as a dark spot on the sun, moving slowly across. If an extrasolar planet passes in front of a far away star, the effect is the same - some of the light from that star is blocked, and it will appear dimmer while the transit is occurring. Of course, we can’t see the actual crossing - the star is too far away for us to resolve it as a disk, so we can only see a point. But the periodic dimming of the star as the planet goes around is detectable, and that’s what they’ve done with these relatively cheap telescopes. Pretty neat, hey? This can only be seen on very bright stars, which is why small telescopes can get involved. It also means we can only detect large planets (Jupiter size) because they’re the only ones that give a big enough dip in brightness to be detected.

Entropy Core (who in turn picked it up from a post on Lambda the Ultimate) has posted a link to an online book on Godel’s Incomleteness Theorem. Actually, it’s only the first 12 chapters so far, but that’s probably enough for most!

Godel’s first Incompleteness Theorem says (quoting the Wikipedia) “In any consistent formalization of mathematics that is sufficiently strong to define the concept of natural numbers, one can construct a statement that can be neither proved nor disproved within that system.” In layman’s terms, what this says is that if you try and make a model that has a set of basic rules and includes the idea of counting numbers (-1,0,1,2,3,etc) then you can always think of statements that are neither true nor false, at least within the model you’ve made. A (sort of) example is the sentence “This statement is false.” If the statement is true, then the statement must be false. Oh. Well, then the statement is false. But then the statement says it must be true, which means it must be false, which means…And so on. It is neither true nor false, neither provable nor disprovable. What’s really interesting is that this theory is completely rigorous and mathematical - it’s not just a philosophical argument.

The book is quite readable for someone (like myself) who’s had experience with mathematical proofs and seen set theory before. If you’re not really a maths person, you might find it tough going. Other sources include the Wikipedia and Google turns up a number of pages. Unfortunately, a lot of it is either very “airy fairy” or hard to understand without a background in mathematics. If I find a good summary, I’ll post it.

So this isn’t strictly physics news, but it’s too good not to post! As I was listening to a vaguely uninteresting talk this afternoon, I got startled by a roar behind me. Was it bears?! Wolves?! Nope! It was a famous physicist (at least within biophysics, who shall remain nameless!) with his head slumped on the desk, snoring. It kind of came in cycles, and by the third time around myself and the girl beside me were nearly in hysterics and I was trying desperately not to guffaw outloud and ruin the talk. Fortunately, at that point the speaker finished and the applause woke up the sleeping physicist.

One can only hope that the speaker remained blissfully unaware…

I got assaulted today. Not by a mugger or even a door-to-door salesman. It was a crank. I was presenting a poster on my work modelling the role quantum mechanics in biological systems. This guy was an experimentalist (I won’t name him, but he’s doing work on the magnetic properties of kidney stones…not a promising start.) who also teaches quantum mechanics. He then basically told me that I need to go back and redo my model because it didn’t include the zero-point energy. This refers to a result in quantum mechanics which says even in a vacuum there is always fluctuations in energy, possibly even infinite amounts. It’s the subject of a lot of experimental research, but a lot of the time, we can just ignore it - treat it as a sort of base line from which all other energy starts (like giving everyone 10 points to start a game of table tennis and going to 31 points instead of 21). Anyway, despite my attempts to explain why it was irrelevant in my model, he insisted that the zero-point energy was the most important result of quantum mechanics, and since he taught it and since I was just a student that I had to listen to him and go back and redo my flawed model. In the end I just agreed with him for the sake of peace.

Perhaps you’ve been sheltered from the world of physics “cranks”. Either you can read on (click “More”) and hear my thoughts on who, what, why and how cranks come about, or you could visit Crank Dot Net and read about some of the cranks on the web today. Either way, remember that these are all just opinions, and, however unlikely, one of these theories might really have some truth in it. If nothing else though, they make a fun read!
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We might have to build a better mousetrap…researchers at Howard Hughes Medical Institute have made Marathon Mice capable of running twice as long as normal mice before being exhausted. They modified just a single gene to produce a human protein, PPAR-delta, which additionally makes the mice resistant to weight gain even on a high fat diet!

A company has already produced an oral drug capable of producing the same protein in humans. From the Wired article, “If genetic modification is perfected in humans, this could lead to an easy way to enhance sports performance.” Some interesting questions arise as to what would happen if this procedure was banned, but you produced the protein ‘naturally’ - would you have to prove it? Do athletes need to have full genetic screenings? Deep questions, particularly in light of all the recent Olympic drug testing.

So I’m here in Gothenburg, Sweden, attending the 5th International Conference on Biological Physics. So expect a few posts on interesting talks, posters, etc that I come across. (I love the internet - would you have known that several of my earlier posts came from the Singapore airport departure lounge?)

This morning there Adrian Persegian gave a talk about pressures and forces involved with DNA. He spoke very well, clearly and concisely, although some of the significance of the talk was lost on me, as I didn’t really have the background. A couple of interesting things were that he was really pushing the aspect of getting interesting “and enjoyable” physics from biololgy, and presenting his work with the angle of why should a physicist be interested. This is interesting, since often biophysics talks are aimed at biologists, and why they might want physicists to help them.

Another interesting thing he did was to say “let’s talk like people” when he thought his last comments were confusing. Then he’d come out from behind the lectern (gasp!) and talk and gesticulate, as if he was having a real discussion, and really wanted us to understand rather than just nod and smile and think how clever he and his research is. He approached his whole talk as less of a “communicate my research” and more of a “why should you care?” kind of talk. A refreshing change! Then again, as an invited speaker, he doesn’t have to convince everyone that he’s good! But if you ever attend a conference, you’ll realise that most physicsists (heck, most people) just aren’t good public communicators. A pleasant start to the conference.

I’m sure that stunt pilots must get bored of their jobs. All those death defying maneuvers, explosions going off on all sides…yep, must be pretty dull. So imagine how excited these guys must be - NASA has hired them to retrieve a capsule returning soon from a three year long mission to the sun.

The Genesis mission was designed to retrieve ions (charged particles) given off by the sun, known as the solar wind. The hope is that analysing these particles will tell us more about how our solar system was formed, which is turn might give us a better idea of the chances of life elsewhere in the universe, among other things. It’s also the first time since the Apollo missions that extraterrestrial material has been brought back to Earth. The helicoptor pilots are going to capture the capsule containing the sample as it re-enters Earth, in about 17 days time, carrying it to a safe (and soft!) landing.

Incidentally, it’s worth looking at the Genesis mission FAQ, just from a psychological perspsective. The first question is basically whether if they miss the capsule or miscalculate its return, could it wipe out a city (or at least, someone’s prize roses). The next asks whether there is any danger of viruses, LGM or what have you, in the extraterrestrial material. This is actually a pretty reasonable question, and a bit of googling should turn up some discussion on it, or you could just read Michael Chrichton’s The Andromeda Strain for a somewhat more sensation (but entertaining!) account of this sort of thing. (And that book really is fiction, despite its attempts to convince you otherwise!) The final question is whether NASA is out to prove or disprove the (Christian) Bible. I’m slightly disappointed that these are the most asked questions, though it probably reflects strongly on today’s sci-fi and creationism vs evolutionism, both of which are in the news far more than the actual science! Guess we’re going to have to change that

New blog up at Entropy Core, talking about science, technology and life as a grad student (a PhD student, for us Aussies!) Check out the tips for grad students, particularly a day in the life of a grad student. Anybody working on a PhD can sympathise with this timeless classic

Really interesting, although perhaps a little controversial, article in New Scientist, where psychologists have studied a tribe which has counting words only for “one”, “two” and “many”. So for three objects or thirty they use the same word. Apparently, they just have very little need to count in daily life.

So what’s interesting here? In a variety of tests, the tribe members were tested on their ability to count objects. “In the simplest, he sat opposite an individual and laid out a random number of familiar objects, including batteries, sticks and nuts, in a row.” [Sticks, nuts and batteries?! Oh well…] The subject would then lay out the same number from their collection. They could do this for 1,2 or 3 objects fine, but got worse and worse for higher numbers. The claim then by psychologist Peter Gordon is that the fact that they have no language for numbers limits their ability to think.

I haven’t read their paper, so I can’t comment for certain, but I would treat claim this with caution. Could a more likely explanation be that a single cause explains both the language and cognitive deficits - namely, the fact that they have no use for counting in day to day lives? Perhaps it reflects more that if you’re never taught to count, and never use it, that you don’t have good counting skills? This has been pointed out by other scientists, who also suggest that the tribespeople may also be simply not be used to the test tasks, and so did poorly.

So personally, I don’t think things are quite as clear cut as New Scientist makes out (which is a whole other post…) To quote psychologist Randy Gallistel, “The question remains highly controversial.” The take home message is to always critically analyse what you’re told, and question the logic that leads to a conclusion. In many ways, I think this is one of the most important quality of a scientist!

Kudos to Slashdot for alerting me to this one, those fabulous little guys the Mars Rovers, Spirit and Opportunity, have found yet more evidence that there used to be a lot of water on Mars. Perhaps not earthshaking (marsshaking?) in itself, but it’s amazing that these guys have gone for twice as long as anyone expected, are still going strong, and are still producing valuable data. Pretty neat!

Trivia for the day! Did you know that Saturn is less dense than water? Its density is only 0.7g/cm³, or 700kg/m³ for those (like me!) who prefer to work in SI units, which are standard all across the world. The density of water is 1000kg/m³, which means that every cubic metre of water ways a tonne, compared to only 700kg for the same volume of Saturn.

What does this mean, then? If you put Saturn in a gigantic bathtub full of water, it would float! Weighty matters indeed!

The Cassini-Huygens probe has spotted two new Saturn moons. They’re only tiny, a few kilometres across, and brings the total number of known moons up to 33. They’re now scouring the gaps in Saturn’s rings, looking for moons that might be hidden there.

I particularly like the quote from the imaging team leader Carolyn Porco, “We can now add the confirmation of two new moons, unnoticed around Saturn for billions of years, until now.” Unnoticed for billions of years? Not that suprising, actually…

More details from the NASA press release.

Sorry it’s been a couple of days since I posted - I go overseas Friday, and things are pretty crazy at the moment!
New Scientist is running a story which comments on the politics of nuclear fusion. Research is very much alive with several countries working towards building the first sustainable (and hopefully profitable!) nuclear fusion reactor, called ITER (International Thermonuclear Experimental Reactor). Unfortunately, the countries involved are still arguing about were the reactor is to be built!

Nuclear fusion refers the process by which the sun generates energy. Protons are fused together to create helium, in the process releasing huge amounts of energy. This is very different to nuclear fission where large atoms (uranium, etc) are split apart. This also releases energy, but has the downside of creating dangerous nuclear waste.

Why don’t we all use fusion? The problem is that to get it working, you basically need to build a star - huge pressures and very high temperatures. This is very hard to do. Cold fusion, where we can produce fusion at room temperature, has been much sought after by science fiction writers, but isn’t generally thought to be obtainable. But you never know…

To host a viable nuclear fusion reactor would give you a clean, renewable energy source, so both Japan and France are very keen to have it. One can only hope that the group can come to a decision, and finally build it. We could sure use some clean energy about now.

Update: More at Physics Today.

At the UQ Department of Physics Colloqium this week, we have Joe Wolfe visiting from the University of New South Wales. He works on the acoustics of musical instruments and the voice. If his websites are anything to go by, he’ll be a fantastic speaker!

The main site is here. There’s lots of fascinating sections - I particularly liked measuring my hearing response curve - that’s mine on the left! The FAQ is also excellent! Do you know why we need to “warm up” wind instruments? Hint: It’s not due to the expansion of the instrument! It’s actually because as the air inside heats up and becomes more humid from our breath, the speed of sound in the instrument changes! The speed of a sound wave and its frequency (pitch) are directly related, so this changes the note played on the instrument.

Other sections are the physics of the speech and of the good ol’ Aussie didgeridoo.

First interesting sideshow game was a simple one - shoot a basketball in the hoop. Easy, right? Except there are a few tricks. First up, the hoop is bent into an oval shape! You don’t notice though, because when you look at a hoop front on, you expect it to look oval shaped due to perspective. I’m guessing that although the hoop is plenty long enough lengthwise, it’s only just deep enough to fit the basketball through. Very tricky! I also wonder if it might mess with our distance perception? Given we expect it to be circular, the more oval shape might make us think it his higher or further away than it really is, further messing up our shot.

But that’s not all! Conveniently, they’ve given us a backboard with a small square on it, presumably to “help” us line up the shots. The catch is, the ring is extended out a lot further from the backboard than normal, something you don’t realise when viewing it front on. My guess is that if you hit that square, like you’ve been trained to do, it’s not going to go in!

I think this is a clever example of mixing physics and psychology to create a very challenging game.

This week is Ekka week in Brisbane, aka the “Brisbane Exhibition”. This is a big display of horses, cattle, produce, etc, as well as wood chopping competitions, railway track laying, etc. It’s also home, however, to Sideshow Alley - home of carnival rides like roller coasters and dodgem cars, and to all sorts of games that look easy but are in fact much harder than they appear! Naturally, I spent an enjoyable hour wandering around analysing the physics of some of these games. I’m going to post some of that in my next few posts. To get started however, here are some interesting carnival physics websites:

Amusement Park Physics - Learn the physics of roller coasters by designing your own, and more!

Midway Physics Day - From University of Southern California, this has some actual measurements made on rides - very interesting! (A bit of maths involved along the way, though!)

Sideshow Alley at the Exploratorium - From the Exploratorium in Canberra, Australia. They’ve set up an awesome collection of sideshow games and rides, and discuss the physics of each. Not too much detail on the web, but it’s great to visit!

Related to my last post, here’s a neat little Q&A page about general relativity. It’s got lots of common questions and paradoxes about Einstein’s famous theory, including questions about what happens as you approach the speed of light, adding more dimensions to our universe and gravity waves. It’s based on on Dr. Sten Odenwald’s “Ask the Space Scientist” page, which has other goodies on it to!

The only minor complaint I have is when it talks about “relativistic mass” and how it “becomes imaginary” if you travel faster than light. Read on for why this is evil!
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Wired News is reporting that Gravity Probe B is almost ready to start testing the last unchecked predictions of general relativity!

The satellite, launched in April but plagued with problems, is equiped with four high precision gyroscopes that will detect the tiny warping of space-time due to the Earth that is predicted by general relativity. What exactly does that mean? Near a massive body like the Earth (and more so for heavier objects - a black hole being the most extreme example!) space itself is bent out of shape - stretched in the same way a trampoline does when you stand on it. This is well understood and agrees with experiment.

What’s being tested here is that a rotating body is predicted to drag space with it, like rotating a spoon in honey. This will exert a force - gravitomagnetism - on the gyroscopes, subtly pulling them out of alignment. If all goes well, this will be a rigorous proof of one of the toughest predictions of general relativity.

A FAQ about the project gives more details.