Archive for October, 2007

The galactic foxtrot revisited

Wednesday, October 31st, 2007

A coupla months back, Michael “Bongo” Longo at the University of Michigan announced that he’d been a-starin’ and a-studyin’ some 200,000 elliptical galaxies up there in the heavens and had noticed something strange about ‘em: they is all pointing in the same direction.

The physics arXiv blog dutifully reported the story but it now turns out Bongo Longo has now withdrawn the paper sayin’:

“This paper has been withdrawn by the author due to the discovery of a serious bias resulting from the systematic dimming of galaxies with larger ellipticities away from the North Galactic Pole. Thus the conclusion that there is a special axis along which the elliptical galaxies tend to be aligned is incorrect.”

Shame really. I know ya’ll wanted to know what they were pointing at.

Ref: arxiv.org/abs/0708.4013: The Axis of Opportunity: The Large-Scale Correlation of Elliptical Galaxies

(Thanks Tim, ‘ppreciate it)

Delayed-choice and double slits

Tuesday, October 30th, 2007

Send single photons through a double slit and they will somehow interfere with themselves to produce an interference pattern, as if they were waves. That’s quantum mechanics for ya. ‘Cept it don’t work if the photons are being watched, in which case each photon appears to pass through one slit or the other, as if it were a particle.

Somehow the photon knows it is being watched, which sends physicists and philosophers a-shiverin and and a-tremblin back to their textbooks.

In 1984, the American physicist John Wheeler dreamt up a way of tricking the photons. He suggested switching the method of observation after the photon had passed through the slit.

That means sending a photon through the slits and only then making the decision to record its arrival observed or unobserved. How would the photon “know” what you’ve decided?

Now Alain “Hidden” Aspect at the Laboratoire Charles Fabry de l’Institut d’Optique in France and a few pals have performed the trick for the first time. They say that photons are not so easily tricked: switching the method of observation actually changes the outcome of the experiment, which means the photon somehow knows what you’ve done.

So how to explain this. Either some unknown laws of physics are telling the photons that a switch has taken place during the experiment (and do so at several times the speed of light) or the wave-particle nature of quantum mechanics is correct.

Take yer pick.

Ref: arxiv.org/abs/0710.2597: Wheeler’s Delayed-choice Thought Experiment: Experimental Realization and Theoretical Analysis

Cellphone records reveal new patterns of human activity

Monday, October 29th, 2007

Switch yer mobile phone on and it checks into the local network giving your location and the time you were there. The network also records the calls you make, their frequency, duration and to whom you make them plus wherever they happen to be too.

Multiply that by the entire popualtion (mobile phone penetration approaches 100 per cent in many western countries) and you’ve got a data set that can give an unprecedented insight into the links between people and the way they move and behave.

Albert-Laszlo “Bar” Barabasi at Northeastern University in Boston and a few pals have been a-grindin’ and a-crunchin’ the data from several million cellphones and are now revealing what they’ve found.

Turns out the data can be used to identify friends and family (from the frequency and duration of calls and whether they are reciprocated), they can show how social groups evolve and how they fall apart.

The data can also suggests how to monitor the way people behave in emergencies in realtime. For example, a pile up on the freeway causes lots of rapidly moving phones grind to a halt, a few call the emergency services while others call the office/spouse/lovers. Spot that pattern and its a pretty good indication that an event has occurred. Location information might even help to determine exactly where the accident took place.

Barbara Rasi has also found previously unknown patterns in human behaviour. For example,  although the number of people making calls varies hugely during the day and night, the percentage who are on the move (ie who make consecutive calls from different lcoations) is always roughly the same. And the average distance they travel between calls in a half hour period is also stable at about 6 km. He says this is just the beginning of what will be possible with this kind of data.

What ya’ll want to know is how anonymous is it? The message is: Big Brother is watching…but he only has access to anonymized data.

But ah don’t buy it. It wasn’t so long ago that the raw data from search engines was thought to be anonymised if a person’s name was removed from it. But that myth was exploded by journalists from the New York Times who tracked down one individual using only her AOL search records.

How long before we see a similar expose with supposedly anonymized mobile phone records?

Ref: arxiv.org/abs/0710.2939: Uncovering Individual and Collective Human Dynamics from Mobile Phone Records

Stones ‘n’ pebbles

Sunday, October 28th, 2007

The shiny leftovers from the physics arXiv this week:

The Galactic Bulge: getting a rise outta star gazin’

The Tibet Air Shower Array

Pioneer Anomaly: evaluating newly recovered data

Clustering at CiteULike

Lake Baikal’s neutrino dreams

Saturday, October 27th, 2007

When a neutrino smashes into matter it generates light, lots of it. So stare into the dark night for long enough and you’ll see ‘em flash as they pass by. The problem is that neutrino hits are rare events. So you need a big volume of dark and whole lot of time to sit back and watch ‘em in.

So the Japanese, they built themselves a giant underground lake at huge cost and lined the sides with photon detectors to peer into the darkness. They called it Super-Kamiokande.

The Russians? They dangled some waterproof cameras into a lake. Same thing, fraction of the cost. In fact, even better cos Super-Kamiokande blew up a couple of years ago because of a design fault.
And what a lake! The Ruskies chose Lake Baikal in Siberia, the largest and deepest body of fresh water on the planet. It’s one bee-yoo-tiful piece of real estate.

That was in the late 1990s. Now the Ruskies are gettin more ambitious. They wanna increase the size of their neutrino telescope to a cubic kilometre and have started testing the technology that they need to do it (they’re basically adding extra cameras over a larger volume). Even the Japanese can’t build underground lakes that big.

But there’s a potential problem on the horizon. Lake Baikal is perfect for neutrino detection cos the water is super clear. In fact, its unique ecosystem seems to remove whatever rubbish and pollutants the Ruskies have so far thrown at it.

The trouble is that them developers have got their eyes on the region and hope to turn the lake into a holiday destination extraordinaire for rich Ruskies. And yer know what that mean: before ya know it, the lake’ll be filled with old beer bottles,  shopping trolleys and worse. Ain’t nobody want a floater bobbing its way through yer neutrino telescope.

Perhaps them Japanese had the right idea after all.

Ref: arxiv.org/abs/0710.3063: The Baikal Neutrino Telescope: Status and Plans

Recipes for other Earths

Friday, October 26th, 2007

It ain’t gonna be long now before we find another Earth orbiting a nearby star and the question is: what are we gonna do when we find one?

(By some accounts we already found at least one but in reality these bodies are too big to be like Earth.)

Eric “Nose” Gaidos at the University of Hawaii and his buddies know. They gonna use it to study various theories about how small rocky planets form. Do they form close in to a star which seems difficult given the inhospitable conditions that exist near stars when they form, or do they form further away and spiral inwards?

Nobody knows which recipe is correct or whether other ideas may eventually trump these ones but they is hoping to find out soon.

Ref: arxiv.org/abs/0710.2366: New Worlds on the Horizon: Earth-Sized Planets Close to Other Stars

How mathematics identifies urban ghettos

Thursday, October 25th, 2007

Ya’ll know how the distribution of crime is closely correlated to the space in which it occurs. Nobody gets mugged on a busy high street. But ya wander down a darkened, deadend alley at ya peril. Right?

In recent years a number of eggheads have been a-speculatin’ and a-wondrin’ about the nature of urban space and whether its essence can be adequately captured mathematically. Can yer build an algorithm that will tell whether a neighbourhood is a crime hotspot without having to risk life and limb explorin’ it?

Now “O” Dima Volchenkov at the University Bielefeld in Germany has come up with a way to do it based on random walks. To work out how well a particular destination in the city is connected to the rest of city, she chooses another point at random and sets off walking at random from there. The number of steps it takes her to reach her destination is measure of its connectedness or segregation.

O Dima says that when you do this for all the nodes in a city you build up a map that clearly shows the most segregated areas.

She’s applied the idea to the canal system in Venice and the most segregated area turns out to coincide with an area called the Ghetto of Venice. That’s no coincidence, she says, because:

“In March, 1516 the Government of the Serenissima Repubblica issued special laws, and the first Ghetto of Europe was instituted. It was an area where Jews were forced to live and which they could not leave from sunset to dawn. The Ghetto existed for more than two and a half centuries, until Napoleon conquered Venice and finally opened and eliminated every gate (1797).”

Whether that corresponds to an area with high levels of crime today is another matter. But O Dima seems to have built herself a handy tool that could be hugely useful for city planners and homebuyers not to mention muggers and rapists.

Ref: arxiv.org/abs/0710.3021: Ghetto of Venice: Access to the Target Node and the Random Target Access Time

The science of the Edelweiss

Wednesday, October 24th, 2007

The Sound of Music always brings a tear to mah eye. And now it’ll have new meaning thanks to the sterling work of Jean Pol “Pot” Vigneron and his buddies at the Facultes Universitaires Notre-Dame de la Paix in Belgium.

Pol Pot has been a-caressin’ and a-cuddlin’ one of the movie’s stars: the Alpine flower Edelweiss, and has discovered that the white hairs covering its leaves are actually photonic structures tuned to ultraviolet wavelengths. So Edelwiess turns out to be one of only a handful of plants that can actually grow photonic structures.

In the Alpine meadows where Edelweiss grows, UV levels are much higher than at lower altitudes and would ordinarilly damage plant cells. But the hairs prevent UV light from reaching the leaves while allowing other colours to pass unhindered. Pol Pot says the hairs are hollow tubs with ridges running along their length that trap light at UV wavelengths.

One outstanding mystery is what happens to the UV light once it becomes trapped in the filament. Pol Pot and his team have been a-contemplatin and a-meditatin on this for a while now and speculate that the tubes may be filled with water which absorbs UV light.

The hairs may even turn out to be be useful. Most UV sun screens rely on nanometre-sized particles of titanium oxide which can be difficult to handle and may not be usable for certain applications such as food packaging. Now we have an alternative: the hairs from the Alpine flower Edelweiss

Ain’t thatta bee-yoo-tiful piece of science?

Altogether now…

Edelweiss, Edelweiss
Every morning you greet me
Small and white,
clean and bright
You look happy to meet me.
Blossom of snow
may you bloom and grow,
Bloom and grow forever.
Edelweiss, Edelweiss
Bless my homeland forever.

Sniff…

Ref: arxiv.org/abs/0710.2695 : Optical Structure and Function of the White Filamentary Hair covering the
Edelweiss Bracts

The birth and death of spookytechnology

Monday, October 22nd, 2007

Quantum mechanics is seriously sexy . That’s what keeps the public coming back for more with the drool hangin from their spittle-flecked lips (repeat this often enough and it might actually come true).

Without a sexy lingo to bamboozle and baffle, physics eggs ain’t got nothing to keep people’s attention ‘cept their rugged good looks and scintillatin’ personalities.

So labs hire hampers of postdocs whose sole task is to invent new words that’ll keep the public a-gazin’ and a-gawpin at every shiny new pebble that is thrown their way.

Yer probably didn’t realise it but all the latest buzzwords were invented in this way: atomtronics, quamputing, brane theory and the ballsheet model of particle physics (OK, ah made that one up).

Normally, these postdocs are thrown a stale crust to keep em happy but otherwise kept under strict lock and key. But this week, one of em has escaped and posted a buzzword on the arXiv without permission.

Charles “Manhat” Tahan is normally locked in the bowels of the Cavendish lab in Cambridge. Let loose, he is brayin’ that physicists are a-stuttering and a-stumblin for want of a word to describe technology that depends on quantum effects that have no classical counterpart. We’re talkin things like entanglement, coherence and superposition–the so-called spooky properties of quantum physics.

Manhat Tahan says the word we need is “spookytechnology”.

Whadaya’ll think? Don’t send no shivers down my spine, I gotta tell yer. Surely ya’ll can come up with something better for this kinda strange stuff. How about quantech or ungodly gear or maniacal machinery or EPR matter or subsubstance or whatever.

And then maybe, just maybe, we can persuade Manhat Tahan to get back into the dungeon before he does some real damage.

Ref: arxiv.org/abs/0710.2537: Spookytechnology and Society

Particle physicists build time machine

Monday, October 22nd, 2007

Back to the future, here we come. A couple a eggheads over at the Steklov Mathematical Institute in Moscow, Russia, reckon that the boys at CERN have a surprise up their sleeves. They’ve gone and built themselves a time machine.

Yep, ya’ll heard right: a time machine.

The fellas at the world’s largest particle physics laboratory are currently tightening bolts and painting go-faster stripes on a shiny new accelerator called the Large Hadron Collider, which they hope to switch on sometime next year.

The plan is to hold one crazy demolition derby by smashing together protons and seeing what comes outta the wreckage. A lotta eggs have been a-ruminatin and a-speculatin on what this smash-em-up is gonna produce. On their wishlist are tiny blackholes, supersymmetric particles and the Higgs boson. It’s gonna be one helluva fireworks show.

Now Irena Aref’eva and Igor Volovich at the Steklov have pipped them all by calculatin’ that the LHC is gonna produce wormholes. Yep, and they say a proportion of these wormholes will form into traversible routes from one point in spacetime to another. In other words, these wormholes are time machines.

Irena and Igor (a lovely couple) say there is one caveat. Their thinkin’ depends on the scale of quantum gravity being very low energy: only a few TeVs and that ain’t likely.

What does it mean for us? Almost certainly nothin’. If Irena and Igor (lovely couple) are right, high energy collisions in the upper atmosphere will have been producing time machines since time immemorial. Our upper atmosphere is probably filled with em’. These time machines are also so short-lived that we can only see them by the signature they leave behind when they annihilate.

Time machines in the atmosphere? Perhaps that explains why we get so many repeats of Star Trek on terrestrial television.

Ya’ll start polishing ya Deloreans, y’hear?

Ref: arxiv.org/abs/0710.2696: Time Machine at the LHC