Archive for January, 2009

I know why the phase-locked wineglass sings

Thursday, January 8th, 2009


Here’s a neat party trick to impress your friends.

Rub your finger around the rim of a wineglass and friction causes it, and any liquid it contains, to oscillate. When this vibration produces an audible pure tone, the wine glass is said to “sing”.

Now Ana Karina Ramos Musalem and pals at the Weizmann Institute of Science in Israel have shown how to couple one singing wineglass to another so the second wineglass sings without anybody touching it.

The trick is to place both wineglasses in a sink of water (without the water overflowing into the glasses).  Rubbing one so that it sings should make the other sing too. This  phenomenon is known as phase-locking and is also responsible for populations of crickets that chirp together and fireflies that flash together.

Phase locking depends on the strength of the coupling. This is greatest when the glasses are closer together and when their resonant frequency is similar. So if you run into trouble, try moving them nearer to each other and matching their frequencies by changing the amount of water in each glass.

Then watch as jaws drop around the dinner table.

(With apologies to Maya Angelou.)

Ref: Phase locking between two singing wineglasses

Next generation search engines could rank sites by “talent”

Wednesday, January 7th, 2009


How will the next generation of search engines outperform Google’s all-conquering Pagerank algorithm?

One route might be to hire Vwani Roychowdhury at the University of California, Los Angeles and his buddies who have found a fascinating new way to tackle the problem of website rankings.


First “movie” of fruitfly gene network aging

Tuesday, January 6th, 2009


One of the major goals in biology is to reconstruct the complex genetic networks that operate inside cells, and to “film” how these networks evolve during the course of an organism’s development.

Today, Eric Xing and buddies at Carnegie Mellon University in Pittsburgh claim to have worked out how the way patterns of gene expression change in fruitflies over the course of their entire development. That’s a world first and no mean feat to boot.


Why Saturn’s rings are so sharp

Monday, January 5th, 2009


Here’s a conundrum for you: why do Saturn’s rings have such sharp edges?

It’s question that has puzzled planetary scientists for many years. Various ideas have been put forward but none adequately explain the structure we see today.

To understand just  how sharp the edges are consider this: pictures from Cassini show that the density of particles at the edge of the outer B ring, for example, drops by an order of magnitude over a distance of only 10 metres or so.

That’s extraordinary given that the ring is 25580 kilometres wide.


Flash ‘n’ cash

Saturday, January 3rd, 2009

The best of the rest from the physics arXiv:

The Hydrodynamics of Swimming Microorganisms

Trapping Ccold Atoms Using Surface-Grown Carbon Nanotubes

Solution of Peter Winkler’s Pizza Problem

Innovative In Silico Approaches to Address Avian Flu Using Grid Technology

Quantum Generalized Reed-Solomon Codes: Unified Framework for Quantum MDS Codes

First stars “powered by dark matter”

Friday, January 2nd, 2009


“95% of the mass in galaxies and clusters of galaxies is in the form of an unknown type of dark matter,” say Katherine Freese at the University of Michigan, Ann Arbor, and buddies. What effect might this huge amount of stuff have on star formation?

The answer according to these guys is astounding. In the early universe, the first stars would have been powered by dark matter.

Here’s the thinking: the concentration of dark matter at that time would have been extremely high meaning that any ordinary stars would naturally contain large amounts of dark matter. Freese and co have calculated the effect of this stuff and say tit would have radically altered the evolution of these stars forming so-called “dark stars”.

Dark stars would have been driven by the annihilation of dark matter particles releasing heat but only in stars larger than 400 solar masses. That turns out to be quite feasible since stars containing smaller amounts of dark matter would naturally grow as they swept up dark matter from nearby space.

When the dark matter runs out, they simply collapse to form black holes

Interestingly, we should soon be able to to see these stars with forthcoming generations of telescopes. And if they are found, that would be further proof of the existence of dark matter.

Keep ’em peeled!

Ref: Dark Stars: the First Stars in the Universe May be Powered by Dark Matter Heating

Flashback: First test of exotic space thruster ends in explosion

Thursday, January 1st, 2009

Over the holiday period the arXivblog is re-running the most popular posts from 2008

23 May 2008: First test of exotic space thruster ends in explosion

In 2006, Mason Peck at Cornell University in Ithaca dreamt up with an entirely new way to control satellites orbiting planets that have a magnetic field. The idea is based on the Lorentz force: that a charged particle moving through a magnetic field experiences a force perpendicular to both its velocity and the field.

Read on…