10 years of the Physics arXiv Blog: 2008

August 12th, 2017
The Physics arXiv Blog is 10 years old today. Over the next few days, we’ll be celebrating by publishing links to the top stories from each year of its existence.
Today, 2007.

The Physics arXiv Blog is 10 years old today. Over the next few days, we’ll be celebrating by publishing links to the top stories from each year of its existence.

Today, 2008.

Cloaking objects at a distance
Quantum communication: when 0 + 0 is not equal to 0
Do nuclear decay rates depend on our distance from the sun?
Feline ballistics
First superheavy element found in nature
Rubik’s cube proof cut to 25 moves
First test of exotic space thruster ends in explosion
Forget black holes, could the LHC trigger a “Bose supernova”?

10 years of the Physics arXiv Blog: 2007

August 11th, 2017

The Physics arXiv Blog is 10 years old today. Over the next few days, we’ll be celebrating by publishing links to the top stories from each year of its existence.

Today, 2007. Enjoy!

The incredible galactic foxtrot

Invasion of the jivin’ nanoshrooms

Breaking the Netflix prize dataset

More changes to the Physics arXiv Blog

September 14th, 2013

From September 2013, The Physics arXiv Blog is moving to Medium.com. Keep up to date with the latest ideas in physics and astronomy at: https://medium.com/the-physics-arxiv-blog

For those of you more interested in technology, I’ll be covering this at Technology Review in a blog called “Emerging Technology from the arXiv” at:  http://www.technologyreview.com/contributor/emerging-technology-from-the-arxiv/

Follow the headlines on Twitter at: https://twitter.com/arxivblog

See you there!

Important changes to the Physics arXiv Blog

March 15th, 2009

From Monday 13 March, the Physics arXiv Blog will appear exclusively on technologyreview.com

This is an exciting move for the blog because it will allow me to concentrate on reading and filtering the fantastic ideas on the arXiv while leaving the increasingly onerous task of administering a popular website to the talented tech guys at TR.

If all goes smoothly, your RSS feeds and email subscriptions will be transferred seemlessly to our new hosts. And if it doesn’t go smoothly, let us know. We’ll be working hard to iron out any teething problems as soon as we can.

The new URL is:  arxivblog.technologyreview.com

I hope you’ll join me.


Chops ‘n’ changes

March 14th, 2009

The best of the rest from the Physics arXiv this week:

A Short History of Hindu Astronomy & Ephemeris

Time Asymmetries in Extensive air Showers: A Novel Method to Identify UHECR species

The Digital Restoration of Da Vinci’s Sketches

Physics of the Shannon Limits

Astronomy, Topography and Dynastic History in the Age of the Pyramids

The secret of world class putting

March 13th, 2009


Watch professional golfers putt and you’ll eventually notice three common features about their style,  says Robert Grober, an expert on the physics of golf at the Yale University.

First, the putter head always moves at a constant speed when it hits the ball. Second, the length of time the putting stroke takes has little impact on the speed of the ball (and therefore the length of the putt). And finally, a professional golfer’s backswing takes about twice as long as the  downswing.

Grober has used these observations to construct a mathematical model of a putting swing and to explore other properties of such a system.

It turns out that the model that best accounts for this behaviour is a simple pendulum driven at twice its resonant frequency.

That explains a number of other observations about professional golfers, says Grober. For example, a common putting tip is that longer backswings equate to longer putts. This model has exactly this characteristic: the length of the backswing is proportional to the speed of the club at impact.

It is also relatively straightforward to get a sense of the tempo of the required putt by swinging the club back and forth in resonance, like a pendulum. The duration of the actual stroke is exactly half the length of the putter cycle (i.e. from the address position moving backward, to the address position moving forward). “In fact, one often observes golfers instinctively doing this before they hit a putt,” says Grober.

So now the secret is out. Make a careful note for next time you’re out on the links.

Ref: arxiv.org/abs/0903.1762: Resonance in Putting

How to narrow the search for ET

March 11th, 2009


The search for extraterrestrial intelligence  needs all the help it can get. Depending on who you listen to, the chances of us spotting an intelligent technological society vary from an almost certainty to practically zero.

The trouble is the sheer size of the search. The Milky Way contains around 10^10 sun-like stars, any one of which may have a planet whose citizens are at this very moment pointing their beady eyes  or antennae in our direction.

But if we want to peer back, in which direction should we look?

Shmuel Nussinov at Tel Aviv University in Israel makes a thoroughly sensible suggestion of narrowing the search: why not look only towards stars that have a reasonable chance of having seen Earth?

We know of several ways to detect planets aroudn other stars but only one that might reveal an Earth-like body and that is to look for changes in brightness that are the signature of a transiting planet.

Earth passes in front of the sun for 13 hours once a year, dimming it by 77 parts per million. Venus transits for 11 hours every 7 months with even less dimming. Mars gives  three-fold weaker eclipse every 1.9 years and Mercury dimming is ten times weaker than Earth’s but occurs four times a year.

Only stars within a narrow angle of the ecliptic will be able to detect these transits. And so only civilisations on planets around these stars could possibly be aware of Earth might be broadcasting our way.

Common sense really.

Ref: arxiv.org/abs/0903.1628: Some Comments on Possible Preferred Directions for the SETI Search

Visible light metamaterials on the cheap

March 10th, 2009


Only a couple of years, more than a few physicists doubted that it would ever be possible to build decent metamaterials with a negative refractive index for visible light.

Metamaterials have bulk properties that depend on the structure of their components rather than the bulk properties of the materials from which they are made. The thinking is that they can make light do all kinds of things that are no possible in naturally occurring stuff such as bending light backwards and imparting it with a reverse Doppler shift.

Metamaterials that bend microwaves backwards are straightforward to make: it’s just a question of arranging components, such as conducting wires and split rings, in a periodic 3D array on a centimetre scale.

It’s easy to think that similar structures would work for visible light were they shrunk to the nanometre scale. But, as many physicists have pointed out, the electrical properties of conducting metals do not scale with wavelength in quite the same way. Instead of transmitting light, many of these designs would be opaque to visible light.

Some people said it may never be possible to make efficient negative refraction index metamaterials for visible light. Others, who were a little more optimistic, were vindicated  last August, Xiang Zhang at the University of California, Berkeley, revealed that a periodic array of parallel silver nanowires embedded in aluminium oxide worked perfectly well as metamaterial with negative refractive index for visible light.

Now Akhlesh Lakhtakia  at Pennsylvania State University and pals have worked out how to make sheets of this stuff using a vapour deposition technique that is common in the optical industry.

So in a couple of years, we’ve gone from having little prospect of a negative refractive index material for visible light to a way of making sheets of it at extremely low cost.

That’ll make negative refractive index materials available to almost anybody who wants to play with them. Expect to see some ingenious applications in the coming months.

Ref: arxiv.org/abs/0903.1177: Vapor-deposited thin Films with Negative refractive Index in the Visible Regime

The fundamental patterns of traffic flow

March 9th, 2009


Take up the study of earthquakes, volcanoes or stock markets and the goal, whether voiced or not, is to find a way to predict future “events” in your field. In that sense, these guys have something in common with scientists who study traffic jams.

The difference is that traffic experts might one day reach their goal. The complexity of traffic flow, while  awe inspiring, may well be fundamentally different  to the complexity of stock markets and earthquake events.

At least that’s how Dirk Helbing at the Institute for Transport & Economics at the Technical University of Dresden in Germany, and his buddies see it.

Helbing says that one long standing dream of traffic experts is to identify the fundamental patterns of traffic congestion from which all other flows can be derived,  a kind of periodic table of traffic flows.

Now he thinks he has found it: a set of fundamental patterns of traffic flow that when identified on a particular road, can be used to create a phase diagram of future traffic states.

The phase diagrams can then be used to make forecasts about the way in which the flow might evolve.

That’ll be handy. But only if it’s then possible to do something to prevent the congestion. And that may be the trickiest problem of all.

Ref: arxiv.org/abs/0903.0929: Theoretical vs. Empirical Classification and Prediction of Congested Traffic States

Sheets ‘n’ pillows

March 7th, 2009

The best of the rest from the physics arXiv this week:

Alkali-Helium Snowball Complexes Formed on Helium Nanodroplets

Holo-Television System with a Single Plane

Towards a Quantum Fluid Mechanical Theory of Turbulence

Social Networking: An Astronomer’s Field Guide

Single-Particle Foucault Oscillator Powered by Laser