Dan Falk, contributor


When science was young, the experiments were simple and the breakthroughs came easily - or so it seems in hindsight. Think of Galileo rolling a ball down an inclined plane, or aiming a simple tube, with a lens at each end, at the night sky. Or picture Michael Faraday discovering electromagnetic induction just by tinkering with a battery, an iron ring and some coils of wire.


Times have changed, and these days it takes a lot more work to shift a paradigm. For one thing, ground-breaking discoveries in physics are now typically made by teams rather than individuals. And, as we strive to peer more deeply into space or further inwards to probe the make-up of matter, we have been forced to build larger and more complex instruments. The scale of experiments has grown from table-top-sized to building-sized - even city-sized. Moreover, these experiments are often located in some of the remotest places on Earth. From these isolated outposts, men and women work under harsh conditions to collect the data that will, perhaps, change the way we conceive of the universe.




Image: NASA balloon over Antarctica, NASA


Anil Ananthaswamy, a science journalist and consultant for New Scientist, has been to more of these lonely locations than just about anyone, and in The Edge of Physics he weaves a remarkable narrative that combines fundamental physics with high adventure. The story takes him from the giant telescopes atop the Chilean Andes to a dark-matter detector deep in a defunct Minnesota iron mine, to the neutrino observatory known as IceCube, whose optical sensors have been placed up to 2.5 kilometres below the surface of the perpetually frozen South Pole.


Check out Anil Ananthaswamy's video of his travels to physics' most extreme sites

Ananthaswamy carefully explains the science relevant to each of these sites, dipping into history where needed to flesh out the background. Ultimately, though, it is the remote, unforgiving locations that anchor the story. "These magnificent telescopes and detectors can work only in the most extreme settings," he writes. "Their surreal environments are the unsung characters in this unfolding story - venues rarely appreciated and often overlooked."


The two sites that bookend the story are, perhaps, the most familiar. We begin at the mount Wilson observatory in California, where Edwin Hubble first deduced that the universe is expanding. At the time, mount Wilson was a pristine, dark-sky site from where astronomers could probe the heavens. Today it lies at the edge of Los Angeles's urban sprawl. The penultimate chapter finds Ananthaswamy at the Large Hadron Collider, built in a tunnel that straddles the France-Switzerland border. The LHC has received enough press in the past few years for it to have become practically a household name; even so, as the author reminds us, it is the largest single science experiment ever devised by our species, and if we are lucky it may tell us if the universe is made of tiny strings or contains hidden dimensions.




Image: Very Large Telescope in Chile, ESO/G.Hüdepohl


Readers might be less familiar with the Baikal Deep Underwater Neutrino Telescope, which rests in the frigid waters of Lake Baikal in Siberia, looking for meagre flashes of light that tell of collisions between neutrinos and molecules of water. The observatory is run on a shoestring, with only one luxury: the traditional Russian banya, or sauna, where "naked men sit in an outbuilding, chuck water on hot stones to raise steam, and beat each other with leafy twigs and branches of birch".

The Edge of Physics is really two stories in one: a travelogue that takes the reader to some of the most desolate places on our planet, and a survey of the most urgent problems in physics and cosmology, from dark energy and string theory to multiple universes. Ananthaswamy is a worthy guide for both journeys.

Book Information:
The Edge of Physics by Anil Ananthaswamy
Houghton Mifflin Harcourt/Duckworth, $25/£16.99

Male sperm count has dropped dramatically over the past 50 years (~50% in some areas) and one of the prime suspects is estrogen like compounds, such as the pesticide atrazine, that have been introduced into the environment. Atrazine is one of the most commonly applied agricultural pesticides in the world (and, curiously, male sperm count has dropped more in agricultural than in metropolitan areas). Hays et al now show that at levels of only 2.5 parts per billion it can completely feminize amphibian males.

Here's our weekly look at your pictures and this time we asked you for photographs on the theme of impressions.

We received more than 240 entries this time, so once again I offer my thanks to all of you who submitted work.

You can see the ones I have selected here.

I hope you enjoy looking at the pictures and if you have any comments to make, you can do so below.

If your picture didn't make this week's selection, why not send us something for next week?

The new theme is "balance".

Interpret this in any way you see fit and send your pictures to us at yourpics@bbc.co.uk or upload them directly from your computer.

Please include the word "balance" in the subject line of your message.

The deadline is midnight GMT Tuesday 16 March 2010, and remember to add your name and a caption: who, what, where and when should be enough, though the more details you give, the better your chance of being selected.

We will publish a selection of your photos this time next week.

You can now see a list of the next four themes on this page which will be updated each week.

Files should be sent as JPEGs. They shouldn't be larger than 10Mb and ideally much smaller: around 1Mb is fine, or you can resize your pictures to 1,000 pixels across.

Please see our terms and conditions, but remember that the copyright remains with you. The pictures will only be used by the BBC for the purposes of this project. Finally, when taking photos, please do not endanger yourself or others, take unnecessary risks or infringe any laws.