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The concept of time as a way to measure the duration of events is not only deeply intuitive, it also plays an important role in our mathematical descriptions of physical systems. For instance, we define an object's speed as its displacement per a given time. But some researchers theorize that this Newtonian idea of time as an absolute quantity that flows on its own, along with the idea that time is the fourth dimension of spacetime, are incorrect. They propose to replace these concepts of time with a view that corresponds more accurately to the physical world: time as a measure of the numerical order of change.

While most people know that the shortest distance between two points is a straight line, this concept is proving even truer in the world of stock trading. In a world where buying low and selling high means all the difference, racing the speed of light between to different financial markets can mean greater profit.

David Keith is Gordon McKay Professor of Applied Physics at Harvard's School of Engineering and Applied Sciences, and Professor of Public Policy at Harvard Kennedy School. The award-winning scientist, who was named one of TIME magazine's Heroes of the Environment in 2009, has worked near the interface of climate science, energy technology, and public policy for twenty years. He divides his time between Boston and Calgary, where he serves as president of Carbon Engineering-a start-up company developing industrial-scale technologies for capture of CO2 from ambient air. Here, Keith answers questions about his research and ideas for reducing climate change using innovative and sometimes controversial methods.

Applications on modern wireless devices make demands on data rate and connectivity far beyond anything experienced in the past. One way to meet these stringent requirements is to give the device multiple antennas or multiple-input multiple-output (MIMO) technology. The problem of physically accommodating these additional antennas in the latest consumer products is investigated in new research from the University of Bristol.

The diversity of the biological world is astounding. How do new species arise? In the traditional view, most speciation events occur under special circumstances, when a physical barrier arises and divides a population into groups that can no longer interbreed. The populations diverge genetically and eventually can't interbreed even if the barrier disappears.

In this month's Physics World, Jason Reese, Weir Professor of Thermodynamics and Fluid Mechanics at the University of Strathclyde, describes the role that carbon nanotubes (CNTs) could play in the desalination of water, providing a possible solution to the problem of the world's ever-growing population demanding more and more fresh drinking water.

ew research from the UK's National Physical Laboratory (NPL) is helping Duvas Technologies Ltd (Duvas) to develop improved air quality monitoring instrumentation. Currently over 1bn people a year suffer from respiratory disease associated with pollution, and according to the World Health Organisation, over 3m a year die from its effects. Duvas is planning to help provide technology to understand and address this problem.

In a recent study published in Nature Climate Change, Dr. Ulrike Burkhardt and Dr. Bernd Karcher from the Institute for Atmospheric Physics at the German Aerospace Centre show that the contrails created by airplanes are contributing more to global warming that all the CO2 that has been caused by the entire 108 years of airplane flight.

The ants may go marching one by one, but they end up forming a superstructure of thousands -- and together they can form a raft that stretches the boundaries of the laws of physics, according to new research released today.

A team of researchers, led by Dr. Yi Cui, of Stanford and Dr. Bruce Logan from Penn State University have succeeded in developing an entropy battery that pulls energy from the imbalance of salinity in fresh water and seawater. Their paper, published in Nano Letters, describes a deceptively simple process whereby an entropy battery is used to capture the energy that is naturally released when river water flows into the sea.

By taking advantage of the properties of periodic systems, physicists have described how to efficiently time-reverse ultrashort electromagnetic pulses. Since a time-reversed pulse evolves as if time runs backwards, time reversal eliminates any distortions or scattering that occurred at earlier times, regardless of the medium the pulse has propagated through.

Flat out wrong. That's what a team of Duke researchers has discovered, much to its surprise, about a long-accepted explanation of how nuclei collide to produce charged particles for electricity - a process receiving intense interest lately from scientists, entrepreneurs and policy makers in the wake of Japan's nuclear crisis.