physics
Thursday 25 September 2014
Fuel Free Aircraft
Aircraft designer Titan Aerospace unveiled in August 2013 its Solara 50 and 60 unmanned aircrafts, the world’s first atmospheric satellites powered by the sun with a mission range of over 4 million kilometres.
An atmospheric satellite is a drone that can conduct most of the operations of an orbital satellite, but is much cheaper and more versatile.
Among the applications of a Solara aircraft there are disaster recovery, weather monitoring, communications relay, oceanographic research and earth imaging.
According to reports, Solara 50 and 60 can be launched at night using power from internal battery banks.
When the sun rises, the solar panels covering the crafts’ wings and tails, store enough energy to allow them ascend to a position of 20 km above the sea level and to stay aloft continuously for five years, without ever having to land and refuel.
The aircrafts will operate in an atmospheric sweet spot known as the tropopause where winds are generally less than 5 knots.
Despite its massive dimensions, Solara 50 only weighs about 160 kg, and can carry a payload of 32 kg. According to reports, differently from satellites, it is possible to get the payload back at the end of its five years endurance.
As for the speed, Solara 50 can travel at 104 kilometres an hour (about 64 MPH).
According to reports, smaller versions of Solara have already flown, and Titan Aerospace is planning to start selling operational systems in less than a year which opens up possibilities like regional internet or a version of Google Maps with real-time images.
Ultimate Pixels Camera
A quantum effect in which excited atoms team up to emit an enhanced pulse of light can be turned on its head to create 'superabsorbing' systems that could make the 'ultimate camera pixel'.
'Superradiance', a phenomenon where a group of atoms charged up with energy act collectively to release a far more intense pulse of light than they would individually, is well-known to physicists. In theory the effect can be reversed to create a device that draws in light ultra-efficiently. This could be revolutionary for devices ranging from digital cameras to solar cells. But there's a problem: the advantage of this quantum effect is strongest when the atoms are already 50% charged -- and then the system would rather release its energy back as light than absorb more.
Now a team led by Oxford University theorists believes it has found the solution to this seemingly fundamental problem. Part of the answer came from biology. 'I was inspired to study ring molecules, because they are what plants use in photosynthesis to extract energy from the Sun,' said Kieran Higgins of Oxford University's Department of Materials, who led the work. 'What we then discovered is that we should be able to go beyond nature's achievement and create a 'quantum superabsorber'.'
A report of the research is published in Nature Communications.
At the core of the new design is a molecular ring, which is charged to 50% by a laser pulse in order to reach the ideal superabsorbing state. 'Now we need to keep it in that condition' notes Kieran. For this the team propose exploiting a key property of the ring structure: each time it absorbs a photon, it becomes receptive to photons of a slightly higher energy. Charging the device is like climbing a ladder whose rungs are increasingly widely spaced.
'Let's say it starts by absorbing red light from the laser,' said Kieran, 'once it is charged to 50% it now has an appetite for yellow photons, which are higher energy. And we'd like it to absorb new yellow photons, but NOT to emit the stored red photons.' This can be achieved by embedding the device into a special crystal that suppresses red light: it makes it harder for the ring to release its existing energy, so trapping it in the 50% charged state.
The final ingredient of the design is a molecular 'wire' that draws off the energy of newly absorbed photons. 'If you built a system with a capacity of 100 energy units the idea would be to 'half-charge' it to 50 units, and the wire would then 'harvest' every unit over 50,' said Kieran. 'It's like an overflow pipe in plumbing -- it is engineered to take the energy level down to 50, but no lower.' This means that the device can handle the absorption of many photons in quick succession when it is exposed to a bright source, but in the dark it will simply sit in the superabsorbing state and efficiently grab any rare passing photon.
Eventually, harvesting sunlight in a highly-efficient way might one day be possible using superabsorbing systems based on our design, but a more immediate application would be building an extremely sensitive light sensor that could form the basis of new camera technology,' Professor Simon Benjamin, a co-author of the report, explains. 'A camera sensor harnessing the power of our superbsorbing rings would have very high time and spatial resolution. And it could pave the way for camera technology that would exceed the human eye's ability to see clearly both in dark conditions and in bright sunlight.'
The research team included scientists from Oxford University, National University of Singapore, University of St Andrews, and the University of Queensland. The work was supported by the UK's Engineering and Physical Sciences Research Council (EPSRC).
Pumping of star Brightness, Gravitational waves
Gravitational waves are hard to observe, but they could have a dramatic effect on stars that we could possibly detect.
In a new paper published by the journal Monthly Notices of the Royal Astronomical Society, researchers suggest that an overlooked component of Einstein’s famous theory of general relativity may be responsible for propagating gravitational waves giving stars a short boost in energy output.
“It’s pretty cool that a hundred years after Einstein proposed this theory, we’re still finding hidden gems,” said Barry McKernan, a research associate in the American Museum of Natural History’s Department of Astrophysics and the Kavli Institute for Theoretical Physics.
Gravitational waves are ripples in space-time and act like ripples on the surface of a pond. Generated massive objects moving through or colliding in space, the universe is thought to be buzzing with gravitational waves.
Gravitational wave experiments such as the Laser Interferometer Gravitational-Wave Observatory (LIGO) have set out to detect the slight change in laser phase as a gravitational wave slightly alters space-time, but have yet to turn up definitive evidence of these ripples passing through local space.
There are, however, indirect means to detect gravitational waves. For example, astronomers have detected the slight slowdown of orbiting white dwarf star binaries; as the stars orbit one another, they stir up space-time, producing gravitational waves. These waves carry energy away from the binary system, thus slowing their orbits down.
In this new study, another indirect means of detection has been proposed: if a star is oscillating at the same frequency as a gravitational wave propagating through it, the two may interact and the gravitational wave may dump its energy into the star, giving it a transient boost in brightness.
“It’s like if you have a spring that’s vibrating at a particular frequency and you hit it at the same frequency, you’ll make the oscillation stronger,” said McKernan. “The same thing applies with gravitational waves.”
This has led to some interesting ideas.
In the case of two colliding black holes for example, the two masses may orbit one another very rapidly, slowly getting closer and closer before they merge. During this time, the orbiting black holes may generate gravitational waves of increasing frequency as their orbital distance decreases. As different gravitational wave frequencies will interact with stars of different oscillation frequencies at different times, one could imagine a cluster of stars with different masses (and therefore different oscillation frequencies) becoming “pumped up” and brightening at different times as the black holes’ emitted waves shift in frequency over time.
This would be an interesting observational campaign to see stars inexplicably brighten and then dim over time. We may eventually derive a method to detect these transient brightenings and then map the propagation of gravitational waves throughout star clusters. Perhaps, as we develop sophisticated observational techniques, we could also watch slight stellar brightenings in neighboring galaxies ripple through galactic disks over the many years it would take for the waves to travel (gravitational waves travel at the speed of light).
Also, if we could find a way of directly detecting gravitational waves, we may observe a counter-intuitive phenomenon: gravitational wave eclipses. Gravitational waves originating from behind the sun may become absorbed by our nearest star, causing them to be blocked from being detected on Earth. Normally when we think of eclipses, it’s usually an object blocking the light from the sun, but in this case it would be the sun blocking gravitational waves.
The next step of the research will be to understand how, practically, a stellar brightening caused by gravitational waves may be detected — a feat that will likely be steeped in statistics and more advanced astronomical techniques than we currently use.
Monday 22 September 2014
Physics Books
http://1drv.ms/1sUBzPZ
lets sahre some new physics books for fellow students all over the world
lets sahre some new physics books for fellow students all over the world
Saturday 20 September 2014
Physics Books
Physics books are usually difficult to buy online or they are very expensive. Here I have collection of some physics books.
http://1drv.ms/XSO9GY
Monday 15 September 2014
The history of thermodynamics as a scientific discipline generally begins with Otto von Guericke who, in 1650, built and designed the world's first vacuum pump and demonstrated a vacuum using his Magdeburg hemispheres. Guericke was driven to make a vacuum in order to disprove Aristotle's long-held supposition that 'nature abhors a vacuum'. Shortly after Guericke, the physicist and chemist
Robert Boyle had learned of Guericke's designs and, in 1656, in coordination with scientist Robert Hooke, built an air pump. Using this pump, Boyle and Hooke noticed a correlation between pressure,temperature, and volume. In time,Boyle's Law was formulated, stating that for a gas at constant temperature, its pressure and volume are inversely proportional. In 1679, based on these concepts, an associate of Boyle's named Denis Papin built a steam
digester, which was a closed vessel with a tightly fitting lid that confined steam until a high pressure was generated. Later designs implemented a steam release valve that kept the machine from exploding. By watching the valve rhythmically move up and down, Papin conceived of the idea of a piston and a cylinder engine. He did not, however, follow through with his design. Nevertheless, in 1697, based on Papin's designs, engineer Thomas Savery built the first engine, followed by Thomas Newcomen in 1712. Although these early engines were crude and inefficient, they attracted the attention of the leading scientists of the time. The concepts of heat capacity and latent heat, which were necessary for development of thermodynamics, were developed by professor Joseph Black at the University of Glasgow, where James Watt worked as an instrument maker. Watt consulted with Black on tests of his steam engine, but it was Watt who conceived the idea of the external condenser, greatly raising the steam engine's efficiency.[27] Drawing on all the previous work led Sadi Carnot, the "father of thermodynamics", to publish Reflections on the Motive Power of Fire (1824), a discourse on heat, power, energy and engine efficiency. The paper outlined the basic energetic relations between the Carnot engine, the Carnot cycle, and motive power. It marked the start of thermodynamics as a modern science. The first thermodynamic textbook was written in 1859 by William Rankine, originally trained as a physicist and a civil and mechanical engineering professor at the University of Glasgow. The first and second laws of thermodynamics emerged simultaneously in the 1850s, primarily out of the works of William Rankine, Rudolf Clausius, and William Thomson (Lord Kelvin). The foundations of statistical thermodynamics were set out by physicists such as James Clerk Maxwell, Ludwig Boltzmann, Max Planck, Rudolf Clausius and J. Willard Gibbs.From 1873 to '76, the American mathematical physicist Josiah Willard Gibbs published a series of three papers, the most famous being "On the equilibrium of heterogeneous substances". Gibbs showed how thermodynamic processes, including chemical reactions, could be graphically analyzed. By studying the energy, entropy, volume, chemical potential, temperature and pressure of the thermodynamic system, one can determine if a process would occur spontaneously. Chemical thermodynamics was further developed by Pierre Duhem, Gilbert N. Lewis, Merle Randall, and E. A. Guggenheim, who applied the mathematical methods of Gibbs.
Robert Boyle had learned of Guericke's designs and, in 1656, in coordination with scientist Robert Hooke, built an air pump. Using this pump, Boyle and Hooke noticed a correlation between pressure,temperature, and volume. In time,Boyle's Law was formulated, stating that for a gas at constant temperature, its pressure and volume are inversely proportional. In 1679, based on these concepts, an associate of Boyle's named Denis Papin built a steam
digester, which was a closed vessel with a tightly fitting lid that confined steam until a high pressure was generated. Later designs implemented a steam release valve that kept the machine from exploding. By watching the valve rhythmically move up and down, Papin conceived of the idea of a piston and a cylinder engine. He did not, however, follow through with his design. Nevertheless, in 1697, based on Papin's designs, engineer Thomas Savery built the first engine, followed by Thomas Newcomen in 1712. Although these early engines were crude and inefficient, they attracted the attention of the leading scientists of the time. The concepts of heat capacity and latent heat, which were necessary for development of thermodynamics, were developed by professor Joseph Black at the University of Glasgow, where James Watt worked as an instrument maker. Watt consulted with Black on tests of his steam engine, but it was Watt who conceived the idea of the external condenser, greatly raising the steam engine's efficiency.[27] Drawing on all the previous work led Sadi Carnot, the "father of thermodynamics", to publish Reflections on the Motive Power of Fire (1824), a discourse on heat, power, energy and engine efficiency. The paper outlined the basic energetic relations between the Carnot engine, the Carnot cycle, and motive power. It marked the start of thermodynamics as a modern science. The first thermodynamic textbook was written in 1859 by William Rankine, originally trained as a physicist and a civil and mechanical engineering professor at the University of Glasgow. The first and second laws of thermodynamics emerged simultaneously in the 1850s, primarily out of the works of William Rankine, Rudolf Clausius, and William Thomson (Lord Kelvin). The foundations of statistical thermodynamics were set out by physicists such as James Clerk Maxwell, Ludwig Boltzmann, Max Planck, Rudolf Clausius and J. Willard Gibbs.From 1873 to '76, the American mathematical physicist Josiah Willard Gibbs published a series of three papers, the most famous being "On the equilibrium of heterogeneous substances". Gibbs showed how thermodynamic processes, including chemical reactions, could be graphically analyzed. By studying the energy, entropy, volume, chemical potential, temperature and pressure of the thermodynamic system, one can determine if a process would occur spontaneously. Chemical thermodynamics was further developed by Pierre Duhem, Gilbert N. Lewis, Merle Randall, and E. A. Guggenheim, who applied the mathematical methods of Gibbs.
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