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20 jun 2005
17 jun 2005
No paradox for time travellers
THE laws of physics seem to permit time travel, and with it, paradoxical situations such as the possibility that people could go back in time to prevent their own birth. But it turns out that such paradoxes may be ruled out by the weirdness inherent in laws of quantum physics.
Some solutions to the equations of Einstein's general theory of relativity lead to situations in which space-time curves back on itself, theoretically allowing travellers to loop back in time and meet younger versions of themselves. Because such time travel sets up paradoxes, many researchers suspect that some physical constraints must make time travel impossible. Now, physicists Daniel Greenberger of the City University of New York and Karl Svozil of the Vienna University of Technology in Austria have shown that the most basic features of quantum theory may ensure that time travellers could never alter the past, even if they are able to go back in time.
The constraint arises from a quantum object's ability to behave like a wave. Quantum objects split their existence into multiple component waves, each following a distinct path through space-time. Ultimately, an object is usually most likely to end up in places where its component waves recombine, or "interfere", constructively, with the peaks and troughs of the waves lined up, say. The object is unlikely to be in places where the components interfere destructively, and cancel each other out.
Quantum theory allows time travel because nothing prevents the waves from going back in time. When Greenberger and Svozil analysed what happens when these component waves flow into the past, they found that the paradoxes implied by Einstein's equations never arise. Waves that travel back in time interfere destructively, thus preventing anything from happening differently from that which has already taken place (www.arxiv.org/quant-ph/0506027). "If you travel into the past quantum mechanically, you would only see those alternatives consistent with the world you left behind you," says Greenberger.
"This is a very nice idea," says physicist Avshalom Elitzur of the Weizmann Institute in Rehovot, Israel, who also suggests that further work in the area could help to clarify the nature of time itself. "Time is a very mysterious thing."
Some solutions to the equations of Einstein's general theory of relativity lead to situations in which space-time curves back on itself, theoretically allowing travellers to loop back in time and meet younger versions of themselves. Because such time travel sets up paradoxes, many researchers suspect that some physical constraints must make time travel impossible. Now, physicists Daniel Greenberger of the City University of New York and Karl Svozil of the Vienna University of Technology in Austria have shown that the most basic features of quantum theory may ensure that time travellers could never alter the past, even if they are able to go back in time.
The constraint arises from a quantum object's ability to behave like a wave. Quantum objects split their existence into multiple component waves, each following a distinct path through space-time. Ultimately, an object is usually most likely to end up in places where its component waves recombine, or "interfere", constructively, with the peaks and troughs of the waves lined up, say. The object is unlikely to be in places where the components interfere destructively, and cancel each other out.
Quantum theory allows time travel because nothing prevents the waves from going back in time. When Greenberger and Svozil analysed what happens when these component waves flow into the past, they found that the paradoxes implied by Einstein's equations never arise. Waves that travel back in time interfere destructively, thus preventing anything from happening differently from that which has already taken place (www.arxiv.org/quant-ph/0506027). "If you travel into the past quantum mechanically, you would only see those alternatives consistent with the world you left behind you," says Greenberger.
"This is a very nice idea," says physicist Avshalom Elitzur of the Weizmann Institute in Rehovot, Israel, who also suggests that further work in the area could help to clarify the nature of time itself. "Time is a very mysterious thing."
Los amigos ayudan a vivir más
BBC.co.uk
Los buenos amigos son aquellos que están siempre allí, para compartir los buenos momentos y para dar una mano cuando se los necesita. También están allí para ayudar a vivir más años.
Los buenos amigos son aquellos que están siempre allí, para compartir los buenos momentos y para dar una mano cuando se los necesita. También están allí para ayudar a vivir más años.
15 jun 2005
Entrenamiento para el cerebro
BBC.co.uk
Un estudio científico sugiere que las respuestas básicas e involuntarias del cerebro pueden ser anuladas.
A esta conclusión llegaron los expertos de las universidades de Queensland y California luego de estudiar las reacciones visuales de 76 monjes budistas tibetanos con experiencia en meditación.
Un estudio científico sugiere que las respuestas básicas e involuntarias del cerebro pueden ser anuladas.
A esta conclusión llegaron los expertos de las universidades de Queensland y California luego de estudiar las reacciones visuales de 76 monjes budistas tibetanos con experiencia en meditación.
13 jun 2005
7 jun 2005
REVOLUTIONARY UNDERWATER BREATHING SYSTEM
LIKE A FISH –
REVOLUTIONARY UNDERWATER BREATHING SYSTEM
An Israeli Inventor has developed a breathing apparatus that will allow breathing underwater without the assistance of oxygen tanks. This new invention will use the relatively small amounts of air that already exist in water to supply oxygen to both scuba divers and submarines. The invention has already captured the interest of most major diving manufacturers as well as the Israeli Navy.
The idea of breathing underwater without cumbersome oxygen tanks has been the dream of science fiction writers for many years. In George Lucas’ movie "The Phantom Menace", Obi-Wan whips out a little Jedi underwater breathing apparatus and dives in. As things tend to happen in our world, yesterday’s science fiction has turned into today's science fact due to one Israeli inventor with a dream.
There are a number of limitations to the existing oxygen tank underwater breathing method. The first is the amount of time a diver can stay underwater, which is the result of the oxygen tank capacity. Another limitation is the dependence on oxygen refueling facilities near the diving site which are costly to operate and are used to compress the gas into the tanks which might be dangerous if not handled properly. The final problem has to do with the actual use of oxygen tanks underwater. When these tanks are in use they empty out and change the balance of the diver in the water.
Engineers have tried to overcome these limitations for many years now. Nuclear submarines and the international space station use systems that generate Oxygen from water by performing 'Electrolysis', which is chemical separation of Oxygen from Hydrogen. These systems require very large amounts of energy to operate. For this reason, smaller, diesel fueled submarines cannot use these systems and are required to resurface to re-supply their oxygen tanks every so often. Divers can't even consider carrying such large machines not to mention supplying them with energy. To overcome this limitation an Israeli inventor, Alon Bodner, turned to fish.
Fish do not perform chemical separation of oxygen from water; instead they use the dissolved air that exists in the water in order to breathe. In the ocean the wind, waves and underwater currents help spread small amounts of air inside the water. Studies have shown that in a depth of 200m below the sea there is still about 1.5% of dissolved air. This might not sound like much but it is enough to allow both small and large fish to breathe comfortably underwater. Bodner’s idea was to create an artificial system that will mimic the way fish use the air in the water thus allowing both smaller submarines and divers to get rid of the large, cumbersome oxygen tanks.
The system developed by Bodner uses a well known physical law called the "Henry Law" which describes gas absorption in liquids. This law states that the amount of gas that can be dissolved in a liquid body is proportional to the pressure on the liquid body. The law works in both directions – lowering the pressure will release more gas out of the liquid. This is done by a centrifuge which rotates rapidly thus creating under pressure inside a small sealed chamber containing sea water. The system will be powered by rechargeable batteries. Calculations showed that a one kilo Lithium battery can provide a diver with about one hour of diving time.
Bodner has already built and tested a laboratory model and he is on the path to building a full-scale prototype. Patents for the invention have already been granted in Europe and a similar one is currently pending examination in the U.S. Meetings have already been held with most major diving manufacturers as well as with the Israeli Navy. Initial financial support for the project has been given by Israel Ministry of Industry and Commerce and Bodner is currently looking for private investors to help complete his project.
If everything goes according to plan, in a few years the new tankless breathing system will be operational and will be attached to a diver in the form of a vest that will enable him to stay underwater for a period of many hours.
REVOLUTIONARY UNDERWATER BREATHING SYSTEM
An Israeli Inventor has developed a breathing apparatus that will allow breathing underwater without the assistance of oxygen tanks. This new invention will use the relatively small amounts of air that already exist in water to supply oxygen to both scuba divers and submarines. The invention has already captured the interest of most major diving manufacturers as well as the Israeli Navy.
The idea of breathing underwater without cumbersome oxygen tanks has been the dream of science fiction writers for many years. In George Lucas’ movie "The Phantom Menace", Obi-Wan whips out a little Jedi underwater breathing apparatus and dives in. As things tend to happen in our world, yesterday’s science fiction has turned into today's science fact due to one Israeli inventor with a dream.
There are a number of limitations to the existing oxygen tank underwater breathing method. The first is the amount of time a diver can stay underwater, which is the result of the oxygen tank capacity. Another limitation is the dependence on oxygen refueling facilities near the diving site which are costly to operate and are used to compress the gas into the tanks which might be dangerous if not handled properly. The final problem has to do with the actual use of oxygen tanks underwater. When these tanks are in use they empty out and change the balance of the diver in the water.
Engineers have tried to overcome these limitations for many years now. Nuclear submarines and the international space station use systems that generate Oxygen from water by performing 'Electrolysis', which is chemical separation of Oxygen from Hydrogen. These systems require very large amounts of energy to operate. For this reason, smaller, diesel fueled submarines cannot use these systems and are required to resurface to re-supply their oxygen tanks every so often. Divers can't even consider carrying such large machines not to mention supplying them with energy. To overcome this limitation an Israeli inventor, Alon Bodner, turned to fish.
Fish do not perform chemical separation of oxygen from water; instead they use the dissolved air that exists in the water in order to breathe. In the ocean the wind, waves and underwater currents help spread small amounts of air inside the water. Studies have shown that in a depth of 200m below the sea there is still about 1.5% of dissolved air. This might not sound like much but it is enough to allow both small and large fish to breathe comfortably underwater. Bodner’s idea was to create an artificial system that will mimic the way fish use the air in the water thus allowing both smaller submarines and divers to get rid of the large, cumbersome oxygen tanks.
The system developed by Bodner uses a well known physical law called the "Henry Law" which describes gas absorption in liquids. This law states that the amount of gas that can be dissolved in a liquid body is proportional to the pressure on the liquid body. The law works in both directions – lowering the pressure will release more gas out of the liquid. This is done by a centrifuge which rotates rapidly thus creating under pressure inside a small sealed chamber containing sea water. The system will be powered by rechargeable batteries. Calculations showed that a one kilo Lithium battery can provide a diver with about one hour of diving time.
Bodner has already built and tested a laboratory model and he is on the path to building a full-scale prototype. Patents for the invention have already been granted in Europe and a similar one is currently pending examination in the U.S. Meetings have already been held with most major diving manufacturers as well as with the Israeli Navy. Initial financial support for the project has been given by Israel Ministry of Industry and Commerce and Bodner is currently looking for private investors to help complete his project.
If everything goes according to plan, in a few years the new tankless breathing system will be operational and will be attached to a diver in the form of a vest that will enable him to stay underwater for a period of many hours.
4 jun 2005
Ten Most Harmful Books of the 19th and 20th Centuries
HUMAN EVENTS ONLINE
HUMAN EVENTS asked a panel of 15 conservative scholars and public policy leaders to help us compile a list of the Ten Most Harmful Books of the 19th and 20th Centuries. Each panelist nominated a number of titles and then voted on a ballot including all books nominated. A title received a score of 10 points for being listed No. 1 by one of our panelists, 9 points for being listed No. 2, etc. Appropriately, The Communist Manifesto, by Karl Marx and Friedrich Engels, earned the highest aggregate score and the No. 1 listing.
HUMAN EVENTS asked a panel of 15 conservative scholars and public policy leaders to help us compile a list of the Ten Most Harmful Books of the 19th and 20th Centuries. Each panelist nominated a number of titles and then voted on a ballot including all books nominated. A title received a score of 10 points for being listed No. 1 by one of our panelists, 9 points for being listed No. 2, etc. Appropriately, The Communist Manifesto, by Karl Marx and Friedrich Engels, earned the highest aggregate score and the No. 1 listing.
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