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Uploaded on Mar 15, 2011
Can the entire universe be explained with a single, unifying theory? This is perhaps the most fundamental question in all of science, and it may also be the most controversial.

Albert Einstein was among the first to envision a unified theory that could account for the behavior of all matter and energy in the cosmos, but a definitive solution has eluded physicists to this day. As the 21st century progresses, "string theory" remains the leading candidate to be the "theory of everything"—although some have come to question whether string theorists are on the right track. Still others doubt that a "theory of everything" exists at all—and consider the search for such a theory an outdated philosophy of our search for cosmic truths.

Join Director of the Hayden Planetarium Neil deGrasse Tyson as he hosts and moderates six of the world's leading voices in this great scientific debate.

Panelists:

Dr. Katherine Freese, professor of physics at the University of Michigan

Dr. Jim Gates, professor of physics at the University of Maryland-College Park

Dr. Janna Levin, professor of physics and astronomy at Barnard College

Dr. Marcello Gleiser, professor of physics and astronomy at Dartmouth College

Dr. Brian Greene, professor of physics and mathematics at Columbia University

Dr. Lee Smolin, theoretical physicist at Perimeter Institute for Theoretical Physics

The talk was recorded at the American Museum of Natural History on March 7, 2011.

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U.S. Army weapon shoots lightning bolts down laser beams

By Darren Quick

June 28, 2012



A lightning bolt travels horizontally down a plasma channel from the LIPC before deviating when it gets close to the target which offers a lower-resistance path to the ground (Photo: U.S. Army)
Thought that title might get your attention, but shooting lightning bolts down laser beams is just what a device being developed at the Picatinny Arsenal military research facility in New Jersey is designed to do. Known as a Laser-Induced Plasma Channel, or LIPC, the device would fry targets that conduct electricity better that the air or ground that surrounds them by steering lightning bolts down a plasma pathway created by laser beams.

The pathway takes the form of an electrically conductive plasma channel that is formed when a laser beam of enough intensity (a 50 billion watt pulse lasting two-trillionths of a second will do) forms an electro-magnetic field strong enough to ionize the surrounding air to form plasma. Because the plasma channel conducts electricity much better than the non-ionized air that surrounds it, electrical energy will travel down the channel.

Then, when it hits its target – an enemy vehicle, person or unexploded ordnance, for example – the current will flow through the target as it follows the path of least resistance to the ground, potentially disabling the vehicle or person and detonating the ordnance. The lightning will also deviate from the channel when it gets close to the target and finds a lower-resistance path to the ground.

That’s the basic physics behind it, but overcoming the technical challenges to actually build the device won’t be easy.

"If the light focuses in air, there is certainly the danger that it will focus in a glass lens, or in other parts of the laser amplifier system, destroying it," said George Fischer, lead scientist on the project. "We needed to lower the intensity in the optical amplifier and keep it low until we wanted the light to self-focus in air.”

The research team also had to synchronize the laser with the high voltage and ruggedize the device so it could be operated under extreme environmental conditions. There is, of course, also the problem of providing enough power to operate the device for extended periods of time. Despite these challenges, the team claims to have made notable progress in recent months after reporting "excellent results" in tests conducted in January, 2012.

Work on the device is continuing.

Source: U.S. Army via engadget. [Ссылки могут видеть только зарегистрированные пользователи]