The cause of thunder has been the subject of centuries of speculation and scientific inquiry. The first recorded theory is attributed to the Greek philosopher Aristotle in the third century BC, and an early speculation was that it was caused by the collision of clouds. Subsequently, numerous other theories have been proposed. By the mid-19th century, the accepted theory was that lightning produced a vacuum. In the 20th century a consensus evolved that thunder must begin with a shock wave in the air due to the sudden thermal expansion of the plasma in the lightning channel. In a fraction of a second the air is heated to a temperature approaching 28,000 (50,000 ). This heating causes it to expand outward, plowing into the surrounding cooler air at a speed faster than sound would travel in that cooler air. The outward-moving pulse that results is a shock wave, similar in principle to the shock wave formed by an explosion, or at the front of a supersonic aircraft. More recently, the consensus around the cause of the shock wave has been eroded by the observation that measured overpressures in simulated lightning are greater than what could be achieved by the amount of heating found. Alternative proposals rely on electrodynamic effects of the massive current acting on the plasma in the bolt of lightning.
The Canberra bushfires of 2003 destroyed about 200 Duffy homes and the local petrol station. Duffy was the suburb that received the most test king damage in the fires. Narrabundah Hill, which borders the western edge of Duffy, is managed by ACT Forests and had contained a mature pine plantation before the fires. As of 2005[update], work was under way to plant a new plantation on the hill and surrounding areas. ___________________________ Clark Experts in mcpd | ccnp | mcitp | mcts USA
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This heating causes it to
This heating causes it to expand outward, plowing into the surrounding cooler air at a speed faster than sound would travel in that cooler air. The outward-moving pulse that results is a shock wave, similar in principle to the shock wave formed by an explosion, or at the front of a supersonic aircraft. More recently, the pass4sure ccna | pass4sure security+ | pass4sure ccnp | pass4sure cissp | pass4sure a+ | pass4sure ccda | pass4sure network+ | pass4sure ccie | pass4sure itil | pass4sure ccsp | pass4sure ccvp | Pass4sure 640-802 | Pass4sure 350-001 | Pass4sure 642-813 | Pass4sure SY0-201 | Pass4sure 642-902 | Pass4sure 642-832 | Pass4sure 640-822 | Pass4sure 642-642 | Pass4sure 640-816 consensus around the cause of the shock wave has been eroded by the observation that measured overpressures in simulated lightning are greater than what could be achieved by the amount of heating found. Alternative proposals rely on electrodynamic effects of the massive current acting on the plasma in the bolt of lightning.
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The cause of thunder has been the subject of centuries of speculation and scientific inquiry. The first recorded theory is attributed to the Greek philosopher Aristotle in the third century BC, and an early speculation was that it was caused by the collision of clouds. Subsequently, numerous other theories have been proposed. By the mid-19th century, the accepted theory was that lightning produced a vacuum. In the 20th century a consensus evolved that thunder must begin with a shock wave in the air due to the sudden thermal expansion of the plasma in the lightning channel. In a fraction of a second the air is heated to a temperature approaching 28,000 (50,000 ). This heating causes it to expand outward, plowing into the surrounding cooler air at a speed faster than sound would travel in that cooler air. The outward-moving pulse that results is a shock wave, similar in principle to the shock wave formed by an explosion, or at the front of a supersonic aircraft. More recently, the consensus around the cause of the shock wave has been eroded by the observation that measured overpressures in simulated lightning are greater than what could be achieved by the amount of heating found. Alternative proposals rely on electrodynamic effects of the massive current acting on the plasma in the bolt of lightning.
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The Canberra bushfires of
The Canberra bushfires of 2003 destroyed about 200 Duffy homes and the local petrol station. Duffy was the suburb that received the most test king damage in the fires. Narrabundah Hill, which borders the western edge of Duffy, is managed by ACT Forests and had contained a mature pine plantation before the fires. As of 2005[update], work was under way to plant a new plantation on the hill and surrounding areas. ___________________________ Clark Experts in mcpd | ccnp | mcitp | mcts USA