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jamman
SCI fan
Registered: 12/14/05
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Radar and Relativity
#5437709 - 03/24/06 09:40 AM (18 years, 8 days ago) |
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I searched for an answer but couldn't find one so I'll ask it. The theory of relativity (if I remember correctly) basically says that one person in motion measures there own time differently than a seperate person (at rest) would measure the moving persons speed? Wouldn't that mean that a police radar, rather stationary or moving, would not measure your speed accurately?
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FlusH
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Re: Radar and Relativity [Re: jamman]
#5437784 - 03/24/06 10:13 AM (18 years, 8 days ago) |
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If I remember correctly, radar determines speed by measuring the length of time the radar beam takes from leaving the gun, reflecting off the target, then back to the gun. The beam is sent many times per second, with each time it is sent having a different value ( because the target is either getting closer or farther). Then compare the difference in time with each value and you should have the speed of the target. But somebody please correct me if I am wrong
I don't think that answer's your question, but you are right, speed testing that way is based on the "fact" that time is a constant, but time is a variable.
Good question!
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Mezcal
Registered: 08/11/05
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Re: Radar and Relativity [Re: jamman]
#5437836 - 03/24/06 10:34 AM (18 years, 8 days ago) |
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Any time-dilation at speeds you could reach in a car would not be measurable by any common radar gun; in other words, the degree of accuracy of the device would not be sufficient to even measure the change.
When you get a speeding ticket, its for a whole-number speed. Any change in speed because of the effects of the theory of general relativity would probably be on the order of 1*10^-100 or smaller.
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jamman
SCI fan
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Re: Radar and Relativity [Re: jamman]
#5437841 - 03/24/06 10:37 AM (18 years, 8 days ago) |
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ahh, I was wondering about that. Makes sense to me
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FlusH
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Re: Radar and Relativity [Re: FlusH]
#5437860 - 03/24/06 10:46 AM (18 years, 8 days ago) |
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It would still be fun to try to get into an argument with an officer,
" I refuse to pay this ticket officer, the theory of realativity states...."
I can see that going over well..
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koppie
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Re: Radar and Relativity [Re: jamman]
#5440477 - 03/25/06 08:49 AM (18 years, 7 days ago) |
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Speed radar tends to work using the Doppler effect. you point a radio wave to a moving target, and the wave bounces off the target with a slightly different frequency. Comparing incoming and outgoing frequencies you find the speed of the car.
Now the relativistic doppler effect does indeed give different results from the non-relativistic doppler effect, but the differences are so small (since compared the the speed of light, even a fast car basically stands stil) that the difference isn't measurable, so from a practical standpoint it is irrelevant.
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HagbardCeline
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Re: Radar and Relativity [Re: FlusH]
#5440557 - 03/25/06 10:11 AM (18 years, 7 days ago) |
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Quote:
FlusH said: It would still be fun to try to get into an argument with an officer,
" I refuse to pay this ticket officer, the theory of realativity states...."
I can see that going over well..
Actually that did go over well with at least one officer. I was forced to take a Defensive Driving class after I had a wreck soon after getting my liscense. The officer teaching the class was telling us on a break that many of them will let people go when they hear an excuse for speeding that they'd never heard before. He told us that another officer he worked with pulled over some kid in college and asked why he was going so fast. "To retain my youthful appearance." was the guy's answer. When the cop requested clarification the guy stated "Einstein's theory of relativity states that the closer to the speed of light you attain, the slower time moves" (something to that effect). The cop laughed and let him go. He also said the "I have to shit" or "I have to piss" really bad is the most used and most likely to still get you a ticket.
-------------------- I keep it real because I think it is important that a highly esteemed individual such as myself keep it real lest they experience the dreaded spontaneous non-existance of no longer keeping it real. - Hagbard Celine
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