kaathrin
05-19-2009, 12:05 PM
Hello All,
I have been challenged by a friend to look into Gravitational waves and some questions he has about them -- but I have always been a slow starter. Took physics with SR in college, got my BSEE, happily can build analog circuitry of all kinds -- but found that certain questions about SR never did get answered by the Prof and have gnawed at me ever since. Now I accept SR by and large -- but don't really accept GR yet -- so gravity waves are still in the Poincaire electrical charge theory realm (and Feynman had some speculation too, if I remember correctly) for me. And I figure, I best resolve the simple issues first before tackling the bigger ones ... a physics oriented crowd has perhaps studied some experiment that I haven't and might already know which of a set of answers is a dead end... hopefully this thread will grow in knowledge and build toward my friends questions -- which intrigue me, and I hope -- you.
So here is a simple gedanken with inertial frames to begin the journey toward gravity. I am not good with Minowski 4 vectors, so -- if you don't use them thanks! -- but if you do, please be very clear what they mean.
I am envisioning a radar trap with a policeman. We can ignore the rotation of the earth and gravity here. I am also envisioning a craft passing the policeman at c/2. Since we are with the policeman at the moment, he is our inertial frame. The craft is another inertial frame -- not accelerating nor decelerating. There is sufficient rest mass with both the policeman and the craft so that the radar gun he fires at the craft does not change the speed between them measurably.
Please correct any assertion that is clearly contradictory:
1. Since there are only two objects -- the policeman and the craft -- the speed measured by one ought to be the same as the speed observed by the other. There is no third body issue.
2. The policeman is firing a low wattage continuous wave radar gun. Eg: let's say 300MHz in his frame -- and he is aiming it at the craft passing him. At T=0 the craft is touching the gun, and thereafter it recedes directly away from the gun at a constant velocity V.
3. Older radar guns work on the Doppler effect (red shift/blue shift). Our police man is using one -- eg: Essentially, he is measuring the beat frequency of his outgoing wave with the incoming one -- and using that to determine the crafts speed. The craft -- for its part -- is made of a superconductor, and is acting as a perfect mirror nicely aimed to give the policeman an accurate reading.
4. Einstein believed in "photons" and the photoelectric effect. Hence, we may view (consistently for his thinking) the police man as ejecting photons with wavelength 1 meter, frequency 300Mhz (assuming c=3x10**8 exactly, otherwise -- scale accordingly for nice math.).
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I have been challenged by a friend to look into Gravitational waves and some questions he has about them -- but I have always been a slow starter. Took physics with SR in college, got my BSEE, happily can build analog circuitry of all kinds -- but found that certain questions about SR never did get answered by the Prof and have gnawed at me ever since. Now I accept SR by and large -- but don't really accept GR yet -- so gravity waves are still in the Poincaire electrical charge theory realm (and Feynman had some speculation too, if I remember correctly) for me. And I figure, I best resolve the simple issues first before tackling the bigger ones ... a physics oriented crowd has perhaps studied some experiment that I haven't and might already know which of a set of answers is a dead end... hopefully this thread will grow in knowledge and build toward my friends questions -- which intrigue me, and I hope -- you.
So here is a simple gedanken with inertial frames to begin the journey toward gravity. I am not good with Minowski 4 vectors, so -- if you don't use them thanks! -- but if you do, please be very clear what they mean.
I am envisioning a radar trap with a policeman. We can ignore the rotation of the earth and gravity here. I am also envisioning a craft passing the policeman at c/2. Since we are with the policeman at the moment, he is our inertial frame. The craft is another inertial frame -- not accelerating nor decelerating. There is sufficient rest mass with both the policeman and the craft so that the radar gun he fires at the craft does not change the speed between them measurably.
Please correct any assertion that is clearly contradictory:
1. Since there are only two objects -- the policeman and the craft -- the speed measured by one ought to be the same as the speed observed by the other. There is no third body issue.
2. The policeman is firing a low wattage continuous wave radar gun. Eg: let's say 300MHz in his frame -- and he is aiming it at the craft passing him. At T=0 the craft is touching the gun, and thereafter it recedes directly away from the gun at a constant velocity V.
3. Older radar guns work on the Doppler effect (red shift/blue shift). Our police man is using one -- eg: Essentially, he is measuring the beat frequency of his outgoing wave with the incoming one -- and using that to determine the crafts speed. The craft -- for its part -- is made of a superconductor, and is acting as a perfect mirror nicely aimed to give the policeman an accurate reading.
4. Einstein believed in "photons" and the photoelectric effect. Hence, we may view (consistently for his thinking) the police man as ejecting photons with wavelength 1 meter, frequency 300Mhz (assuming c=3x10**8 exactly, otherwise -- scale accordingly for nice math.).
Keyword Research (http://www.keywordspy.com/)
Free Plastics Surgery (http://www.freebeautymakeover.com)