Millisecond Pulsar Frequency - Update

BoJangles · Dec 5, 2008

Q1 - How precise is the frequency of a millisecond pulsar? I.e. How stable is their frequency, or between what resolution/range are these things pulsating as compared the cycles of an atomic clock? Are they more or less accurate and if so by how much?Q2 - Would the MSP frequency change slightly with regards to the earth’s proper motion around the sun? <div class="Discussion_UserSignature"> -------------- Let me start out with the standard disclaimer ... I am an idiot, I know almost nothing, I haven’t taken calculus, I don’t work for NASA, and I am one-quarter Bulgarian sheep dog. With that out of the way, I have several stupid questions... *** A few months blogging can save a few hours in research *** </div>

Saiph · Dec 6, 2008

Q1:  Quite stable, though I don't think it's on the order of atomic clock accuracy.Q2: Yep, it would change a bit due to standard doppler effects. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

BoJangles · Dec 6, 2008

Ok thanks.Although it’s an Em pulse and not necessarily in the visible light spectrum, is this an example of a large Michelson–Morley experiment? Aren’t we measuring a change in the speed Em propagates in our reference frame in relation to our proper motion through space? If that makes sense. <div class="Discussion_UserSignature"> -------------- Let me start out with the standard disclaimer ... I am an idiot, I know almost nothing, I haven’t taken calculus, I don’t work for NASA, and I am one-quarter Bulgarian sheep dog. With that out of the way, I have several stupid questions... *** A few months blogging can save a few hours in research *** </div>

derekmcd · Dec 8, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Ok thanks.Although it’s an Em pulse and not necessarily in the visible light spectrum, is this an example of a large Michelson–Morley experiment? Aren’t we measuring a change in the speed Em propagates in our reference frame in relation to our proper motion through space? If that makes sense. Posted by Manwh0re</DIV>Stable indeed, though they do decay over time due to radiation of gravitational waves.  See:http://en.wikipedia.org/wiki/Hulse-Taylor_binary As for testing for aether, I don't see the corelation. <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

BoJangles · Dec 8, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Stable indeed, though they do decay over time due to radiation of gravitational waves.  See:http://en.wikipedia.org/wiki/Hulse-Taylor_binaryAs for testing for aether, I don't see the corelation. Posted by derekmcd</DIV> Ok thanks for your time; I was starting to think I was being ignored for my idiocy.I may have muddled the last question.Isn’t the basis of relativity that light is measured at the same speed in all directions, regardless of refrence.I thought one of the proofs for this is the Michelson Morley experiment, i.e. that light is measured the same speed in all directions. regardless of your actual motion through space, so  if you measured the speed it took light to travel N distance no matter what your relative speed the light will always = c in your reference frameI was just wondering, because if that is the case and the speed of a pulsar is increased or decreased ever so slightly with regards to earths proper motion around the sun, isn’t this a way of saying that the pulse which should be governed by the speed of light, is actually not constant in our reference frame, its speeding up and slowing down with respect to my proper motion. To pre-empt an answer , is it the case that the pulsar frequency is not changing at all ( apart from the decay ) and it’s the fact the pulsar is actually just red and blue shifted slightly as we rotate the sun?Ps thanks for the link <div class="Discussion_UserSignature"> -------------- Let me start out with the standard disclaimer ... I am an idiot, I know almost nothing, I haven’t taken calculus, I don’t work for NASA, and I am one-quarter Bulgarian sheep dog. With that out of the way, I have several stupid questions... *** A few months blogging can save a few hours in research *** </div>

BoJangles · Dec 8, 2008

I ripped this from wikiAfter timing the radio pulses for some time, Hulse and Taylor noticed that there was a systematic variation in the arrival time of the pulses. Sometimes, the pulses were received a little sooner than expected; sometimes, later than expected. These variations changed in a smooth and repetitive manner, with a period of 7.75 hours. They realized that such behavior is predicted if the pulsar were in a binary orbit with another star.After composing this post I think I see the error in my ways, I might try and do some more research into relativity and its explanation of light As it seems I’m getting stuck on the fact that while pulsars change frequency we must be measuring a difference in the propagation of light in regards to earths reference frame. I.e. the pulsar is speeding up and slowing down, or oppositely the pulsar is moving away or closer.my head hurts :/   <div class="Discussion_UserSignature"> -------------- Let me start out with the standard disclaimer ... I am an idiot, I know almost nothing, I haven’t taken calculus, I don’t work for NASA, and I am one-quarter Bulgarian sheep dog. With that out of the way, I have several stupid questions... *** A few months blogging can save a few hours in research *** </div>

BoJangles · Dec 10, 2008

Sorry to beat this out, it’s just been bugging me for a while.---OK after a day of light pondering (pardon the pun), I’ve tried to break down my misunderstanding into palatable components.From my understanding of SR the following is trueLight travels, and can be measured, at a constant speed no matter what your relative motion is. That’s to say, if we were to conduct twin Michelson and Morley experiments; the first being on the surface of the earth (relatively motionless to earth) and the second on a speeding train travelling at 0.5 * c , light will be measured at the same speed in every direction consistently.So in that case what happens in the following scenario?On an impossibly long stretch of road in the middle of the night, a person flashes a torch at precise regular intervals (1 second on 1 second off) into the distance. At the opposite end a person gets in a car fitted with 2 very sensitive light detectors on front and back window, the idea is when light passes through these detectors they will record time and state change. I.e. on or off and what time the occurrence happens on A and B detectorJust then, for seemingly no apparent reason the person in the car drives towards the light and reaches 0.5 * c. Q. Does the detector log show the flashing speeding up? I.e. half second on half second off, or just a change in the red shift of the light.I expect the answer to be no, as we are not supposed to be detecting a change in the speed of light (I guess).Though intuitively I think the flashing will speed up, and if it does, is that not detecting a change in the speed of light? And if this is the case, has this got something to do with length contraction or time dilation or something or just plane Doppler affect.PsAlthough it may not seem like I'm learning anything here (as some of you may be sick of my questioning), I just sometimes need to explore things for myself to appreciate them fully.Thanks for your time and I look forward to your response.ppsMaybe there should be forum topic called "Physics and astronomy for dummies"

or "Ask the angry physicist"

<div class="Discussion_UserSignature"> -------------- Let me start out with the standard disclaimer ... I am an idiot, I know almost nothing, I haven’t taken calculus, I don’t work for NASA, and I am one-quarter Bulgarian sheep dog. With that out of the way, I have several stupid questions... *** A few months blogging can save a few hours in research *** </div>

derekmcd · Dec 10, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>From my understanding of SR the following is true Light travels, and can be measured, at a constant speed no matter what your relative motion is. That’s to say, if we were to conduct twin Michelson and Morley experiments; the first being on the surface of the earth (relatively motionless to earth) and the second on a speeding train travelling at 0.5 * c , light will be measured at the same speed in every direction consistently.</DIV>That wasn't really the intended function of the M and M experiment, but yes... light (or any massless particle) will travel at C in a vacuum no matter the observer's reference frame. Replying to: <DIV CLASS='Discussion_PostQuote'>So in that case what happens in the following scenario? On an impossibly long stretch of road in the middle of the night, a person flashes a torch at precise regular intervals (1 second on 1 second off) into the distance. At the opposite end a person gets in a car fitted with 2 very sensitive light detectors on front and back window, the idea is when light passes through these detectors they will record time and state change. I.e. on or off and what time the occurrence happens on A and B detectorJust then, for seemingly no apparent reason the person in the car drives towards the light and reaches 0.5 * c. Q. Does the detector log show the flashing speeding up? I.e. half second on half second off, or just a change in the red shift of the light.I expect the answer to be no, as we are not supposed to be detecting a change in the speed of light (I guess).Though intuitively I think the flashing will speed up, and if it does, is that not detecting a change in the speed of light? And if this is the case, has this got something to do with length contraction or time dilation or something or just plane Doppler affect.PsAlthough it may not seem like I'm learning anything here (as some of you may be sick of my questioning), I just sometimes need to explore things for myself to appreciate them fully.Thanks for your time and I look forward to your response.ppsMaybe there should be forum topic called "Physics and astronomy for dummies"

or "Ask the angry physicist"

Posted by Manwh0re</DIV>All that is happening with binary pulsars and the changing frequency of the pulses of radiation is that the distance between the pulses is increasing or decreasing depending on their radial velocity in the direction of the observer.  The speed of the light is not changing, only the distance the light has to travel to reach the observer.  If the pulsar is travelling towards the observer, the frequency will increase.If I were carrying a flashing light travelling towards you at .9999~% of C flashing my light once every second for 10 seconds, you as the observer you see all 10 pulses of my flashlight at very nearly the same time (not once every second) because, in your reference frame, I am travelling WITH the beam of light.And yes, there is also a doppler shift, but that has nothing to do with the change in frequency except that the radial velocity can be measured using the red/blue shift.There is also a gravitational time dilation that changes the frequency when the two pulsars are closer together creating a deeper gravity well compared to when they are farther apart, but I wouldn't think that would be very much (though measureable) complared to the radial velocity.  <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

Saiph · Dec 10, 2008

In the car approaching the guy with the flashlights: The detectors will notice a change in the frequency of the flashes.  This does NOT mean the speed of light is changing.  The speed of light, and the frequency of the light, or the frequency of the flashes of light are independent. Here's what's happening, the light leaving the flashlights is traveling at C, and always at C (assuming vacuum of course

).  However, if the source and observer are moving towards, or away, from eachother the distance between them is not the same.   Lets set up the experiment with all the pertinent details:I flash a light every second, and you are a mile away.  If I don't move, you will see the light flash every second.  However, if I either of us moves the distance between us changes.  Say I start moving towards you, the first flash and you are 1 mile away, the next flash you are less than 1 mile away.  The first flash takes the same amount of time to reach you as when we are stationary.  HOWEVER, the second flash takes less time, not because the speed of light is different, but because it doesn't have to travel as far.  The faster I approach you, the bigger the change in distance between each flash, the bigger the change in travel time it takes light to reach you.This creates a shift in the frequency of the flashes.  If I approach you, the frequency is shortened, as each flash has less distance to travel than the previous one.  This basically gives the following flashes a "head start" on the previous ones, which allows the flashes to "bunch up" and shorten the frequency.  If I walk away, the distance each flash has to cover is greater, giving them a handicap...meaning the period of flashes stretches out and the frequency is lengthened. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

BoJangles · Dec 10, 2008

Oh ok thanks guys that was very informative and exactly how I needed to hear it.Let’s see if I can apply this correctly.So basically, as related to above, no matter how fast the car is heading towards the flash light (or vice versa) the detectors will not log a change in the time it takes each individual pulse to cover the distance between the detectors. Nor will it notice a change in the time it takes any particular pulse to pass through any respective detector. D = Distance between each pulseT1 = The time registered when a pulse of light has passed through the first detector.T2 = The time registered when that same pulse of light passes through the second detector.No matter how fast the distance between the light source and the detectors decrease t1 – t2 will always be constant, and you will only notice a change in D, plus a little red shift.How did I do? <div class="Discussion_UserSignature"> -------------- Let me start out with the standard disclaimer ... I am an idiot, I know almost nothing, I haven’t taken calculus, I don’t work for NASA, and I am one-quarter Bulgarian sheep dog. With that out of the way, I have several stupid questions... *** A few months blogging can save a few hours in research *** </div>

Saiph · Dec 10, 2008

Nope, time isn't constant in the scenario.  The frequency of the pulses is defined by the time between them.  This changes!  The only thing that does not change is the speed of the wave/signal/pulse itself.The distance shortens, but the speed remains the same. Thus the time required to cross the distance shortens as well.  This decrease in time required to cross the gap causes a shift in the frequency.This is how doppler shifts can be used to detect the motion of objects. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

derekmcd · Dec 10, 2008

Distance between A and B is 900,000km.  Each hash mark represent 25,000km.  One pulse per second.  If the distance between the pulse and the detector remain at 900,000 km, then detector will recieve 1 pulse per second and it will take 3 seconds for the first pulse to arrive. Now, if your source is moving at .5c and still emitting 1 pulse per second (which began at time=0), then;  After 1 second the first pulse (1) will have travelled 300,000km and the source (s) will have travelled 150,000km.  A - - - - - s - - - - - 1 - - - - - - - - - - - - - - - - - - - - - - - BAfter 2 seconds, pulse 1 will have travelled 600,000km and pulse 2 (which started at 150,000km) will have travelled 300,000 (being 450,000km from point A).A - - - - - - - - - - - s - - - - - 2 - - - - - 1 - - - - - - - - - - - BAfter 3 seconds, the first pulse will arrive at B, pulse 2 will be at 750,000km and the 3rd pulse (3) will be at 600,000km.A - - - - - - - - - - - - - - - - - s - - - - - 3 - - - - - 2 - - - - - 1@B   As you can see, the source has covered half the distance.  Each second, the souce covers half the distance that each pulse does.  Even though the source is doing 1 pulse per second, you can see that the detector (B) will recieve each pulse at 1/2 second intervals as they are only 150,000km apart.   <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

BoJangles · Dec 10, 2008

Ok thanks again guys, I got the pulse frequency sorted now; I can see how they pile up, because each pulse gets a relative head start on the pulse before as the source moves towards its destination.Just for completeness, let’s reversed this around a bit just for fun and only deal with 1 pulse that goes for 1 second, and move the detectors towards the source at the same time at half cS = Source, E = Destination, a = Detector 1, b = Detector 2, w = a single pulse---Scenario 1a and b detectors are seated on the front and back of a train obviously a very long train travelling at half c, some person flashes a light on and off for the duration of a second some distance away <img src="http://sitelife.space.com/ver1.0/Content/images/store/10/15/cadde0c2-1e6e-41a5-8f6f-4c0981e7cd95.Medium.jpg" alt="" /> a = t3b = t5  ---Scenario 2a and b detectors are seated on the ground and someone flashes a light on and off for the duration of a second some distance away <img src="http://sitelife.space.com/ver1.0/Content/images/store/13/9/fdd498d7-6b07-41ee-89cc-73a6d7596df2.Medium.jpg" alt="" /> a = t2b = t5  So the time differential registered between the 2 detectors is not constant over the 2 scenarios’? (Remembering this is only 1 pulse and the detectors are only interested in the first photon to register on/true).If this is the case I think I’ve found the error in my ways. I assumed the train ( in the first scenario) was a reference frame; and the time differential between the detectors as they detect the first photon in a pulse of light as it passes by would be constant, due SR and what is says about reference frames and the speed of light? I.e. light (or any massless particle) will travel at C in a vacuum no matter the observer's reference frame. <edit>Ahh I think I see what’s happening now, even with the detectors the same affect is happening; the distance is shortening, not the speed of light being measured differently?  <div class="Discussion_UserSignature"> -------------- Let me start out with the standard disclaimer ... I am an idiot, I know almost nothing, I haven’t taken calculus, I don’t work for NASA, and I am one-quarter Bulgarian sheep dog. With that out of the way, I have several stupid questions... *** A few months blogging can save a few hours in research *** </div>

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