Relativity and Rotating Reference Frames

observer7 · May 15, 2008

<p><font size="3">I recently ran across this article "Relativistically Rotating Frames and Non-time-orthogonality" by Robert D. Klauber. (available at <span class="a">arxiv.org/abs/gr-qc?papernum=9812025)</span></font></p><p><font size="3">Now I have a pretty good understanding of relativity (not mathmatical but I've got the principles down) and this messes with me.  The article may be junk, but the idea of being able to measure different velocities for light in a rotating reference frame causes me some problems.  </font></p><p><font size="3">Here's the situation.  Imagine you are on a giant clockface at the 12 o'clock position.  Around the rim of this disk you have two fiber optic cables, call them cw and ccw (for clockwise and counterclockwise).  Now this clockface is huge, a radius of several AU say and it is rotating at a rate that makes the "absolute" velocity at the rim 99.9% of the speed of light (c).  I send a light pulse down both of my cables.  Asume I'm rotating in a cw direction.  The cw pulse will have to travel a full 360 degrees, plus the distance I move in the time it takes to complete the circuit.  The ccw pulse will run into me before completing a full 360 degree rotation.  Each light pulse travels 360 degrees around the clockface (i.e. each pulse covers the same distance) but I measure the times as different and therefore the speed of light for me (on this rotating reference frame) is not invarient.</font></p><p><font size="3">Now this brings up a couple of questions that I would like to see what the brains on this forum come up with.  First, how do electronics work in this crazy frame?  The neccesity for light being consistent in all reference frames comes from Maxwell equations governing electric interactions.  If light speed changes what happens to my computer?</font></p><p><font size="3">Second, I know that special relativity only applies to inertial reference frames and the rotating frame is not inertial.  But general relativity should apply.  What does GR say about the forces and effects in this frame.  Aurguments for length contraction in the direction of motion lead to curvature of the disk, which would manifest in both the rotating and non-rotating frame, providing a special position for the rotating observer. (isn't this another thing that is not allowed?)</font></p><p><font size="3">Finally, in my rotating frame I can determine my "absolute" (hence the quotes earlier) velocity.  I am moving because I feel forces.  I can determine my rate of rotation and the cirumference of my frame and get an invarient non-relativistic measure of my velocity.  What gives?</font></p><p><font size="3">I don't think this violates Uncle Albert's theory, but I have never seen any explainations of this and quite frankly it shocked me when I discovered this and gave it some thought.  Your opinions and wise council are eagerly anticipated.</font></p><p><font size="3">07</font> </p><p> </p><p> </p><p><font size="3"> </font></p><p><font size="3"> </font></p> <div class="Discussion_UserSignature"> <em><font size="2">"Time exists so that everything doesn't happen at once" </font></em><font size="2">Albert Einstein</font> </div>

DrRocket · May 15, 2008

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I recently ran across this article "Relativistically Rotating Frames and Non-time-orthogonality" by Robert D. Klauber. (available at arxiv.org/abs/gr-qc?papernum=9812025)</DIV></p><p>As near as I can tell this paper is a shorter version of a 31 page paper that appeared elsewhere.  Apparently he did not receive widespread acceptance and there is another paper by T.A. Weber that contests Klauber.  If you are interested in the Weber paper (about $20 worth of interested) it can be purchased here.</p><p>http://scitation.aip.org/vsearch/servlet/VerityServlet?KEY=AJPIAS&CURRENT=NO&ONLINE=YES&smode=strresults&sort=rel&maxdisp=25&threshold=0&pjournals=AJPIAS&pyears=2001%2C2000%2C1999&possible1=946&possible1zone=fpage&fromvolume=65&SMODE=strsearch&OUTLOG=NO&viewabs=AJPIAS&key=DISPLAY&docID=1&page=1&chapter=0</p><p>I don't think I want to invest the $, and my personal guess is that Klauber is all wet.  If Einstein had been that wrong we would have heard by now.  And Klauber would be famous.  Who is he ?<br /></p> <div class="Discussion_UserSignature"> </div>

DrRocket · May 15, 2008

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I recently ran across this article "Relativistically Rotating Frames and Non-time-orthogonality" by Robert D. Klauber. (available at arxiv.org/abs/gr-qc?papernum=9812025)Now I have a pretty good understanding of relativity (not mathmatical but I've got the principles down) and this messes with me.  The article may be junk, but the idea of being able to measure different velocities for light in a rotating reference frame causes me some problems.  Here's the situation.  Imagine you are on a giant clockface at the 12 o'clock position.  Around the rim of this disk you have two fiber optic cables, call them cw and ccw (for clockwise and counterclockwise).  Now this clockface is huge, a radius of several AU say and it is rotating at a rate that makes the "absolute" velocity at the rim 99.9% of the speed of light (c).  I send a light pulse down both of my cables.  Asume I'm rotating in a cw direction.  The cw pulse will have to travel a full 360 degrees, plus the distance I move in the time it takes to complete the circuit.  The ccw pulse will run into me before completing a full 360 degree rotation.</p><p><font color="#0000ff">I think I need to learn more about general relativity before I am certain, but it seems to me that in your rotating reference frame, both pulses of light go 360 deg.  Your statement would perhaps apply in the refrence frame of an external observer, but even in special relativity it is sometimes difficult to get the correct interpretation for an outside observer (not impossible, just difficult).  I think the resolution of your delemma likely lies in analyzing this from your perspective in the rotating reference frame.</font></p><p><font color="#0000ff">You may want to invest the $ to see Weber's paper.  I suspect that it will shed some light on this issue.  </font></p><p> </p><p> Each light pulse travels 360 degrees around the clockface (i.e. each pulse covers the same distance) but I measure the times as different and therefore the speed of light for me (on this rotating reference frame) is not invarient.</p><p><font color="#0000ff">Why?  I don't follow the reason that you measure different times.  I am not sure in what frame you are measureing distance or degrees.  But if you stick to your own rotating reference frame, I don't see any difference between the CW and CCW times or distances.  I am, however, not positive about the GR effects.</font></p><p><br />Posted by observer7</DIV><br /></p> <div class="Discussion_UserSignature"> </div>

derekmcd · May 15, 2008

<p>If I am understanding your thought experiment correctly, both observers in both reference frames would see the beam of light travel 360 degrees (60 seconds) on the clock at the same speed.  </p><p>The difference is, the observer on the outside would see you travel slightly behind that beam of light (let 59 seconds be the point where the outside observer sees you when the beams meet).  The observer outside your frame of reference would not recognize the time dilative effects until a comparison was made.  You, on the other hand, would only travel say 1 second on the clock face and recognize the beams meeting behind you.  When the 2 observers meet and compare the results, they will notice that you have aged only 1 sec compared to the outside observer aging 59 seconds, but the beam of light travelled at the same speed and covered the same distance.</p><p>Not sure If I explained that properly... (it makes sense in my head)</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

Mee_n_Mac · May 16, 2008

Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Here's the situation.  Imagine you are on a giant clockface at the 12 o'clock position.  Around the rim of this disk you have two fiber optic cables, call them cw and ccw (for clockwise and counterclockwise).  Now this clockface is huge, a radius of several AU say and it is rotating at a rate that makes the "absolute" velocity at the rim 99.9% of the speed of light (c).  I send a light pulse down both of my cables.  Asume I'm rotating in a cw direction.  The cw pulse will have to travel a full 360 degrees, plus the distance I move in the time it takes to complete the circuit.  The ccw pulse will run into me before completing a full 360 degree rotation.  Each light pulse travels 360 degrees around the clockface (i.e. each pulse covers the same distance) but I measure the times as different and therefore the speed of light for me (on this rotating reference frame) is not invarient.      <br />Posted by <strong>observer7</strong></DIV><br /><br />Let me stick with just the bit above for the moment. You've got one mightly big ring laser gyro there ! If the rotation rate wasn't relativistic would you still have a conceptual problem ? In that case it's no different then beaming a pulse at a mirror and, while it's inflight, taking a step towards that mirror. You've decreased the round trip distance and unless you account for this your v=d/t calcs will be off. <div class="Discussion_UserSignature"> <p>-----------------------------------------------------</p><p><font color="#ff0000">Ask not what your Forum Software can do do on you,</font></p><p><font color="#ff0000">Ask it to, please for the love of all that's Holy, <strong>STOP</strong> !</font></p> </div>

observer7 · May 16, 2008

<p>I agree that it is sometimes hard to get the perceptions correct by reference frame.  However, apparently there is some experimental evidence that supports different velocities for the cw and ccw light beams.  A device similar to the MichelsonMorley experiment is set up with one light beam taking the cw route and the other a ccw route.  A laser is used and if the device is rotating the recombined beams are slightly out of phase.  I'm at work so I don't have the reference in front of me (I'll post it later).</p><p>I'm certatinly not saying that Albert is wrong.  I believe that what we have here is an unexplored area and I found it interesting.  I'm not even sure what practical or theoretical applications this may or may not have.  I just find it to be a neat and somewhat different thought experiment on relativity. </p> <div class="Discussion_UserSignature"> <em><font size="2">"Time exists so that everything doesn't happen at once" </font></em><font size="2">Albert Einstein</font> </div>

observer7 · May 16, 2008

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>If I am understanding your thought experiment correctly, both observers in both reference frames would see the beam of light travel 360 degrees (60 seconds) on the clock at the same speed.  The difference is, the observer on the outside would see you travel slightly behind that beam of light (let 59 seconds be the point where the outside observer sees you when the beams meet).  The observer outside your frame of reference would not recognize the time dilative effects until a comparison was made.  You, on the other hand, would only travel say 1 second on the clock face and recognize the beams meeting behind you.  When the 2 observers meet and compare the results, they will notice that you have aged only 1 sec compared to the outside observer aging 59 seconds, but the beam of light travelled at the same speed and covered the same distance.Not sure If I explained that properly... (it makes sense in my head) <br /> Posted by derekmcd</DIV></p><p> </p><p>I disagree.  The path is indeed 360 degrees for each beam, however as was pointed out in another post you have to take into account your motion toward or away from the beam.  Therefor moving toward the beam shortens the travel time, moving away lengthens the travel time, but both beams cover the same distance.  Thus, different velocities.</p><p> </p><p>Now like I said I'm no expert, but I have never come across any "thought experiments" that explain this in relativistic terms.  I'm sure that uncle al's work has an explaination but I can't fathom it from what I do know about relativistic effects.</p><p> </p><p>I'm curious (see previous post about the experimental evidence) if it has to do with the "coriolis" force acting like gravity?  This would just be another (although special) example of acceleration and gravity being equivalent.</p><p> </p><p>What about the second part of the OP dealing with being able to determine and absolute velocity?  How do we explain that away? </p> <div class="Discussion_UserSignature"> <em><font size="2">"Time exists so that everything doesn't happen at once" </font></em><font size="2">Albert Einstein</font> </div>

DrRocket · May 16, 2008

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'> I disagree.  The path is indeed 360 degrees for each beam, however as was pointed out in another post you have to take into account your motion toward or away from the beam.  Therefor moving toward the beam shortens the travel time, moving away lengthens the travel time, but both beams cover the same distance.  Thus, different velocities.Posted by observer7</DIV></p><p>How does your logic apply if you take the radius to be very large?  It seems to me that in that situation,  as the radius increases without bound, you ought to recover the problem in a setting of special relativity.  That would be light beams being directed towards a moving receiver from a two distant sources in opposite directions from the receive.  In that case, the fundamental hypothesis of special relativity is that the speed of light from both sources is the same.</p><p>If you look at this probelem from the point of view of an observer who is rotating along with the coordinate system, the travel distances do not differ for the ccw vs cw beam.  It is important to recognize that in relativity any frame of reference is valid, and that apparent paradoxes most commonly arise when one tries to explain phenomena from a reference that makes things more complicated, or tries to look at questions from two reference frames simultaneously.<br /></p> <div class="Discussion_UserSignature"> </div>

observer7 · May 19, 2008

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>How does your logic apply if you take the radius to be very large?  It seems to me that in that situation,  as the radius increases without bound, you ought to recover the problem in a setting of special relativity.  That would be light beams being directed towards a moving receiver from a two distant sources in opposite directions from the receive.  In that case, the fundamental hypothesis of special relativity is that the speed of light from both sources is the same.If you look at this probelem from the point of view of an observer who is rotating along with the coordinate system, the travel distances do not differ for the ccw vs cw beam.  It is important to recognize that in relativity any frame of reference is valid, and that apparent paradoxes most commonly arise when one tries to explain phenomena from a reference that makes things more complicated, or tries to look at questions from two reference frames simultaneously. <br /> Posted by DrRocket</DIV></p><p> </p><p>*Blinding light goes off in brain**</p><p>Thanks, I was definitly crossing my reference frames.  I think some of the other effects (the absolute speed thing) are also eliminated when I stay in the right frame.  One of the problems I was experiencing is that the acceleration force is perpendicular to the direction of motion in the rotating frame.  It makes it harder to keep things lined up in my thought experiments, but once I got passed that it all seems to make sense.</p><p>Thanks for your input. </p> <div class="Discussion_UserSignature"> <em><font size="2">"Time exists so that everything doesn't happen at once" </font></em><font size="2">Albert Einstein</font> </div>

unclefred · May 19, 2008

<p>    As mee-n-mac said a couple of posts back,  what you are describing is a ring laser.  It is a standard product used to measuring angular rotation.  The difference in light paths clockwise and counter-clockwise is well known and is observable at extremely slow rates as well as high rates.  It has nothing to do with relativity.</p><p>    Your statement "that in relativity any frame of reference is valid" is wrong.  Einstein said that all INERTIAL reference frames are equal.  A rotating frame is not inertial.  The two beams see different distances and there is nothing strange about it.  </p><p> </p>

observer7 · May 20, 2008

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>    As mee-n-mac said a couple of posts back,  what you are describing is a ring laser.  It is a standard product used to measuring angular rotation.  The difference in light paths clockwise and counter-clockwise is well known and is observable at extremely slow rates as well as high rates.  It has nothing to do with relativity.    Your statement "that in relativity any frame of reference is valid" is wrong.  Einstein said that all INERTIAL reference frames are equal.  A rotating frame is not inertial.  The two beams see different distances and there is nothing strange about it.    <br /> Posted by unclefred</DIV></p><p>I understand a rotating frame is not inertial (see my OP).  I was looking at general relativity effects.  As I said previously I thought this was interesing and now that I've got this "right" in my head I see where the confusion was.</p><p> </p><p>O7 </p> <div class="Discussion_UserSignature"> <em><font size="2">"Time exists so that everything doesn't happen at once" </font></em><font size="2">Albert Einstein</font> </div>

DrRocket · May 20, 2008

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>    As mee-n-mac said a couple of posts back,  what you are describing is a ring laser.  It is a standard product used to measuring angular rotation.  The difference in light paths clockwise and counter-clockwise is well known and is observable at extremely slow rates as well as high rates.  It has nothing to do with relativity.    Your statement "that in relativity any frame of reference is valid" is wrong.  Einstein said that all INERTIAL reference frames are equal.  A rotating frame is not inertial.  The two beams see different distances and there is nothing strange about it.    <br />Posted by unclefred</DIV></p><p>You statemen is appropriate in special relativity, but not in general relativity.<br /></p> <div class="Discussion_UserSignature"> </div>

DrRocket · May 20, 2008

Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>You statemen is appropriate in special relativity, but not in general relativity.  In general relaltivity an inertial reference frame is one that is locally Lorentzian, i.e. essentially in free fall.  For instance, a reference frame attached to an orbiting satellite is inertial.  A falling box represents a Lorentzian frams.<br />Posted by DrRocket</DIV><br /> <div class="Discussion_UserSignature"> </div>

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