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Thread: Relativity: electron beam vs. laser beam?

  1. #1 Relativity: electron beam vs. laser beam? 
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    It occurred to me that electrons can be accelerated very close to the speed of light (over 99%) but Relativity handles electrons differently than photons.

    A hypothetical scenario:
    1. a beacon with a laser beam and an electron beam is set up in space
    2. a ship that controls those beams is stationary relative to the beacon (say at 5 light minute distance)
    3. the ship initiates simultaneous pulses with both beams towards itself
    4. the ship begins to travel at 0.5*c towards the beacon and the pulses

    According to Relativity the ship can not accelerate relative to the laser pulse, but it can accelerate relative to the electron pulse.

    Will the ship encounter the electron pulse first?


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    What on Earth?!

    You have some SERIOUS misunderstandings.

    The speed of light will always be ~300,000 km/s relative to the ship, so the light pulse will always be closing on the ship at ~300,000 km/s whereas the closing speed of the electron pulse will differ, but will always be slower than the light-pulse!

    The ship will never encounter the electron pulse first.


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    Quote Originally Posted by SpeedFreek View Post
    What on Earth?!

    You have some SERIOUS misunderstandings.
    Oh. I'm sorry… Can you enlighten me on what I got wrong?
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    The relativistic addition of velocities never adds up to more than c.

    http://math.ucr.edu/home/baez/physics/Relativity/SR/velocity.html

    So, if two spacecraft are travelling towards each other, each having accelerated to 0.75 c, their closing speed (measured from either spacecraft) will still be less than c.
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    Quote Originally Posted by SpeedFreek View Post
    The relativistic addition of velocities never adds up to more than c.
    Ok. So can you clarify on this a bit more...

    The speed of the electron pulse can be arbitrarily chosen. If the electron pulse is fired at 0.3*c and the ship travels towards the beacon at 0.5*c, what will be the speed of the pulse relative to the ship in this case?
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    See the link I added to my previous post.
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    The formula is



    Where s is the closing speed, v is the ship speed, u is the electron pulse speed and c = 1. So for a ship travelling at 0.5c closing on a beacon that shot an electron pulse at 0.3c towards the ship, the closing speed between the ship and the pulse as measured from the ship is:







    ~0.695 c.

    And for a ship travelling at 0.5c towards the beacon where the beacon shot an electron pulse at 0.9c towards the ship, the closing speed as measured by the ship would be:









    ~0.9655 c.

    This is why the electron pulse would always be travelling towards the ship slower than the speed of light.

    (I hope I did these calculations correctly, maths is not really my strong point!)
    Last edited by SpeedFreek; December 7th, 2013 at 07:02 PM.
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    Quote Originally Posted by van erst View Post

    Will the ship encounter the electron pulse first?
    Never.
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    Quote Originally Posted by SpeedFreek View Post
    The formula is



    Where s is the closing speed, v is the ship speed, u is the electron pulse speed and c = 1. So for a ship travelling at 0.5c closing on a beacon that shot an electron pulse at 0.3c towards the ship, the closing speed between the ship and the pulse as measured from the ship is:







    ~0.695 c.

    And for a ship travelling at 0.5c towards the beacon where the beacon shot an electron pulse at 0.9c towards the ship, the closing speed as measured by the ship would be:









    ~0.9655 c.

    This is why the electron pulse would always be travelling towards the ship slower than the speed of light.

    (I hope I did these calculations correctly, maths is not really my strong point!)
    No, this is not correct. The closing speed is simply the sum of speeds, so:


    1. For electron beam , it is
    2. For laser beam, it is

    You mixed up the notion of closing speed with the notion of relativistic speed.
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    Polar jet - Wikipedia, the free encyclopedia

    Might be an interesting read on the subject.
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    Hmm.. This is a bit odd...

    Suppose we have two ships traveling towards the beacon from opposite directions and constantly being equidistant from the beacon. Lets say both ships travel at speed 0.6*c relative to the beacon. In order to pass the beacon at the same time the relative velocity between the ships has to be 1.2*c. Is this not correct? If this is not correct, how could they reach the beacon at the same time?
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    Quote Originally Posted by xyzt View Post
    No, this is not correct. The closing speed is simply the sum of speeds, so:


    1. For electron beam , it is
    2. For laser beam, it is

    You mixed up the notion of closing speed with the notion of relativistic speed.
    Sorry, I didn't quite understand this. The ship will measure the closing speed of 1.5*c for the laser pulse? So the relative speed between the laser pulse and the ship will exceed c?
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    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by SpeedFreek View Post
    The formula is



    Where s is the closing speed, v is the ship speed, u is the electron pulse speed and c = 1. So for a ship travelling at 0.5c closing on a beacon that shot an electron pulse at 0.3c towards the ship, the closing speed between the ship and the pulse as measured from the ship is:







    ~0.695 c.

    And for a ship travelling at 0.5c towards the beacon where the beacon shot an electron pulse at 0.9c towards the ship, the closing speed as measured by the ship would be:









    ~0.9655 c.

    This is why the electron pulse would always be travelling towards the ship slower than the speed of light.

    (I hope I did these calculations correctly, maths is not really my strong point!)
    No, this is not correct. The closing speed is simply the sum of speeds, so:


    1. For electron beam , it is
    2. For laser beam, it is

    You mixed up the notion of closing speed with the notion of relativistic speed.
    But this is supposed to be the closing speed as measured from the frame of one of the objects involved. I mean, the occupants of the spaceship can't calculate the electron pulse is closing on them at 1.4c and the laser pulse is closing on them at 1.5c, as nothing can be moving at more than c relative to themselves.

    I might have used the wrong terminology (closing speed), but I am sure that the answer for the speed at which the electron pulse approaches the spaceship cannot be 1.4c from the frame of the spaceship. What formula should be used for this calculation?
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    So in terms of "closing speed" we should expect to be able to measure relative speeds greater than c for light?
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    Quote Originally Posted by SpeedFreek View Post
    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by SpeedFreek View Post
    The formula is



    Where s is the closing speed, v is the ship speed, u is the electron pulse speed and c = 1. So for a ship travelling at 0.5c closing on a beacon that shot an electron pulse at 0.3c towards the ship, the closing speed between the ship and the pulse as measured from the ship is:







    ~0.695 c.

    And for a ship travelling at 0.5c towards the beacon where the beacon shot an electron pulse at 0.9c towards the ship, the closing speed as measured by the ship would be:









    ~0.9655 c.

    This is why the electron pulse would always be travelling towards the ship slower than the speed of light.

    (I hope I did these calculations correctly, maths is not really my strong point!)
    No, this is not correct. The closing speed is simply the sum of speeds, so:


    1. For electron beam , it is
    2. For laser beam, it is

    You mixed up the notion of closing speed with the notion of relativistic speed.
    But this is supposed to be the closing speed as measured from the frame of one of the objects involved.
    You continue to mistake relativistic speed composition for closing speed. Closing speed, as the name suggests it, is the speed with which TWO entities (in the OP case, the light front/electron beam front and the rocket) cover a certain distance measured in a THIRD frame (in this case, the frame of the rocket BEFORE it started accelerating at 0.5c)


    I mean, the occupants of the spaceship can't calculate the electron pulse is closing on them at 1.4c and the laser pulse is closing on them at 1.5c, as nothing can be moving at more than c relative to themselves.
    The occupants of the rocket do not calculate the closing speed, the closing speed is calculated in the frame in which the rocket was initially at rest. By definition (see above).


    I might have used the wrong terminology (closing speed), but I am sure that the answer for the speed at which the electron pulse approaches the spaceship cannot be 1.4c from the frame of the spaceship. What formula should be used for this calculation?
    Indeed, you used the wrong terminology. The speed at which the electron beam approaches the rocket as measured in the rocket frame is indeed given by the relativistic speed composition formula you used.
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    Quote Originally Posted by van erst View Post
    So in terms of "closing speed" we should expect to be able to measure relative speeds greater than c for light?
    Closing speed and relative speed are TWO DIFFERENT notions, so, your sentence makes no sense.
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    Quote Originally Posted by van erst View Post
    In order to pass the beacon at the same time the relative velocity between the ships has to be 1.2*c. Is this not correct?
    You do not understand the difference between closing and relative speed. Look at the explanation I gave Speedfreak.
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    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post
    So in terms of "closing speed" we should expect to be able to measure relative speeds greater than c for light?
    Closing speed and relative speed are TWO DIFFERENT notions, so, your sentence makes no sense.
    Aren't closing speeds still just relative speeds? I would assume that the pulse of light has only one relative speed that the ship can measure. Or am I wrong?
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    Quote Originally Posted by van erst View Post
    So in terms of "closing speed" we should expect to be able to measure relative speeds greater than c for light?
    xyzt's answer is in the frame of reference of the beacon. SpeedFreek's answer is in the frame of reference of the ship.
    There are no paradoxes in relativity, just people's misunderstandings of it.
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    Quote Originally Posted by KJW View Post
    xyzt's answer is in the frame of reference of the beacon. SpeedFreek's answer is in the frame of reference of the ship.
    Will they disagree which pulse hits the ship first?
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by KJW View Post
    xyzt's answer is in the frame of reference of the beacon. SpeedFreek's answer is in the frame of reference of the ship.
    Will they disagree which pulse hits the ship first?
    No. In both cases the light pulse is faster than the electron pulse.
    There are no paradoxes in relativity, just people's misunderstandings of it.
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    Quote Originally Posted by KJW View Post
    No. In both cases the light pulse is faster than the electron pulse.
    Ok. So if I understand this correctly, in the frame of the ship the laser pulse will be traveling at 1.5*c and the electron pulse slightly slower towards the ship. And in both frames they agree that the pulses travel (closing speed) faster than the speed of light relative to the ship.
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by KJW View Post
    No. In both cases the light pulse is faster than the electron pulse.
    Ok. So if I understand this correctly, in the frame of the ship the laser pulse will be traveling at 1.5*c and the electron pulse slightly slower towards the ship. And in both frames they agree that the pulses travel (closing speed) faster than the speed of light relative to the ship.
    No, the frame of the ship is SpeedFreek's answer. In the frame of the beacon, the light pulse travels at c and the ship is moving at 0.5c in the opposite direction. Therefore the separation between them decreases at a rate of 1.5c. But nothing is actually travelling at 1.5c. The ship sees the light pulse travelling at c.
    There are no paradoxes in relativity, just people's misunderstandings of it.
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    Quote Originally Posted by KJW View Post
    No, the frame of the ship is SpeedFreek's answer. In the frame of the beacon, the light pulse travels at c and the ship is moving at 0.5c in the opposite direction. Therefore the separation between them decreases at a rate of 1.5c. But nothing is actually travelling at 1.5c. The ship sees the light pulse travelling at c.
    Ok. I think I understand now what you're saying. It is a misconception that the relative physical speed limit would only apply to light/photons but rather there is a relative "compression" of the whole spectrum of velocities between separate inertial frames within the model.
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    Quote Originally Posted by xyzt View Post
    Indeed, you used the wrong terminology. The speed at which the electron beam approaches the rocket as measured in the rocket frame is indeed given by the relativistic speed composition formula you used.
    I must apologise for using the wrong terminology, but I would have thought the phrase

    Quote Originally Posted by speedfreek
    the closing speed between the ship and the pulse as measured from the ship is:
    would have made it clear what I was referring to. I am glad I got the calculation correct, as that was what van erst was asking about in the first place.

    I hadn't realised that the term "closing speed" is only ever used from a third frame of reference, so thank you for that, I will make sure I do not misuse it in future.
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  27. #26  
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    Quote Originally Posted by van erst View Post
    there is a relative "compression" of the whole spectrum of velocities between separate inertial frames within the model.
    That seems like a fair statement.

    Imagine ship 1 moving at 1m/s relative to some rest frame, ship 2 moving at 1m/s relative to ship 1 in the frame of reference of ship 1, ship 3 moving at 1m/s relative to ship 2 in the frame of reference of ship 2, ..., ship N moving at 1m/s relative to ship N–1 in the frame of reference of ship N–1, etc. Then this can be continued ad infinitum, and yet no ship will exceed c relative to the rest frame or any other ship.
    There are no paradoxes in relativity, just people's misunderstandings of it.
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    Suppose there are three ships: 1, 2, and 3. Suppose that ship 2 is moving at velocity relative to ship 1 in the reference frame of ship 1, and ship 3 is moving at velocity relative to ship 2 in the reference frame of ship 2. Then what is the velocity of ship 3 relative to ship 1 in the reference frame of ship 1? If the motion of the three ships are collinear, then consider the Doppler ratios between the ships. Ship 1 sends a light beam of frequency to ship 2. Ship 2 receives that light beam redshifted with frequency:



    Also, ship 2 sends a light beam of frequency to ship 3. Ship 3 receives that light beam redshifted with frequency:



    But as the light beam from ship 1 passes ship 2 and onwards to ship 3, ship 3 can consider that light beam as originating from ship 2. Therefore, we can equate:



    And therefore ship 3 sees the light from ship 1 redshifted with frequency:



    But ship 3 can also apply the Doppler formula directly to the light from ship 1, with the light from ship 1 redshifted with frequency:



    Therefore:



    In other words, Doppler ratios multiply.

    Solving this equation for in terms of and gives the relativistic velocity "addition" formula.
    Last edited by KJW; December 8th, 2013 at 01:44 PM.
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post
    So in terms of "closing speed" we should expect to be able to measure relative speeds greater than c for light?
    Closing speed and relative speed are TWO DIFFERENT notions, so, your sentence makes no sense.
    Aren't closing speeds still just relative speeds? I would assume that the pulse of light has only one relative speed that the ship can measure. Or am I wrong?
    Your follow-on is a non-sequitur since your initial question is nonsensical.
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by KJW View Post
    xyzt's answer is in the frame of reference of the beacon. SpeedFreek's answer is in the frame of reference of the ship.
    Will they disagree which pulse hits the ship first?
    No, they will not disagree. KJW gave you a more detailed answer. You seem to be still looking (in vain) for contradictions inside relativity, you won't find any.
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    Quote Originally Posted by xyzt View Post
    Your follow-on is a non-sequitur since your initial question is nonsensical.
    Yes, I understand the problem with the original post now after reviewing the mathematical properties within the model.

    Quote Originally Posted by xyzt View Post
    You seem to be still looking (in vain) for contradictions inside relativity, you won't find any.
    I am merely trying to enhance my own understanding by rooting out any possible misconceptions I might have with regards to Relativity. The only way to do that is by asking questions on the subjects that I have trouble understanding. I am only happy to be corrected as in this case also.
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    I was thinking about the methods of using relativistic calculations in a networked computer game / simulation. One thing keeps puzzling me about aiming these beams towards opponents to fire pulses at them.

    Say that there are two space ships in relative sideways movement and one of them fires at the other. From his perspective he can not aim directly at the other ship but instead he has to aim where he predicts the ship will be in his frame when the fired pulse reaches it. So the ship that fires can not aim directly at the other ship.

    How about from the perspective of the ship that is being fired at, does that ship agree that the other ship can not aim the beam directly at them?
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    Quote Originally Posted by van erst View Post

    Quote Originally Posted by xyzt View Post
    You seem to be still looking (in vain) for contradictions inside relativity, you won't find any.
    I am merely trying to enhance my own understanding by rooting out any possible misconceptions I might have with regards to Relativity. The only way to do that is by asking questions on the subjects that I have trouble understanding. I am only happy to be corrected as in this case also.
    Based on the jist of your posts, I don't think you are telling the truth. If you really wanted to learn, you would have taken a class. Your questions are always a setup in an attempt to showcase an internal contradiction in the theory of relativity. It is true that you have somewhat toned it down but your intentions still show.
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    Quote Originally Posted by van erst View Post
    I was thinking about the methods of using relativistic calculations in a networked computer game / simulation. One thing keeps puzzling me about aiming these beams towards opponents to fire pulses at them.

    Say that there are two space ships in relative sideways movement and one of them fires at the other. From his perspective he can not aim directly at the other ship but instead he has to aim where he predicts the ship will be in his frame when the fired pulse reaches it. So the ship that fires can not aim directly at the other ship.

    How about from the perspective of the ship that is being fired at, does that ship agree that the other ship can not aim the beam directly at them?
    Yes, they both agree that they need to fire at angle different than , Janus and I have talked to you about "aberration" in another thread.
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    Quote Originally Posted by xyzt View Post
    Based on the jist of your posts, I don't think you are telling the truth. If you really wanted to learn, you would have taken a class. Your questions are always a setup in an attempt to showcase an internal contradiction in the theory of relativity. It is true that you have somewhat toned it down but your intentions still show.
    I know my own intentions, I have stated them multiple times. If you are a believer you can believe whatever you want. Intentions never show. Intentions are thoughts and thus can never be seen.

    It is quite foolish to make claims about intentions of others but you do what you want.
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    Quote Originally Posted by xyzt View Post
    Yes, they both agree that they need to fire at angle different than , Janus and I have talked to you about "aberration" in another thread.
    Well to me it just seems a bit weird. In the rest frame of the ship that fires the pulse, the pulse just travels directly away from the ship towards the direction it was fired. The weird part is that in the frame of the other ship another relative velocity component is added to the original velocity vector of the light pulse. The pulse does not travel towards the direction it was fired at in the frame of the ship that is being fired at…
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Yes, they both agree that they need to fire at angle different than , Janus and I have talked to you about "aberration" in another thread.
    Well to me it just seems a bit weird.
    Doesn't matter how "it feels" to you. What matters is how it is. You should really try taking a class. BTW, you are fishing again and you are wrong again.
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    Quote Originally Posted by xyzt View Post
    Doesn't matter how "it feels" to you. What matters is how it is. You should really try taking a class. BTW, you are fishing again and you are wrong again.
    I'm only presenting my wish to understand. The notion within Relativity is that it is not allowed to add to the velocity of light. Then you just go and add to the velocity of light. Perhaps you could explain to me why the velocity addition is done to help me understand. I am simply just accepting the fact that currently I don't understand and a feasible explanation does exist.

    For my part there is nothing here to be wrong about, I am asking a question, not making a claim.
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Doesn't matter how "it feels" to you. What matters is how it is. You should really try taking a class. BTW, you are fishing again and you are wrong again.
    I'm only presenting my wish to understand. The notion within Relativity is that it is not allowed to add to the velocity of light. Then you just go and add to the velocity of light.
    False. Instead of making crackpot statements , go take a class.



    For my part there is nothing here to be wrong about, I am asking a question, not making a claim.
    You just made a claim.
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    Quote Originally Posted by xyzt View Post
    For my part there is nothing here to be wrong about, I am asking a question, not making a claim.
    You just made a claim.
    Huh? What was my claim?
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    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Doesn't matter how "it feels" to you. What matters is how it is. You should really try taking a class. BTW, you are fishing again and you are wrong again.
    I'm only presenting my wish to understand. The notion within Relativity is that it is not allowed to add to the velocity of light. Then you just go and add to the velocity of light.
    False. Instead of making crackpot statements , go take a class.
    Are you indicating that the bold text here that I wrote was that claim of mine and you say it is false?

    They were your words that both ships agree that the pulse must be aimed not at the ship. So it is your claim and not mine
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Doesn't matter how "it feels" to you. What matters is how it is. You should really try taking a class. BTW, you are fishing again and you are wrong again.
    I'm only presenting my wish to understand. The notion within Relativity is that it is not allowed to add to the velocity of light. Then you just go and add to the velocity of light.
    False. Instead of making crackpot statements , go take a class.
    Are you indicating that the bold text here that I wrote was that claim of mine and you say it is false?

    They were your words that both ships agree that the pulse must be aimed not at the ship. So it is your claim and not mine
    Crackpot. Persistent.
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Doesn't matter how "it feels" to you. What matters is how it is. You should really try taking a class. BTW, you are fishing again and you are wrong again.
    I'm only presenting my wish to understand. The notion within Relativity is that it is not allowed to add to the velocity of light. Then you just go and add to the velocity of light. Perhaps you could explain to me why the velocity addition is done to help me understand. I am simply just accepting the fact that currently I don't understand and a feasible explanation does exist.
    It is perfectly okay to add to the velocity of light, you'll just end up with answer where the speed of light is always c. The point is that velocity is speed and direction, and while the speed remains constant, the velocity might not.

    If you add velocities which are parallel to each other you can use:


    (where U and V are measured as fractions of the speed of light).

    Thus when U = c =1, you get



    Both speed and direction remain unchanged and thus the velocity remains the same

    If the velocities are orthogonal to each other, you can use



    Again, if U=c=1,





    The speed remains c, however the direction does change, so does the velocity.

    It is not that the velocity of light is constant, but that its speed is.
    Last edited by Janus; December 10th, 2013 at 10:27 PM.
    Howard Roark and van erst like this.
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    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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    Once again, this situation is analogous to Einstein's light clock, where light is bouncing back and forth between two parallel mirrors. If the mirrors were a light second apart, then the light would take 1 second to go from one mirror to the other. But to an observer for whom those mirrors are moving sideways, the light takes more than 1 second to go from one mirror to the other.


    The reason the light takes longer when the light clock is moving relative to an observer is not because anything is happening to the speed of light, it is because the distance the light has to travel between the mirrors has increased. So, if the light takes 1 second to move between the mirrors in the rest frame of the mirrors, it will take more than 1 second to move between the mirrors in any frame of reference where the mirrors are in motion. This is where time-dilation comes from.
    "Ok, brain let's get things straight. You don't like me, and I don't like you, so let's do this so I can go back to killing you with beer." - Homer
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    Quote Originally Posted by Janus View Post
    The speed remains c, however the direction does change, so does the velocity.

    It is not that the velocity of light is constant, but that its speed is.
    Ok. So essentially addition of another relative velocity component to light velocity is allowed under certain conditions. Mainly it is done always, unless the relative velocity vector of movement is parallel to the light velocity vector. Roger that.

    This means that the notion that one could not move relative to light is another misconception.

    Quote Originally Posted by xyzt View Post
    Crackpot. Persistent.
    Instead of leaving these nonsensical comments you should learn from Janus above.
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    Quote Originally Posted by van erst View Post

    This means that the notion that one could not move relative to light is another misconception.
    Only in your head, you cannot attach a frame of reference to light.
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    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post

    This means that the notion that one could not move relative to light is another misconception.
    Only in your head, you cannot attach a frame of reference to light.
    What does that even mean?

    As we already concluded above, relative velocity components are added to light velocities. Just the speed c has to remain, and it is achieved via time dilation.
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post

    This means that the notion that one could not move relative to light is another misconception.
    Only in your head, you cannot attach a frame of reference to light.
    What does that even mean?
    It means that you can't attach a frame of reference to light, contrary to your fringe claim.

    As we already concluded above, relative velocity components are added to light velocities.
    This doesn't mean that we've attached any frame of reference to light.


    Just the speed c has to remain, and it is achieved via time dilation.
    Nothing to do with time dilation.You still don't want to take a class? Why?
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    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post

    This means that the notion that one could not move relative to light is another misconception.
    Only in your head, you cannot attach a frame of reference to light.
    What does that even mean?
    It means that you can't attach a frame of reference to light, contrary to your fringe claim.

    As we already concluded above, relative velocity components are added to light velocities.
    This doesn't mean that we've attached any frame of reference to light.


    Just the speed c has to remain, and it is achieved via time dilation.
    Nothing to do with time dilation.You still don't want to take a class? Why?
    What are you talking about???

    Above we came to the conclusion that relative velocity components are added to light velocities. This by definition means that as an relativistic observer you CAN move relative to light. I thought that this was the common agreement above. What is your problem, are you now suddenly disagreeing? If so, why?
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post

    This means that the notion that one could not move relative to light is another misconception.
    Only in your head, you cannot attach a frame of reference to light.
    What does that even mean?
    It means that you can't attach a frame of reference to light, contrary to your fringe claim.

    As we already concluded above, relative velocity components are added to light velocities.
    This doesn't mean that we've attached any frame of reference to light.


    Just the speed c has to remain, and it is achieved via time dilation.
    Nothing to do with time dilation.You still don't want to take a class? Why?
    What are you talking about???

    Above we came to the conclusion that relative velocity components are added to light velocities.
    Yes. They can be added, always producing "c":




    This by definition means that as an relativistic observer you CAN move relative to light.
    Nope, you cannot attach a frame of reference to light, take that class I recommended to you. Beats spouting nonsense.
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    Quote Originally Posted by xyzt View Post
    Nope, you cannot attach a frame of reference to light, take that class I recommended to you. Beats spouting nonsense.
    Why do you keep twisting what I say?

    Relativistic observers can move relative to a pulse of light. That's all I said. You're the one spewing nonsense. Do you have some sort of obsession to desperately find disagreement?
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Nope, you cannot attach a frame of reference to light, take that class I recommended to you. Beats spouting nonsense.
    Why do you keep twisting what I say?

    Relativistic observers can move relative to a pulse of light. That's all I said.
    No, they can't, basic relativity teaches you that cannot reference anything to a pulse of light. You keep persisting in your crackpottery.
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    Quote Originally Posted by xyzt View Post
    No, they can't, basic relativity teaches you that cannot reference anything to a pulse of light. You keep persisting in your crackpottery.
    It seems that you have misunderstood basic relativity.

    If a laser pulse is fired at you, can you not move relative to it while it is traveling to avoid it hitting you? Can you not dodge a laser pulse?
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    No, they can't, basic relativity teaches you that cannot reference anything to a pulse of light. You keep persisting in your crackpottery.
    It seems that you have misunderstood basic relativity.
    Nope but you clearly do.


    If a laser pulse is fired at you, can you not move relative to it while it is traveling to avoid it hitting you? Can you not dodge a laser pulse?
    This doesn't mean that you can attach a reference frame to the light pulse. Not only that you are ignorant, you are also persistent in your ignorance, despite your claims that you "want to learn".
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    Quote Originally Posted by xyzt View Post
    This doesn't mean that you can attach a reference frame to the light pulse. Not only that you are ignorant, you are also persistent in your ignorance, despite your claims that you "want to learn".
    You're the one babbling about attaching a frame of reference to the light pulse. I didn't say anything about that.

    You just move relative to the pulse to avoid it hitting you. Now stop babbling nonsense!
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    This doesn't mean that you can attach a reference frame to the light pulse. Not only that you are ignorant, you are also persistent in your ignorance, despite your claims that you "want to learn".
    You're the one babbling about attaching a frame of reference to the light pulse.
    Because this is precisely what you have been babbling about. :-)
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    Quote Originally Posted by xyzt View Post
    Because this is precisely what you have been babbling about. :-)
    YOU are the only one here that has mentioned attaching a reference frame to light.
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    Quote Originally Posted by van erst View Post
    This means that the notion that one could not move relative to light is another misconception.
    Obviously, you don't even understand the meaning your of own words. Yet, you pretend that you are here "to learn". You are just lying.
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    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post
    This means that the notion that one could not move relative to light is another misconception.
    Obviously, you don't even understand the meaning your of own words. Yet, you pretend that you are here "to learn". You are just lying.
    You clearly have no idea what you are talking about. Suppose I have fired a laser pulse at some direction into open space. I want to move relative to that pulse that I fired.

    Here is a simple question for you:
    If I move to left, then right, and keep repeating these movements, will the modeled path of the pulse in my own rest frame form a sawtooth pattern or a direct line?
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post
    This means that the notion that one could not move relative to light is another misconception.
    Obviously, you don't even understand the meaning your of own words. Yet, you pretend that you are here "to learn". You are just lying.
    You clearly have no idea what you are talking about.
    Actually, I do. This is why I can point out your crank ideas so easily (see redline).

    If I move to left, then right, and keep repeating these movements
    The motion is relative to the frame you were originally at rest, not with respect "to light". Stop trolling, take the class I recommended for you.

    will the modeled path of the pulse in my own rest frame form a sawtooth pattern or a direct line?
    Neither, take a class.
    Last edited by Howard Roark; December 11th, 2013 at 02:43 PM.
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    Quote Originally Posted by xyzt View Post
    will the modeled path of the pulse in my own rest frame form a sawtooth pattern or a direct line?
    Neither, take a class.
    Huh? If I want to model that path of the pulse in my rest frame, how would I model it? What kind of pattern would its path form in my rest frame?
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    will the modeled path of the pulse in my own rest frame form a sawtooth pattern or a direct line?
    Neither, take a class.
    Huh? If I want to model that path of the pulse in my rest frame, how would I model it?
    Every time I point out your mistakes, you come up with new questions. Acknowledge your mistakes, after that I will teach you the answer to your new questions.
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    Quote Originally Posted by xyzt View Post
    Every time I point out your mistakes, you come up with new questions. Acknowledge your mistakes, after that I will teach you the answer to your new questions.
    I don't quite understand what I got wrong here as I thought we found an agreement when Janus posted his quite reasonable post. Sure, I'll accept that my understanding might be totally wrong, I may have mistaken and I make no claims here.

    Can you now answer the above question about modeling the path of the pulse in the rest frame?
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Every time I point out your mistakes, you come up with new questions. Acknowledge your mistakes, after that I will teach you the answer to your new questions.
    I don't quite understand what I got wrong here as I thought we found an agreement when Janus posted his quite reasonable post. Sure, I'll accept that my understanding might be totally wrong, I may have mistaken and I make no claims here.

    Can you now answer the above question about modeling the path of the pulse in the rest frame?
    Nope, because you are evading admitting that you are wrong.
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    Quote Originally Posted by xyzt View Post
    Nope, because you are evading admitting that you are wrong.
    Wrong about what exactly? I didn't make any claims.
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    Quote Originally Posted by van erst View Post
    It occurred to me that electrons can be accelerated very close to the speed of light (over 99%) but Relativity handles electrons differently than photons.

    A hypothetical scenario:
    1. a beacon with a laser beam and an electron beam is set up in space
    2. a ship that controls those beams is stationary relative to the beacon (say at 5 light minute distance)
    3. the ship initiates simultaneous pulses with both beams towards itself
    4. the ship begins to travel at 0.5*c towards the beacon and the pulses

    According to Relativity the ship can not accelerate relative to the laser pulse, but it can accelerate relative to the electron pulse.

    Will the ship encounter the electron pulse first?
    The way you phrased the initial question demonstrates your level of crackpottery. The bottom line is that the ship will always encounter the laser pulse first in your above scenario. Now, that your question has been answered by several people, could you stop trolling?
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    Quote Originally Posted by xyzt View Post
    The way you phrased the initial question demonstrates your level of crackpottery. The bottom line is that the ship will always encounter the laser pulse first in your above scenario. Now, that your question has been answered by several people, could you stop trolling?
    I thought I already expressed it clearly that the original question had a premise that was a misconception. This is why it is good to ask these questions. To get the misconceptions revealed.

    In the initial post I was wrong. Is that what you wanted? I was wrong. Can you now answer the question about modeling the path?
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    The way you phrased the initial question demonstrates your level of crackpottery. The bottom line is that the ship will always encounter the laser pulse first in your above scenario. Now, that your question has been answered by several people, could you stop trolling?
    I thought I already expressed it clearly that the original question had a premise that was a misconception. This is why it is good to ask these questions. To get the misconceptions revealed.

    In the initial post I was wrong. Is that what you wanted? I was wrong.
    Yes, this is what I wanted. You were wrong. Not only in the initial post but in the subsequent ones as well.


    Can you now answer the question about modeling the path?
    Since you are oscillating left-right, the light beam will oscillate right left, like a pendulum wrt to you.
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    Quote Originally Posted by xyzt View Post
    Since you are oscillating left-right, the light beam will oscillate right left, like a pendulum wrt to you.
    So essentially I am able to move relative to the pulse of light, am I not?
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Since you are oscillating left-right, the light beam will oscillate right left, like a pendulum wrt to you.
    So essentially I am able to move relative to the pulse of light, am I not?
    That is the problem with you, you persist in your crackpottery, every question is a setup. There is no "relative to a pulse of light", get this?
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    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Since you are oscillating left-right, the light beam will oscillate right left, like a pendulum wrt to you.
    So essentially I am able to move relative to the pulse of light, am I not?
    That is the problem with you, you persist in your crackpottery, every question is a setup. There is no "relative to a pulse of light", get this?
    Take a look at your own writing in the red. Moving with respect to the pulse is the same thing as moving relative to the pulse.

    You said the same thing as I.
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Since you are oscillating left-right, the light beam will oscillate right left, like a pendulum wrt to you.
    So essentially I am able to move relative to the pulse of light, am I not?
    That is the problem with you, you persist in your crackpottery, every question is a setup. There is no "relative to a pulse of light", get this?
    Take a look at your own writing in the red.


    No, for the last time, you cannot move relative to light, you cannot attach a frame of reference to light.. So, no , you are not saying the same thing I am saying.

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    Quote Originally Posted by xyzt View Post

    The redlined writing is your OWN.
    I colored your writing in red. Your post #67. Not my writing.
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    Quote Originally Posted by xyzt View Post

    No, for the last time, you cannot move relative to light, you cannot attach a frame of reference to light.. So, no , you are not saying the same thing I am saying.
    Oh.. You edited your post after I had responded to it.

    Ok… So. You said the pulse of light will "oscillate right left" with respect to me. How is that possible if I'm not able to move relative to it?
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post

    The redlined writing is your OWN.
    I colored your writing in red. Your post #67. Not my writing.
    Crank. Persistent. Incorrigible.
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    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post

    The redlined writing is your OWN.
    I colored your writing in red. Your post #67. Not my writing.
    Crank. Persistent. Incorrigible.
    I'm sorry I responded to you post while you were editing it… Can you respond to post #73?
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    Quote Originally Posted by van erst View Post

    Ok… So. You said the pulse of light will "oscillate right left" with respect to me. How is that possible if I'm not able to move relative to it?

    Mainstream physics teaches you "how". Take the class, stop trolling.
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    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post

    Ok… So. You said the pulse of light will "oscillate right left" with respect to me. How is that possible if I'm not able to move relative to it?

    Mainstream physics teaches you "how". Take the class, stop trolling.
    Sigh… Well according to Relativity light does not propagate like a slow pendulum wrt to me. So it must be my movement wrt the pulse of light that only makes it appear that way, right?
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post

    Ok… So. You said the pulse of light will "oscillate right left" with respect to me. How is that possible if I'm not able to move relative to it?

    Mainstream physics teaches you "how". Take the class, stop trolling.
    Sigh… Well according to Relativity light does not propagate like a slow pendulum wrt to me. So it must be my movement wrt the pulse of light that only makes it appear that way, right?
    Didn't I and Janus try to teach you about "aberration"? Several times. Why don't you go back and read our answers?
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    Quote Originally Posted by xyzt View Post
    Didn't I and Janus try to teach you about "aberration"? Several times. Why don't you go back and read our answers?
    Aberration does not deal with light propagating away from me, does it?
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Didn't I and Janus try to teach you about "aberration"? Several times. Why don't you go back and read our answers?
    Aberration does not deal with light propagating away from me, does it?
    We were discussing a different scenario, your moving right left , why can't you stay on topic?
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    Quote Originally Posted by xyzt View Post
    We were discussing a different scenario, your moving right left , why can't you stay on topic?
    I thought I was on topic. Wasn't it I that hypothetically fired the pulse of light?
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    We were discussing a different scenario, your moving right left , why can't you stay on topic?
    I thought I was on topic. Wasn't it I that hypothetically fired the pulse of light?
    But you changed it to a DIFFERENT scenario, the one where you oscillate right left, when you claimed the "sawtooth" pattern. You are a troll.
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    Quote Originally Posted by xyzt View Post
    But you changed it to a DIFFERENT scenario, the one where you oscillate right left, when you claimed the "sawtooth" pattern. You are a troll.
    You were happily discussing that scenario until now. That was the simple scenario about modeling the pulse of light in my rest frame when I move after firing the pulse of light.

    What's wrong now then?
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    Quote Originally Posted by van erst View Post
    Sigh… Well according to Relativity light does not propagate like a slow pendulum wrt to me. So it must be my movement wrt the pulse of light that only makes it appear that way, right?
    If you are repeatedly moving to the left and right of a light-beam, that means you are no longer in an inertial frame of reference, and the equations of special relativity no longer hold, and you need general relativity to describe the propagation equations of the light within the accelerated frame of reference.

    The point xyzt was making is that light does not form a valid frame of reference as light can never be at rest (in a vacuum). One can't speak of objects moving relative to light. Instead, one describes the trajectory of light in other frames of reference, and the motion of objects is described in these other frames of reference. If one does speak of an object moving relative to light, then it is to be understood that this is within some other valid frame of reference and not the frame of reference of the light itself.
    Howard Roark likes this.
    There are no paradoxes in relativity, just people's misunderstandings of it.
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    Quote Originally Posted by KJW View Post
    If one does speak of an object moving relative to light, then it is to be understood that this is within some other valid frame of reference and not the frame of reference of the light itself.
    Sure. I thought this was the agreement we came to earlier. It is obvious that in the universe we observe we can move side ways relative to a pulse of light to avoid it hitting us.

    Within Relativity one can not change the time it takes for a pulse to reach them once the pulse is fired. If an observer is 10 light minutes away from the device that fires a pulse, no amount of acceleration will change the amount of time the pulse takes until it will reach them. It reaches them in exactly 10 light minutes.
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    Quote Originally Posted by van erst View Post

    Within Relativity one can not change the time it takes for a pulse to reach them once the pulse is fired. If an observer is 10 light minutes away from the device that fires a pulse, no amount of acceleration will change the amount of time the pulse takes until it will reach them. It reaches them in exactly 10 light minutes.
    False. Elapsed time is frame dependent. In one frame the elapsed time may be 10lm, in frames moving wrt that frame, the elapsed time is more. You really need to stop posting nonsense.
    Besides, the amount of time is where is the speed of the observer. This guarantees, that contrary to your erroneous claim,
    Last edited by Howard Roark; December 14th, 2013 at 12:56 PM.
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    Quote Originally Posted by xyzt View Post
    False. Elapsed time is frame dependent. In on frame the elapsed time may be 10lm, in frames moving wrt that frame, the elapsed time is more. You really need to stop posting nonsense.
    Why are you constantly looking for disagreement?

    If an observer does this:
    1. remotely trigger a pulse at them from 10 light minutes distance
    2. ensure that in their frame they begin to accelerate away from the pulse simultaneously when the pulse fires
    3. constantly accelerate until the pulse hits them

    For them, does it take exactly 10 minutes from the beginning of the acceleration to the pulse hitting them?
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    False. Elapsed time is frame dependent. In on frame the elapsed time may be 10lm, in frames moving wrt that frame, the elapsed time is more. You really need to stop posting nonsense.
    Why are you constantly looking for disagreement?
    I simply disagree with the rubbish you keep posting.
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    Quote Originally Posted by xyzt View Post
    I simply disagree with the rubbish you keep posting.
    Are you capable of answering the last question?
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    I simply disagree with the rubbish you keep posting.
    Are you capable of answering the last question?
    Yes, you do not even understand my corrections to the rubbish you keep posting.
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    Quote Originally Posted by xyzt View Post
    Yes, you do not even understand my corrections to the rubbish you keep posting.
    If your answer is yes to the question below then my post was not rubbish.

    Quote Originally Posted by van erst View Post
    If an observer does this:
    1. remotely trigger a pulse at them from 10 light minutes distance
    2. ensure that in their frame they begin to accelerate away from the pulse simultaneously when the pulse fires
    3. constantly accelerate until the pulse hits them

    For them, does it take exactly 10 minutes from the beginning of the acceleration to the pulse hitting them?
    Can we get an answer for this question?
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Yes, you do not even understand my corrections to the rubbish you keep posting.
    If your answer is yes to the question below then my post was not rubbish.
    Your posts are anti-mainstream rubbish. Consistently.

    Quote Originally Posted by van erst View Post
    If an observer does this:
    1. remotely trigger a pulse at them from 10 light minutes distance
    2. ensure that in their frame they begin to accelerate away from the pulse simultaneously when the pulse fires
    3. constantly accelerate until the pulse hits them

    For them, does it take exactly 10 minutes from the beginning of the acceleration to the pulse hitting them?


    Nope. You keep repeating the same errors.
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    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post
    If an observer does this:
    1. remotely trigger a pulse at them from 10 light minutes distance
    2. ensure that in their frame they begin to accelerate away from the pulse simultaneously when the pulse fires
    3. constantly accelerate until the pulse hits them

    For them, does it take exactly 10 minutes from the beginning of the acceleration to the pulse hitting them?
    Nope. You keep repeating the same errors.
    Wait. Are you saying that the observer is able to accelerate away relative to the pulse so that it takes some other time than 10 minutes to reach them?
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post
    If an observer does this:
    1. remotely trigger a pulse at them from 10 light minutes distance
    2. ensure that in their frame they begin to accelerate away from the pulse simultaneously when the pulse fires
    3. constantly accelerate until the pulse hits them

    For them, does it take exactly 10 minutes from the beginning of the acceleration to the pulse hitting them?
    Nope. You keep repeating the same errors.
    Wait. Are you saying that the observer is able to accelerate away relative to the pulse so that it takes some other time than 10 minutes to reach them?
    I am saying that you are a crank and that you are unteachable. We have been over this subject several times.
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    Quote Originally Posted by xyzt View Post
    I am saying that you are a crank and that you are unteachable. We have been over this subject several times.
    I am only asking questions to try to understand what you mean. I thought we already found an agreement but now you seem to want to disagree on absolutely everything.

    Can the observer move relative to the pulse so that it takes longer than 10 minutes to reach them? My understanding was that they can not move relative to the pulse.
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    I am saying that you are a crank and that you are unteachable. We have been over this subject several times.
    I am only asking questions to try to understand what you mean.
    No, you are not, you are making (incorrect) statements and I correct them. You try to cover your errors by making other incorrect statements, on top of the initial ones.



    I thought we already found an agreement but now you seem to want to disagree on absolutely everything.
    I cannot agree with the rubbish you post. As long as you post rubbish, I will continue to disagree with you.
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    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    I am saying that you are a crank and that you are unteachable. We have been over this subject several times.
    I am only asking questions to try to understand what you mean.
    No, you are not, you are making (incorrect) statements and I correct them. You try to cover your errors by making other incorrect statements, on top of the initial ones.



    I thought we already found an agreement but now you seem to want to disagree on absolutely everything.
    I cannot agree with the rubbish you post. As long as you post rubbish, I will continue to disagree with you.
    Now I did not make any statement. I asked you a question. Can you please answer it?
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    Quote Originally Posted by van erst View Post
    I did not make any statement.
    You are lying. See here.
    You keep resorting to the same tactic: you make a crank statement, you are told that it is in error, then you pretend to be asking questions in order to cover up.
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    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post
    I did not make any statement.
    You are lying. See here.
    You keep resorting to the same tactic: you make a crank statement, you are told that it is in error, then you pretend to be asking questions in order to cover up.
    You have edited your post ~30 minutes after I read it.

    Sure. Lets say I made an error. Can you answer the last question? Can the observer accelerate relative to the pulse so that it takes something else than 10 minutes for it to reach them?
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    Quote Originally Posted by van erst View Post
    Quote Originally Posted by xyzt View Post
    Quote Originally Posted by van erst View Post
    I did not make any statement.
    You are lying. See here.
    You keep resorting to the same tactic: you make a crank statement, you are told that it is in error, then you pretend to be asking questions in order to cover up.
    You have edited your post ~30 minutes after I read it.

    Sure. Lets say I made an error.
    You did. Multiple.


    Can you answer the last question? Can the observer accelerate relative to the pulse so that it takes something else than 10 minutes for it to reach them?
    I already answered that. Get this: it always takes less than 10min.

    1. In the initial frame of the observer, before it started accelerating, it takes
    Remember that .

    2. In the frame co-moving with the observer , so, it takes even less time.

    Please go away for a while, take a break from trolling and reflect on the information you received.
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