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A Serious Question from an Educated Layman

  1. May 24, 2005 #1
    Point 1. All speed is relative to an observer and is never absolute (because there is no absolute frame of reference from which one can observe and measure).

    Point 2. The laws of physics hold true for all frames of reference (i.e., an inch is an inch no matter how fast you are traveling).

    Point 3. An object in motion will remain so until interfered with (by gravity, air friction, collision with another object, et cetera).

    I have been struggling with the logic behind the theory that light speed cannot be achieved by matter nor exceeded by anything. Using these three points, it doesn’t add up. I would like to illustrate my reasoning herein for a moment and submit it for a sort of peer review. I do not speak the language of tensor calculus, so my line of reasoning will come from my logical deduction. I conceptualize abstract ideas in my mind visually as opposed to mathematically, so please bear with me.

    The atomic clock aboard the fast airplane which fell behind its land-based twin seems to prove the theory that motion somehow affects time. The problem I see with this is that (point 1) motion is relative and cannot be absolutely measured, therefore motion itself cannot be the factor which causes the time dilation.

    But time dilation does occur…so something has to be the factor. There has to be interference because (point 3) objects in motion remain unaffected unless acted upon. Obviously there is gravity to consider. It constantly pulls down on the plane and the atomic clock as it travels over earth’s surface. Also, there is the earth’s magnetic field which the plane and clock are passing through at high speeds. And magnetic fields are well known for causing strange things to happen to atoms who pass through them at high speeds.

    Perhaps time dilation and length shortening of objects approaching the speed of light only occur because the things we have observed and experimented with were passing through magnetic and gravitic fields. It just doesn’t make sense logically that mere motion (which is not absolutely measurable) would have absolute effects. It is unfortunate we do not have a pure vacuum in which we can experiment outside the influence of gravity and magnetism.

    Perhaps photons going from the back of the plane to the front of the plane only appear to be making the distance at the speed of light because (A) the length of the plane is being shortened by passing through the magnetic/gravitic fields, or (B) the photons themselves are being hindered by the increased motion through the magnetic/gravitic fields. I’ve never heard of anyone creating a chamber which is void of geomagnetic or gravitic interference, so I know that no one has been able to prove or disprove the theory…which is obviously why it is still a theory and not a law.

    So, considering these three points and the above illustration, my questions to the scientific community are as follows:

    I. If light speed cannot be exceeded (or even achieved by matter without converting it to energy in the process), where is the absolute frame of reference which is being used to determine this?
    II. What is the factor which is interfering with the atoms that are in motion that causes the observable effects such as time dilation and length shortening if not magnetic and gravitic fields?
    III. What is to stop an object of matter from achieving or even exceeding the speed of light, provided the object has the fuel needed and is traveling through a perfect void where gravity and magnetism are not even factors?
    IV. How do we know there isn’t something out there beyond the reach of our universe which is right now traveling beyond the speed of light?

    I am posing these questions seriously because I want a straight answer—in layman’s terms, without the mathematics—which either disproves my logic point-for-point, or explains to me how some other genius physicist has also come to this conclusion and is trying right now to create the proper formulae to prove it mathematically (which would mean I’m not completely crazy by thinking this way and I should consider myself worthy of at least some credit for having sound logical deduction as my biggest talent).
  2. jcsd
  3. May 24, 2005 #2
    I think that's all inertial frames of reference, i.e. ones at which the object is at rest or travelling in a straight line with constant velocity. You could easily conceive of an experiment which yields different results at rest and in an accelerating vehicle.

    Ah, but the time dilation is also relative. The object in motion would not feel time pass any differently in its frame of reference, but to another frame of reference in which it is moving, there would be disagreement about how much time had passed. A third frame of reference would lead to a third value for how much time had passed. Time dilation is a consequence of relative motion.

    That would be amazingly coincidental, as Special Relativity does not touch on either, and yet the conclusions of it are remarkably accurate.

    ? You're quickly abandoning a theory supported by observed phenomena and proposing one that isn't.

    I think you're forgetting that photons are both massless and chargeless. The photon has relativistic mass, so will obey the laws of gravity, but the effect on a photon moving from one end of the plane to the other will be so close to zero you can call it zero. It still doesn't have charge though.

    ANY frame of reference. In the frame of reference in which a particle is at rest, it will undergo no mass increase. In a frame of reference in which it is moving near to the SoL, it will have a large mass increase (large amount of energy). A third, different FoR will yield a different relativistic mass (a different amount of energy). This is not derived from any absolute frame, but is derived differently in all inertial frames.

    Again, nothing is interfering with the atoms themselves. It's varying velocity across varying frames of reference will show that time has passed less for the object than for something at rest in those frames of reference. The amount depends on the velocity of the object in that frame of reference alone. A different frame may always be chosen and different values yielded.

    First, if you're talking about an object travelling with a given velocity, you must be doing so relative to a frame of reference in which that object has that velocity. In this frame of reference, by nature of the object's velocity the object will appear to increase in relativistic mass, and does so more and more the faster the object travels. In a sense, when you provide energy to an object with a given velocity, in the frame of reference in which the object has that velocity, more of that energy will be converted to relativistic mass rather than kinetic energy the faster that object is travelling.

    Relative to what?
  4. May 24, 2005 #3

    Tom Mattson

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    Not quite: The speed of light is absolute.

    That's correct. Although if you want to avoid tensor calculus you have to specify that the frames are inertial, as Hombre points out.

    Naturally, it won't add up if you look at them only as a set of premises without regard for their content. Requiring the corrected Point 1 as well as Point 2 above leads inexorably to the Lorentz transformation, from which the light speed barrier is predicted.

    It's OK if you don't know tensor calculus. Einstein deduced it with algebra and some basic calculus.

    I'd like to stop here and ask you if the correction to Point 1 changes your argument at all.
  5. May 24, 2005 #4


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    Need clarification as to your expectation here.

    An inch is an inch when measured by an observer making a measurement of something that's at rest with respect to her. But an inch measured of an object moving with respect to her will not measure an inch.

    Agree? Disagree?
  6. May 25, 2005 #5
    With regard to all the Points, these were quoted from the theories/laws. They mean whatever the author meant.

    In point 1, it seems quite clear that ANYTHING in motion can equally call its observer the one who is in motion. If this is true, we are all traveling light speed right now, relative to the photon's point of view. It's an impossible paradox! On a smaller scale, we are the ones traveling thousands of miles per hour away from the Cassini probe, so it is OUR clocks which should be going slower...but only from the perspective of the probe.

    In point 2, the words say one thing (that an inch is an inch and a minute is a minute, no matter what frame you are in) but they seem to be getting interpreted to mean another (an inch is an inch only to an observer WITHIN his own particular frame, not outside it). Has anyone proved that items shorten in length as motion is increased? If so, everything we see should be constantly shortening in length from the perspective of thousands of travelers in the airspace right now. Again, a seemingly impossible paradox.

    In point 3, I try to give some sort of rational explanation for the results science is giving us. Atoms shouldn't be affected by nothing more than motion (which is relative and means nothing without a relatively stationary observer), but they most definitely ARE affected by gravity and magnetism. Why would an atom on a plane act a certain way while the atoms on the ground refuse to? The atoms on the ground have just as much a reason to slow time and shorten in length as the ones on the plane, if the theory is to be considered. Because the ground is moving the speed of the plane in the opposite direction. Paradox!

    As I understand inertia, it refers to the effect caused by changes in motion...not by motion itself. That would be a whole different animal. When I speak of motion, I refer to the abstract idea of an object moving from A to B, even though in reality there is no A or B except what an observer dictates. From the "moving" observer, he is standing still while it is A and B which are moving. Both are right and wrong at the same time, so why should the atoms on one be affected differently than the atoms on another? It doesn't make sense logically.

    (And thanks for your polite responses. It's refreshing to not be shunned.)
  7. May 25, 2005 #6


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    I don't think your author correctly represented relativity. This can be derived rigorously from two postulates that sound a little like your author's, but the devil is in the details.

    1) ("Galilian relativity") Physics is the same in every unertial frame. Falling bodies, clocks, all physical experiments all come out the same for every observer who isn't accelerated.
    2) The speed of light is measured the same in every inertial frame. This is really an extension of the first, because measuring the speed of light is a physics experiment. But it has to be stated explicitly because it is contrary to Newtonian expectations.

    From these two postulates, or principles, you can derive the Lorentz transformations which describe length contraction, time dilation, and the relativity of simultenaity.
  8. May 25, 2005 #7


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    OK, couple of points to clarify:
    1] "anything in inertial motion (i.e not accelerating) can equally call its observer the one who is in motion". As soon as one of the objects is under the influence of a force that alters its velocity, it is no longer relative. We can determine which one is which. Remeber, relativity applies only in inertial frames of reference.

    2] "If this is true, we are all traveling light speed right now, relative to the photon's point of view." Photons do not have a 'point of view'. This is not merely mincing words. Nothing that has mass can be moving at the speed of light. Nothing. No object of any sort that could conceivably have a point of view is capable of moivng at the speed of light. What do photons experience? They do not experience anything at all. Photons quite simply do not experience the passage of time.
  9. May 28, 2005 #8

    This is what I meant: objects in an unchanging state of relative motion.

    And as for photon's points of view, let's forget photons. Say an observer on a ship traveling 99% light speed relative to a planet. Why would the traveler experience time dilation and length shortening while the planet does not? Why would the atoms on the ship act differently than the atoms on the planet if both can say that the other is the one in motion and both would be correct? It doesn't make sense! There is no physical difference between the atoms on the ship and the atoms on the planet. Everything is relative to everything else when it comes to defining objects in an unchanging state of motion. You CAN'T have the effect on one plane and not the other without some outside influence. It's impossible!
  10. May 28, 2005 #9


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    I'll see if I can straighten this out for you:

    "There is no physical difference between the atoms on the ship and the atoms on the planet. "

    Correct; but given say a rod at rest with respect to the ship frame, it doesn't follow that the length of that rod measured by a ship observer will equal the length of the rod as measured by a planet observer.
    In this case, the planet observer's length measurement of the rod will be smaller than the ship observer's length measurement of this rod.

    Similarly, consider a rod at rest with respect to the planet frame (which, obviously, is a different object than the rod at rest in the ship frame).
    In this case, the ship observer's length measurement will be less than the planet observer's length measurement.
    Last edited: May 28, 2005
  11. May 28, 2005 #10
    If that's true, there is no physical effect at all. It's all a matter of skewed perspective. They would only APPEAR to change in length. So what about time dilation? The same thing is true there as well, is it not?
  12. May 28, 2005 #11


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    Same thing with time dilation; however, you ought to be a bit careful when you use the word "skewed perspective":

    In its own rest frame, muons have an exteremely short life-time "t" (half-life value, if you like).
    When they enter the Earth's atmosphere, they have a velocity measured in the Earth frame very close to the speed of light.
    The Earth observer can, on basis of the muon's observed velocity, and the distance the Earth observer measures from the entrance point in the atmosphere to the ground estimate the time "T" it takes for the muon to reach the ground.

    Now, if we proceeded in a Newtonian manner, we would calculate the fraction of muons actually reaching the ground by comparing "t" and "T", i.e, regarding "t" as the correct life-time value of the (moving) muons as seen from the Earth.
    But that fractional value we'd get is totally false!!

    What we need to do, in the Earth frame, is to take into account the time dilation factor, which in the muon/Earth case amounts to that for the Earth observer, the muon lives about 22 times longer than its rest frame life-time "t".
    If we do this, we get the right answer.

    From the muon perspective, it is the distance from the entrance point to the ground which has contracted by the same factor, yielding the same final fractional value of how many muons actually reaches the ground as when we do the computation in the Earth frame.
  13. May 28, 2005 #12


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    You are falling into the trap of trying to attach a "mechanistic" cause for the effects of Relativity. Relativity is about the nature of time and space and how we measure them.

    Frames in motion relative to each other simply do not measure distances and times the same. One meter as measured by me would be 1/2 meter as measured by someone moving at 0.866c relative to me, and vice versa. One second measured by me would be 2 sec as measured by him, and vice versa.

    A third effect mentioned earlier, the "relativity of simultaneity", adds another wrinkle. The two frames will not agree as to whether events happen at the same time or not.

    Consider two events separated by a distance that lies along the axis of the relative motion. In one frame these events are simultaneous. From a frame in relative motion, they will not be. Again this effect is reciprical, events simulataneous in the seconf frame will not be so in the first.

    Using the muon example: according to the Earth clock, the muon enters the atmosphere at 0.00 and reaches the surface at time some time later t.

    The muon undergoes a time dilation by a factor of 22 and thus ages t/22 during the trip.

    From the muon's point of view, the Earth's atmosphere is only 1/22 the thickness it is as measured form the Earth and thus it only takes 1/22 the time to cross the atmosphere by the muon's clock to reach the surface, or t/22. Thus both the muon and Earth observer agree as to how much the Muon ages crossing the atmosphere.

    However, according to the muon, it is the Earth clock that undergoes time dilation by a factor of 22, and thus ages by an amount of t/484 in the time it takes for the muon to cross the atmosphere.

    This is where the relativity of simultaneity comes into play. While according to the Earth clock, the event of the muon entering the atmosphere and the clock reading 0.00 are simultaneous, they are not so for the muon. According to the muon, the Earth clock reads a time of t(1-1/484) at the instant the muon enters the atmosphere.

    The upshot is that while both the muon and earth observer agree as the both the age of the muon and what time the Earth clock reads when the muon reaches the surface, they do not agree as to why this result happens and neither's viewpoint on the sequence of events is any more valid than the other.
  14. May 28, 2005 #13


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    Note that Janus' and my posts do not contradict each other; rather, we're looking at the same problem in distinct, yet equally valid ways.
    Last edited: May 28, 2005
  15. May 28, 2005 #14
    About the simultanieity thing.

    What stops someone from taking his own velocity into account?

    The space ship you are on is going 100,000 mps relative to the sun & you see a meteor strike on Mars in front of you and then another on Earth behind you a few seconds later. Why could you not calculate your speed relative to the planets to determin 'when' each strike happened ?
  16. May 28, 2005 #15


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    Given the data established in one inertial frame (the time&space-coordinates of some event), you may calculate what the coordinates of the same event would be in another inertial frame by using a suitable Lorentz transformation.
  17. May 28, 2005 #16


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    You can, that's the whole point. Assume there is an observer at the midpoint between Earth and Mars and at rest with respect to the Sun. He sees the two meteor strikes at the same time, and knowing the distance to each is equal, determines that they occured simultaneously. You reach the midpoint at the same instant as he sees the strikes, so you also see them at the same time.

    You, however, taking into account your relative velocity to the Sun and the fact that light travels at c wrt yourself, "backtrack" the light signals back to the strikes, and determine that in order for you to have seen the light from each strike at the same time, the two strikes would have had to have occured at different times and not simultaneously.
  18. May 29, 2005 #17
    This was only true for the special theory of relativity; the general theory of relativity got rid of the need to make the distinction between an accelerating body and a body in uniform motion. Both can be said to be at rest:

    - Albert Einstein, Relativity: The Special and General Theory, Section 28
  19. May 29, 2005 #18
    Exactly my point. Both perspectives cancel each other out.

    But according to the traveling muon, it is the earth's atmosphere and surface which are traveling rather than it. It doesn't make sense that any special calculation need be made from either perspective that cannot be cancelled out by a complete change of perspective. The earth is moving toward the muon just as the muon is moving toward the earth. The muon is aging just the same as the earth is. The length of the muon craft is shortening by a factor exactly the same as the earth's atmosphere is. Any changes in time or length or distance that one observer measures will be the same for the other. If not, there is some third factor involved which applies to one and not the other. Thickness of atmosphere doesn't seem to cut it...that's just a matter of distance and has to be accounted for from both perspectives equally.

    Why would the earth be different just because it has an atmosphere? The muon's spacecraft or meteor also has physical features that have to be taken into account!
  20. May 30, 2005 #19


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    right, that is why from the Muon's frame it is the Earth and it's atmosphere that undergoes length contraction
    This statement doesn't make any sense. Within any frame the measurements in that frame do not change, only measurements of objects moving with respect to that frame change. There is nothing to "cancel out.
    The muon is not moving as far as the muon is concerned and thus does not contract or undergo time dilation in that frame.
    Rule 1: Time dilation and length contraction only happen to the "other guy".
    According to the Muon it is the Earth and its atmosphere that undergo time dilation and length contraction.
    According to the Earth is the muon that undergoes time dilation and length contraction.

    According to the Earth, the muon hits the atmosphere when it clock reads 0.00

    According to the muon it hits the atmosphere when the Earth clock read t(1-1/484) where t is the time the Earth clock reads when the muon reaches the surface.

    According to both, the Earth clock reads t when the muon reaches the surface.

    You can analyse the situation from either the Earth's frame or the muon's. But whichever you choose, you do not take the other's frames perspective into account. The muon does not care or is affected by how events appear to the Earth and the Earth does not care or is affected by how events appear to the Muon
  21. May 30, 2005 #20
    Let me take a stab at providing a suitable explanation. If you are only thinking in terms of time dilation and length contraction, then, no, relativity makes absolutely no sense. The "third factor" which you are searching for, as has been pointed out by others (although not plainly), is what is called relativity of simultaneity, and including this makes everything else make sense. Since we are in Michio Kaku's forum it seems quite fitting to quote from his book, Hyperspace. He gives a good, easy to understand example of how the apparent paradox you are confused about can be solved with the relativity of simultaneity.

    Kaku starts by describing a train moving at nearly the speed of light. As it speeds down the tracks, we would see it squished in the direction of its motion. We would also see everyone moving in slow motion on the train, because time will tick slower for people on the train from our perspective. But how does this look to someone moving on the train? According to the principle of relativity, any reference body can be chosen to be called "at rest" and all velocities can be based on that (ie: someone sitting on the train is justified in saying he is sitting still and the Earth is hurtling toward him--although this does seem to be a bit weird way of thinking of things, since we're used to thinking of trains as being the body in motion). Because of this, we know that someone sitting on the train would see a squished version of the Earth and everything on it. A passenger on the train would also see everything in the outside, squished world moving in slow motion, because the Earth's time would move slower than his, due to the velocity of the Earth moving toward him. This is where the paradox arises. How can they both claim the other is squished and how can both of their clocks be moving slower than each other? The answer lies in the relativity of simultaneity, as Kaku explains:

    - Michio Kaku, Hyperspace, Notes: Chapter 4, note 3

    Since you seem to be interested, I recommend reading a few books about relativity and the universe in general. Hyperspace is a great book to start with; it covers a wide range of ideas and Kaku explains things using very easy to understand analogies.
    Last edited: May 30, 2005
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