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The EXPERIENCE of Relativity

  1. Apr 12, 2003 #1

    Les Sleeth

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    In Lifegazer’s thread on relativity, he raised the issue of the experience of relativity, then Fliption gave what I thought was a solid interpretation of that idea, and I raised the matter again in my thread on potential. So far no one has offered any suggestions on what to expect and so I remain very curious to hear opinions on this. I’ve framed the question in GR’s twins paradox.

    The question is, would each twin's experience of time be the same? Say the traveling twin were gone five years according to shipboard clocks, and when he came back to Earth saw that 40 years had passed according to Earth clocks.

    Although only five years had passed would the traveling twin feel like it had been the longest five years he'd ever experienced? That is, though his physical situation had been subject to time constriction, did it also make his consciousness fully relative to the physical circumstances?
     
  2. jcsd
  3. Apr 12, 2003 #2
    You try spending five years cooped up on a rocketship and tell me it isn't the longest five years of your life. (sorry, just had to get that in.)
     
  4. Apr 12, 2003 #3

    Les Sleeth

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    That's funny Wuli, but not a bad point either. For the sake of proper control in this experiement, I suppose we'd have to make the space ship a Galactica-type, so it was big enough to keep someone from going nuts.
     
  5. Apr 12, 2003 #4
    You just answered your question, if in fact your'e allowed to provide for everyone's comfort and "well being."
     
  6. Apr 12, 2003 #5

    Les Sleeth

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    Not really. The idea is simply to not have excessive discomfort be the cause of judging "time" as longer than usual.

    What we are after is if all other factors are constant, will the experiences of those in significantly different frames of GR reference be noticable?
     
  7. Apr 12, 2003 #6
    If I feel comfortable and I feel fine, then I doubt if I'm going experience anything other than "what's normal." Including time.

    Otherwise we'll need to address those "ill-effects," lest we get sick and die.
     
  8. Apr 12, 2003 #7

    ahrkron

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    Not at all. They would experience time in exactly the same way.

    Think of it this way: up to the moment one of them turns around (breaking the symmetry of the system), there is no way of telling who will be the youngest brother when they get back together.

    Another way of undestanding it is this: relativistic time dilation affects all processes that you can use as measures of time. This not only includes quartz chrystals and radioactive decays, but also all those electrochemical processes that happen while you experience what you call "thinking".

    The heart of the issue is that you cannot say that one twin has the "real" time, while the other is "delayed". This would be the same as assuming the existence of a preferred frame (plus the indefensible assumption that one of the twins is at, or closer to, the "right" time).
     
  9. Apr 12, 2003 #8

    Les Sleeth

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    I probalby should have made it more clear that I've assumed the twins grew up together, and so when the space trip happens, the traveling twin will have an experience of time that is different from that in which he grew up. I do NOT mean one frame of reference is preferred; I mean one frame of reference conditions the traveling twin to expect a certain pace of time.

    True for purely material processes, which it seems you are assuming that consciousness is fully a product of. But even "thinking," on this issue at least, is preceded by the traveling twin's experience. I am asking if the traveling twin's consciousness will notice the difference in the rate of time.
     
  10. Apr 13, 2003 #9

    Janus

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    There is no "difference in time rate" to notice (at least not in the way you are thinking of it). Instead, for the "traveling twin", the distance "traveled" is shorter than that measured by the "stay at home" twin, and thus takes less time to traverse.
     
  11. Apr 13, 2003 #10

    Les Sleeth

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    I am going to question you further, not because I necessarily disagree, but because I do not yet believe what I am asking you answered.

    First, let me be certain I understand your interpretation. When you say there is no difference in time rate to notice, are you saying that time has not been constricted for the traveling twin during the journey? It is "space-time" is it not that has been altered?

    If time is not an issue, then how can it be the traveling twin finds his brother 35 years more aged than himself?
     
  12. Apr 13, 2003 #11
    Spacetime isn't truly "altered" at all, it is just percieved in different ways. In any case, both twins' clocks, brains, rulers, bodily functions, lightbulbs, control pannels, anything, seem completely normal. The twin who comes home to find himself younger than everybody else will be very surprised, because his clock said it only took a little while, at no time did he feel as though time was being slowed down, at no time did anything seem unusual, unless he had decided to take a look at his surroundings closely.

    And, as archaron has said, it's not as though the twin on the rocket is in motion and the other is at rest. Halfway through the whole cherade, while the rocket twin is still on his way off, niether twin can be said to be older. From the perspective of the earth-twin, the rocket twin should be younger. From the perspective of the rocket twin, the earth-twin should be younger. It is when the rocket-twin turns his ship around and starts heading back that he has altered things to the point that he, is for sure, the one that will have aged less. He passed through 2 different realms of time (with respect to the earth-twin.)
     
  13. Apr 13, 2003 #12
    This statement is so full of inconsistencies. The major one being between your first sentence, and your final sentence.

    LWS... What you should realise about Relativity, is that it states all observers experience a different/unique universe. They literally experience a different universe. In the case of the twins, one might see his whole universe age 5 years, and the other twin 40 years.
    Let's imagine if we sent 2 brothers to watch a game of football from different positions in the stand (this analogy loosely mirrors the spacetwin scenario, whereby the universe can be equated to ~the game~). If we sit next to the person who experiences the whole game (representing the earth-twin), we can know via the Lorentz-transformation, that the other observer (the spacetwin) has yet to see the second-quarter start.
    Paradoxically; what would now happen if the guy who had already seen the game was now to go and 'sit with the observer' (have motion and position like the spacetwin) who has not yet seen the whole game? [Let's imagine that this observer (earthtwin) has the capacity to catch-up with the other observer in a matter of seconds - which wouldn't be difficult if they shared the same radial-of-orbit, as in my thread's example.]. Would he see the second-quarter (or catch the end of the game) again as he met up with his brother? Of course not. This would require time to actually reverse.
     
  14. Apr 13, 2003 #13

    Les Sleeth

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    I can almost agree that "both twins' clocks, brains, rulers, bodily functions, lightbulbs, control pannels, anything, seem completely normal." What you assume is that every element of a human being will be subjected to relativity; I am wondering if experientially he will be made to fully accomodate relativity.

    Because relativity is only a physical principle, the question becomes one of the nature of consciousness. If it is purely mechanistic and purely matter generated, then we'd expect consciousness to be fully subject to relativity. But if there is an immaterial aspect to consciousness (and I don't necessarily mean "divine," just "non-material"), then we might expect it to notice that its physical environment is aging slower than it had gotten used to on Earth despite the fact that clocks, rulers, and all other measuring devices registered "normally."
     
    Last edited: Apr 13, 2003
  15. Apr 13, 2003 #14

    Les Sleeth

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    Yes, but isn't it that the traveling twin's one year equals the Earth twin's eight years? Isn't it that the universe itself ages at a rate independent of the observers, and that it is measurement that is affected?

    I freely admit that relativity paradoxes can make my brain ache, and I am open to learning all I can from anyone who understands relativity better than I. Yet in this thread at least I am not so interested in the details of relativity as I am in understanding how consciousness would be affected. In my example the traveling twin was already used to Earth's rate of time. Since relativity is a physical effect, and I don't believe consciousness is 100% physical, then it seems to me that the traveling twin will have some sense that his shipboard five years was the longest five years he'd ever experienced.
     
  16. Apr 13, 2003 #15
    Yes. That's my point also.
     
  17. Apr 13, 2003 #16

    Janus

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    Let's break it down into what is measured from each frame.

    Earth twin:

    He sees his brother accelerate up to some large fraction of c Relative to himself and then coast. As a result, he sees his brother's time rate as running slower than his own. After coasting for some distance(Let's say to Alpha Centauri), his brother decelerates, and comes to a stop relative to him (the Earth twin). The space twin then accelerates back towards Earth, Coasts again, and then decelerates to a stop again next to him again.

    According to the Earth twin, his brother's clock should show less elapsed time and his brother should have aged less than him, because of the large relative velocity difference between them during the majority of the trip.

    Space twin:

    His sees the Earth accelerate away from himself, while Alpha Centauri accelerates towards him. He also notes that there is a g-force acting on everything in the ship, acting in the same direction as the Earth and Alpha Centauri are Accelerating, and with a force that equals the rate of that acceleration.

    This can be explain in two ways, that he is accelerating towards Alpha C, Or, He is standing still in a uniform Gravitational Field, and Earth and Alpha C are falling in it. Either assumption will give the same result because of the Equivalence Principle (equating Accleration and Gravitation), So we will use the second interpretation, as it allows us to treat the space twin as "fixed" frame of reference".

    Therfore the Space twin sees the Earth fall away from him and Alpha Centauri fall towards him. As a result, he wil see the combination of two effects on his brother's time rate; one due to the Earth's increasing relative velocity, and one due to the Earth's position in the gravity field. Since Clocks lower in a gravity field will appear to run slower as measured form a frame higher in that field, he will see his Earth twin's brother's time rate as running slower. This is compounded by the fact that the Earth has an increasing Relative velocity, which will also decrease its time rate.

    The g field leaves ( This corresponds with what the Earth twin sees as the "coasting" period.) Earth and Alpha C. now maintain a constant relative velocity with respect to him. He will see the time rate on Earth as running slower than his. He also will see length contraction in both the Earth, Alpha C and the distance between them (Earth and Alpha C are just two points in the same frame that is moving relative to him.) It will take some time (t) for this frame to go from The Earth being near to Alpha C being Near. This time will be shorter than that measured by his Earth Brother during this same period. (His Earth brother see him (travel 4.3 ly at a given speed taking a certain time. He sees Earth and Alpha C Fly by him at the Same speed, measures the Distance between them as less than 4.3 ly, thus the transit takes less time.

    The g field returns, but this time it points the other direction. (Earth is now Higher in the Field.) But not only is Earth now higher in the Field, it is much higher than it was lower earlier.(He is close to Alpha C and Far from Earth) The Earth's time rate will now be measured as running faster than his own (much faster than it was running slower before.) Fast enough, that by the time the g field leaves again and the Earth and Alpha C are once again at rest relative to him, all the time he saw it losing during the other periods are made up, plus some. This "plus some" will be exactly the amount that the Earth twin will have seen as due to the Space twin's time rate moving slower.

    The second half (That where the Earth returns to being next to him) will be just a mirror image of the first.

    Meaning that when the twins are re-united they agree as to which twin has aged the least(or most) and by how much, but not as to why. By each twin's frame the time difference is due to the combinations of length contractions and time dilations his brother went through.
     
  18. Apr 13, 2003 #17

    Janus

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    And herein lies a problem. The devil is in the details. If you don't have a grasp on them, you'll never be able to relate them to your question.
     
  19. Apr 13, 2003 #18

    Les Sleeth

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    Thank you Janus for such a thorough explanation; it was one of the best I've seen here and cleared up a couple of points for me about the physical side of relativity.


    I am not sure you understand where I am coming from. That the details are crucial for sound understanding of relativity I do not doubt. But it seems you automatically assume a consciousness raised in Earth's frame of reference will "follow" physical relativity on the space ship journey because, I suspect, you see no difference between the consciousness and physical reality.

    That really is what my point addresses. Since consciousness and brain are equated, I think the materialist position will be that the traveling twin will not notice any difference (even though he grew up on Earth) because his entire frame of reference, including his brain, adjusted to the rates of change during his journey. As for me, I am not convinced I wouldn't notice that my rate of change had slowed (relative to my prior experience on Earth) because I don't think consciousness is 100% determined by physical factors.
     
    Last edited: Apr 13, 2003
  20. Apr 13, 2003 #19

    Janus

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    Here you go again, spouting off about Relativity, when you don't know what you're talking about.

    Both twins would see the exact same proportion of the "game" played. One will just say that it took longer to play out. While One twin will say the first half took 1 1/2 hrs, the other will say it took 3. If the twins compared notes at any point of the "game" they would agree exactly as to which play just transpired, But wouldn't agree to how much time has expired(By their clock) since the Game started. Either one Twin will see the game progress in slow-motion or the other will see it progress in fast motion. (Or one will see it in fast motion while the other sees it in slow motion.) Also, if either twin took his field glasses of the field to scan the stands to find his brother, he will see him (and those sitting around him), as either moving in fast or slow motion.

    Who sees what depends on each twin's "position" (relative velocity and Gravitational potential) Relative to the the "field" and each other.
     
  21. Apr 13, 2003 #20

    Janus

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    I think you missed the point of this statement:

    By each twin's frame the time difference is due to the combinations of length contractions and time dilations his brother went through.

    Put simply: "Relativistic effects always happen to the other frame.

    You never have to worry about how your "consciousness" reacts to Relativistic effects, because you or nothing else in your frame experiences them. It is always the other frame in which the effects are measured (by you or anything in your frame).

    This is what "no prefered frame of reference means".
     
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