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Difference in age ?

  1. May 28, 2009 #1
    Difference in age ??

    NOTE : THIS IS JUST AN IMAGINATION !

    Imagine that 2 babies are born on the same day & time (with names A & B)..A is allowed to live on earth .But B is taken in a rocket and is sent to space .(this rocket can travel in the speed of light!) A is now 10 years old .....on A's birthday B (from space) returns to earth....Will there be any difference in their ages ?
     
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  3. May 28, 2009 #2

    chroot

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    Re: Difference in age ??

    This is a widely known thought experiment called the Trwin Paradox. It is not really a paradox, though, because it has many explanations within the theory of relativity.

    - Warren
     
  4. May 28, 2009 #3
    Re: Difference in age ??

    In your example the twin that went on a space trip could be as little as 1 year old on return, depending on how close to c it was travelling.

    I have often pondered the possibility of a twin returning at 25 years of age to find his or her twin dead of old age.
     
  5. May 28, 2009 #4
    Re: Difference in age ??

    The closer B gets to the speed of light, the slower time goes from his perspective.
    B will therefore be younger than A since B is in kind of a bubble which makes time pass differently, than for A.
     
  6. May 28, 2009 #5

    Dale

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    Re: Difference in age ??

    http://math.ucr.edu/home/baez/physics/Relativity/SR/TwinParadox/twin_paradox.html" [Broken]
     
    Last edited by a moderator: May 4, 2017
  7. May 29, 2009 #6

    Roo

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    Re: Difference in age ??

    Does anybody else think this whole aging/time dilation situation is just a bit too far fetched, irrespective of whatever is in GR/SR and experiments (and yes, I have read about all the experiments with atomic clocks and muons etc)?

    How can time 'slow down' just because of a very high speed? If a body ages less at very high velocities (as compared to a body on Earth), or clocks go out of synch why can't it be because of nothing more than numerous forces reacting with the body's own replication system or the 'mechanics' of function etc.? Why has it got to be because 'time slows down'.

    It would be nice to hear views of people who also feel this sounds quite peculiar despite the 'evidence' to support this.

    Roo.
     
  8. May 29, 2009 #7

    Dale

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    Re: Difference in age ??

    If there is a conflict between your prejudices and the evidence then the evidence always should take precedence.
     
  9. May 29, 2009 #8

    HallsofIvy

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    Re: Difference in age ??

    I am sure you can find whole websites for people who don't understand relativity and so believe it is wrong. Lorentz, for whom the "Lorentz formulas" of relativity are named, tried, pre-Einstein, to explain the null result of the Michaelson-Morley experiment in exactly the way you suggest- that "numerous forces" such as increased magnetic force in the direction of travel caused it. A slight variation on the Michaelson-Morley experiment, called, I believe, the Kennedy experiment showed that that cannot be true. It must be space itself that "shrinks". Einstein showed that as well as that time itself slows in relative motion.

    It doesn't matter how "far fetched" a theory sounds if it matches experiment and other theories don't!
     
  10. May 29, 2009 #9
    Re: Difference in age ??

    "Could someone please psychologically reinforce my wrong ideas for me?"

    This is a science forum. You are asking for the opposite of science.
     
  11. May 29, 2009 #10

    Roo

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    Re: Difference in age ??

    Correct - this is a science forum. But without challenging even 'proved' theories, many scientific truths would still remain hidden. But please don't mistake the challenging of theories (even highly regarded ones) as a lack of intelligence or even worse, ignorance. Challenging long held, supposedly proven and universally accepted theories happens in all branches of academia. This is equally about science as the original theory.

    Are you telling me that experiments which have supposedly proved/disproved a theory haven't themselves been replaced by other ones that have had the opposite effect?

    However, for sure, after numerous experiments have proven the same believed outcome it is right to accept that a particular theory is correct. But also, some theories have to be directly proved before they can be believed and not through experiments of a lateral nature. But you know for me, with certain theories, I will only accept they are right when the application of that theory has been proved in the human sense. I.e. that intense gravitational fields from a spacecraft actually 'warps' space-time or that occupants piloting a spacecraft after travelling at velocities near the speed of light, return to Earth and walk out looking a lot less older than the rest of us.

    So until that happens, I will still doubt certain theories regardless of maths, formulae and experiments suggesting otherwise. However, I will also be the first to be utterly amazed, to hold my hands up in graceful defeat and be happy to admit I'm wrong if indeed these things do happen in the future.

    So to me, this is science - not just the mere acceptance of a theory.

    Roo
     
  12. May 29, 2009 #11

    Dale

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    Re: Difference in age ??

    That is not science at all. That is stubborn refusal to examine solid and reproducible experimental evidence simply because it is a muon instead of a human whose lifetime has been extended. What a ridiculous and prejudiced position. In any case, GPS is a remarkably successful application of relativity on a human scale.

    This does not happen. When a theory has been experimentally validated then all future theories must agree with the proven theory in the domain for that experiment. For example, Newton's laws have an immense amount of experimental support. Although Einstein predicts different results as v->c Einstein predicts the same results as Newton for v<<c (the domain for which all of the experimental support for Newton exists). The experimental support for Newton still exists and will continue to exist, and Newton's theories will continue to be used for that reason. Similarly with Einstein. Surely future science will uncover new realms where Einstein's theories are also inaccurate and new theories will emerge, but that will not change the fact that any such new theories must predict time dilation as that is an experimentally validated fact.
     
    Last edited: May 29, 2009
  13. May 29, 2009 #12

    chroot

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    Re: Difference in age ??

    How to be a crackpot:

    1) Pick a piece of reputable science that seems beautiful to you, preferably one at a high-school or earlier level (since, after all, you didn't take any collegiate science courses). Bonus points are assigned for choosing a piece that has been proven wrong and abandoned by modern science. The Bohr "solar-system" model of the atom, for example, will do nicely.

    2) Misunderstand some fundamental point of your pet scientific principle.

    3) Read about your pet scientific principle in a variety of $5.95 paperbacks sold at the front counter of the newsstands in malls.

    4) Misunderstand even the qualitative descriptions and word-bound "math" provided therein.

    5) Use that one piece of trivial scientific theory to explain everything in the observable universe. Yes, the beginning of time, the size of the Universe, black holes, and all the rest. Ascribe some silly properties to things that don't actually have those properties; for example, talk about the "speed" of electrons, and use the speed to explain the beginning of time. Don't be greedy and try to involve any other bits of real science; your theory has to have a definite focal point. What better focal point is there for an all-encompassing theory of the Universe than that piece of beautiful outdated science you learned in ninth grade?

    6) Forego all use of math, since math is hard (you abandoned real science for the same reason, remember?). Besides, you've already convinced yourself that no one would ever order a Universe so complex that you'd actually need something as hard as math to describe it. If you do attempt to use math, make sure it's entirely unrelated to your thesis. Make use of the prettiest symbols as often as possible -- if say, you like the looks of the symbol for an integral over a closed region, just make all of your integrals over a closed region. Since you're making up dimensions, quantities, and symbols anyway, you can do what you like. Just think of the symbols as window dressing.

    7) Make up at least a dozen new words. Even better, reuse the same words scientists use, but give them new, entirely different, meanings. Be careful not to give them precise definitions, though; leave a little wiggle room. Using your new lexicon, you can escape the barrage of criticism you'll receive later by revealing "your" definitions piecemeal. This bait-and-switch tactic soon wears out any would-be critics; when they give up on you, pat yourself on the back for having created an impregnable fortress of a theory.

    8) Write at least one sentence that uses all of your new words at the same time. Make liberal use of nested prepositional phrases and passive voice. Since you don't actually understand science, you read a science book and see nothing but meaningless jumbles of words grouped into complicated sentence structures; it makes sense that you should emulate this as best you can. This "topic sentence" also becomes a great tool for weeding out your crackpot fellows from the background noise of reputable scientists. Anyone who reads the sentence "The force of magnetism is the result of a torque generated by the energy vortex Shadows associate with electromagnet energy, which causes a 'tilting' of the W axis of the fourth spatial dimensions." and actually claims to "get it" is immediately identified as a colleague.

    9) Do your best to ignore every shred of the contrary evidence collected by hundreds of thousands of independent scientists, in millions of experiments, over the span of hundreds of years. There are a variety of ways in which you can dodge the evidence:

    - You can simply ignore it.
    - You can explain that all of those scientists, helplessly unarmed by having not yet experienced the epiphany embodied in your theory, simply did the wrong experiments, or intepreted the experimental results incorrectly.
    - You can refer to the International Scientific Conspiracy, who has encased all of the real scientists (who would immediately give you the Nobel prize for your discovery) in concrete, leaving only the riff-raff underachievers to do such poor experiments.
    - You can make use of the paranoid idea that the only experiments which are conclusive are those which involve the human senses directly. If you can't feel it heating up with your hand, or see it glowing with your eye, then you haven't done a real experiment. Why should anyone, especially you, believe anything that a machine says? After all, the International Scientific Conspiracy certainly has a few well-stocked machine shops.

    10) Whenever someone criticizes you, be sure to try to make him feel guilty for being so closed-minded that the only thing he'll accept is cold, hard reality. Tell him that scientists like Einstein invented new branches of physics only by being as open-minded as you are; ignore the fact that the assertion is not true (or invoke the International Scientific Conspiracy).

    11) Submit your paper to reputable scientific authorities, like PRL and Nature. When no one bothers to even respond with a rejection letter, come to one of two possible conclusions: either that modern science has no rebuttal to your theory, you have shattered their collective scientific ego with your brilliance, and they have chosen not to respond because they are too proud to admit defeat; or that the International Scientific Conspiracy has immediately destroyed your paper because you got too close to the Truth. Either way, your theory is actually strengthened by the silent dismissal, and that's all that really matters anyway. Now you can tell anyone who cares to listen that modern science cannot rebut your theory, so it must be right. You can go a step further, become proactive, and actually solicit rebuttals directly from individuals in the reputable scientific community. When none of these scientists is willing to waste his time trying to teach you tenth-grade physics, you can proudly announce that science cannot disprove your theory.

    12) Misunderstand the essence of the scientific method. Forget the fact that theories must provide falsifiable or directly verifiable predictions to be taken seriously. Since your theory is a crackpot theory, it is incapable of providing directly verifiable predictions. You were careful to avoid making your definitions precise, weren't you? The same wiggle room that allows your theory to explain just about any experimental result is also responsible for preventing your theory from making any concrete predictions of anything. It doesn't matter what number pops out of the particle physicist's machine; your theory doesn't even use math, so any number you'd like can be explained by it. Your theory is immune to the scientific method, and that makes it better. Your theory cannot be proven wrong, so it must be right.

    13) Make up a name for your theory. Reputable scientific theories have wacky-sounding names like "Quantum Electrodynamics" and "Special Relativity," so yours should, too. Use latin whenever possible, since latin sounds scientific; nevermind that you don't understand how to conjugate latin verbs. "Genesis Continuous," "Shadows," and "Time Cube" are all excellent names. Bonus points are assigned for crackpots who manage to bastardize the names of reputable theories. For example, "God Almighty's Grand Unified Theory" is at least ten times as good as "Shadows," because it provokes fear and awe while simultaneously including a catch-phrase that has recently attracted a great deal of reputable attention.

    14) Found your very own organization dedicated to the research of your new theory of everything. It doesn't matter if some of your compatriots are actually 18th century French poets, are imaginary, or are canines -- all that matters is that you have an organization. Give it a good official-sounding name. You've surely heard of Caltech and MIT; using the "Institute of Technology" moniker will definitely make everyone take you seriously for a change. The "Offapit Institute of Technology," for example, is repsonsible for "God Almighty's Grand Unified Theory," which is poised to change the way all of humankind thinks about science, if only the editors of PRL will give up their hubris and accept its superiority.....

    - Warren
     
  14. May 29, 2009 #13
    Re: Difference in age ??

    Nah, some people do think there's somethings wrong with Relativity, I have no problem with them, but face it, the theory is proven to be true, at least at the present.

    About the problem, it's the famous Twin Paradox. It's not a simple question though, because when the space shuttle comes back to earth, it changes its speed, thus Special relativity can't be applied. General relativity must involve with some very complex calculations (to me) :D

    If the space shuttle with the baby B flies with a fix speed (oh yeah, compared to A on Earth), then it sends a radio signal to Earth to tell how old the B is, then A will find that B is younger than him. But if A sends signal to B, and then B will find that A is younger. Relativity, no argue.

    But the situation becomes complex if B comes back to earth. The question is, why B must be younger than A, if everything is relative, we can say that A has traveled and comes back, so A must be younger than B. Here comes the General Relativity. It says the difference between A and B is that A does NOT change his speed but B does, so he generate acceleration while A doesn't. Therefore, it is different if considering A is the traveling one :D

    Come to think about it. First I found it weird because things move with acceleration seem to 'absolutely' move. A train accelerates, if u sit in there u can feel it and tell firmly that the train is moving, not the earth. The special relativity can't solve it, but the general can. U should find more about it, I find it hard to explain due to my bad physics English :D

    In my imagination, it's like the whole matter in the universe creates a gravity field, and things accelerate comparing to that field. So matter accelerates only in compare to matter, it's still relative (I think the theory says that gravity itself create the inertia)
     
  15. May 29, 2009 #14

    George Jones

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    Re: Difference in age ??

    While it is true that general relativity must be applied in this situation, the reason is not because the shuttle changes speed (non-zero acceleration), the reason is that gravitational time dilation must be taken into account.

    Special relativity handles situations that involve non-zero accelerations in flat spacetime just fine.
     
  16. May 29, 2009 #15

    Roo

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    Re: Difference in age ??

    Wow - what an awesome response.

    Still, I fully stand behind my opinion but look forward to seeing if I'm right or wrong some day!

    Though one theory has been proved right without doubt tonight - that being if anyone gives an opinion on a believed established fact (even one based on nothing more than a personal viewpoint), the blue touch paper gets well and truly lit!

    Roo
     
  17. May 29, 2009 #16

    Dale

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    Re: Difference in age ??

    :rofl: Thanks Warren, this was a great laugh.
     
  18. May 29, 2009 #17
    Re: Difference in age ??

    Yeah, technically it's true, but I just want to make it simple :) After all, non-zero acceleration and gravity are somehow, the same. In a elevator move quicker and quicker in the universe, one will find the same like in a gravity field.
     
  19. May 30, 2009 #18
    Re: Difference in age ??

    I wonder if you could match the speed of the rocket to have the same effect on slowing a persons biological clock as the gravity of the earth does. By this i mean that you could do the exact same situation with baby A and baby B and have baby B come back to earth and be the exact same age.

    Just a thought
     
  20. May 30, 2009 #19
    Re: Difference in age ??

    I wonder if you could match the speed of the rocket to have the same effect on slowing a persons biological clock as the gravity of the earth does. By this i mean that you could do the exact same situation with baby A and baby B and have baby B come back to earth and be the exact same age.

    Just a thought
     
  21. May 30, 2009 #20
    Re: Difference in age ??

    opps,
    i sent that twice
     
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