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Topics in modern theoretical physics with interesting philosophical implications

  1. Aug 4, 2009 #1
    What are in your opinion the most interesting areas or topics in foundational physics? (that have or could have profound philosophical implications) I want to see what's out there.
     
  2. jcsd
  3. Aug 4, 2009 #2

    QM, GR and definitely String theory(or any other TOE).
     
  4. Aug 6, 2009 #3
    For me it's the interpretations of QM. Copenhagen still seems seems to be preferred while Many Worlds is the runner up. Neither can be falsified so post-Wittgenstein philosophy would say they're metaphysical.

    In terms of proven physics, it's got to be entanglement and non-locality. This stuff is really weird, but it can't be ignored. It challenges the very idea of space and time.
     
  5. Aug 6, 2009 #4

    EnumaElish

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    Does the theory of relativity have substantive implications about determinism, free will, etc., or is it a trivial, or open-and-shut question?

    The question of "frozen time vs. free will" occurred to me as I was recently reading Synchronicity by Carl Jung. I searched the web and found out that it had occurred to other people before me: see, for example, http://www.thenakedscientists.com/forum/index.php?topic=21777
     
  6. Aug 6, 2009 #5

    The block view of the universe, that flows out of GR, is pretty compelling towards determinism and poses serious challenges to the idea of free-will.
     
  7. Aug 6, 2009 #6
    Why? An astronomer can look at the Andromeda galaxy from one end to the other all at once, despite the fact that it's perhaps 150,000 light years across. Just because we can conceive of a block universe doesn't say anything about our free will. Time passes at the same rate for a person in a starship traveling at some fraction of lightspeed relative to earth as it does for that person on earth. Moreover, if that person measured the speed of light aboard the ship, he or she would still get c. Matter, including matter that may have free will, can't travel at lightspeed. Photons, I'm sure, don't have free will anyway.
     
    Last edited: Aug 6, 2009
  8. Aug 6, 2009 #7

    Time is relative, it does not pass equally for observers moving in different frames of reference and there is no such thing as a Universal Now(Present).
     
  9. Aug 6, 2009 #8
    Right. That's exactly what I'm saying. But clocks aboard the starship run at the same rate for observer aboard the starship as clocks run for the observer if the observer were on earth. The observer gets c for the speed of light on the starship and gets c for the speed of light on earth. Now if the passenger on the starship had a twin on earth, then the passenger would be younger than his twin when he returned to earth. Read what I wrote:".. time passes for the person in the starship at the same rate as it does for that person on earth."
     
    Last edited: Aug 6, 2009
  10. Aug 6, 2009 #9


    But clocks do not run at the same rate when compared between different moving frames of reference. Clocks do run at the same rate within the same FOR though. You said this:

    And it is not true.
     
  11. Aug 6, 2009 #10
    I'm sorry. I'm not getting through to you. If you get on starship that goes 50% lightspeed you will not observe time slowing down. It will seem to pass at the same rate. When you returned to earth you would be younger than your twin, but you will not notice time "speeding up". Of course clocks run at different rates for different frames of reference moving at different velocities relative to each other. But the observer can't be in two places at the same time, can he?
     
    Last edited: Aug 6, 2009
  12. Aug 6, 2009 #11

    That's right. I got the impression that you were saying the opposite with your initial statement. Sorry

    Otherwise, in a block universe, the past, present and future exist at once. Hence what you are about to experience has already happened in another frame of reference. There is no room for free will or free choices if everything is pre-determined.
     
  13. Aug 6, 2009 #12
    The point I'm making is that for any observer, time will always pass at the same rate. There is a past and a future. If it were possible to go 99.9% of lightspeed in a starship relative to earth, you would still experience time passing as if you were on earth. If you have free will on earth, you have free will in the starship. Note I'm not saying free will exists or does not exist, but its existence or non-existence has IMHO nothing to do with photons. As I said, I'm sure photons DO NOT have free will.
     
    Last edited: Aug 6, 2009
  14. Aug 6, 2009 #13


    OK, hopefully this post will bring some clarity. Block universe isn't about photons. It's about your FOR not being priviliged in any way over all others. From your FOR, it's the year 2009. I could always find FOR's where it's still 1000 years after the Big Bang or FOR's where the dinosaurs have not died out yet. Take the FOR of an electron that moves at 75% of c. Because of time dilation, from the point of view of that electron, the universe is still 3 billion years old. All these parallel views of the universe exist at once, past, present and future in GR exist at once(in a block universe and in different FOR). Einstein was aware of this bothering consequence of his own theory and he discussed its philosophical implications in "The World as I see It".
     
  15. Aug 6, 2009 #14
    I see where you coming from, but I still maintain that an observer can be in only one FOR at a time. Therefore wherever you are in any FOR your experience of time will not change. Now it may be true that our calculation of the age of universe will be different in the starship than it would be on earth. The fact we say that the universe is 13.7 Gy old is related to our FOR, but the apparent movements of galaxies over a fairly large distance is small relative to c. However, in IMO, this still does not effect any free will we might have in any FOR we might find ourselves in.

    Now if you want to say that a single observer can be in more than FOR at the same time, because "at the same time" may not be well defined, that's a different story altogether.
     
    Last edited: Aug 6, 2009
  16. Aug 7, 2009 #15
    This does not indicate that your future wasn't already settled. We cannot touch the Sun and take its temperature, but this doesn't stop us from corectly inferring its temperature from experimental observations and calculations. In fact the existence of past, present and future in different FOR indicate the opposite. What free will can there ever be, when there are FOR's where you are, say, 77 years old(even if you cannot access them)?


    Why? Any time traveller to a single-history future wipes the floor with the idea of Free Will.
     
  17. Aug 7, 2009 #16
    How would we ever know?

    You are going to have to more clear here. I don't follow your reasoning. Are talking about parallel universes? If you are, you're dealing with what is by definition metaphysics.

    You can, in a sense, travel into the future as when you return to earth after a high velocity journey, but you can't return to the past. What does this have to do with free will?
     
    Last edited: Aug 7, 2009
  18. Aug 7, 2009 #17

    I cannot be any more clear than that, sorry. I think it's rather obvious that if there is ONLY ONE single history in store for you(a deterministic block view of the universe), that definitely means, that absolutely everything has already been pre-determined. You have provided zero arguments why this isn't so, and i believe human logic dictates that this idea is impossible.

    You can google "block universe free will" as additional reference.
     
  19. Aug 7, 2009 #18
    You can make any assumption you want and assert a logical consequent from that premise. If there is X, then Y. In science, you have to provide evidence. Is X supported by some evidence or some method to find evidence? If there is a single history, then......? If there are multiple histories, then.....? You haven't given any way to experimentally evaluate this issue. The simple fact is that we only can know our world lines retrospectively. Whether or not we have free will is untestable. Whether or not there are multiple futures or just one future for any particle is, as far as I know, untestable. QM deals in probabilities (the probabilities in QM are determined however), and I think the same approach is our best way to deal with future events on a macroscopic scale. If you like metaphysics, that's fine but it's not science. At a certain level, under certain conditions we can make highly accurate predictions, but if we can't, we have to fall back to probabilistic models based on well founded theory or past experience. As far as I know, General Relativity provides no way to predict our personal futures.
     
    Last edited: Aug 7, 2009
  20. Aug 10, 2009 #19

    EnumaElish

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    Consider:

    photon 1 was released yesterday;

    photon 2 is released today, from the exact same location as photon 1.

    Do the two photons have an identical "picture" of the universe ?
     
  21. Jan 8, 2010 #20
    This is from a thread in the Quantum PHysics section:
    I just wanna make sure I understand some of the greater implications of discoveries made by quantum physics experiments and theories like the double slit experiment and Schroedinger's cat.

    Because observation effects results, it becomes clear that an observer cannot extract themselves from the system, and are indeed a part of it.
    True, yes?

    And I'm curious what people think about the implications of this for science in general. I mean sure, these things more or less disappear when you reach macroscopic levels, right? But then, what about more complex systems?
    Is it possible to observe biological systems without effecting it? Do effects actually matter?

    Really I'm interested in this because a recent criticism I've heard of science is that it has objectivity, which really doesn't exist, built in as an assumption. Do you think that's true, and does it matter? If not why not? Is thinking that we can be separate from things an unhealthy habit to get into?
    I'm certainly of the opinion that even tiny bits do add up and make a difference, and that even subtle differences are compounded over time/space to eventually have large effects.
     
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