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A minimum speed?

  1. Apr 10, 2003 #1

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    I wonder, since c presents a maximum speed limit to the universe, is it plausible for there to be a theoretical minimum (and non-zero) speed limit too?
    Such a limit would certainly have interesting implications...
     
  2. jcsd
  3. Apr 10, 2003 #2
    This seems vaguely familiar to me though I don't have any serious knowledge of physics. I was thinking that if the electrons themselves slowed down to nil that the gig we know as the universe would be up.

    [edit]
    Ok, I just saw the part about non-zero. Maybe someone would like to explain the details of my post for me?
     
  4. Apr 10, 2003 #3
    Well correct me if I'm wrong but.. Heisenberg: ΔxΔp = h/4π so if Δp→0 then Δx doesn't make sense anymore, so there must be some minimum jitternig speeds to prevent this. But I might be wrong...
     
  5. Apr 10, 2003 #4

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    Uh... by non zero I meant no annoying replies saying that you can't get a speed less than zero and stuff like that. I am wondering if there is a minimum speed above zero, or whether there is a theoretical reason why zero-speed, relative to anything, is impossible.
     
  6. Apr 10, 2003 #5
    You would be correct climbhi.

    Quantum claustrophobia is what it is referred to.
     
  7. Apr 10, 2003 #6
    I wish I could remember what someone who thought he knew told me about zero speed. I don't know if everything just ceases to be, implodes, or what the heck. I think the gist of it was that movement was essential. That’s really all I can throw into the arena.
    Could it be something like absolute zero where you can't actually get there except through extrapolation?
     
  8. Apr 10, 2003 #7
    Is this in reference to my post showing you couldn't have zero speed with Heisenberg? If so sorry, I thought it was valid (apparantely Brad does too...) Am I mistaking what you're refering to?
     
  9. Apr 10, 2003 #8
    It is possible to speak of minimum speed relatively a zero point only. That you offer to take as zero point?
     
  10. Apr 10, 2003 #9
    Well, you're not wrong per se... but I believe that the &Delta;p you have shown refers to the variance (or might say the standard deviation... the square root of the variance) of the expectation <p> (ie <p2> - <p>2). So, I believe the correct way to interpret this result is to say that the velocity of an object is centered around a certain value with an uncertainty given by this deviation. In that sense, the probability of measuring the velocity of a rest object at exactly zero is more probable than measuring it at any other value... but this probability is still zero.

    Actually in solid state physics, people are often concerned with calculating phonon modes in low dimensional systems.

    Side Bar: For those of you not in the know... a phonon mode in an array of atoms is analogous to the vibration found in a matrix of balls with each ball attached to its nearest neighbors by springs.

    There is a lowest energy value a system can have... due to your reasoning. It is refered to as the zero point energy.

    eNtRopY
     
  11. Apr 11, 2003 #10
    1/c

    seriously though...

    I don't think such a speed could be said to exist.

    remember all objects must be at rest with respect to themselves. All other speeds are relative. So zero speed is possible.
     
  12. Apr 11, 2003 #11
    All speeds in space are relative therefore it is impossible to determine either a maximum or minimum speed except in relation to an object whose true speed is unknown.
     
  13. Apr 11, 2003 #12
    I would like to further elaborate and say that you have a zero probability of finding any object at any exact speed due to the argument originally posted by climbhi.

    eNtRopY
     
  14. Apr 11, 2003 #13
    I'm pretty sure that 1/c is not it if there was a lowest speed. Afterall think of how fast your toe nails grow, prolly pretty close to 1/c
     
  15. Apr 11, 2003 #14
    But assume that light, originating from the 5th dimension offers our only reference point to absolute motion. Being that we have mass when we are standing still, we must all be moving together at some rate. But due to entropy (no pun intended)... the chaos of the motion defines no absolute direction of motion. As time goes by, it will only become more chaotic, making reaching minimum speed the more difficult, if we can even slow ourselves down somehow.
     
  16. Apr 12, 2003 #15
    The constant exist. The Constant this NOT CHANGEABLE VALUE. Any measured comparatively constant a value will be absolute, not relative. Exactly a constant is a zero point. This obviously. It is difficult to explaine the reason people prefer to stand on head...
    Certainly, I am saying about the speed of light "c".
     
  17. Apr 12, 2003 #16
    Very interesting.
    I personally do not see any reason for having a minimum speed, so i believe the minimum speed of any object will be 0.
    Some quotes ...
    Well, although speeds are relative, we find a maximum (relative) speed, which is (c), but this is not a good enough reason to think there is a minimum speed too .
    I don't go with you in this point at all (i see Entropy was right in this point).
    If [del]p->0 it does not mean that p->0, (therefore it does not mean that v->0) so the HUP will be useless to find any good result in this conversation.
     
  18. Apr 23, 2003 #17
    Speed is distance/time. Minimum speed is planck length/planck time. Hmm, isn't it like "c"?

    I'd add another view. What is speed? motion. What is motion? Interaction. So, zero speed is zero interaction. Now the big one - what does it mean to exist? If two particles never interact, do they exist relative to each other? Isn't stopping to complete standstill equivalent ceasing to exist? Virtual vacuum comes to mind.
     
  19. Apr 23, 2003 #18

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    wimms: by that argument, there can be no minimum speed, since as t decreases, the speed increases.
     
  20. Apr 23, 2003 #19
    FZ, yes I noticed. By that argument any movement at all must occur at c. Effective speed of complex body may be whatever upto c, but instant change at planck scale can only occur at c. Photons don't move slower.. Maybe mass either. I'd subscribe to that.

    T can decrease only upto a point, it can't be zero, this has no sense and no reality. I'd bet that minimum really possible t is actual cause for speed of c. When we talk about absolute minimum speed, we have to talk about planck scale, then planck length comes to mind as smallest possible length. Smallest possible length in face of smallest possible time is smallest possible velocity. Any other type of movement must be averaged complex movement.
     
  21. Apr 24, 2003 #20
    You have drawn a hand near to the shining truth and... immediately pull it back.Why? Does it powerfully burns? Or a heavy cargo was hanged in your hand and you can't move it?
     
  22. Apr 25, 2003 #21
    Michael, I don't understand what you mean. Care to elaborate?
    ps. did you get my pm?
     
  23. Apr 26, 2003 #22
    My guess is that matter is partly defined by it's motion so at zero speed matter ceases to exist as what we know matter to be, maybe it releases a lot of energy at this point, maybe nothing, maybe it'll never happen, and matter moving at the square of the speed of is equal to it's energy.

    Did you know that when light is passed through a Bose-Einstein condensate it slows to nearly 30mph...weird stuff.


    All speeds in space are relative therefore it is impossible to determine either a maximum or minimum speed except in relation to an object whose true speed is unknown. -Elas

    From this one might wonder what if at the speed of light a thing was seen as light(from our reference point) but from the reference point of the thing moving at light speed, light speed things looked like normal matter moving very slowly... and what if when a thing stopped moving from our point of view it slipped into a lower "reference frame of motion" and becamse something moving very fast at near the speed of light...
    Is this crackpot enough?
     
  24. Apr 27, 2003 #23
    I believe the slowest speed possible is 0. The universe is travelling at 0 speed, for there is nothing that it is moving relative to (That is, of course, assuming that there is nothing outside the universe).

    However, this is somewhat paradoxical because Jammieg brings up an excellent point that matter at 0 speed is not matter as we know it due to the nonexistence of energy. But then again, I'm not sure the universe is just "matter as we know it."...[?]
     
  25. Apr 27, 2003 #24
    FZ+!!

    if there was the lowest nonzero speed in a form of V=constant i will right awy invent coresponding V=const special relativity.
     
  26. Apr 27, 2003 #25
    This reminds of the turtoise and the hair paradox about light speed and beyond...?
    I've read somewhere that matter can pop in and out of existence, how does that happen! Maybe our universe is only existing on one light speed band, then again how would anyone prove something like that or why would they want to?
     
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