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B Smallest possible velocity

  1. Jul 22, 2017 #1
    Hey I wonder if there is a smallest possible velocity. There should be mathematically speaking.

    Smallest possible distance: planck unit
    Smallest possible time: planck time
    Velocity: distance/ time

    If we have fundamental distance and time then we have fundamental velocity.
     
  2. jcsd
  3. Jul 22, 2017 #2

    Dale

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    Planck distance/Planck time = c which is the largest possible speed, not the smallest.

    I agree that it is the fundamental velocity
     
  4. Jul 22, 2017 #3

    Vanadium 50

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    Not true.

    There is nothing magical about Planck units. The Planck resistance is 30 ohms. Resistances both above and below this occur all the time.
     
  5. Jul 22, 2017 #4

    Nugatory

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  6. Jul 23, 2017 #5
    But you guys are contradicting my math? Im deriving minimal possible values from other minima.
     
  7. Jul 23, 2017 #6

    lewando

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    If you are looking for small velocity, then d should be small and t should be large.
     
  8. Jul 23, 2017 #7
    But then how do we measure the smallest change in position per unit time aka the smallest velocity?
     
  9. Jul 23, 2017 #8
    Do you know and understand what things you are using in your math? Planck lenght is not the smallest possible distance. We don't even know if there is one!
     
  10. Jul 23, 2017 #9

    DrGreg

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    We're not contradicting your maths. We are contradicting your initial assumptions:

    That is simply wrong. Did you not read the following?

     
  11. Jul 23, 2017 #10

    Merlin3189

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    I've no idea what Plank's units are (I promise I'll read the Insight), but " the smallest change in position per unit time" means simply, the smallest change in position per arbitrary amount of time. So the result could be anything (well, perhaps not zero nor infinite.)
    Unit time is a second in SI, but could have been chosen to be a minute, an hour, a year, the time it takes the earth to rotate by one radian, the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of some other atom, etc. The unit of time known as the second can hardly be the shortest possible time if we can divide it into 9 192 631 770 parts.
     
  12. Jul 23, 2017 #11
    And I would say that the smallest possible speed is 0, in any units you choose :wink:
     
  13. Jul 23, 2017 #12

    Dale

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    In addition to what others have said about Planck units not being minima, if you want something small do you want to divide by a large number or a small number?
     
  14. Jul 23, 2017 #13
    I did not say I "wanted something small". I mathematically proved a minimum velocity based on minimal distance and time.
     
  15. Jul 23, 2017 #14

    SammyS

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    A velocity based on minimal distance and time is not a minimum at all. That's what Dale was referring to.
     
    Last edited: Jul 23, 2017
  16. Jul 23, 2017 #15
    Um, no. You did not prove anything. You didn't even finish your calculations! If you did, you would notice that (as Dale said in post #2) what you got is speed of light which is the largest possible speed.
     
  17. Jul 23, 2017 #16

    Nugatory

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    If there were a minimum distance and a minimum time (and there isn't, because the Planck time and distance aren't what you think they are), you'd be able to prove a maximum velocity, not a minimum. The maximum possible speed would be one minimum distance per minimum time, but nothing would prevent an object from taking longer than the minimum time to cover the minimum distance - and that's a slower speed.
     
  18. Jul 23, 2017 #17

    Dale

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    A minimum is a smallest possible value.

    Let me ask this question. If you want to have the minimum monthly payment, do you want to get a (0% interest) loan with the minimum duration or the maximum duration?
     
    Last edited: Jul 23, 2017
  19. Jul 23, 2017 #18
    That has nothing to do with planck units, correct me if I am wrong. I am talking about the smallest observable change in location per unit time.
     
  20. Jul 23, 2017 #19

    phinds

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    And you are doing it very badly. It has been pointed out to you that the Plank Length is NOT the smallest unit of distance. Do you not believe this?
     
  21. Jul 23, 2017 #20

    Dale

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    You are wrong and have been corrected multiple times. Please answer the question. Here is the same question in a more relevant form:

    If Alice drove 100 km in 1 hour and Bob drove 100 km in 2 hours, then who drove slower?
     
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