How long (in seconds) is one planck time?

Discussion in 'Indie Related Chat' started by Jamie W, Jan 26, 2009.

  1. Jamie W

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    So in a vacuum, the amount of time it takes for light to travel 0.0000000000000000000000000000000000016 meters equates to 1 planck time.

    That's the smallest meaningful (to humans) measure of time ... but many seconds is that?

    I guess you divide the distance (in meters) that light travels in one second, by 0.0000000000000000000000000000000000016 ...

    Any ideas?
     
  2. Jamie W

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    So, how far does light (in a vacuum) travel in one second?
     
  3. Sol_HSA

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  4. jcottier

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    speed of light 299,792,458 meters/second

    So to travel a distance of M the light needs M/299,792,458 seconds.

    So 1 planck = 0.0000000000000000000000000000000000016/299,792,458 seconds

    > So, how far does light (in a vacuum) travel in one second?
    299,792,458 meters that's just the speed of light

    Now I have no idea what a planck and a vacuum are ....

    JC
     
  5. Jamie W

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  6. jcottier

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    Ok, after seing your other thread ;) I think you need this tip:
    Always check the units.

    For example, in your first question, you are looking for a time, so you final value need to be in second.

    You know the speed of light, and speed is expressed in meter/second
    You know the distance traveled in on plank... and that's in meter.

    When we do this:
    0.0000000000000000000000000000000000016/299,792,458
    we are diving meter by (meter/sec):
    (meter)/(meter/sec)
    == meter/(meter*(1/sec))
    == (meter/meter)/(1/sec)
    == (1)/(1/sec)
    == sec

    so my result is in second... witch is what I was looking for... so, my calculation is probably right.

    Using this check, you would have know that your previous calculation where wrong...

    JC
     
  7. AlexWeldon

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    It's not the smallest unit of time meaningful to us. It's far too small to be meaningful to us. It's the quantum of time - that is, the laws of physics themselves do not allow for anything to happen in increments less than the Planck time.

    Planck units don't exist because we can't measure things any smaller. Our tools for measurement are WAY cruder than that. Planck units come out of theoretical predictions - confirmed indirectly by experiment - that the Universe really is quantized at very small scales. Space and time really aren't infinitely divisible as the ancient Greeks thought (and most non-physicists today still think)... if they were, effects like quantum degeneracy would not be possible. If quantum degeneracy didn't exist, neutron stars and white dwarves would collapse into black holes - the fact that they exist as stable objects confirms quantum theory.

    By analogy: Imagine a very high-tech computer screen, with pixels much too small to be distinguished, even with a microscope. Although the image appears continuous to the user, the information is still quantized into pixels at the level of the computer's memory. No instrument available to the user will allow him to distinguish one pixel from the next, but a very clever user might be able to infer the existence of the pixels because certain larger-scale behaviour is inconsistent with the idea that the image is truly continuous.

    Incidentally, that analogy is occasionally pointed to by particularly paranoid geeks as possible evidence that we are, in fact, living in a computer simulation a la Matrix.
     
    #7 AlexWeldon, Jan 26, 2009
    Last edited: Jan 26, 2009
  8. Jamie W

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    It does (what you just said Alex) give the impression that the universe is running at 60fps or something a bit faster than that?

    Is the universe running at (0.0000000000000000000000000000000000016/299,792,458) fps?

    Maybe that's a vastly over-simplistic point of view I'm getting ...

    Jamie, confussed and bufuddled. :confused:
     
  9. AlexWeldon

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    That's actually a pretty good way of thinking about it. Time is actually divided into "frames" of length equal to the Planck time, and space is actually divided into "pixels" with dimensions equal to the Planck length. Everything else - energy, momentum, etc. - is also quantized in a similar way.

    If it helps, here's how quantum degeneracy works, as best I can explain it to a layperson:

    The Pauli exclusion principle states that no two fermions (a classification of particle) can occupy the same quantum state simultaneously. One way of thinking about it (since people tend to like to personify physical principles) is to say that these particles are completely described by their quantum numbers, and so the rules of the Universe prevent them from ever having exactly the same set of numbers, because otherwise it wouldn't be able to tell them apart anymore.

    How this leads to the phenomenon of degeneracy pressure (by which white dwarves and neutron stars are held up) is as follows:

    A white dwarf is just an incredibly dense ball of hot carbon left behind after a dying star sheds its exterior gasses. As there is no nuclear fusion happening inside it anymore, there is no energy being produced to create an outward pressure to resist its gravitational collapse.

    However, as the star collapses, the atoms get pressed together ever more tightly, and their electrons get squished together. The electrical repulsion of these electrons is not nearly enough to hold the star up. However, as they're pushed together, eventually lots of electrons get forced to occupy the same regions of space.

    The quantum numbers for electrons are their positions, their momentums and their spins (intrinsic angular momentum). However, there are only two possible values for spin (+1/2 and -1/2), so once you start packing a bunch of electrons into the same region of space, they're forced to have different momentums.

    Finally, what you get is a "degenerate" state, in which all the lower momentum states are already occupied, so for any new electrons to be permitted into the space, they must go into a higher momentum state. This increase in momentum (and thus velocity) creates a pressure, which holds the star up.

    Neutron stars work on the same principle, except the gravity is so strong that the momentums and energies get so high that the electrons get packed into the nuclei, merging with the protons to form neutrons. After all the atoms collapse in this way, the neutrons pack themselves together until neutron degeneracy takes over, the same way electron degeneracy held up the white dwarves. Thus, neutron stars are a couple of orders of magnitude more dense than white dwarves. I don't remember the exact numbers, but I think white dwarves have a few hundred tons of mass per teaspoon, while neutron starts are several tens of thousands of tons per teaspoon.

    Add even more mass, and even neutron degeneracy doesn't cut it. The star compresses below its own event horizon and becomes a black hole.
     
  10. Jamie W

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    Wow, that's really interesting Alex. Did you do a Physics degree? I was really quite interested in Physics at school, even so, we never covered topics so fascinating..

    With this planck time thingy, what I don't understand, it's not just that it's the smallest measure of time, we humans have; there are actual real world reasons why that exact measure of time is the smallest unit of time possible (not just measurable).

    The bit I don't understand, is the reasons why it's the smallest amount of time possible, unless it's all tied in with the granular nature of space-time?

    Also, I only have a limited scope for comprehending what time actually is, it all gets filtered through my human faculties and capabilities to apprecieate and percieve such things (as time).
     
  11. AlexWeldon

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    Astrophysics, yeah. Only did the bachelor's, though, then decided I wasn't willing to devote my whole life to physics and moved on to other things.

    One of the reasons that I got tired of physics is that pretty much everything discovered past 1900 simply doesn't make any sense. It's not that it just doesn't make sense to laypeople - it doesn't make sense to physicists either. They just hide behind math and pretend that solving equations is the same as understanding what's going on. To quote one well-known physicist (I forget who... Google it if you like): "The Universe is not stranger than we imagine. It is stranger than we can imagine."

    The Planck length comes from the physical constants of the Universe. It's essentially the smallest little box that anything can be put in. The pixels of the Universe. One of those things that can only be understood mathematically, and only proven because predictions that come out of that math end up matching up with observations of larger scale things that actually do make sense to us.

    The Planck time is just the Planck length divided by the speed of light. That, at least, makes intuitive sense. If there's such a thing as "the smallest possible distance," and "the fastest possible speed," then obviously the shortest possible time is the time it takes something to move the smallest possible distance when travelling at the fastest possible speed.
     
    #11 AlexWeldon, Jan 27, 2009
    Last edited: Jan 27, 2009
  12. Pyabo

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    That would be pretty slow wouldn't it? :)

    It's running at 1 / (0.0000000000000000000000000000000000016/299,792,458) fps.
     
  13. Jamie W

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    But do we see the universe as IT is, or do we see it as WE are?

    Physics (seemingly) assumes a seperation between the object we observe, and the tool we use to do the obsevation (ourselves), when surely these two are an integral oneness?

    But are these planck 'spacial units' aligned neatly in a 3d grid? Or can they move about? (i.e. sub-pixel stylee) .. oh never mind .. I'd be here forever quizzing you.

    Better get back to the day job!

    Cheers,
    Jamie. :)
     
  14. Jamie W

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    Yes, that's right!

    ... and each 'frame' only lasts 0.0000000000000000000000000000000000016/299,792,458 seconds.

    Talk about smooth animation!
     
  15. Sol_HSA

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    So, as an approximation, the value is:
    0.5337025523 * 10 ^ -44 seconds per.. frame?

    or

    0.1873702863 * 10 ^ 45 "frames" per second

    :)
     
  16. Nikster

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    or:

    very fookin' fast


    Which I think more people can relate to :)


    However, had you said "How long (in seconds) is one plankton" that would be easy, the answer is 4.00pm.
     
  17. Sol_HSA

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    Okay, would 0.2 billion billion billion billion billion fps be easier? =)
     
  18. James C. Smith

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    Are you crazy? It is a proven fact that we are indeed living inside a computer simulation. It would be silly to suggest otherwise.
     
  19. undergrowth

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    The problem with the fps analogy of the universe is that the universe isn't synchronized to a clock. Time is relative, and varies when two objects are travelling at different velocities (especially near the speed of light), and also time becomes "unsynchronized" the longer it takes light to travel between them (i.e. the further they are apart).

    So perhaps you could say each "pixel" is running at 0.187e45 FPS, and each pixel will only travel in planck lengths relative to its own frame of reference. So maybe everything in the universe works like a computer, at a set FPS and along an XYZ grid, but only relative to itself.

    I haven't formally studied physics though, and I'm not sure if I should be mixing quantum psychics and relativity, as I don't think anyone's really worked out how they fit together. But correct me if I'm wrong.
     

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