How do we know the Planck length is the absolute limit of small?

There is no limit to big, so why would there be a limit to small? From our perspective it may seem that way, but if someone were to be actually living on that scale, then there would be a lot more room looking down, would there not?

11 Answers

  • Clive
    3 days ago

    Because on the smallest scale, the universe genuinely IS “fuzzy” and random. So there is a genuine limit to small. Down on that scale, it’s impossible to actually say where something is and how fast it is moving – this is the Heisenberg uncertainty principle. There just can’t be anyone living on that scale.

    This also has to do with wave-particle duality. On our scale there are solid objects with definite edges, but not when you get that small – everything is kind of wave-like so you can’t definitely say where its edge is.

  • nineteenthly
    3 days ago

    No. There are no hidden variables. If quantum effects were due to a smaller mechanism, that would show in the maths. They are generally truly random.

  • Anonymous
    3 days ago

    There’s no limit to our imagination — just the evidence so far

  • Jeffrey K
    3 days ago

    When quantum mechanics is applied to space and time, the very concepts of space and time break down. No one knows what concept replaces them. The smallest distance that makes sense before the space concept breaks down is the plank lenght. The shortest unit of time is the plank time. 10^ -43 seconds.

  • Quadrillian
    3 days ago

    There is a limit to big: it is called the cosmic horizon. Similarly there is a limit to small: it is called the Planck length.


  • Raymond
    3 days ago

    We do not know that it is the “absolute”.

    We do know that, given our present knowledge of physics, any smaller length makes no sense.

    It is somewhat related to the Heisenberg uncertainty principle. The smaller a “thing”, the more uncertain its position. Also, the smaller a “thing”, the more its “wave-particle duality” wavers towards wave.

    A photon with a wavelength equal to a Planck length would have too much energy to fit into a Planck-length neighborhood.

    Some scientists, when trying to explore the infinitely small, end up accepting that “distances” (whatever that means inside a Planck length) actually get longer as you divide the distance.

    Go figure.

  • quantumclaustrophobe
    3 days ago

    Mathematically, you’re right. Whatever length you have, you can divide by two forever to get a smaller number. However, there’s a point (which may or may not be Planck length) where one point in space is indistinguisible from another.

    The definition says ‘where classical ideas about gravity and space-time cease to be valid’ – a planck length from one point in space-time is the minimum distance needed to detect a different point in space-time.

  • Tom S
    3 days ago

    There is a limit to “big” also, space is most likely finite. Also, something could be smaller than Planck scale, but our knowledge of physical laws don’t work at that scale, not could we measure anything less than that scale, not just in a technical aspect but not even in theory.

  • Anonymous
    3 days ago

    I think because you can’t measure all of universe but you can measure objects within reach to the lowest scale

  • megalomaniac
    3 days ago

    It would seem logical to assume that but when things get that small even logic seems to break down (of course logic is still logic but I suppose I meant that things don’t behave as expected). The world of the ultra small is very weird, that’s about all I can say about that.

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