I’ve heard some conflicting things, is the Planck Length the smallest possible length or not?


I’ve heard some conflicting things, is the Planck Length the smallest possible length or not?

In: Physics

The Planck Length is the smallest possible *physical* length. You can write down a number that’s smaller, of course …. but you can’t do actual physics with distances smaller than the Planck Length and still get results that make sense.

So, technically, the Planck Length is the smallest possible length that is meaningful under the current Standard Model of physics. If there is a breakthrough in something like string theory, the situation could change, and it could become possible in the future to deal with smaller scales.

If we talk about tiny things there will be one type of thing that could claim to be the smallest thing. The distance between things is not a thing. There can always be a smaller distance than the one light shows us and maybe there are things smaller than light. There are numbers smaller than Planck scales so maybe there are smaller things in the world.

The planck length is a distance sufficiently short that our current math cannot well describe what happens at shorter distances. This is, if I recall, because quantum gravity becomes important at such distances and we do not yet understand quantum gravity.

Thus, it is not the smallest possible length, but it is the approximate smallest length that we can predict things at.

“Smallest possible length” is a useful, albeit a very simplified way to conceptualize the Planck length. Granted, anything in quantum physics that isn’t a page full of equations can be described as “very simplified”.

More precisely, it is the smallest length that makes any sense to talk about using our current understanding of our universe. It is a little bit like trying to spend a billionth of a cent, the mere act of trying to think about it costs more than that.

It is possible a new theory might be able to go beyond Planck limitations, but current theory (mostly) works just fine without having to assume something more is out there.