Planck's length has absolutely no known physical significance. It is just a combination of fundamental constants that happens to have the dimension of a length.
The so called Planck system of units, proposed by him in 1899, when he computed what is now called Planck's constant, is just an example of how a system of fundamental units must not be defined. To explain exactly the mistakes done by Planck then requires a longer space than here.
Unfortunately, probably because most textbooks of physics do an extremely poor job in explaining the foundation of physics, which is the theory of the measurement of the physical quantities, most people are not aware that the Planck system of units is completely bogus, like also a few other similar attempts, like the Stoney system of units.
Thus far too often one can see on Internet people talking about the "Planck units" as if they would mean something.
Unlike with the "Planck units", there are fundamental constants that really mean something. For instance, the so called "constant of fine structure", a.k.a. Sommerfeld's constant, is the ratio between the speed of an electron and the speed of light, when the electron moves on the orbit corresponding to the lowest total energy around a nucleus of infinite mass.
This "constant of fine structure" is a measure of the strength of the electromagnetic interaction, like the Newtonian constant of gravitation is a measure of the strength of the gravitational interaction. The Planck length and time are derived from the Newtonian constant of gravitation, and they are so small because the gravitational interaction is much weaker, but they do not correspond to any quantities that could characterize a physical system.
For now, there exists no evidence whatsoever of some minimum value for length or time, i.e. there exists no evidence that time and length are not indefinitely divisible.
The so called Planck system of units, proposed by him in 1899, when he computed what is now called Planck's constant, is just an example of how a system of fundamental units must not be defined. To explain exactly the mistakes done by Planck then requires a longer space than here.
Unfortunately, probably because most textbooks of physics do an extremely poor job in explaining the foundation of physics, which is the theory of the measurement of the physical quantities, most people are not aware that the Planck system of units is completely bogus, like also a few other similar attempts, like the Stoney system of units.
Thus far too often one can see on Internet people talking about the "Planck units" as if they would mean something.
Unlike with the "Planck units", there are fundamental constants that really mean something. For instance, the so called "constant of fine structure", a.k.a. Sommerfeld's constant, is the ratio between the speed of an electron and the speed of light, when the electron moves on the orbit corresponding to the lowest total energy around a nucleus of infinite mass.
This "constant of fine structure" is a measure of the strength of the electromagnetic interaction, like the Newtonian constant of gravitation is a measure of the strength of the gravitational interaction. The Planck length and time are derived from the Newtonian constant of gravitation, and they are so small because the gravitational interaction is much weaker, but they do not correspond to any quantities that could characterize a physical system.
For now, there exists no evidence whatsoever of some minimum value for length or time, i.e. there exists no evidence that time and length are not indefinitely divisible.