system
Given the following post, respond as if you're commenting on Reddit:
human
What are Planck units (mostly Planck time, but also the others) actually used for?

I read somewhere that there were more Planck time units in one second than there were seconds that had elapsed since the beginning of the universe. Whether that statistic is actually true or not, what could possibly happen so quickly that a unit of time that short is needed to measure it? And, if I understand correctly, the other Planck units are also extremely small. What are they actually used for as well?
gpt
The reason we use Planck units is convenience. The scaling of the Planck units is based on a number of universal constants (speed of light, gravitational constant, and others). That means that when using Planck units, those constants actually have the value 1.

And because of that, many equations that feature these constants can be rewritten without them, because multiplying or dividing by one can be ignored. This makes equations simpler and makes it easier to understand the relation between various physical quantities.

And while our regular units, be they meters, miles, grams or pounds, are rooted very much in our own history and are therefore very human-centric, the Planck units are based only on universal constants. A hypothetical alien civilization would derive the same equations based on these units, while they would have no notion of human units like meters, seconds, etc...

The Planck units don't fundamentally alter the physics. If an equation holds in regular units, it'll hold in imperial (US) units and it'll hold in Planck units, after rescaling it correctly. But for many branches of fundamental physics, working with Planck units is more convenient.