system
Given the following post, respond as if you're commenting on Reddit:
human
How did we find out electrical currents are made of negative charges, rather than positive?

As I understand it (I may have it wrong) the reason conventional current flows in the "wrong" direction is that Benjamin Franklin (and I assume other people of his time) thought electrical currents were made out of positive charges.

How and when did we realize this was not the case?
gpt
Which charge is negative and which is positive is purely a matter of convention, i.e. you could decide to interchange them without the physics being affected. By extension this also means that the direction of current is a matter of convention; Franklin picked a direction that corresponds to the flow of positive charges though, unbenknownst to him, the things that are actually moving are "negatively" charged electrons.