The warning label for radioactive substances (technically, the warning label for ionizing radiation) was born in 1946, at the UC Berkeley Radiation Laboratory, and the now iconic symbol began life a bit different from how we know it today, originally colored with a very hip magenta "trefoil" on a blue background.
The shape of the three-bladed trefoil is quite specific and purposeful - drawn with a central circle of radius R, an internal radius of 1.5R, and an external radius of 5R for the blades, which are separated from each other by 60° of empty space.
It's shape is tightly defined because it is to noticeably and clearly warn you against the dangers of ionizing radiation, which at their very worst would cook you instantly like an egg, or in less worse conditions, still potentially cause life-changing mutations to your cells and DNA.
The yellow and black trefoil is supposed to be a literal warning (the IAEA and ISO adopted this new coloring in 2007) of course, but labeling something radioactive carries with it a metaphorical weight as well. And, it too demands a cautious interaction from the user.
In the motorcycle industry, we have our fair share of radioactive elements, though few come with a warning label. On Episode 45 of the Two Enthusiasts Podcast, you may have heard me refer to a motorcycle company as being radioactive. I thought it was worth spending some words on what that means in that context.