Some stuff is truly hard to get your head around. Even if your head is relatively large to begin with.
Stuff such as how long it takes depleted uranium to transmogrify into something really, really dangerous. The exact level of alcohol a person can have in her blood before becoming a clear and present danger. The degree of dumb that envelopes the operator of a motor vehicle when he is also talking on his smartphone. The environmental and health threats posed by gravel pits and e-cigarettes and higher-alcohol beer and a few million flimsy plastic bags.