"I haven't experimented with either of those. How do you come up with these things?" she wonders.

"I'm very creative," says Bella. "You are old enough to drink, right? I'm assuming. Perhaps you are an absurd prodigy with a PhD at age twenty."

"Arguably I am an absurd prodigy, but not quite that absurd, no."

"How old are you then?"

"Twenty-six. I started my PhD when I was twenty, is that absurd enough for you?"

"That is quite absurd," says Bella, congratulatory.

"Thank you," says Bridget, amused.

"So you can see if you can get a hangover, and if you can't, increasing attempts at liver poisoning would be fascinating, although I'll understand if you don't care to risk the latter."

"I haven't experimented with hangovers, but I feel pretty safe in saying I don't get them."

Bella chuckles. "I'm led to understand that you are lucky in this respect as in others."

"Yeah, so I've gathered."

"If you and something else experience a lot of friction, like if you'd fallen off my bike and gone skidding across the road, does it generate heat that simply fails to hurt you, or fail to generate heat at all? I think it would be obvious if you were absolutely frictionless, but in the same sense that your wrist failed to go past a certain point perhaps you don't generate friction past a certain point?"

"Good question. I haven't investigated it specifically."

"You probably don't have any sandpaper or matches or whatever, either," says Bella, sighing.

"Have I mentioned you have a vicious imagination?"

"Something to that effect, yes. Do inform me if I become creepy."

"As promised. But I don't creep easily."

"Which is why you're getting to hear the vicious ideas instead of me keeping them to myself. Hmm. I suppose if you were tossed into a large piece of machinery, it would break, and you would give whoever threw you there a withering look, but could you actually get out? I mean, are you only particularly tough when stuff is trying to break you, or can you exert the same defensive force outward and break stuff at the location you prefer? Be all 'no, comically enormous clockwork, you cannot move my arm there before this gear twists into uselessness, do it here instead'."

"...I'm having trouble picturing exactly what you mean, but the images I'm generating are hilarious," says Bridget.

"Okay, lemme pick an easier to imagine example than comically enormous clockwork. Suppose you stick your arm through the bars of a cage which contains a tiger. It bites you. It can't break the skin, but you aren't made of rock, so it can get hold of you and pull anyway. Can you just stand there - can you basically lean on the fact that your shoulder will not come out of its socket and the teeth will not go through your skin, to also keep your feet planted - or is the tiger going to get you up against the bars of the cage and hold you there until it gets bored?"

"Good question," she says. "Although I refer you to the chainsaw example—if your tiger bites hard enough, it'll break teeth."

"It is a relatively friendly tiger," Bella suggests.

"Well, I'm not keen to wrestle any tigers to find out, but it's possible I might break its teeth in the process of trying to get my arm back."

"Interesting. But can you just break stuff when your bodily integrity isn't so obviously on the line? If you push on a wall really hard, that probably won't hurt you even if you fail, but if you did it hard enough it might make a regular person's hand slightly uncomfortable - would the wall break rather than 'pushing back' enough to make you slightly uncomfortable?"

"If you can suggest a test, I'm all for finding out."