hysteresis

“Spare me the history, sis!”

Daryl’s coffee time was being disrupted by a conversation on his iPhone (it was unusual to see him using it to talk to someone). His sister was evidently having an attack of the fantods.

“OK,” he said, “I understand… OK… OK OK OK…” He held the phone away from his head for a moment, his hand over the microphone. “She’s in hysterics,” he explained. “I’m trying to get to the bottom of it.” He winced as he returned it to his ear.

Jess and I exchanged glances, rolled our eyes, and sipped our coffees.

“So wait,” he said. “You wouldn’t have been there if she hadn’t gone to the wrong place. OK. And she went to the wrong place because she saw you at that store that you were at only because she had previously said to go to the other one, and she said to you to go to the other one because you were talking to Millie, which only happened because… wait, why?”

Pause. Pause pause pause.

“So you’re upset now precisely because you were happy before and then you thought it changed, and you were happy before because you had really needed that dress, and you really needed that dress because you had been told that you were going, but you were told you were going only because you were at… wait, I’m getting dizzy.”

Jess’s eyebrows were arching higher and higher.

“OK,” said Daryl, “so everything’s fine right now, right? So it turned out OK? …Well… Well, so why are you so upset?” Pause. He pulled a face of disbelief. “Oh, for heaven’s sake. Count your blessings and let me drink my coffee. …Goodbye.” He thumbed his phone off rather pointedly and turned to us. “She’s upset because of what she previously thought was the case, even though it wasn’t the case and everything’s fine. And she only thought that because before that she had…”

“Spare us,” Jess said. “Your sister clearly has a case of hysteresis.”

“Yeah,” said Daryl, “she’s the history sis, alright, and hysteria is her métier.”

“Amusing that neither history nor hysteria is related to hysteresis,” Jess added nonchalantly, and sipped her coffee again.

“Well, how is that possible?” Daryl asked. “Wait, what does it mean again?” He started thumbing things into his iPhone.

“You’ll find, when you look it up,” said Jess, with a little smile, “that it’s from Greek husteros, ‘late’, and refers to time lag or coming in behind. It means the current state of a given thing depends on its previous state or on a previous input. The current state of a thing can lag a bit behind what’s causing its state, so that while cause is on G effect is still on F, and so on, just like your sister’s emotions. The current state can also be dependent on the previous state, just as each step in your sister’s history was contingent on the previous one. The short of it is that for something that exhibits hysteresis, you can’t determine its present state just by looking at its current input; you need to know what happened before.”

“Oh, I see,” Daryl said, looking at the screen on his device. “Here’s a nice page by a dude from Cornell.” (He was looking at www.lassp.cornell.edu/sethna/hysteresis/WhatIsHysteresis.html.) “It’s an essential property of magnetic memory: it has to be able to remember the state change from its previous input.”

“Yup,” said Jess, “your phone doesn’t just convey hysteresis, it requires it.”

Daryl kept scanning the page. “Right, history is sure relevant, but there’s no etymological connection… Oh, how amusing.”

I looked over. “What?”

He read it out. “‘Many hysteretic systems make screeching noises as they respond to their external load (hence, the natural connection with hysteria).’ Ha. Dry humour.”

“Well,” Jess said, looking at his iPhone, “screeching seems about right.”

“Hissing, too,” Daryl added, hosltering his phone decisively. He picked up his coffee and looked at it. “Damn. The whipped cream has all dissolved.”

Today’s word was requested by Barry Gibbs.

One response to “hysteresis

  1. Pingback: phronesis | Sesquiotica

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