He-Who-Must-Be-Preserved works for a software company that makes wearable gadgets that track your movement; its most obvious application is for people who want to know how many calories they’re burning when they exercise, that kind of thing. He was talking about it this morning and I misheard him (I hadn’t had any coffee yet); what I heard him say was that he was eager to finish this piece of software that would allow him to “detect all of my emotions,” but what he actually said was “detect all of my motions.”
That misheard phrase catapulted me into a speculative science-fictional duck-rabbit hole, partly, I think, because I had already been thinking about the mood organ in Do Androids Dream of Electric Sheep?. 
Here’s my imaginary gadget: it detects and reports your own emotions to you. Maybe you think you don’t need one of those, because, duh, you, like, already have one of those? It’s called a mind?
But wait just a minute before you cast my make-believe gadget into the imaginary dustbin of fictional inventions, o ye of little faith. Here’s the difference between your mind and my gadget. My gadget is external (let’s say it’s worn around the wrist, or, perhaps, hanging from the neck, like a pendant, resting upon your sternum; that would be a little visual joke about Momus’s glass)  and its data may be seen and read by anyone you care to show it to. So, say you’re sitting listening to someone tell you a long story and they break off and say, irritably and accusingly, “you’re not listening to a word I’m saying, you’re clearly bored out of your mind!” And say that in fact they are misreading your expression, you could then whip out your gadget, which might say, “Moderate to high levels of interest-excitement!!” And you could say, “see, I was paying attention,” and whomever you were talking to would have no choice but to back the fuck down. 
Genius, right? 
So, how would this work, you ask?
Well, I’ve given this some thought, as is my wont, and I think it could work the same way as the software for measuring motion does. The first stage would be data collection. So, for example, perhaps you would hang around hospitals and measure all of the biometrics of people who have just been told that a close relative has died: voilà, you’ve captured grief. Then, while you were there, you could hop over to the maternity ward and measure the biometrics of mothers who had just given birth and were all flooded with endorphins. Joy: done. Or not done, actually, because you’d want to be able to account for all the different spectra of joy. So, on the way home from the hospital, you’d stop off and take the biometrics of all the preschoolers skipping home from school. 
So then you just program all that information into the wearable device and then it measures your individual physiological responses against those of all of the thousands or perhaps millions of data-suppliers and tells you how you are feeling. This would be useful in any situation in which the authenticity of your professed feelings was challenged. So, it would be similar to a lie-detector test but oh-so-much-more nuanced in the kinds of readings it would provide.
Conveniently, the younger flopsy-duckit supplied me this morning with a perfect example of how my gadget might be put to use in practice. She had just complained of a stomach-ache and I had suggested she have a glass of water. After she took one sip she declared, improbably, “It feels better now!”
“Good!” I said, giving her what I thought was a look that communicated the following: affection-amusement-skepticism-sympathy-love.
But then she frowned at me. “Why are you always making those sad faces?” she asked scornfully.
“I wasn’t making a sad face!” I protested.
“Yes you were!” she insisted.
Then she walked over to me (I was sitting on a chair in the living room) and stood right in front of me so that she was about an inch in front of my face, her eyes at my eye level. She stared hard.
“You can’t see your face,” she said. “Because your eyes are your face. So you don’t know.”
I was impressed and had to concede her point. “You’re right,” I said. “My eyes are in my face, so I can’t see my own face.” 
“But I can see your face,” she asserted.
And here is when I could have whipped out my gadget and shown her that, despite my facial expression, I was not actually sad. And that having been established, we would then have been in a position to conclude either that the younger is not very good at interpreting facial expressions, or that I am not very good at making facial expressions that reflect my feelings.
Clearly the younger was convinced of the latter, because she then started manipulating my mouth in an effort to coach me: she curled the corners of my mouth up, upon which she would exclaim “happy!” before turning the corners down and then exclaiming “sad!” She did this a number of times until I protested.
At this point you may be thinking to yourself, that’s all well and good, Duck-Rabbit, but the fact that this device might resolve a few quibbles surely doesn’t qualify it to be hailed as the greatest scientific invention of the 21st century.
But think of the wider applications! It could resolve inter-generational and cross-cultural misunderstandings on a much bigger scale (“Arrogant? No, she’s just British!) We could cut prison populations (“Why he is genuinely remorseful, just like he said he was!”); we could solve world conflicts (“group x doesn’t hate group y; they’re terrified of them).
With that said, I will wait humbly for the call from the Nobel Committee.
 See my comment on Day 44.
 “If the fixture of Momus’s glass in the human breast, according to the proposed emendation of that arch-critick, had taken place,——first, This foolish consequence would certainly have followed,—That the very wisest and very gravest of us all, in one coin or other, must have paid window-money every day of our lives.
And, secondly, that had the said glass been there set up, nothing more would have been wanting, in order to have taken a man’s character, but to have taken a chair and gone softly, as you would to a dioptrical bee-hive, and look’d in,—view’d the soul stark naked;—observed all her motions,—her machinations;—traced all her maggots from their first engendering to their crawling forth;—watched her loose in her frisks, her gambols, her capricios …” (from Tristram Shandy Volume I, Chapter 23).
 Interest-excitement is one of the six basic affects identified by Silvan Tomkins in Affect Imagery Consciousness (1962-1991). I like the idea that the punctuation could also be a shorthand. So interest-excitement would be an exclamation point, and there would be fewer or more exclamation points depending on the level of interest-excitement registered.
 This could also be useful if you are trying to figure out if somebody is a philistine. Here is another version of the mood-tracker envisaged by the Director of the Center for the Future of Museums; she imagines a device that would be able to determine an individual’s level of “cultural engagement”: http://futureofmuseums.blogspot.com/2014/05/the-biometrics-of-cultural-engagement.html I for one am scared by this possibility because it would reveal that I am actually bored about 75% of the time in museums, my enjoyment soaring in the gift shop and the café. I always used to think, when I was living in London, that the cake you would get to eat in the café afterwards was the whole point of going to museums, but I must confess that I’m often disappointed by the cake-selection available at many museums in this country, e.g. the Getty, which clearly has enough money to have a much better selection of cakes than it offers.
 I have to explain here why I titled this post “The Greatest Scientific Invention of the 21st Century.” It is in tribute to a question that I was once asked (by a highly-esteemed reader of this blog) in an interview for an academic job, an interview that I spectacularly bollocksed up. The question was “What do you regard as being one of the greatest scientific inventions of the eighteenth century?” This was a complete softball of a question given that at the time I was a fellow at the Max Planck Institute for the History of Science and had boldly declared myself in my job letter to be a veritable expert on the intersections between eighteenth-century science and literature. However, my mind went completely blank and after some throat clearing I muttered (because I needed to buy more time) something vague about the eighteenth-century responding to seventeenth-century scientific discoveries. By this time, a few inventions had popped into my head but for every invention I thought of (the steam engine, gas street lights), my second thought was, but was that invented in the eighteenth century? Gah! Eventually, what I blurted out, without any explanation, was “F = ma.” That was all I said. I didn’t say anything else. My interviewees looked at me silently with expressions that I could not read. Later, I realized that, since Newton’s second law of motion is, uh, not generally referred to as an “invention,” they probably were completely nonplussed by my response. It all went downhill from there, but so kindly was the poser of the question that I strongly suspect that he was more distraught by my awkward response than I was.
 Or adults skipping! I skipped much of the way to preschool this morning with the younger F-D, and found that it’s really, really difficult to skip without having a silly grin on your face.
 I was reminded at this moment of the following sequence in Scott McCloud’s brilliant Understanding Comics: