The Universe of Discourse

Sun, 12 May 2024

As I walk around Philadelphia I often converse with Benjamin Franklin, to see what he thinks about how things have changed since 1790. Sometimes he's astounded, other times less so. The things that astound Franklin aren't always what you might think at first. Electric streetlamps are a superb invention, and while I think Franklin would be very pleased to see them, I don't think he would be surprised. Better street lighting was something everyone wanted in Franklin's time, and this was something very much on Franklin's mind. It was certainly clear that electricity could be turned into light. Franklin could have and might have thought up the basic mechanism of an incandescent bulb himself, although he wouldn't have been able to make one.

The Internet? Well, again yes, but no. The complicated engineering details are complicated engineering, but again the basic idea is easily within the reach of the 18th century and is not all that astounding. They hadn't figured out Oersted's law yet, which was crucial, but they certainly knew that you could do something at one end of a long wire and it would have an effect at the other end, and had an idea that that might be a way to send messages from one place to another. Wikipedia says that as early as 1753 people were thinking that an electric signal could deflect a ping-pong ball at the receiving end. It might have worked! If you look into the history of transatlantic telegraph cables you will learn that the earliest methods were almost as clunky.

Wikipedia itself is more impressive. The universal encyclopedia has long been a dream, and now we have one. It's not always reliable, but you know what? Not all of anything is reliable.

An obvious winner, something sure to blow Franklin's mind is “yeah, we've sent people to the Moon to see what it was like, they left scientific instruments there and then they came back with rocks and stuff.” But that's no everyday thing, it blew everyone's mind when it happened and it still does. Some things I tell Franklin make him goggle and say “We did what?” and I shrug modestly and say yeah, it's pretty impressive, isn't it. The Moon thing makes me goggle right back. The Onion nailed it.

The really interesting stuff is the everyday stuff that makes Franklin goggle. CAT scans, for example. Ordinary endoscopy will interest and perhaps impress Franklin, but it won't boggle his mind. (“Yeah, the doctor sticks a tube up your butt with an electric light so they can see if your bowel is healthy.” Franklin nods right along.) X-rays are more impressive. (I wrote a while back about how long it took dentists to start adopting X-ray technology: about two weeks.) But CAT scans are mind-boggling. Oh yeah, we send invisible rays at you from all directions, and measure how much each one was attenuated from passing through your body, and then infer from that exactly what must be inside and how it is all arranged. We do what? And that's without getting into any of the details of whether this is done by positron emission or nuclear magnetic resonance (whatever those are, I have no idea) or something else equally incomprehensible. Apparently there really is something to this quantum physics nonsense.

So far though the most Franklin-astounding thing I've found has been GPS. The explanation starts with “well, first we put 32 artificial satellites in orbit around the Earth…”, which is already astounding, and can derail the conversation all by itself. But it just goes on from there getting more and more astounding:

“…and each one has a clock on board, accurate to within 40 nanoseconds…”

“…and can communicate the exact time wirelessly to the entire half of the Earth that it can see…”

“… and because the GPS device also has a perfect clock, it can compute how far it is from the satellite by comparing the two times and multiplying by the speed of light…”

“… and because the satellite also tells the GPS device exactly where it is, the device can determine that it lies on the surface of a sphere with the satellite at the center, so with messages from three or four satellites the device can compute its exact location, up to the error in the clocks and other measurements…”

“…and it fits in my pocket.”

And that's not even getting into the hair-raising complications introduced by general relativity. “It's a bit fiddly because time isn't passing at the same rate for the device as it is for the satellites, but we were able to work it out.” What. The. Fuck.

Of course not all marvels are good ones. I sometimes explain to Franklin that we have gotten so good at fishing — too good — that we are in real danger of fishing out the oceans. A marvel, nevertheless.

A past what-the-fuck was that we know exactly how many cells there are (959) in a particular little worm, C. elegans, and how each of those cells arises from the division of previous cells, as the worm grows from a fertilized egg, and we know what each cell does and how they are connected, and we know that 302 of those cells are nerve cells, and how the nerve cells are connected together. (There are 6,720 connections.) The big science news on Friday was that for the first time we have done this for an insect brain. It was the drosophila larva, and it has 3016 neurons and 548,000 synapses.

Today I was reading somewhere about how most meteorites are asteroidal, but some are from the Moon and a few are from Mars. I wondered “how do we know that they are from Mars?” but then I couldn't understand the explanation. Someday maybe.

And by the way, there are only 277 known Martian meteorites. So today's what-the-fuck is: “Yeah, we looked at all the rocks we could find all over the Earth and we noticed a couple hundred we found lying around various places looked funny and we figured out they must have come from Mars. And when. And how long they were on Mars before that.”

Obviously, It's amazing that we know enough about Mars to be able to say that these rocks are like the ones on Mars. (“Yeah, we sent some devices there to look around and send back messages about what it was like.”) But to me, the deeper and more amazing thing is, from looking at billions of rocks, we have learned so much about what rocks are like that we can pick out, from these billions, a couple of hundred that came to the Earth not merely from elsewhere but specifically from Mars.

What. The. Fuck.

Addendum 20240513

I left out one of the most important examples! Even more stunning than GPS. When I'm going into the supermarket, I always warn Franklin “Okay, brace yourself. This is really going to blow your mind.”

Addendum 20240514

Carl Witty points out that the GPS receiver does not have a perfect clock. The actual answer is more interesting. Instead of using three satellites and a known time to locate itself in space, as I said, the system uses four satellites to locate itself in spacetime.

Addendum 20240517

Another great example: I can have a hot shower, any time I want, just by turning a knob. I don't have to draw the water, I don't have to heat it over the fire. It just arrives effortlessly to the the bathroom… on the third floor of my house.

And in the winter, the bathroom is heated.

One unimaginable luxury piled on another. Franklin is just blown away. How does it work?

Well, the entire city is covered with a buried network of pipes that carry flammable gas to every building. (WTF) And in my cellar is an unattended, smokeless gas fire ensures that there is a tank with gallons of hot water ready for use at any moment. And it is delivered invisbly throughout my house by hidden pipes.

Just the amount of metal needed to make the pipes in my house is unthinkable to Franklin. And how long would it have taken for a blacksmith to draw them by hand?

Addendum 20240723

If Franklin's eyes are good enough, get him to examine your t-shirt. At first he'll be astounded at the fineness of the weave. But you point out that it stretches in all directions, not just on the bias, which shows that it's not woven. Then the mind-blowing reveal: it's a knit.

Watch Franklin trying to imagine the tiny, tiny knitting needles, and think about how long it takes one person to make a knit sweather with normal-sized needles.

Addendum 20240728

I said:

The things that astound Franklin aren't always what you might think at first.

We (Franklin and I, that is) ran into an example yesterday. We saw the Regional Rail train go by, and I explained it was called a train because it was a series of rail cars each pulling the one behind it.

“But there were only two,” observed Franklin.

“Usually the train is longer than that, but they make it shorter on Saturday because not as many people are riding. Its main job is to take people to work.”

Long pause.

“People here don't work on Saturdays?”

Addendum 20241002

Only eighteen months later we have mapped the brain of an adult fruit fly. It has 139,255 neurons (up from 3,016 in the larva) and 54.5 million synapses (up from 548,000).

Wow.

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