A Nerd Cool Miscellanea

Jul 28, 2021 oklo space klein bottle möbius strip cherenkov radiation isotropy homomorphic encryption recursion

As a teenager I read an unholy quantity of sci fi of variable quality. The golden age stuff in particular is strong on ideas and slightly hand-waving science. Not so strong on how humans work. Anyway, over the years one acquires a little personal vocabulary of cool sciencey stuff (sometimes from other sources - I read a lot of pop science too) that colours one’s view of the world. Here are a few excerpts from mine.

If any of these trigger a Lucky 10,000 moment for you then that’s all I ask.

The Oklo Nuclear Reactor

If you’re trying to come up with a list of the natural world’s bounty, a nuclear reactor is probably not to the forefront of your mind. It’s a bit brain-bending therefore the first time one discovers that an all-natural in no way man-made nuclear fission reactor is a thing that existed. On Earth. In Oklo, Gabon, central Africa to be exact. To be absolutely clear, this is not science fiction.

As far as anyone knows it only happened in that one place 1.7 billion years ago albeit “running” (what’s even the right word there?) for several hundred thousand years.

That juxtaposition of an ore with the right groundwater characteristics. It’s astonishing. Even more so as it couldn’t happen much later due to the naturally declining proportion of the appropriate isotope necessary to sustain the reaction.

Space elevator

So far nobody has built a space elevator or expects to any time soon. It’s engineering, rather than physics that prevents it from happening though, and given our propensity as a species for solving big engineering challenges, it seems inevitable we’ll solve this one too if we don’t wipe ourselves out first.

The general idea is that if one ties a weight to a string and whirls the weight around and around, the string is held taut. By tying some string of epic tensile strength and length at one end to earth and the other end to a space station the earth will indeed whip the space station around and around and hold the string taut. One can then climb up the string. Or, rather, attach a lift to it and have that climb the string.

Farcical though this sounds, the physics work out. There are tricky bits, and the necessary strength of the string is possibly the least of them, but it does all add up in theory. Even better, it’s not subject to the tyranny of the rocket equation so one would pay dollars for electricity instead of millions for rocket fuel to get into space.

At least nowadays when we launch a rocket we don’t always throw the whole thing away.

Möbius strip & Klein bottle

Down on the more immediately accessible end of mathematics, I still think it’s kind of amazing that you can have a real physical thing that has one surface and one edge. It’s kind of satisfying that when you then make various cuts in it you get correspondingly surprising results.

Since a Möbius strip is effectively a 2 dimensional object (in the same way that any piece of paper is) it’s naturally fun to think about whether one could do the same thing with a three dimensional object. The result can, alas, only be done conceptually as we don’t have free access to a fourth spacial dimension. However the result, if one could, would look a bit like a Klein Bottle.

Back in 1989 when I was a budding computer nerd (as well as a sci fi nerd) there was a terrific book written about an amateur tracking down a computer hacker in his network. That book was The Cuckoo’s Egg by Clifford Stoll. Aside from being one of the internet’s official treasures he nowadays has a sideline in selling glass Klein Bottles.

I have one (a gift from my wife) and adore it. The purchasing process was full of lovely personal touches from Cliff so the whole tying together of my computing and scientific enthusiasms was delightful.

Cherenkov radiation

Nothing can go faster than light. Some sci fi books rather gloss over this and their space ships just do anyway. Others make it a fundamental plot point (travel to even close stars thus takes decades). I don’t suppose I’m the only child of the Star Wars era who finds the limit a bit frustrating.

It’s a bit surprising, though, to discover one of the caveats; it’s not possible to go faster than light’s speed in a vacuum (i.e. the universal constant c) but it is possible to go faster than the speed of light in some other medium. When this happens an effect analagous to a sonic boom occurs and radiation is emitted.

In particular, if you shield a radioactive brick with water, some of the emitted beta particles will exceed the speed that light travels at in water and radiate light as a consequence. It’s a rather nice shade of blue.

The Casimir Effect

If you put two pieces of metal close enough together there’s a force that will push them the rest of the way. Bizarrely this comes, literally, out of nothing.

Specifically, the vacuum, empty space, is simultaneously teeming with particles and antiparticles that probabilistically pop into existence and then annihilate each other as if they regretted the whole thing.

Put two pieces of metal close enough together, however, and there won’t be room between them for some of those particles to pop into existence. More specifically, there won’t be room for some of the particles with longer wavelengths. The resulting discrepancy between the inner and outer spaces is what forces them together.

The interest is piqued, particularly for sci fi readers, by the fact that it’s

That last one is relevant to a bunch of implausible-but-apparently-maybe-possible options in relativity that allow for wormholes and warp drives. The loopier sci fi just goes “whoo, free energy,” and uses it as a technobabble excuse for pretty much anything.

Isotropy

This one’s a bit more esoteric. There’s a clever idea from the famous mathematician John Conway of the Game of Life. In this one follows (or preferably has a computer follow) terrifically simple rules and the result is a superbly complicated world springing fully formed out of those rules and allowing for all sorts of astoundingly complex constructions within it.

Playing around with it for a bit inspires all sorts of fizzy ideas about the possible connections between some ultimate underlying simple physics and the astounding complexity of the physical world around us.

On the other hand it’s a grid. That results in preferred directions. Things move more naturally in some directions rather than others. But the observable universe has no such preferred direction. So the universe is not based on a grid. Or hexagons (waves to the board-gamers) or likely anything else with innate preferred directions.

It seems to go hand in hand, somehow, with the assumption that where we are in the universe isn’t anywhere special. Though that is very mildly in conflict with the anthropic principle.

Homomorphic encryption

Computer nerds have a passing familiarity with computer security. In particular we usually know a bit about encryption. Most of us (hopefully) know we’re not smart enough to design our own, but we do have a good grip on the capabilities.

Usually that’s stuff like

Also, in general, it’s a matter of using the right library the right way. There are a thousand ways to screw it up, but we try not to.

Typically we might think in terms of one of these flows:

But what if one doesn’t trust the person doing the work on the data? Surely you can’t keep that safe - they’ll need to decrypt the data in order to do any useful work on it, right? … Right?

Nope. It’s possible to protect the data throughout, or in other words

Kind of mind-blowing to me, though I gather that it’s currently also mind-blowingly inefficient so you can’t do much practical work like this. But we all know how rapidly computers got faster and we’re not quite done with that wild ride yet so who knows? I’d bet on it having practical uses some time soon.

Recursive definition of ancestor

Finally, there is a notion of recursion which allows you to express certain things in a very dense and self-referential way. I was originally introduced to it with this entirely non-technical example in a college course:

Q: Who are are your ancestors?

A: Well, my ancestors are my Mum and Dad and then my grandparents on both sides, and then my great-grandparents for all of them, and so on.

It’s a rather loose definition and not very satisfying with that “and so on” at the end, but that’s hard to express efficiently in every day English. But the recursive definition is this:

My ancestors are my parents and my parents' ancestors

Isn’t that neat?

© 2017 - 2021 Dave Minter