N_Johnston

Spaceships in particular are notoriously hard to construct, and almost surely can't be found by hand (e.g., by just "trying things" in a Life viewer and hoping that something works), with the exception of the 4 really common ones (glider, lightweight spaceship, middleweight spaceship, and heavyweight spaceship). While those 4 spaceships were all found in 1970, the next one wasn't found until (if memory serves...) 1989, and it was found via a specialized search program.

We're still discovering tiny new spaceships that feel like they should have been found decades ago, since they're just that hard to find. The copperhead is a tiny one that wasn't found until 2016 (also via a search program).

I'm sure Dave will have a better anecdotes and stories related to early Life on underpowered computers than me, since he started playing around with Life decades before me (I started in grade 12, which was sometime around year 2000). But I can try to answer the question regarding Life as an allegory for biological life.

Nick Gotts wrote a really nice paper that explores this question---the idea is that, even though complicated lifeforms are rather rare, once they become sufficiently complicated they start to dominate and appear to be non-rare at much later times.

For example, if you fill the Life plane with random sparse junk, then early-on, you won't see much of anything interesting happen. Mostly just chaotic explosions and junk. But at some point, somewhere in the infinite Life plane, there will be a complex mechanism that is capable of doing things like duplicating itself and/or making other lifeforms to send out to other parts of the plane. And once those mega-lifeforms have had time to do their thing, they will dominate.

Which seems quite analogous to actual evolution: most mutations or sporadic things that could lead to life don't, but given enough time and space, things will line up just right to create lifeforms that are capable of then making life prolific.

The book actually already has a CC license posted on its git repo, but we admittedly haven't made that clear on the main book website yet. We'll fix that up.

People can use it to teach, and even edit it as long as they provide attribution.

The problem with math jokes is that there are only a handful of them, so I find myself hearing the same ones over and over and getting sick of them. So maybe instead of posting my favourite, I'll post the most recent one I heard and appreciated (and haven't gotten sick of yet):

What's the opposite of ln(x)?

Duraflame, the unnatural log.

(Credit goes to Bo Burnham)

I wish I could give a short answer to this, but I can't! This is exactly the point of the textbook -- to gradually build up to constructing things like the pi calculator.

OK, let me at least sort of try at a short answer: most huge patterns use some combination of gliders and Herschels to send signals from one place to another. Then patterns like Snarks can move those gliders around, and patterns called Herschel conduits can move the Herschels around. By combining all of these things, you can implement computations and constructions (via glider synthesis) of basically anything.