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Comment by adzm | Hacker News Reader

Notably it only fits within a 1 cell high bounding box during at least one of its phases, not all.

I'm not a GoLtician myself but I don't think that would be possible under the "standard" rules anyway, except the trivial case of stasis/death.

I'm really charmed by the linked thread and all the passion and work it belies. Congrats to those involved!

Why do you think it would not be possible?

To make a new cell "live" it must be neighbored by three live cells. And in 2d, a cell only has two neighbors.

s/2d/1d/ right?

Oh, right.

I see what you're saying, but I think it's a misunderstanding. 1D here only means that there's some state where the active cells are confined to one row — but one row within the ordinary 2D GoL plane. I'm sure the next iteration leaps off the line immediately. Search for "Blinker" here to imagine how it could start spreading off the line.

https://en.wikipedia.org/wiki/Conway%27s_Game_of_Life

The GP understood that.

Right, but that's not what adzm was asking about.

A 1d row of cells also affects nearby cells above and below the line. Consider a row of three cells:

https://parkscomputing.com/page/conways-game-of-life?boardSi...;

That produces a spinner, because the empty cells above and below the 1d row have three live cells nearby.

Yes, which is not what adzm asked for.

I found this line in the first line of the first page of this thread:

>It's still an open problem as to whether there exists a spaceship in B3/S23 which fits within a 1-by-N bounding box in one of its phases.

So they use the "typical" rule here.

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