I always thought that the difference between a shuttle and a hassler is in what the other components do:mniemiec wrote: ↑June 22nd, 2021, 2:06 pmpcallahan wrote: ↑June 22nd, 2021, 10:26 amThe question gave me a flashback to 49P88, which I have never thought of as a shuttle, despite taking a 180° turn. I still would not call it a shuttle. The classic shuttles are p30 and p46, which are both symmetric (ignoring catalysts) and can be thought of as flips as well as 180° turns. Maybe that is too strict as a definition, but I think it's my intuition when looking at something and deciding if it's a shuttle.The LifeWiki definition is close, but I don't think it's exactly correct, at least from my memory of how the term was initially used back in the Scientific American and Lifeline days. They key feature of shuttles (as distinguished from other pulsators) is that their active regions move a substantial distance. While it's true that all of Life's common natural shuttles (e.g. queen bee and twin bees) share two additional properties (i.e. bilateral glide symmetry, and the fact that their mechanisms must be assisted by additional non-moving components), these are not necessary properties, and there are common shuttles in other rules that don't share them, e.g. ones that operate without any outside assistance, or ones with C4 rotational symmetry, or ones with no glide symmetry, that move forwards and backwards using different mechanisms (so are capable of having odd periods).MathAndCode wrote: ↑June 22nd, 2021, 10:34 amI would arguable that 49P88 is more of a shuttle than the p29 pre-pulsar hassler, which is commonly called a shuttle, because in 49P88, the hassled region goes both directions in the same way, which is impossible for any odd-period oscillator.
– a shuttle regenerates itself and other components are needed (if needed) only to suppress exhaust;
– a hassler involves a reaction that regenerates itself only after interacting with other active components;
– and something like 49p88 is neither, it's just a track / conduit loop (with no active hasslers, just eaters).
This seems further somewhat analogous to tagalong versus escort / pushalong, where the former depends on a spaceship for its growth in the first place but the latter depends on a spaceship just for stabilization.