A fuse is a wick that burns at one end, possibly creating byproducts. A clean fuse is much to be desired, even one leaving no residue. The messier the debris, the harder it would be to combine it with something else. Like pure glider generators, fuses were of early academic interest in the 1970s and often reported in Lifeline issues, but nowadays fuses that are not reburnable have been found to be so numerous that new examples no longer receive much attention.
Fuse may also refer to a still life component consisting of a diagonal line of two or more livecells. This article is about the first definition, above.
Various details which can be observed while examining the history of a burnt fuse:
It is usually named for a noteworthy initial condition or avatar, which may or may not reappear as the fuse burns. If it reappears, the smallest, or most symmetrical, phase would probably have been chosen as the namesake and initiator.
During and after startup a fuse may leave no residue, leave an initial residue which could change form or altogether disappear after a time, or persist for a long time.
Three times are important statistics for the fuse:
the transient time, after which it has entered a cycle
the length of the internal cycle, after which the avatar repeats
the length of the external cycle, which is the time for debris left by the burning to repeat, which may be a multiple of the internal cycle since it may require time to settle down. As the externally visible cycle, it is the one cited as the period of the fuse.
A fuse may arise from a moving phase change in a wick without destroying the integrity of the wick, as for the phoenix-tub eater or the lightspeed wire. Indeed, all equilibria might be so regarded.
harvester:[1] transient time 5, cycle 4, period 4 discovery: David Poyner, February 1971 Scientific American column[2] (click above to open LifeViewer) RLE:herePlaintext:here
As suggested by Bill Woods on Lifeline,[4] a reverse fuse is not so much the name of a fuse as a description of fuse behavior. Given that a wick is a stable one dimensional Life pattern and that a fuse and its burning refer to a progressive disruption of the wick, the expectation is that a growing cloud of debris will form as the wick progressively disintegrates. So, the reverse of this scenario would be that the combustion settles down into an orderly process.
Although the term refers to no particular fuse, a simple example will serve to illustrate the principle. Whereas a diagonal string of live cells constitutes a stable wick, a semiinfinite string burns by dropping the cell at the tip of its tail every generation. But a cluster of live cells surrounding the tail complicates the evolution; the simple variant of placing a domino at the tip is shown in the first figure.
That fuse will burn for a while, leaving a residue behind. But eventually it will evolve into the form shown in the second figure; a pattern which reproduces itself in displaced form every fourth generation.
The raw diagonal fuse is a prolific source of variants, many of them reverse fuses.
