Added to the introduction of the Replacement catalyses section, modified block replacement guide, fixed link, and modified some examples in the Bonus catalyses section
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The green still life interacts with the white object, and recovers to its original state by [[generation]] 15. In this tutorial, you'll learn the main types of catalyses and their applications. But first, we need to cover some important definitions.
The green still life interacts with the white object, and recovers to its original state by [[generation]] 15. In this tutorial, you'll learn the main types of catalyses and their applications. But first, we need to cover some important definitions.
==Important terms==
== Important terms ==
* '''Stable catalyst''': a catalyst which is a still life. Most catalyses are of this form. In this tutorial we will only focus on stable catalyses, as periodic catalyses are as of now quite underdeveloped.
* '''Stable catalyst''': a catalyst which is a still life. Most catalyses are of this form. In this tutorial we will only focus on stable catalyses, as periodic catalyses are as of now quite underdeveloped.
* '''[[Periodic catalyst]]''': a catalyst which is an [[oscillator]]. These are generally considered "less useful" than stable catalysts, because a periodic catalyst usually does not work in every possible [[phase]].
* '''[[Periodic catalyst]]''': a catalyst which is an [[oscillator]]. These are generally considered "less useful" than stable catalysts, because a periodic catalyst usually does not work in every possible [[phase]].
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__TOC__
__TOC__
==Types of common catalyses==
== Types of common catalyses ==
===[[Fishhook]] (eater 1)===
=== [[Fishhook]] (eater 1) ===
Here are some examples of [[eater 1 reaction|fishhook catalyses]]: <center>{{LV:Viewer|
Here are some examples of [[eater 1 reaction|fishhook catalyses]]: <center>{{LV:Viewer|
Snake catalyses are examples of rocks, or catalysts which do not change even temporarily when interacting with an object. They must function this way due to the fact that the two cells in the center would die from overpopulation due to already having three live neighbors.
Snake catalyses are examples of rocks, or catalysts which do not change even temporarily when interacting with an object. They must function this way due to the fact that the two cells in the center would die from overpopulation due to already having three live neighbors.
Non-rock tub catalyses can be tricky to find, but they are most likely to work when the frontend of the active reaction is two or three cells long, like one of the examples below:
Non-rock tub catalyses can be tricky to find, but they are most likely to work when the frontend of the active reaction is two or three cells long, like one of the examples below:
<center>{{LV:Viewer|
<center>{{LV:Viewer|
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}}
}}
===[[Ship]]===
=== [[Ship]]===
Observe the following reaction:
Observe the following reaction:
<center>{{LV:Viewer|
<center>{{LV:Viewer|
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The ship is turned into a relative of the [[I-heptomino]] (specifically a great-uncle) then is turned back into a ship by a perfectly-timed temporary induction. The ship rarely recovers by its own, but it's worth trying because it has replacement catalysts that recover much more often.
The ship is turned into a relative of the [[I-heptomino]] (specifically a great-uncle) then is turned back into a ship by a perfectly-timed temporary induction. The ship rarely recovers by its own, but it's worth trying because it has replacement catalysts that recover much more often.
==Replacement catalyses==
== Replacement catalyses ==
So, you've tried to catalyze a reaction, but the common catalyst fails! Luckily for you, this is not a complete disaster, since many replacement catalysts exist exactly to assist you when your fishhook or block doesn't just work out.
So, you've tried to catalyze a reaction, but the common catalyst fails! Luckily for you, this is not a complete disaster, since many replacement catalysts exist exactly to assist you when your fishhook or block doesn't just work out.
Also, note that in some cases, a replacement catalyst may work when even the original catalyst works but also in additional situations, which can be handy if the chaos comes back and interacts with the catalyst again or if the "replacement" catalyst is easier to [[weld]] in certain circumstances than the original catalyst. This is sometimes also true when multiple replacement catalysts work, but only one survives the chaos coming back, or only one can be welded in the necessary way.
===Fishhook replacements===
Also, there may be cases where both catalysts initially work, but they modify the active region in different ways, so the chaos comes back to the original catalyst and destroys it but does not come back to the replacement catalyst. Also, even if both the original and replacement catalyst survive, the fact that they modify the active region in different ways allows more possibilities when searching for conduits, so it is worth trying both; this last principle also applies when two replacement catalysts modify the active region in different ways.
=== Fishhook replacements ===
The most common way for a fishhook to fail is something like this:
The most common way for a fishhook to fail is something like this:
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(Note: Patterns for replacement guide shown here and below are in [[Rule:EV2QuadColor|a custom multistate rule]] designed for annotating purposes. Please go to the link and copy/paste the rule tree definition in Golly first, before copying the pattern from LifeViewer and pasting in Golly.)
(Note: Patterns for replacement guide shown here and below are in [[Rule:EV2QuadColor|a custom multistate rule]] designed for annotating purposes. Please go to the link and copy/paste the rule tree definition in Golly first, before copying the pattern from LifeViewer and pasting in Golly.)
===Block replacements===
=== Block replacements ===
Sometimes, a block that fails only needs to be supported with another catalyst, not replaced entirely. Take this partial [[PT9B]], for example: <center>{{LV:Viewer|
Sometimes, a block that fails only needs to be supported with another catalyst, not replaced entirely. Take this partial [[PT9B]], for example: <center>{{LV:Viewer|
This trick works in a variety of circumstances where a block fails because unwanted cells are born to one side. Also, the fishhook can often be replaced by a block. This sometimes works even if a fishhook doesn't work.
This trick works in a variety of circumstances where a block fails because unwanted cells are born to one side. Also, the fishhook can often be replaced by a block, which sometimes works even if a fishhook doesn't work.
<center>{{LV:Viewer|
<center>{{LV:Viewer|
x = 185, y = 44, rule = B3/S23
x = 185, y = 44, rule = B3/S23
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Here is a block replacement guide by Entity Valkyrie and MathAndCode:
Here is a block replacement guide by Entity Valkyrie and MathAndCode:
Sometimes, the snake needs to be replaced them with a similar catalyst which does the same thing but might have better clearance. For example, if a snake is required to be in close proximity to a fishhook, the fishhook's interaction might destroy the snake (and subsequently the fishhook). In this case from the conduit [[L112]], replacing the snake with a higher-clearance second fishhook (or aircraft carrier) can prevent the interaction:
Sometimes, the snake needs to be replaced them with a similar catalyst which does the same thing but might have better clearance. For example, if a snake is required to be in close proximity to a fishhook, the fishhook's interaction might destroy the snake (and subsequently the fishhook). In this case from the conduit [[L112]], replacing the snake with a higher-clearance second fishhook (or aircraft carrier) can prevent the interaction:
<center>{{LV:Viewer|
<center>{{LV:Viewer|
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[[ GRID THUMBNAIL THUMBSIZE 2 ]]}}</center>
[[ GRID THUMBNAIL THUMBSIZE 2 ]]}}</center>
===Tub replacements===
=== Tub replacements ===
Sometimes, a single dot at the end of the tub parent is replaced with a line of three cells, causing the tub to turn into a block instead of recovering:
Sometimes, a single dot at the end of the tub parent is replaced with a line of three cells, causing the tub to turn into a block instead of recovering:
The ship family is fairly unique as a catalyst family. For most catalyst families, one places the namesake catalyst expecting it to work, and the replacement catalysts are reserves. However, a ship will almost always fail when attempting a ship-type catalysis, and it is much more often the case that one of the replacement catalysts works. However, it is usually worth initially placing lone ships (as opposed to initially placing a replacement catalyst) for three reasons:
The ship family is fairly unique as a catalyst family. For most catalyst families, one places the namesake catalyst expecting it to work, and the replacement catalysts are reserves. However, a ship will almost always fail when attempting a ship-type catalysis, and it is much more often the case that one of the replacement catalysts works. However, it is usually worth initially placing lone ships (as opposed to initially placing a replacement catalyst) for three reasons:
# It takes less time to draw a ship than to draw any of the replacement catalysts;
# It takes less time to draw a ship than to draw any of the replacement catalysts;
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[[ GRID THUMBNAIL THUMBSIZE 2 T 4 PAUSE 1 ]]}}</center>
[[ GRID THUMBNAIL THUMBSIZE 2 T 4 PAUSE 1 ]]}}</center>
==Bonus catalyses==
== Bonus catalyses ==
Here are some extra catalyses which might come in useful. This section is optional as the catalysts used are fairly rare.
Here are some extra catalyses which might come in useful. This section is optional as the catalysts used are fairly rare.
===[[Eater 3]]===
=== [[Eater 3]] ===
You might notice that when you hit a loaf with a glider in a certain way, the loaf flips around:
You might notice that when you hit a loaf with a glider in a certain way, the loaf flips around:
The eater 3 has some other applications besides eating gliders, for example the [[rectifier]]. Typically the eater 3 is used when a fishhook fails on a corner (in at least one orientation), and there aren't any replacement catalysts that work.
The eater 3 has some other applications besides eating gliders, for example the [[rectifier]]. Typically, the eater 3 is used when a fishhook fails on a corner (in at least one orientation), and there aren't any replacement catalysts that work.
Sometimes, the chaos does not clear up during the reaction. In that case, a long version of [[moose antlers]] might work. However, it relies on a [[domino]] [[spark]] to restore it, so it is not guaranteed to work, and in fact will rarely work.
Sometimes, the chaos does not clear up during the reaction. In that case, [[Moose antlers]] might work. However, it relies on a [[domino]] [[spark]] to restore it, so it is not guaranteed to work, and in fact will rarely work.
<center>{{LV:Viewer| x = 34, y = 15, rule = B3/S23
<center>{{LV:Viewer| x = 34, y = 15, rule = B3/S23
Sometimes, shortly after interacting, a residual spark interacts with the loaf and messes up its recovery. In these cases, one might be able a drifty variant of the eater 3, called the Hickerson eater, that catalyzes in the same way (shown as the example catalyst at the top of this page) but recovers differently, which gives any residual sparks more time to clear. While it has a lower population and bounding box, it has a much lower side [[clearance]].
Sometimes, shortly after interacting, a residual spark interacts with the loaf and messes up its recovery. In these cases, one might be able a drifty variant of the eater 3, called the Hickerson eater, that catalyzes in the same way (shown as the example catalyst at the top of this page) but recovers differently, which gives any residual sparks more time to clear. While it has a lower population and bounding box, it has a much lower side [[clearance]].
Besides its usage in the eater 3, the loaf has a pseudo-transparent catalysis that can eat a certain beehive predecessor (taken from a variant of [[RF28B]], for example), a certain grandparent of the R-pentomino, or two block predecessors that are similar to each other.
Besides its usage in the eater 3, the loaf has a pseudo-transparent catalysis that can eat a certain beehive predecessor (taken from a variant of [[RF28B]], for example) or two block predecessors that are similar to each other.
Sometimes, the Eater 4 needs to be replaced with a similar catalyst which does the same thing but might have better side clearance. There is a variant specially for that:
Sometimes, the Eater 4 needs to be replaced with a similar catalyst which does the same thing but might have better side clearance. There is a variant specially for that:
<center>{{LV:Viewer|
<center>{{LV:Viewer|
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This may seem pretty niche, but it is actually a fairly common application, for example in [[p32 blinker hassler 2]].
This may seem pretty niche, but it is actually a fairly common application, for example in [[p32 blinker hassler 2]].
===Supported ship===
=== Supported ship ===
Another diagonally symmetric catalysis involving a [[ship]] starts when the ship converted to a [[butterfly]]. If that happens, a period-doubling [[half-bakery]]/[[ship-tie]] catalyst can restore it. This reaction works when there is a line of three or more diagonal cells that all formed in the same generation. This catalyst was found via semi-natural soup search. Note that this is unique in the fact that there is no known non-period multiplying version known.
Another diagonally symmetric catalysis involving a [[ship]] starts when the ship converted to a [[butterfly]]. If that happens, a period-doubling [[half-bakery]]/[[ship-tie]] catalyst can restore it. This reaction works when there is a line of three or more diagonal cells that all formed in the same generation. This catalyst was found via semi-natural soup search. Note that this is unique in the fact that there is no known non-period multiplying version known.
Sometimes the beehive will be destroyed. If it is converted into a [[traffic light]] when the leading edge is one cell off-center, this variant will work.
Sometimes the beehive will be destroyed. If it is converted into a [[traffic light]] when the leading edge is one cell off-center, this variant will work.
The tub-with-tail eater can catalyse from multiple directions, as well as having a high [[clearance]]. A single protruding cell of the [[tub]] (or [[boat]] or [[loaf]], depending on the variant) is temporarily turned off, and then is restored by interaction with surrounding catalyst cells. With the variants using a boat, the boat temporarily turns into a [[wing]].
The tub-with-tail eater can catalyse from multiple directions, as well as having a high [[clearance]]. A single protruding cell of the [[tub]] (or [[boat]] or [[loaf]], depending on the variant) is temporarily turned off, and then is restored by interaction with surrounding catalyst cells. With the variants using a boat, the boat temporarily turns into a [[wing]].
Sometimes, the tub-with-tail eater needs to be replaced with a similar catalyst which does the same thing but might have better clearance relative to the active region. There are variants specially for that:
Sometimes, the tub-with-tail eater needs to be replaced with a similar catalyst which does the same thing but might have better clearance relative to the active region. There are variants specially for that:
Sometimes, an active reaction will have this frontend:
Sometimes, an active reaction will have this frontend:
<center>{{LV:Viewer|
<center>{{LV:Viewer|
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[[ GRID THUMBNAIL THUMBSIZE 2 GPS 10 T 2 PAUSE 0.8 T 7 PAUSE 5 GPS 1 ]]}}</center>
[[ GRID THUMBNAIL THUMBSIZE 2 GPS 10 T 2 PAUSE 0.8 T 7 PAUSE 5 GPS 1 ]]}}</center>
==Finding new catalysts==
== Finding new catalysts ==
Mike Playle's [[Bellman]] is a search program specifically designed to search for new catalysts, given a reaction to be perturbed. It discovered the [[Snark]], as well as many other highly notable patterns. This part of the tutorial hasn't been written yet, so consult the [https://conwaylife.com/forums/viewtopic.php?f=9&t=1139|Bellman discussion thread] and [https://sourceforge.net/projects/bellman/files/?source=navbar|Bellman's original documentation].
Mike Playle's [[Bellman]] is a search program specifically designed to search for new catalysts, given a reaction to be perturbed. It discovered the [[Snark]], as well as many other highly notable patterns. This part of the tutorial hasn't been written yet, so consult the [https://conwaylife.com/forums/viewtopic.php?f=9&t=1139|Bellman discussion thread] and [https://sourceforge.net/projects/bellman/files/?source=navbar|Bellman's original documentation].
Another catalyst finding program is [[CatForce]], which is a brute force placement program of certain given catalysts in a given area, and can also find transparent catalysts if they're restored quickly enough. It has also discovered quite a few interesting things, like [[B60]], [[58P37]], and the [[p84 honey farm hassler]].
Another catalyst finding program is [[CatForce]], which is a brute force placement program of certain given catalysts in a given area, and can also find transparent catalysts if they're restored quickly enough. It has also discovered quite a few interesting things, like [[B60]], [[58P37]], and the [[p84 honey farm hassler]].
==External links==
== External links ==
* {{LinkForumThread|f=2|t=1599|title=The Hunting of the New Herschel Conduits}}
* {{LinkForumThread|f=2|t=1599|title=The Hunting of the New Herschel Conduits}}
* {{LinkForumThread|f=2|t=1849|title=The Hunting of the Elementary Conduits}}
* {{LinkForumThread|f=2|t=1849|title=The Hunting of the Elementary Conduits}}
Latest revision as of 23:09, 11 April 2026
A catalyst is a stationary object (usually a still life) which can interact with an active reaction and later return to its original state. Catalysts are very useful in many applications, including conduits and hasslers. Here is an example of a stable catalyst:
The green still life interacts with the white object, and recovers to its original state by generation 15. In this tutorial, you'll learn the main types of catalyses and their applications. But first, we need to cover some important definitions.
Important terms
Stable catalyst: a catalyst which is a still life. Most catalyses are of this form. In this tutorial we will only focus on stable catalyses, as periodic catalyses are as of now quite underdeveloped.
Periodic catalyst: a catalyst which is an oscillator. These are generally considered "less useful" than stable catalysts, because a periodic catalyst usually does not work in every possible phase.
Transparent catalyst or transparent object: an object which is destroyed completely (all of its cells being off at the same time) then restored (in the same position and with the same orientation)
Pseudo-transparent catalyst: a catalyst that loses all of its cells but not at the same time (i.e. for each generation, at least one of its cells is alive)
Recovery time: the time it takes for a catalyst to return back to its original state after interacting. In the example above, the recovery time is 15.
Replacement catalyst: When a common catalyst fails, another, less common, catalyst must be used.
Rock: A catalyst which does not lose any of its cells, even temporarily, during the interaction process. The snake-type catalyses below are examples of rocks.
Let's explore the different types of catalysts now!
The marked white cells should always be on in a fishhook-type catalyst. Sometimes, the fishhook may engage in a more unusual manner, but these are rarer:
Recognizing when to use a fishhook catalysis is really a matter of experience. For practice, try placing an eater 1 somewhere within this blue field to eat the middleweight spaceship (click on the thumbnail below to draw cells in LifeViewer using the pencil icon):
They typically occur when there is a two cell leading edge, which is marked. Boat catalyses fail very often, so see the "Replacement catalysts" section below for potential replacement catalysts. As a general rule, boats are most likely to succeed when a cell adjacent to the leading edge (shown in blue) will turn on in the following generation.
There is a secondary boat catalysis that works on objects with a line of three or more cells, but it's important here that the red cell does not turn on:
Snake catalyses are examples of rocks, or catalysts which do not change even temporarily when interacting with an object. They must function this way due to the fact that the two cells in the center would die from overpopulation due to already having three live neighbors.
Three example snake catalysts are shown below. The white cells should always be on to trigger the important next generation, where the snake functions as a rock:
Conduit 1 is an example of a conduit using a snake catalyst. Try to catalyze the reaction below with a snake in the blue field (as a hint, the cell which should trigger the rock interaction is marked):
Non-rock tub catalyses can be tricky to find, but they are most likely to work when the frontend of the active reaction is two or three cells long, like one of the examples below:
The reactions start differently but end up the same way through the same general mechanism:
On generation 1, one cell (marked in white) is born next to the tub;
On generation 2, two more cells are born next to the tub. This causes the three white cells to die;
By generation 3, the cells in the center have died and what remains is a 5-cell parent of the tub. In all tub catalyses, the tub should turn into this 5-cell parent.
The tub has a secondary catalysis where it acts as a rock. For it to work, there must be a line of four or more cells, and the cell marked in blue must turn on in the next generation.
Thirdly, the tub has a very specific use where it can eat a fully formed beacon. Parity is not a concern, as the reaction only begins when the beacon is in its dense phase.
The ship is turned into a relative of the I-heptomino (specifically a great-uncle) then is turned back into a ship by a perfectly-timed temporary induction. The ship rarely recovers by its own, but it's worth trying because it has replacement catalysts that recover much more often.
Replacement catalyses
So, you've tried to catalyze a reaction, but the common catalyst fails! Luckily for you, this is not a complete disaster, since many replacement catalysts exist exactly to assist you when your fishhook or block doesn't just work out.
Also, note that in some cases, a replacement catalyst may work when even the original catalyst works but also in additional situations, which can be handy if the chaos comes back and interacts with the catalyst again or if the "replacement" catalyst is easier to weld in certain circumstances than the original catalyst. This is sometimes also true when multiple replacement catalysts work, but only one survives the chaos coming back, or only one can be welded in the necessary way.
Also, there may be cases where both catalysts initially work, but they modify the active region in different ways, so the chaos comes back to the original catalyst and destroys it but does not come back to the replacement catalyst. Also, even if both the original and replacement catalyst survive, the fact that they modify the active region in different ways allows more possibilities when searching for conduits, so it is worth trying both; this last principle also applies when two replacement catalysts modify the active region in different ways.
Fishhook replacements
The most common way for a fishhook to fail is something like this:
This was a bit cheating, however. Sometimes, we need a genuinely new catalyst. Here are two almost-catalyses where the fishhook almost recovers, but an extra spark destroys it or an extra cell gets attached to its recovering phase:
The most common replacement catalyst for a fishhook is the handy eater 2. An eater 2 recovers differently from an eater 1, making it more versatile (and its symmetry means that it can eat from two directions). It can handle both of our problems:
There are many, many more cases in which neither an eater 1 nor an eater 2 works. This guide, by Entity Valkyrie and MathAndCode, addresses many of these:
(Note: Patterns for replacement guide shown here and below are in a custom multistate rule designed for annotating purposes. Please go to the link and copy/paste the rule tree definition in Golly first, before copying the pattern from LifeViewer and pasting in Golly.)
Block replacements
Sometimes, a block that fails only needs to be supported with another catalyst, not replaced entirely. Take this partial PT9B, for example:
This trick works in a variety of circumstances where a block fails because unwanted cells are born to one side. Also, the fishhook can often be replaced by a block, which sometimes works even if a fishhook doesn't work.
Also, if the fishhook recovers too quickly but otherwise works, then like other examples where a fishhook recovers too quickly but otherwise works, it can sometimes be replaced with an eater 2.
Another example where a block catalyst can be fixed by supporting the block with another catalyst comes from the following example, where the block is turned into a first cousin of the century then crashes into a boat.
This trick only works if there is something for the century cousin to crash into (and even then, not always), but luckily, there is an actual replacement catalyst for when the block is turned into a century cousin with nothing to hit. (It also works in the above example if one does not need to get rid of the boat.)
It should be noted that when a block fails in one of the most recent two ways, it can often be replaced with a hook with tail (although the hook with tail is not a replacement catalyst for the block in the strictest sense).
Two fishhooks or a cis-mirrored bookend can be used in that case. This often modifies the active region in a different way from supporting the block with a fishhook, so it is useful to know both.
In addition, there is a fourth way in which a block is sometimes turned into a crotchet. In this case, it can be replaced with a claw with tail supported by a fishhook.
For one particular type of block catalysis (specifically where the block is turned into a grin but not through the six-cell grin parent in pentoad 2), the block can be replaced with a long hook with tail. For example, if a block is used with the eater 5 (which will be explained next) in this case, the chaos hits and destroys it (then destroys the tub with tail).
In this case, alternatively moving the block by one cell often also results in a successful catalysis, but it often modifies the active region in a different way, so it is useful to know both.
In this example, the white cell at generation 4 gets turned on when it shouldn't. We have a fix for this, as usual. Replace the boat with a tub with tail and block (this catalyst is called an eater 5 or tub-with-tail eater):
Sometimes, the snake needs to be replaced them with a similar catalyst which does the same thing but might have better clearance. For example, if a snake is required to be in close proximity to a fishhook, the fishhook's interaction might destroy the snake (and subsequently the fishhook). In this case from the conduit L112, replacing the snake with a higher-clearance second fishhook (or aircraft carrier) can prevent the interaction:
A problem that sometimes occurs with snake catalyses is that a certain cell above the snake (marked in red) will be born when the snake is supposed to be done interacting. When this happens, try replacing the snake with a hook with tail.
Sometimes, a single dot at the end of the tub parent is replaced with a line of three cells, causing the tub to turn into a block instead of recovering:
The ship family is fairly unique as a catalyst family. For most catalyst families, one places the namesake catalyst expecting it to work, and the replacement catalysts are reserves. However, a ship will almost always fail when attempting a ship-type catalysis, and it is much more often the case that one of the replacement catalysts works. However, it is usually worth initially placing lone ships (as opposed to initially placing a replacement catalyst) for three reasons:
It takes less time to draw a ship than to draw any of the replacement catalysts;
It is easier to see which replacement catalyst, if any, will work by observing a lone ship than by observing any single replacement catalyst;
A lone ship will occasionally work. (If a lone ship works, none of the replacement catalysts will work.)
Often, the ship is turned into a loaf, such as in the BLx19R converter. Adding a fishhook turns it back into a ship:
Sometimes, the ship is almost turned into the necessary loaf predecessor, then a further interaction turns it into a loaf with the opposite orientation.
A fishhook still works in this case, as well as additional ways in which the ship can be turned into a loaf.
x=122, y = 16, rule = B3/S23
76bo15bo$21bo34b2o18b2o15bo17b2o7bo$20bobo30bo38b2o17b2o7b2o$19b2ob2o
31bo2bo36b2o21bo2bo$o16bobo2b2o11bob2o14b3ob2o19b2o12bob3o9b3o2b2o3b2o
$2o17b2o2bo9b2o3b2o15bob2o13bo2b3o14b4o17bo4bo$3bo15bo13bobo2b2o12b2ob
ob2o13bo2bo18bo16b2o$bo2bo13b2ob2o10bo4b3o16bo16bo36bo$bobo2b2o9bo2bo
3b2o16b2o9b4o3b2o16b2o16b2o16b2o$6bobo10b2o3bobo15bobo8b2o5bobo10b2o3b
obo15bobo15bobo$7b2o16b2o16b2o16b2o16b2o16b2o16b2o2$4b2o16b2o16b2o16b
2o16b2o16b2o16b2o$5bo17bo17bo17bo17bo17bo17bo$2b3o15b3o15b3o15b3o15b3o
15b3o15b3o$2bo17bo17bo17bo17bo17bo17bo!
[[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 X -29.5 Y -0.5 ZOOM 7.87 ]]
If the loaf parent has an extra cell in a certain position (so that it becomes a great-uncle of the I-heptomino), there's another replacement catalyst that works (which was discovered fairly recently to use in the R49 conduit, so it is often called the "R49 catalyst"):
If the R49 catalyst functions properly, but the active reaction interferes (either at the same time or at a different time) with the side opposite the fishhook, a different catalyst consisting of a transparent loaf and a large block replacement catalyst may work instead. Note that the red cell must not be born in generation three for the secondary replacement catalyst to work.
Lone ships, ship-fishhook pairs, and R49 catalysts are more likely to work when the cell that "activates" them survives into the next generation, while a fishhook bridge fishhook catalyst is more likely to work if by the next generation, the cell that "activated" it has died, and it has a two-cell edge to "slam" into. Common examples of the latter are a grin (like in 30P6.1) and a certain edgeshootable beehive predecessor.
For this reason, as well as the fact that a ship takes less time to draw than a fishhook bridge fishhook (and you can still tell whether or not a fishhook bridge fishhook will work by observing a ship), It is best to place a lone ship instead of a fishhook bridge fishhook even in situations that look like a fishhook bridge fishhook is the most likely ship-type catalyst to work.
Occassionally, instead of simply becoming the aforementioned blockade predecessor, the ship will become that blockade predecessor with three additional cells, and if one uses a fishhook bridge fishhook, it will mostly recover but with three extra cells in the same position. When this happens, a beehive works.
This is quite inconvenient for us because we can't use the loaf again (unless we flip it back around with another glider as shown in the viewer, which is unlikely), but a stable catalyst does exist to turn the loaf back around. Here is the eater 3:
The eater 3 will work with objects that have either the three yellow cells or six green cells turned on. The catalysis involving the yellow cells very rarely fails if the chaos clears quickly.
The eater 3 has some other applications besides eating gliders, for example the rectifier. Typically, the eater 3 is used when a fishhook fails on a corner (in at least one orientation), and there aren't any replacement catalysts that work.
Sometimes, the chaos does not clear up during the reaction. In that case, a long version of moose antlers might work. However, it relies on a dominospark to restore it, so it is not guaranteed to work, and in fact will rarely work.
Sometimes, shortly after interacting, a residual spark interacts with the loaf and messes up its recovery. In these cases, one might be able a drifty variant of the eater 3, called the Hickerson eater, that catalyzes in the same way (shown as the example catalyst at the top of this page) but recovers differently, which gives any residual sparks more time to clear. While it has a lower population and bounding box, it has a much lower side clearance.
One example of how its slower recovery can be useful is when a dot spark (at the position marked in red in generation 4) next to the parent of the reflected loaf causes it to turn into a phi spark predecessor instead of a loaf (although it hits the catalyst meant to flip the loaf back before actually becoming a phi spark).
Another example where a Hickerson eater can replace an eater 3 is when the domino spark marked in red is present at generation 5, turning the loaf predecessor into a traffic light predecessor.
It is capable of many more types of catalyses. Examples can be found in this forum post.
Also, there are situations where an eater 3 recovers, but a Hickerson eater may still work better. One example is this failed RBx22B conduit, where an eater 3 survives and causes the B-heptaplet to be formed but leaves behind an extra block, which then interacts with the B-sequence.
x=22, y = 21, rule = LifeHistory
13.A$12.A.A$13.A2$11.5A$11.A4.A$13.BAB.A$13.B2A.A2.A$11.A4B.A.A.A$5.
2B3.ABAB3.A2.A$2.D5B2.A2BA2.2A$.D6B.2B2A$2D2BC6B$.2DB2C5B$2.D2C5B$2.
7B$3.8B$4.B4.2A$9.A$10.3A$12.A!
[[ GRID THUMBNAIL THUMBSIZE 2 T 22 PAUSE 0.6 ]]
A Hickerson eater perturbs the active region in the same way at first, causing the B-heptaplet to still be formed, but its different recovery causes it to interact with a block that cleanly deletes it without destroying the Hickerson eater, thus yielding a successful conduit.
x=17, y = 17, rule = LifeHistory
9.2A$9.A.A.2A$11.A.A$10.2A.A$8.4B.A.2A$5.2B.2B4A2.A$2.D6B.AB2.2A$.D9B
3A$2D2BC6B2.A$.2DB2C5B2.A.A$2.D2C5B4.2A$2.7B$3.8B$4.B4.2A$9.A$10.3A$
12.A!
[[ GRID THUMBNAIL THUMBSIZE 2 T 22 PAUSE 0.6 ]]
For situations where that doesn't work, the Hickerson eater also comes with a variant that produces a thumbspark, in case a spark is needed and sparking eater fails.
Besides its usage in the eater 3, the loaf has a pseudo-transparent catalysis that can eat a certain beehive predecessor (taken from a variant of RF28B, for example), a certain grandparent of the R-pentomino, or two block predecessors that are similar to each other.
This can also come in handy sometimes; for example the recently-discovered L122 conduit.
In order for the eater 4 to recover, it needs to stay diagonally symmetric. If there is a line of two on each side, it will receive dot sparks on both sides, stay symmetric, and recover properly.
However, if there is a line of two on one side and a line of three or more on the other side, it will receive a dot spark on one side but not the other, so it will lose its symmetry and fail.
Sometimes, the Eater 4 needs to be replaced with a similar catalyst which does the same thing but might have better side clearance. There is a variant specially for that:
Alternatively, if the Eater 4 is used to eat a half of a traffic light, a transparent ship can be used to substitute, at the cost of a higher recovery time.
This may seem pretty niche, but it is actually a fairly common application, for example in p32 blinker hassler 2.
Supported ship
Another diagonally symmetric catalysis involving a ship starts when the ship converted to a butterfly. If that happens, a period-doubling half-bakery/ship-tie catalyst can restore it. This reaction works when there is a line of three or more diagonal cells that all formed in the same generation. This catalyst was found via semi-natural soup search. Note that this is unique in the fact that there is no known non-period multiplying version known.
The double beehive push catalyst can also work as a 2c/3 wire injector. This application has been used to create injectors with the lowest repeat times, the fastest theoretically having a repeat time of 29.
The tub-with-tail eater can catalyse from multiple directions, as well as having a high clearance. A single protruding cell of the tub (or boat or loaf, depending on the variant) is temporarily turned off, and then is restored by interaction with surrounding catalyst cells. With the variants using a boat, the boat temporarily turns into a wing.
Sometimes, the tub-with-tail eater needs to be replaced with a similar catalyst which does the same thing but might have better clearance relative to the active region. There are variants specially for that:
This catalyst is one cell further from the active region, using the long hook with tail instead of a block.
The sidesnagger can be used if it is required to be spartan, or if the active region interferes with both the block and long hook with tail. Notice the significantly longer recovery time, and also the slightly reduced clearance: a glider that's traveling in the same direction as the SW-traveling input glider in the example below, has to be at least three half diagonals northwest of the input lane. Other eater 5 variants need only two half diagonals of clearance.
When that happens, a bi-boat might be able to catalyze the reaction if it is placed two generations earlier.
x=49, y = 22, rule = LifeHistory
2.A14.A12.3A$2.A12.A.A11.A14.2A$2.A.A9.A3.A9.A5.A9.A.A$2.A.CD10.A.CD10.
2ACD10.A.CD$.DCACD9.DCACD9.DCACD9.DCACD$3.D13.D13.D13.D8$2.A14.A12.3A
$2.A12.A.A11.A14.2A$2.A.A9.A3.A9.A5.A9.A.A$2.A.A11.A.A11.3A11.A.A$2.3A
11.3A11.3A11.3A2$.A3.A9.A3.A9.A3.A9.A3.A$A.A.A.A7.A.A.A.A7.A.A.A.A7.A
.A.A.A$.2A.2A9.2A.2A9.2A.2A9.2A.2A!
[[ GRID THUMBNAIL THUMBSIZE 2 GPS 10 T 2 PAUSE 0.8 T 7 PAUSE 5 GPS 1 ]]
Finding new catalysts
Mike Playle's Bellman is a search program specifically designed to search for new catalysts, given a reaction to be perturbed. It discovered the Snark, as well as many other highly notable patterns. This part of the tutorial hasn't been written yet, so consult the discussion thread and original documentation.
Another catalyst finding program is CatForce, which is a brute force placement program of certain given catalysts in a given area, and can also find transparent catalysts if they're restored quickly enough. It has also discovered quite a few interesting things, like B60, 58P37, and the p84 honey farm hassler.