a thoughtful web.
comment by kleinbl00
kleinbl00  ·  403 days ago  ·  link  ·    ·  parent  ·  post: Teaching stuff is resolved.

You're making my head hurt. Also, perhaps part of the problem is that's not how Karma works.

Here are the actual rules for Karma exchange:

1. A person with good karma will increase their good karma by helping a person with good karma.

2. A person with good karma will increase their good karma by helping a person with bad karma.

3. A person with bad karma will increase their good karma by helping a person with good karma.

4. A person with bad karma will increase their good karma by helping a person with bad karma.

The steady-state of Karma is enlightenment - we all break free of the wheel and vanish into the universe in a cloud of patchouli-scented bliss. It may not be a good example for invariance. That might be what got you in trouble - you flippantly picked a religious concept you don't understand perfectly and then used it incorrectly to make your point.

Which - even accepting your terms, even accepting your math - I still don't understand and I have an engineering degree:

While trivial, it is indeed an invariant of the operation as it will work for any object.

WHAT is indeed an invariant of the operation? What are we defining here? An integer plus its negative integer will equal zero - so is that an invariant operation? But that's "invariant" as adjective, not "an invariant" as noun.

I get the condition of invariance - the Conway glider is a great example. But in the Conway glider example, what is the invariant? This is why I gave a counter-example of catalysts - you need them for the reaction, but their mass returns to solution in the course of the process.

bfv  ·  403 days ago  ·  link  ·

WHAT is indeed an invariant of the operation? What are we defining here? An integer plus its negative integer will equal zero - so is that an invariant operation? But that's "invariant" as adjective, not "an invariant" as noun.

The invariant is a property. If you're a mathematician, a property is a thing you can define an indicator function for.

kleinbl00  ·  403 days ago  ·  link  ·

So "properties" are like "metadata" of the equation. They're not in it but they're a 2nd order quality that can be analyzed or used in other equations. They're not like catalysts, because the catalyst is actually in the equation - they're more like molarity.

bfv  ·  403 days ago  ·  link  ·

So invariants are generalized from geometry. Angles being invariant under isometries is probably the ur-example. If you have a triangle, the measure of the angle A is a property of the triangle. If you translate the triangle, the image of A has the same measure as A. Another definition of a property is a one-argument predicate; it's something you can say about an object. If you know an invariant holds before an operation, you know it holds after; that's what's interesting about them.

Something is only a catalyst in a particular reaction, so I would think it would only make sense to say "C is a catalysts" is a property of the reaction as a whole. My chemistry is beyond rusty though.

Devac  ·  403 days ago  ·  link  ·

Sorry. This is getting saved to motivate me to develop some sort "you are too sleepy to write" test.

That might be what got you in trouble - you flippantly picked a religious concept you don't understand perfectly and then used it incorrectly to make your point.

Can't argue with that, although I wouldn't say I was flippant intentionally. Regardless, I get your point.

But in the Conway glider example, what is the invariant?

Really useful frame-by-frame visualisation

Invariants:

1. Number of black squares after each step.

2. Direction of movement.

3. Distance it will move between each complete cycle.

4. There will always be only one black square that is connected to the rest of the structure by its vertex.

Some of them are invariants for a whole cycle, others work for each frame.

This is why I gave a counter-example of catalysts - you need them for the reaction, but their mass returns to solution in the course of the process.

Yes. The catalyst can be thought of as an invariant of a specific chemical reaction. Again, sorry for my more than underwhelming response earlier. I hope that this one is clearer.