I’ve always thought “imaginary” vs “real” was an unfortunate naming convention.
I don’t know about other fields, but electrical engineering uses imaginary numbers with AC circuits and changing electrical fields. Since electricity moves as waves, imaginary numbers let you represent what’s coming 90 degrees later in a compact way.
don’t forgot signal processing. Complex number theory is used a lot when it comes down to Fourier transforms of discrete or continuous functions.
but yea the naming convention of “imaginary numbers” is pretty bad, we did the same thing for negative numbers (we called it imaginary) when people couldn’t comprehend of a negative quantity.
negative numbers are defined from a conservative system, basically a gain/loss relationship: if I have 2 apples and I give away 1 to a friend, I have 1 apple left, that loss – that apple I gave to a friend – is the negative quantity. For imaginary numbers, we don’t really have a way to comprehend an imaginary quantity; what does it mean that I have sqrt(-1) apples.
Yeah, I think it causes unnecessary difficulties. I actually think they’re introduced at a time when you could instead teach them as two-dimensional vectors with pointwise addition and a special multiplication and division rule, and prove that (0, 1)×(0, 1) = (-1, 0) using that rule, so that sqrt(-1, 0) = (0, 1).
Then you can establish a convention that you write (a, b) as a + bi (and i = (0, 1)).
This is too abstract for younger students, but nowadays I don’t think they learn complex numbers anyway, and I think it would be less spooky for the older students.
Also tbf, rational numbers are just the lattice modded out by the equivalence relations (a, b) ~ (c, d) iff ad = bc, and the equivalence classes just happen to form an ordered field. If you show an undergrad math/science student this esoteric definition of rationals, the motivation of “2D numbers” makes a lot more sense. Of course, please don’t show this to an elementary or middle schooler, a high schooler might be able to handle this if they’re passionate about math.
Of course, please don’t show this to an elementary or middle schooler, a high schooler might be able to handle this if they’re passionate about math.
Lol, I was thinking this as I was reading.
The neat thing about complex numbers defined this way is that you don’t need to understand quotient spaces because under addition ℂ is already isomorphic to ℝ²!
Yep, it is bad naming. I took it in highschool but it didn’t really make sense till I saw how it described electric fields with the wave 90 degrees into the flat page.
Electrical engineers also use them as a simple way of solving differential equations with laplace transforms. Much easier as long as you don’t care about what happens at infinity.
Infinity is too far away. We’ll deal with it when it gets closer.
Is that just an EE thing?
Not just electricians.
3d graphics are all about about quaternions (4d version of imaginary numbers).
Quaternions are useful, but no means necessary or intrinsic to 3d graphics.
They are useful for describing rotations in 3d space, but the same can be done with a matrix, or even Euler angles. It’s just a more calculations.
That said, basically all the major game engines use quaternions, so unless you are creating your own 3d renderer, you have to learn at least the basics about them.
Quaternions really shine at spherical interpolation (Slerp - yes thats the real terminology) between two rotations.
I’d say Quaternions are necessary purely because they avoid gimbal locking common with 3 axis Euler rotations.
I know in Blender all other rotation options are really just quaterinions under the hood. But an advantage Euler rotations have over quaternions is continuous rotation. I can set 2 key frames with linear extrapolation and have them just continue along each axis forever. Everything quaternion ideally should be bounded to the 4d unit circle.
Just one more axiom bro and it will all make sense… just one more I swear it’s consistent… BRO I just NEED one more conjecture and it will BE complete… tHe pRincIPles ARe sOLid BrO jUST TruST mE!
It’s more complex than that…
cmon, get real
Think rationally
But it’s plain to see…
*plane
It’s not like the regular numbers behave themselves. Have you ever heard a coherent, non-self referential definition of the number 3?
3 is a sideways nutsack
W is a nutsack getting elaborately crushed
It’s 2 plus 1
Oh yeah? Prove it
3 = . . .
the only numbers that actually exist are 0 and 1. everything else is a reference to those
I can define zero as the absence of 1. But also 1 itself is a reference to the infinitely fractional 0.00…1 and I’d consider that a different number to the whole number 1
that doesn’t actually exist in the standard number system; there is no single real number that’s immediately next to 0, you can always get closer. some number systems have infinitesimals, but real numbers don’t. and any very small real number with a terminating decimal expression is simply the inverse of a very large number, which is simply a long string of 1+1+1+1+1…
λ f. λ x. f (f (f x))
Succs to succ.
{{},{{}}} (I think)
That would be 2. 3 would be {{},{{}},{{},{{}}}}.
Then they invented quarternions.
All numbers are imaginary. So are words.
for real, which is imaginary
Especially for solipists.
alright wise guy, what IS the square root of -1 then?
alright wise guy, what IS -1divided by 0 then?
-1 / 0 can be defined to be a special new number, ⭐.
This system of numbers is actually mathematically consistent and has all the properties that a number system should have. But using simple algebra, you can prove that in this new number system, ⭐ = 0. And then you can also prove that all other numbers equal zero.
This number system is known as the zero ring, and it’s the ring where the only number is 0 and the following operations are defined:
- 0 + 0 = 0
- 0 - 0 = 0
- 0 × 0 = 0
- 0 ÷ 0 = 0
- 0^0 = 0
All other symbols, including 1, 2, and ⭐, are just alternative labels for 0 in this number system. In other words, defining division by zero is essentially the equivalent of reality collapsing in mathematics.
So yes, you can validly define division by zero. You just get degenerate mathematics if you do. So be careful what you wish for.
-1/0 = Boom
But more literally, the answer is undefined.
Instead of thinking of division as a “proper” operator, think of it as shorthand for “x0 = -1". Since the multiplication operator already defines "x0 => 0” and “-1 != 0”, there literally is no answer by definition. So “undefined”.
For “0/0”, it’s a little different. Since “x*0 => 0”, literally every number satisfies “0/0”. Since we’re expecting a single number as the answer, we call the answer to this “undefined” too.
So without i, sqrt(-1) would be… Undefined?
That’s probably accurate, but I’m no mathematician. Specifically if you confine yourself to the set of real numbers, it’s undefined.
If you confine yourself to the set of rational numbers, integers, or natural numbers, you could get a bunch more undefined equations. For example, if you’re only working with the set of natural numbers, sqrt(4) is defined, but sqrt(5) through sqrt(8) are undefined because there are no whole numbers between 2 and 3 (2^2 and 3^2). Similarly, sqrt(-1) is undefined in this case because -1 isn’t part of the set of natural numbers, so any expression you used a negative number in would be undefined.
A more intuitive example might be to try using a non-number in an expression. Sqrt(🐱) is undefined. And 🦆-🦢 is also undefined. The operators aren’t defined to include cats or birds.
Why should I care?
They’re just closure-minded.
Physicists (only because I watch Sabine, and this is what she says they do)
That’s the face I make when someone mentions she is watching Sabine (only because I watch prof Dave)
“Quārum hī vitiō moriānis?”
“Moriānis‽ Moriānis vestris incipivit rem tōtam!”
“Et herem facĕre debēre īre stultum.”
