Weekend Cat Blogging: Luna in Sunshine

Luna can usually be found in the morning enjoying the sunshine on one of the dining-area chairs, often underneath the glass surface of the table. It does look warm and relaxing.

If only we could all have mornings like this.

The blog has been even more cat-centric than usual this week, but I notice no one is complaining. Nonetheless, we have some music and art reviews coming up soon.

Weekend Cat Blogging #384 is hosted by Patchouli at pam’s sidewalk shoes.

The Carnival of the Cats will be up this Sunday at iMeowza.

And the http://themodulator.org/archives/003622.html”>Friday Ark is on hiatus.

DJ CatSynth on The World of Wonder (KUSF in Exile)

I am now an official host for The World of Wonder on San Francisco Community Radio (KUSF in Exile), alternating weeks with Matt Davignon, and my first show is tonight at midnight PDT. You can listen live online here and find an archive via podcast after the fact.

Each week we will be presenting a variety of music that most people don’t hear everyday, a mixture of esoteric, avant-garde, idiosyncratic and many other kinds of music. I do encourage readers of this site to tune in.

Weekend Cat Blogging: Angry Birds

Luna is spending a few minutes playing with her newest toy, a gift to her from recent visitors to CatSynth HQ:

For those who are not familiar with this particular critter, it is the original Angry Bird from the mobile and web game Angry Birds. It’s a rather silly but fun game, more in the style of arcade games than those really annoying “casual games” that were all the rage in the tech startup world and now thankfully on the decline. We don’t play a lot of computer games these days, though Luna did have fun with her toy.

I think Luna prefers the real angry birds that she sees through the window, especially the big fat city pigeons.

Weekend Cat Blogging #382 is hosted by the late great Meowza at iMeowza.

Meanwhile, Ritzi will be hosting Carnival of the Cats tomorrow at iInfidel.

And the Friday Ark is at the modulator

Eye to Eye: Imaginary Exponentiation

The term “imaginary number” is an unfortunate one. It makes these numbers seem strange and separate from more familiar “real” numbers, when in fact there is very little difference. I prefer the term complex numbers that encompasses the closed set of all real and imaginary numbers with the usual arithmetic operators. Recall that the imaginary numbers are numbers that are less then zero when squared, with the imaginary constant i representing the square root of -1:

i 2 = -1

One can add, subtract, multiply and divide with it just like other numbers. One can not only square it to get -1, but also take its square root, which turns out to be another complex number.

√ i  = √2/2 + i √2/2

But what about raising i to the ith power?

Surely, that must be some sort of weird “very imaginary” number, right? But in fact, it is just a real number, approximately 0.2078796…

The same mechanism that allows us to take the square root of i can be used to explain why ii is real. Just as real numbers can be visualized on the familiar number line, complex numbers can be represented by a plane where the horizontal axis represents real numbers and the vertical axis represents imaginary numbers.

Any complex number x + yi can also be expressed with an angle and a radius: rcosθ+risinθ. Using the angular representation on the plane, we can then visualize any exponentiation operation (take the square, the square root, etc.) as a rotation around the origin.

Squaring a number means doubling the angle. Taking the square root means cutting the angle in half. The imaginary constant i has a radius of 1 and an angle of 90 degrees (or π/2 radians). Doubling it to 180 degrees rotates to the position of -1 on the complex plane. SImilarly, taking the square root of i reduces the angle to 45 degrees, moving it into the position of √2/2 + i √2/2.

But how does one rotate an angle by an imaginary amount? To accomplish this, we turn to one of my favorite formulas in all of mathematics, Euler’s identity:

eiθ = cosθ+isinθ

This identity unites trigonometry and exponentiation using the complex plane and rotations. It is more than just a curiosity and has practical applications including signal processing that we use for synthesizers and audio effects. However, it does allow us to also calculate the value of ii:

ii = cos(πi/2) + isin(πi/2) = eiπi/2 = e-π/2 ≈ 0.20787957635076193…

It is odd how rotating an imaginary number by an imaginary factor yields a real number.