Ask Lemmy

I can't answer for dual numbers, but I can answer for imaginary numbers in circuit design.

Imaginary numbers are those that include an imaginary component, that squares into a negative number. Traditionally, i^2 = -1, but electrical engineers like to use j instead (I tends to be a variable used to describe electrical current).

Complex numbers, that include a real component and an imaginary component, can be thought of as having an "angle," based on how much of it is imaginary and how much of it is real, mapped onto a 2-dimensional representation of that number's real and imaginary components. 5 + 5j is as real as it is imaginary, so it's like having a 45° angle. The real number 5 is completely real, so it has a 0° angle.

Meanwhile, in alternating current (AC) circuits, like what you get from your wall outlet, the voltage source is a wave that alternates between a maximum peak of positive voltage and a bottom trough of negative voltage, in a nice clean sinusoidal shape over time. If you hook up a normal resistor, the nice clean sinusoidal voltage also becomes a nice clean sinusoidal current with the exact same timing of when the max voltage matches up with the max current.

But there's also capacitors, which accumulate charge so that the flow of current on the other side depends on its own state of charge. And there are inductors, that affect current based on the amount of energy stored magnetically. These react to the existing current and voltage in the system and manipulate the time relationship between what moment in time a peak current will happen and when the peak voltage was.

And through some interesting overlap in how adding and subtracting and delaying sinusoidal waves works, the circuit characteristics line up perfectly with that complex angle I was talking about, with the imaginary numbers. So any circuit, or any part of a circuit, can be represented with an "impedance" that has both an imaginary and real component, with a corresponding phase angle. And that complex number can be used to calculate information about the time delay in the wave of current versus the wave of voltage.

So using complex phase angles makes certain AC calculations much, much easier, to represent the output of real current from real voltage, where the imaginary numbers are an important part of the calculation but not in the actual real world observation itself.

So even though we start with real numbers and end with real numbers, having imaginary numbers in the toolbox make the middle part feasible.

Since there's a reasonably strong link to calculus, and mechanics as you've already found, it could theoretically help in physics simulations either in a computer or on paper.

As for practical application, well, emulating physics is pretty important in a lot of computer games, or getting robots (assembly line arms, androids, automated vacuum cleaners) around the place and to do what they need without accidentally catapulting themselves into next Tuesday.

How that's actually programmed might not involve dual numbers at all, but they're one way of looking at how those calculations might be done.