Everything in modulation

Food is never more delicious than after you've gone a while without eating. Happiness after a period of sadness is more intense and vice versa. That feeling of relaxation after working hard is so good, but when you relax too much doing work again can seem impossible. The transitions between these things seem in some ways more important than the things themselves. Why is this?

Modulation is the idea of varying one thing in relation to another thing to transmit information. It's the "mo" in "modem", but every wireless system uses modulation of some kind. Radios use analogue modulation, where the thing you vary is the frequency (FM) or amplitude (AM) of a waveform at a certain frequency. Modern digital devices tend to use more complex systems, encoding information using a fixed number of particular frequencies (FSK), phases (PSK) or both (QAM).

One thing that all of these systems have in common is that they depend on a fixed reference called a carrier wave. Usually that's just a simple sine wave at a given frequency. In the old days, you would transmit the carrier along with the signal, but that's pretty inefficient. Instead, when you know the frequency and phase you can just generate your own carrier wave.

But what happens when your reference isn't fixed? If the transmitter is moving relative to the receiver you get a doppler shift, and even without that there are often small variations between the carrier waves generated by different hardware. There's every chance your wave and their wave will be slightly out of sync. Compensating for this is known as carrier recovery and is, uh, fairly complicated.

There's a pretty neat technique that makes this much easier called differential coding, where instead of looking at the absolute value of the signal, you look at the difference between its current and previous value. Or, to put it another way, you use the signal as its own carrier. It's still the same modulation idea, varying one thing in relation to another, but the two things are the same signal at different points in time.

It seems to me that, since we tend to lack any kind of global fixed reference, we also look for meaning in difference. It would be great if there was some kind of absolute reference that we could measure everything by, and sometimes we can create one in certain circumstances, but everything is relative in the end. It may be that our greatest strength as a species is our flexibility, so in some sense it shouldn't be surprising that we are optimised for change.

So perhaps it is better to aim for, instead of a life of constancy, a life of constant transition. If we concentrate on meaningful transitions between high and low, busy and relaxed, over and under-achievement, we can avoid the impossible task of maintaining one particular situation in perpetuity. And although that might be difficult to deal with, it is in its own way quite liberating. Rather than relying on some external signal to give us meaning, we get to make it for ourselves, riding our own carrier wave out to wherever it might take us.