Moore's law and its analogues

Kevin Kelly has a great new essay up, "Was Moore's Law Inevitable?", examining a series of examples of exponential growth in technological capability from a wide range of fields - and makes the very interesting point that all these examples are "prisoner[s] of physics, the periodic table, manufacturing technology and economics" - but some of them proceed rapidly and some do not. The interesting question is why?

One answer he gives is in the "scale-down" of solid-state technologies: it has proven relatively easy to pack more stuff into smaller areas, and so technical advances related to increasing smallness are ripe for this sort of growth. But other examples don't have that smallness aspect, and yet grew exponentially just the same: the growth of the railroads in the 19th century, the increase in the speed of aircraft in the first half of the 20th century, the cost per unit for DNA sequencing in recent years. Examples that are not growing rapidly now where it would seem very useful if they were include such things as the cost per unit production of solar cells, or the energy storage capacity per unit volume or mass of batteries. Every technology seems like it would benefit from a Moore's law-type progression - so why are we seeing it for some but not for others?

This all suggested to me that the key criterion in whether a technological trend follows a “Moore’s law” of rapid growth or not is the level of continuing investment society puts into that technology, relative to the real costs and constraints of chemistry/physics/information.

If the level of investment is high enough, rapid (2-year or faster doubling) growth comes naturally and is driven by continued demand against the falling cost. If the level of investment is lower than some threshold (solar cells, batteries, spaceflight, …) then growth in technical capability is forced to a much slower curve, constrained by the ratio of investment level to that threshold.

I would guess the threshold investment level also grows exponentially with that capability level, and when the curves of available investment capital vs. threshold cross, you hit the top of that S curve and innovation slows again. But new technology ideas can drop that threshold and re-ignite growth again…

The level of investment capital available would be constrained in a market economy by the basic level of demand for whatever product it is, and the availability of alternative technologies. For example, in energy markets the availability of fossil fuels as alternatives greatly suppresses the level of investment available in solar photovoltaics or batteries. An argument for government intervention?

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Any exponential curve looks

Any exponential curve looks flat behind you and increasingly steep in front of you.
But the step changes aren't visible til you've passed them.

Aside:
(I recall someone observing years ago that technology often improves at least one big step beyond the point at which it's become obsolescent -- Hughes's plywood "Spruce Goose" aircraft, or the very last and greatest steam locomotive were the examples given.
I suspect the superultraefficient coal plants also qualify -- they run much hotter than any commercial fission pile, so they're energetically more efficient (difference between heat source and heat sink). With luck they're proving the materials that will be needed for fusion power, which would be comparably hot. But they're dedicated to using coal -- obsolescent already.)

Semiconductors went through repeated step changes.

Recall the days when circuit diagrams were painted on the walls of huge warehouse/hangar-sized buildings and focused with meter-diameter lenses onto chips for photo-etching. When the industry stepped away from that technology those Fresnel lenses were briefly available dirt cheap at surplus places.

Energy storage hasn't had that kind of big obvious step change --- looking backward, it all looks kind of flat.
But put yourself back in the 1960s with your D-cell flashlight, with carbon batteries and incandescent bulbs. Compare that to your current LED flashlight, a tenth the size, brighter, and longer-lived.

But watch the video from the ISS -- the astronauts are using big old D-cell MagLights. They haul all that extra mass?
Well, yeah, lithium-ion cells do cause nasty fires when they fail. Not ready for life critical use yet.

If you put your point of view far enough back you can see that what looks like a slow increase in retrospect would have looked like a steep improvement, from back then. I suspect photovoltaic is about the same, our perspective isn't long enough.

Looking forward, well, we can hope the supercapacitors work out.

Perhaps it is often the

Perhaps it is often the opposite. Perhaps, it is the ease at which technological progress can be made that drives investment rather then the amount of investment driving the amount of technological progress. Well, it has to be a bit of both. People will invest where there is a market which is large and has a good rate of return. If technological investment plays a significant factor in market share then much of that investment will go into research and development as opposed to other forms of capital investment.