There is enormous energy "embodied" in uranium, too. If (when?) the time comes that we can no longer sustain our economies on fossil fuels, we will increasingly turn to nuclear power, which should last us for several more generations.

I'm not promoting this; I'm just predicting it. The sustainability of fossil fuels will be reflected in prices. More demand, political restrictions, and fewer new discoveries: prices go up; conservation, carbon sequestration/removal tech, and growing efficiencies supplemented by new sources such as fracked gas: prices relax. At some point (you say "very near", I say no one knows), hydrocarbon prices will go so high that the developed world will either have to voluntarily undevelop (not going to happen politically) or pay what it costs to solve some nuke problems and live with others, and we will continue to grow our use of energy.

The spread of robotics will proceed apace.

Good points - and note that I wasn't saying robotics and AIs were not going to happen, just that it will have some added plot twists - but I would argue that this is not true:

> (you say "very near", I say no one knows)

Given that our energy spending grows exponentially, it's certainly going be sooner than later.

Technology could be used to solve the problems that it's causing. E.g. better utilization of existing resources (self-driving cars), alternative sources of energy, and perhaps even space colonization.

"However, that won't last, and energy-wise, life is far more energy-efficient than machines for most tasks"

I really have to question this. Humans are notoriously inefficient at converting nutrition to usable energy.

Even if you calculated as embodied energy instead of just looking at the energy spent directly on a task? Because a large part of the "inefficiency" of living creatures is physical maintenance of the body. If that is included for machines as well, I'm not so sure if they're better off. For now, of course - as soon as we realise energy is a real constraint, we'll surely start optimising for it.

The third link I posted references Geoffrey West who has an interesting high-level physics approach to this issue, but it doesn't really do justice to his points. But I figured posting this 40 minute one, which is much more comprehensive, would be a bit much to ask:

https://www.youtube.com/watch?v=DFFVSvAr7Wc

(also has a lot more phycisist's arrogance in the form of cursing, which I find entertaining myself)

Actually, given that city energy spending also grows sublinearly, robot and AI networks probably would as well. So that argument likely won't hold against it.

> life is far more energy-efficient than machines for most tasks

I'll be blunt and say that that is just bullshit for quite obvious reasons. Your [1] does not support the claim.

"Obvious reasons" is not a very convincing argument, and and I am quite curious why you are saying that a link that literally states things like:

"A human-controlled punching machine is 25 to 35 times more efficient than a laser cutter when producing a standard part"

"Fibre laser cutters are more efficient than CO2-laser cutters, but their power consumption is still 10 times larger than that of a slower but equally powerful human-controlled nibbling machine"

... and has tables like:

http://krisdedecker.typepad.com/.a/6a00e0099229e8883301a73d8...

(which is per item, by the way)

... is not supporting the claim that manual labour is more energy efficient for many tasks.

A human-controlled punching machine is not a living thing, a human-controlled nibbling machine isn't a living thing. Thus none of the sentences support the notion that "life is far more energy-efficient than machines for most tasks".

There might be some manually controlled machines that are more energy efficient than some automatic machines, but that would be a very very different fact, and I don't see any reason to believe that it would hold in general. For example the table you linked to doesn't say how much that is produced per energy unit, which would be the relevant measure, and it doesn't take into account that the operator uses a lot of energy. With your kind of arguing I could show that a hand saw was infinitely more efficient than a chainsaw because the hand saw in itself doesn't use any energy at all and we don't count the operator.

A human in standby (resting) consumes about 80W power, and a human that does any kind of work much more than that. Humans use extremely inefficient fuel that takes many times more energy to produce than it makes available to do any kind of work. For most physical work it is easy to find a machine that does the same work using much less energy. In those areas where computers can replace humans they also do the same work using much less energy but also much faster. And then we haven't even taken into account that the human only works for 40 hours per week, need a house that keep her warm and uses a shitload of energy every day just to get back and forth to their workplace.

Might be better to just point at http://en.wikipedia.org/wiki/Basal_metabolic_rate