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Comment by cfallin | Hacker News Reader

Why not, though? Energy is energy -- we (humans) oxidize food, basically burning it slowly, to power our bodies. Whether the energy is carried by glucose/ATP or electric current is just an implementation detail.

Comparisons are frequently made in other domains as well -- e.g., cyclists measure power outputs in watts.

The rule of thumb I've understood is that the brain runs on about 20 watts (peak power), and a human on average runs on about 100 watts. That's 8.64 MJ/day, which converts to 2064 food calories (kcal), at 4184 J/kcal.

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One is saying how much computers use of a global resource pool, the other is how much brains use of their host body. They're completely different things so it doesn't make sense to compare those two percentages.

If you wanted to compare them, cite the percent that the CPU uses of its PSU, or cite the percent that human brains use of global energy consumption. Otherwise they're completely different things that have no meaning in relation to each other.

Exactly. It's a meaningless and even misleading analogy.

If forced to draw a comparison, you could maybe talk about the energy dissipation of a single neuron and compare that to, say, the energy dissipation of a single transistor. And in that case, considering a human brain is powered by something on the order of 10^10 neurons, the energy efficiency of the brain comes out looking pretty good.

One is viewing society as a "body" with computers being its "brain". The other is viewing the human body as a "body" with its brain being its "brain". The comparison is of the energy used by each "brain" relative to the total energy used by its "body".

The comparison is valid if you accept the analogy, although I think you could easily dispute the analogy. E.g. you could just as easily view the network of humans in a society as its "brain" and all the things we build (including computers) as its "body".

> you could just as easily view the network of humans in a society as its "brain"

You could far more easily view the brains of humans in a society as its "brains."

> Energy is energy

Even this isn't quite true, since it's not fungible, except in the narrow use-case of creating heat[1].

> Whether the energy is carried by glucose/ATP or electric current is just an implementation detail.

This implementation detail means that converting between these forms incurs a tremendous cost (in lost energy) and, perhaps more importantly, is nowhere near instantaneous.

[1] Even the slightly broader use case of heating (e.g. increasing the temperature of a home) can be done with a heat pump, and those don't tend to run off of fungible energy.

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