[hwillis]

Actually, no! Producing ATP is ~30% efficient, which is much better than premium consumer solar panels. And while that heat is technically waste, even if it was more efficient we would still generate heat other ways just to keep warm.

What's even more shocking is that conversion of food to energy period is ~90% efficient, which is crazy to me. The fact that you can burn food and measure the energy given off, and that's very close to how much energy you get from eating it- that's insane.

The efficiency of the human body is all over the place. Muscles are only ~30% efficient, and the rest is waste heat... but humans walk using orders of magnitude less power than any walking robot. As far as I know we have never made a powered walking machine that is 10% as efficient as a person. The only way we can beat it is with a carefully balanced, specially-lubricated pair of legs that is leaned downhill on a treadmill and powered by gravity.

[Workaccount2]

To be fair, our food to energy conversion is so efficient because the foods we eat are already in a very energy ready state. Our bodies don't bother with stuff that is harder to convert.

[hwillis]

true, but recycling proteins is also pretty amazing. These are the most complex machines we know of, elegant atomic factories that do the seemingly impossible... and you dip them in acid and then you can pop them apart like a string of beads, to be reassembled into a totally new molecular miracle.

[bgnn]

What's also insane is the mitochondria are evolved from proteobacteria.

[fragmede]

I'd wait until walking robots are commonplace before discounting our ability to make an efficient one. I don't think I've seen one in person yet.

[hwillis]

I wouldn't. We have been trying[1]; humans are genuinely shocking in this way. Mechanical systems should have so many advantages over humans; springs are 10x better than tendons, motors are 3x better than muscles. It's possible humans evolved walking as a predatory tactic. Even if we develop a super-efficient walking robot, humans are efficient at several speeds, and keep that efficiency while varying their stride and foot placement, and with one of the largest most complex brains of any animal. And the ratio of leg/torso length is pretty variable among humans! Not to mention the flexible spine and swinging hips should be a huge energy sap, but they just kind of... aren't.

Beating human locomotion in the general case is pretty far off. It's a combination of body plan, extreme optimization of joints and energy storage, and really good algorithms.

One killer feature of the human body is synovial fluid. It's very thin, non-newtonian, self-replenishing and contained in particularly low-friction bearing surfaces. It's certainly better than 99.9% of mechanical joints, because these surfaces filter, heal and re-lubricate themselves. Mechanical joints have sticky grease so they stay lubricated without maintenance, and work in the presence of water and grit. It's doubtful that any joint that doesn't heal itself can compete, long-term.

[1]: https://spectrum.ieee.org/durus-sri-ultra-efficient-humanoid...

[fragmede]

A very select group has tried for not very long, but I think the most gains in efficiency are going to come from giving bipedal robots rollerblades.

[hwillis]

Absolutely correct, evolution will never ever beat a 10 cent ABEC-7 bearing. Skateboards really changed manufacturing by making a specific size of wildly precise bearing incredibly cheap. One day a robot will be able to step directly onto ice skates, but meanwhile I'm looking forward to the blooper reel because it's gonna be funny as hell

[marcosdumay]

As long as they have decent brakes... Because stairs and obstacles exist, and getting over them beats overall efficiency almost every time.