Ultrasound, thermodynamics, and robot overlords (2014) | Hacker News Reader

Ultrasound, thermodynamics, and robot overlords (2014)

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> considering all the exceptions that exist for every other set of physical laws, thermodynamics has exactly zero exceptions

Actually, conservation of energy doesn't hold on cosmological scales, at least with the usually accepted meaning of conservation of energy. [0]

That's not relevant to the author's argument, but I think it's dangerous to perpetuate the idea that thermodynamics is somehow an inviolate theory that doesn't break down under certain conditions just like every other physical theory.

[0]: http://www.preposterousuniverse.com/blog/2010/02/22/energy-i...

It's interesting that the only theory that seems to be treated as inviolatable is the one that has big parts built on statistical, aggregate behaviour which doesn't hold on the small scale.

The author of the linked article points out there are competing interpretations under which mass-energy is still conserved on the small scale. It's just that if you introduce the variable of local gravitational energy you wind up with a system of more variables than equations. We don't presently know of any laws that further constrain the system of equations to a unique solution unless we take local conservation of energy as an axiom... which of course prevents us from proving local conservation of energy.

However, we don't have any observations that are inconsistent with local conservation of energy if gravitational energy is taken into account.

That's a bit misleading. As the author of your linked article points out, the ere interpretations of all observed phenomena that are still consistent with conservation of energy. I think the least-confusing way to state it is "to the best of our knowledge, the mass-energy of the Universe is constant, but due to ambiguities in accounting for gravitational energy, we cannot presently prove that this holds true for sub-divisions of the Universe".

The author states that he prefers to ignore the energy of the gravitational field because there isn't a unique solution to apportioning the energy of the gravitational field to some subdivision of the Universe unless one takes local conservation of energy as an axiom.

So, conservation of energy of the whole Universe is still believed to hold if one takes gravitational energy into account. We can take conservation of energy of a block of space (accounting for gravitational energy) as an axiom and get consistent equations. It's just that we don't (at least as of yet) have other equations that prevent us from apportioning the gravitational energy in a way that violates conservation of energy for a given block of space. Maybe we'll later discover other laws that force us to apportion the gravitational energy in a way that proves conservation of energy for sub-divisions of the Universe, or maybe we'll discover other laws that force us to apportion gravitational energy in a way that's inconsistent with local conservation of energy. Maybe we'll never discover any additional laws that force us either way.

EDIT: bringing it back to the original context: to the best of our knowledge, locally violating conservation of energy to charge a phone ultrasonically at a rate higher than the energy is being put into the sound waves would involve manipulating the gravitational field, and many people would consider the local violation of conservation of energy to just be an accounting trick.

This really does have a stench of scam and a whiff of foolish VC on it. But just like cold fusion you hope deep down that it might be possible.

I took a look at the patents which are easily found by searching on google patents for ubeam as assignee and there just wasn't that much disclosed. Sort of vague references to steering a beam. It did not appear to be enough to 'enable one skilled in the art to practice the invention.'

http://www.google.com/patents/US20150214764 (for example)

I did notice one thing: mention is made of capactivie micro-machines ultrasonic transducers https://en.wikipedia.org/wiki/Capacitive_micromachined_ultra... which seem to be in the same family as the micromachined mirror arrays commonly used in DLP projectors. My only experience with ultrasonic is with piezo.

One thing that I learned back then was that ultrasonics -bounce-. Aiming would be really, really hard. Not to mention that one thing people worry about in this field of steered array ultrasonics is 'necrosis' (which I don't like the sound of). Turns out that people use high powered steered beams to peer into peoples' skulls and to do things to the grey matter:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3002099/

Even assuming arguendo that it would be possible to transmit measurable power via a steered ultrasonic beam, I certainly don't want to do it anywhere near my head!

Yep I'm a layman when it comes to this stuff but everything I've read pretty much says that a ubeam that functioned correctly would be effectively a short range ultrasound weapon.

Near perpetual motion machines, near infinite compression schemes, nearly magical medical solutions: people keep pouring money into stuff that qualified scientists say is simply not possible. If the majority of people with relevant expertise say something is not possible, people should just believe them. They will say more careful things like 'there are technological difficulties' or "I don't see how you could make that work, but I guess it could be possible" if there is a possibility something will work.

Years ago the same kind of idea was charging phones by wifi and other EM radiation ubiquitously available. A short calculation by any physics undergraduate shows that it is simply impossible. Nevertheless people invested in companies pursuing the idea. A prototype was presented at expos. The result: nothing. On the other hand, charging by induction was never said to be impossible.

> When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong. - Arthur C Clarke.

However when all the scientists say you are wrong and your device requires violating the most fundamental theory in Physics then its a different case.

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