Well to be cynical - if most people are blithering idiots and most people don't amount to much, it could be true that most smart people don't amount to much and most people in charge are idiots while still true that being smart makes you much more likely to be in charge :o)
I wonder if there's a way you could help this with software. I remember reading a long time ago about singing pitch training by realtime headphone feedback (like - if you're singing flat, you are feed back your voice distorted even more flat[1]). I wonder if you could detect and exaggerate differences in prononciation.
you could have a ring of people, with their own loyalty cards, use them for a bit, rotate around, offset any loyalty points differences with a bitcoin transfer.
In my experience, 90% of the time the clerk will swipe their own loyalty card if you claim you don't have one, so you get the benefit of any available discounts while remaining anonymous.
Highly depends on the store. In my experience only one supermarket here will do that, every other store will not. Another point, you can't earn gas points and save money on gas later on doing that. Another point, with my loyalty card on certain purchases at Walgreens and every time I fill a prescription there I earn points which can then be spent like cash there later on. It's a pretty generous program, actually, I have earned a couple hundred dollars.
Aside from tiny losses like tunnelling, scattering from vacuum excitations and thermally-generated fields, etc., a perfect optical cavity will store light indefinitely. No laser required, only light of the appropriate wavelength and phase.
The combination of Fabry-Perot cavities and power-recycling in the optics of the LIGO gravitational wave observatory "gains" a ~100 W laser up to a few megawatts. If a cavity is formed in free space, like LIGO, then careful attention to vacuum is required to prevent loss.
ULE clock reference cavities have quality factors that are much higher, and need no vacuum, as the light propagates entirely within a glass substrate.
Edit: I should add that the "tiny losses" mentioned at the outset are precisely what prevent you from making a "perfect cavity". As the quality of a cavity/oscillator increases, the number and deviousness of loss mechanisms does too. This is especially the case at frequencies that are low compared to those at which an experimenter can iterate.
For HN, consider building a host that can run uninterrupted for 10^12 seconds (30,000 years).
...but the effective storage time of the power recycling cavity in LIGO is about 1 second. This is a rather long time by optical standards, but I'd say it's a long way from "indefinitely".
Agreed. My post may have been more tautological than I'd hoped (in the absence of loss, a cavity is lossless). Thank you for the important reminder that in nature, there is no DC.
In the sense in which I'd understood the question "Cavity losses are often dominated by reflectivity losses at the mirrors: does an improved mirror make a big difference?", I think my reply is relevant.
Since the effect only works at an angle of 35 degrees, you couldn't just use two mirrors. Maybe you could arrange them in a ring... all you have to do is find a regular polygon with internal angles of 35 degrees :)
For 35 degrees, you don't need 3D; a ring of 72 35-degree angles is a cycle (with a star pattern, rather than a polygon). There is a similar solution for any rational fraction of a full revolution (equivalently, any angle which is rational when measured in degrees (or gradians), but not radians).
However, the article said “about 35 degrees” so the actual number is probably something 34.5 ≤ x ≤ 35.5 but not actually 35.
My geometric intuition says that in 3D you can always construct a cycle but I don't know how to formalize it. Imagine a flat zig-zag chain of alternating bends; you can reshape it to a curve of arbitrary radius (around the axis of the width of the chain) by turning each bend slightly relative to its neighbors (about the axis of the beam), in alternating directions. Then you can choose a radius which makes the ends meet exactly.
Lasers even LEDs have terrible effecency vs battery's. What's worse is converting light back to electricity is also terribly inefficient so even if these worked as advertised you would be stuck with a terrible battery.
Ah... a "can of light" as a practical energy storage mechanism. I think it's safe to say that this will remain a complete fantasy for the foreseeable future.
Example: my laptop battery has an energy storage of about 100 Watt-hours = 360 kJ. Suppose we want to store the same amount of power in an optical cavity (two mirrors pointed at each other) with a length of 0.5 meter. The time required by light to make a roundtrip in this cavity is 2L/c = 3 nanoseconds. Thus the power incident on the mirror at any given instant is (360 kJ)/(3 nanoseconds) = 10^14 watts!
This power is high enough that I suspect that even the vacuum itself couldn't conduct it without strange effects (production of particles, for instance).
This is the kind of thinking that could lead to better battery technology. Wouldn't it be amazing if the energy density of a system like this beat out gasoline?
Only if you ignore some of the operative words in the announcement: "virtually", "Just the right angle (about 35 degrees)".
For this to work as a storage medium it would have to work at an angle much closer to 90 degrees to avoid excessively large equipment and there would have to be a near perfect conversion both on the input side and on the output side (which as far as I know we currently don't have).
Aaah, good old "in a vacuum," surely one of physics most convenient simplifications, together with frictionless surface, the point particle and it's big-boned cousin perfect sphere and of course the infinite featureless plane. Except that a vacuum is actually kinda sorta possible in the real world too.
