andars

Borrowing from an a old comment of mine:

On one hand, on some scales, Newtonian mechanics is correct "enough" to give results that work, and so in that sense it is just incomplete in that its domain is restricted. On the other, relativity and QM change everything. These new theories may reduce to Newtonian mechanics given certain assumptions, but Newtonian physics assumes things about the structure of spacetime that are fundamentally incorrect (e.g. velocity is not additive). In this sense, one can fairly say that Newton's mechanics are not just incomplete or missing some fine details, but wrong.

I think there is more to the foundations than just the best numbers we can come up with for a given experiment. Our numbers for the gravitational constant, for example, are pretty similar (if more precise) to the numbers in 1891, but the setting in which that number is completely changed. There is no aether, no absolute space, velocities don't add (even though it's "mostly" right on most scales we experience and measure, it is false), space and time get mixed up, etc. Those were all pretty foundational ideas just over a hundred years ago.

"Pony up" must mean something different for me than it does for you. I don't know what it means to OP, in my comment I mistakenly assumed my understanding of the phrase was fairly universal.

Realistically, if the government didn't tax and the benefits were available without payment, how many people would voluntarily pay? Many (most?) will accept a free ride when it is available.

The strength of that "unspoken contract" diminishes as you move from personal friend to distant organization.

I agree that this software has value and it would be nice for people to support it monetarily, but it seems unreasonable to get upset when people don't.

But their software is also free as in beer? It seems strange to make something available without payment and then get mad when people don't pay.

I understand the other non-monetary freedoms that the FSF advocates, this is not about those.

Could you clarify what is nonlinear about that system? From your description, it sounds like a high (4+) order (mostly) linear system. The motor probably has nonlinear dynamics, but so does everything and treating it as linear should work ok.

I suspect the difficulties you've experienced stem not from nonlinearity, but from trying to control a system poorly approximated by a second order system with a second order controller. By cascading, both PID controllers effectively "see" a plant that looks more or less second order, so the controllers are much more effective.

Sorry, I'm not qualified to give a good answer.

I would guess that the relatively long wavelength of ultrasound could potentially cause resolution issues.

I'm not very familiar with the plasma dots approach, but from a cursory look it appears that it is not capable of RGB. On the other hand, there is nothing that can fall out of confinement so the display is probably more stable.

That page says the femtosecond plasma display is pretty safe. This display was - and I believe still is, though I could be wrong - using a UV laser for confinement, which is sorta scary.

> Can you levitate multiple particles at the same time?

Yes, but their device currently is only capable of levitating a single particle. With the current approach, the device would need one laser for confining each particle. The lasers used for RGB could potentially be multiplexed between particles, but this is less likely to work for the confinement due to the instability of the trap.

> How fast are they moving?

Pretty slow. All the "big" images (Leia, grad student, etc) are long-exposure. You can see the particle moving in real-time at about 0:50. In the videos, you can see the device can almost do real-time persistence of vision for volumes substantially smaller than a fingertip.

> How sensitive is it to disturbances in the air?

As I mentioned above, the confinement is weak and the trap is pretty unstable. Its possible that they have improved the longevity of the trap in the last few months, but when doing long-exposure the device is surrounded by a heavy cloth barrier to block both external light and air movement.

The cellulose comes from the black liquor on a spoon (see 0:46 in the video). The put the spoon at the focus of the laser and with luck some particles get confined. After the trap is lost, the particle just sort of drifts away in the air, since they are only tens of microns.

Nonetheless, everybody calls the displays in Star Wars "holograms". Smalley notes this, and the title is using the word in this colloquial sense. There is an unfortunate disconnect between the technical and colloquial meanings of "hologram".

I've seen this in operation and am acquainted with the researchers. I may be able to attempt to answer some questions about it.

Or he plans on growth in other segments (solar, batteries, ?)

> Tesla rockets

Tesla is distinct from SpaceX.

Jobs had a $1 salary and no bonuses. That doesn't say anything about stock options, grants, etc. It sounds like Musk will get minimum wage and no stock anything if Tesla doesn't meet the thresholds.