Forgot your password?

Comment: Re:Tentative summary (Score 1) 149

by Immerman (#48281169) Attached to: Researchers At Brown University Shattered a Quantum Wave Function

Hmm, that's not how I read it (though I still haven't gotten around to reading the paper, so please let me know if I'm going off-track). It sounds like the bubbles are *created* by the electrons as they enter the fluid - no electrons equals no electrostatic repulsion field repelling the surrounding helium equals no bubble. And it's not that the paths through the liquid have different wavefunctions, it's that fractional wavefunctions created when an electron is partially reflected from the liquid's surface create smaller, faster bubbles than those containing a "whole" electron. Perhaps the wavefunction is splitting even further within the fluid, forming multiple even smaller bubbles, but I would think that the same electrostatic repulsion that creates a bubble in the helium would also tend to constrain the electron near it's center. It could be though that splitting due to "escapees" is responsible for the rarer apparent continuous spectrum of speeds.

Given the speculation that at least some of the "bubbles" might be due to ion contamination, I suspect they're probably directly measuring charges reaching the detector, rather than the bubbles directly - if you could directly detect the tiny bubble created by a single electron then you could probably also detect that there was a massive ion in it rather than an essentially sizeless, massless electron. So if you've got 10 "1/2 wavefunction" bubbles formed at the surface then all ten reach the detector ahead of schedule, but only five (on average) will actually be detected, with the remaining five electrons collapsing into having been reflected at the surface.

And yes, that would mean that you presumably get bubbles formed and sustained by electrons that "weren't there" - that would seem to be the natural corollary to having bubbles being formed by an impossibly small charge that "couldn't" be there. What appears to me to be so revolutionary about this experiment (assuming it's being properly interpreted) is that for the first time we're observing a situation where you can't construct a coherent classical description of the path of a single particle. In every previous case, while we could detect quantum wavefunctions in the distribution of results, each individual detection still corresponded to a valid classical path.

Comment: Re:Go ahead, restrict yourself out of business (Score 1) 267

by Immerman (#48280771) Attached to: MPAA Bans Google Glass In Theaters

Alternately they could radio-shield the theater - which is something some opera houses and the like are actually doing. Wouldn't stop devices that carried their own considerable storage, but those depending on "the cloud" would be castrated (and really, in an age where the leaked film typically hits the pirate sites before the grand opening, why does anyone even bother filming? To say nothing of why do the publishers care. Inertia I suppose.) Plus it would have the added benefit of making it impossible for anyone to talk on their phones without first leaving the room.

Comment: Re:Anyone still going to the movies? (Score 1) 267

by Immerman (#48280673) Attached to: MPAA Bans Google Glass In Theaters

>Why is the cinema experience in America so utterly miserable?

Politeness has gone out of fashion. The business owners aren't polite enough to deliver more than the bear minimum experience necessary to get your money, and enough of the audience members to ruin the movie aren't even polite enough to eat neatly and remain dark and quiet enough to avoid ruining the experience for everyone else. After all the world is all about ME.

Comment: Re:Not Planets (Score 1) 179

by jc42 (#48280401) Attached to: Most Planets In the Universe Are Homeless

Perhaps that discover will put a stake in that silly redefinition of the word.

And, anyway, this always seemed like the obvious truth. I'd have been shocked if there weren't massive numbers of primary-less planets out there. If you plot star masses versus size, the quantity goes up and up as the mass goes down, to the point they stop radiating. At that point we can't really see them anymore, but there's no reason to doubt that the curve keeps extending.

Some years back (probably in the 1980s), I read an article by an astronomer who had collected lots of info on what was known of the distribution of mass of various sizes. It included a graph of mean size-vs-density, from monatomic H through various common small molecules, on to dust clouds, planets, and stars of various sizes, for our galaxy and a few others that had enough data to be useful. The graph had a long gap between planets (then known only for our solar system) and stars. The writer commented that there was no data at all in this gap, but the two ends did appear to extend to meet each other. So the obvious conjecture was that the distribution continued through the gap, and if so, it would come close to accounting for the "missing mass" needed to explain galaxy rotation.

This was pure conjecture, of course, and since little is actually known about planet formation outside our solar system, it wouldn't be surprising if the actual distribution has dips at various size ranges. But assuming that the gap has the value zero is not very sensible. The obvious approach would be to say that we don't actually know, and Further Research Is Needed.

I wonder if I could find that article again ...

Comment: Re:Not Planets (Score 1) 179

by jc42 (#48280273) Attached to: Most Planets In the Universe Are Homeless

The IAU definition only applies to objects in this solar system. It says nothing about objects outside this solar system. It is very clear about that.

So obviously there are no "planets" at all outside our solar system. ;-)

Maybe astronomers should just make up a new term for the concept. Or maybe several terms. After all, how useful is a term that includes both Mercury and Jupiter? Especially if it excludes Pluto, Titan and Sedna.

Comment: Re:Two points (Score 1) 179

by Immerman (#48280125) Attached to: Most Planets In the Universe Are Homeless

Actually, sounds like most of them probably never had parents to begin with - they created themselves with no help from anyone, and just couldn't finish the job because the first planets to the party had already gobbled most the gas for themselves to become stars, and then proceeded to scatter the remaining gas to make the job even *more* difficult for the latecomers.

Maybe we should call these planets the galactic 99.9%.

Comment: Re:Very odd... (Score 1) 179

by Immerman (#48279993) Attached to: Most Planets In the Universe Are Homeless

Actually, I suspect multi-body interaction would be the most common form of capture, far more common than impact (aerobraking included). Impacting a planet requires hitting a pinprick in a football field almost dead center, there are many orders of magnitude more paths that will result in a near miss and gravitational slingshot, half of which will rob you of angular momentum. You'd likely need to hit several such "losing" planetary slingshots in a row before being captured by the sun, but the odds would still seem to be far higher than ever managing a direct collision.

Comment: Re:Drake equation (Score 1) 179

by Grishnakh (#48279933) Attached to: Most Planets In the Universe Are Homeless

Exactly. Biological life seems to need a certain amount of warmth; a rogue planet, which doesn't receive any heat from a parent star, is going to have a very cold surface, even if the interior is warm. Life as we know it wouldn't probably evolve on such a planet; it'd just be an ice world.

So this finding is interesting, but I don't see how it would affect the Drake Equation. If we want to find life that resembles us, we're probably only going to find it in star systems, on rocky planets within the star's habitable zone.

Comment: Re:this is why the aliens haven't invaded yet (Score 1) 179

by Immerman (#48279589) Attached to: Most Planets In the Universe Are Homeless

Maybe. The core's probably a pretty unpleasant place though, with radiation levels so high i's unlikely that life could evolve. Though admittedly by the time a race masters interstellar travel it's probably well on it's way to being able to colonize the galactic core, provided they don't mind living entirely indoors.

An optimist believes we live in the best world possible; a pessimist fears this is true.