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Comment Arid zones have less mold from rains (Score 1) 457

At least as far as stuff like fruit and leaf crops, not having as much mold (like right before harvest) which causes rot and destroys the crop's commercial value is a big reason CA agriculture has been so successful compared to places that get a lot of rain like the US South East. It turns out it is easier to deal with the lack of water (by taking it from others) than deal with the risk of rain at the wrong time. Indoor agriculture may change that eventually though.

Comment Re:Copenhagen Interpretation (Score 1) 82

OK, I'll try again. YOU DON'T. All you see is electrons being "consumed" as they hit the screen, forming the interference pattern.

If you DO look for them as they pass through the slits -- where one can do this without "consuming" them by e.g. putting a conducting loop around the slit that will experience a voltage pulse as the electron passes THROUGH it or by illuminating the volume right behind one of the slits with intense light that can scatter off of the moving electron and hence detect the slit the electron passed though -- then the interference pattern goes away.

This is a fundamental sort of "goes away". It isn't just that we gave a small extra push to the electron, as in principle you can CLASSICALLY make the detection so weak that it wouldn't affect the classical trajectory. It is that the detection itself shifts the PHASE of the electron and hence destroys its coherence with the electron(s) passing through the other slit, so there is no longer any interference.

Also, you can read:


which both walks through all of this and provides you with references to at least some of the actual experiments that verify it.

Comment Re:Copenhagen Interpretation (Score 1) 82

It is. The point is that if you measure which slit it passes through, the interference pattern that implies that it passed through both AS A WAVE, not a particle, disappears. The rule for this sort of thing is that if you measure wavelike properties, you don't get a definite particle position/state. If you measure a definite particle position/state, you don't get wavelike behavior any more. This is called complementarity and is the basis of the uncertainty principle. Electrons and photons alike behave the same way. Even at very low intensities where you can effectively observe single photons or electrons AT THE DETECTOR, if you don't look to see which slit they go through you get interference, implying that the electron passed through both as a wave (function). If you do look and measure the slit the photon or electron passes through, no more interference pattern, no more waves.

The electron in some sense isn't in two places at once -- it is "everywhere" at once, but with a low probability, if it has a very well defined momentum and hence wavelength. If you measure it or confine it to some specific location, you do so at the irreducible expense of having a well-defined momentum (and hence wavelength).

I'm actually teaching this stuff right now at the most elementary level. There aren't a lot of good intro level books on it, but I'm using Harris's "Modern Physics", which is at least pretty readable and has some of the real math in it. Beyond intro modern physics books, you can try Wikipedia (often has surprisingly good articles on this sort of thing) or a real quantum textbook. Or two. Or three or four. It takes years to not quite understand quantum mechanics, and an important step along the way is to UNlearn all of the nonsense you "learned" about it in English statements and to concentrate on the consistent mathematical and conceptual formulation of the theory.


Comment Re:Copenhagen Interpretation (Score 1) 82

Hey, somebody had to do it. Using English with embedded classical logic to describe quantum phenomena is a waste of time. And even most physicists have never read Schwinger or studied the Nakajima-Zwanzig equation and hence have little idea of how to formally obtain the classical measurement projection in an open system interacting with a classically described statistical bath when the combined closed system is in a stationary state and has no probabilities at all. And then there is relativity and time reversal invariance.

I'm just sitting here, wondering if the back of the envelope computation is dead. When did we get to the point where we could resolve 30+ orders of magnitude effects in the lab? We haven't even -- as far as I know -- experimentally verified whether normal matter gravitation attracts or repels antimatter, which seems like it would be a pretty important first step in building a QFT with gravity or GR, but even that seems beyond us so far.


Comment More likely to be killed by your own clothes... (Score 1) 476

... than by an immigrant terrorist http://www.vox.com/2016/9/13/1...
"Virtually all the deaths from immigrant attacks (98.6 percent) came from one event: 9/11. Other than that, fatal immigrant-linked terrorist attacks in the US were vanishingly rare -- and ones linked to refugees specifically rarer still. The average likelihood of an American being killed in a terrorist attack in which any kind of immigrant participated in any given year is one in 3.6 million -- even including the 9/11 deaths. That is a very, very, very low number. To put that in perspective, I've produced the following chart, which compares the average annual likelihood of American pedestrians being hit by a railway vehicle, dying due to their own clothes melting or lighting on fire, and being killed in a terrorist attack perpetrated by an immigrant. "

Comment Re:"Helping our galaxy on its journey" (Score 3, Informative) 149

Mod +1. This is the second or third time I've seen summaries of the press announcement, and the first time it has been even obliquely acknowledged that the so called "repeller" is nothing more than a localized lack of PULL, not any sort of actual gravitational "push". -1 to the article itself for being misleading bullshit and creating a "dipole" like an electron and an electron hole create a "dipole" in a uniform neutral metal, no more.

Surely there is nothing surprising about this. People have been doing cosmological simulations for a LONG time with a large number of pointlike objects interacting with GMm/r^2 attractive forces but to simulate galactic evolution and universal evolution from the big bang. The interesting point being that in the center of a uniform mass distribution, there is no net force but nevertheless 1/r^2 forces with any kind of inhomogeneity in the underlying free mass distribution tends to accrete in some places and abandon others, especially if it can inelastically interact and clump together into bound subsystems. This must have been seen in simulations pretty much every time, and should come as no surprise in nature.

Comment Re: I feel that lone sysadmin's pain (Score 5, Interesting) 356

Having used the "sweet rm" trick back in the 80's somewhere (with much more limited space, and a cron FIFO groomer) it also doesn't protect you from a wide variety of file corruption issues and overwrites. Remove a file, recreate it, remove it again? Delete two files from different parts of your tree -- e.g. README -- that have the same name? Original file gone (unless you don't just alias rm, you write a very complicated script). If you run out of space and have an alias/script like "flush" to take out the trash and make room for more, it just moves the problem one notch downstream.

With that said, it did save my ass a few times. Then I learned personal discipline, started using version control (SCCS at the time, IIRC) onto a reliable server to not just back up any files of any importance I create but to save reversible strings of revisions back to the Egg, and stopped using my reversible rm altogether after one or two of the disasters it still leaves open.

Moral: Version control with frequent checkins usually leaves your working image itself on your working machine. Keeping the repository on a different machine is already one level of redundancy. Keeping it on a server class machine in a tier 1 or tier 2 facility with reliable, regular backups and RAIDed disk is suddenly very, very, very reliable. As the current incident shows, not perfectly reliable. Human error, multiple disk failures in an array, nuclear war, internal malice or incompetence or just plain accident can still cause data loss, but in this case what is being reported isn't disaster -- they had 6 hour backups! Even though I'm sure there will be some folks who are inconvenienced, MOST of the users will still have usable, current working copies and be out anywhere from zero to a few hours of work. I've been on both sides of the sysadmin aisle in data loss server crashes, and -- they happen. Wise users use a belt AND suspenders to the extent possible lest they find their pants gathered around their ankles one day...

Submission + - Beware new "can you hear me" telephone scam (cbsnews.com)

Paul Fernhout writes: CBS News informs us: "The "can you hear me" con is actually a variation on earlier scams aimed at getting the victim to say the word "yes" in a phone conversation. That affirmative response is recorded by the fraudster and used to authorize unwanted charges on a phone or utility bill or on a purloined credit card. ... If you do answer a call from an unfamiliar number, be skeptical of strangers asking questions that would normally elicit a "yes " response. The question doesn't have to be "can you hear me? " It could be "are you the lady of the house? "; "do you pay the household telephone bills?"; "are you the homeowner?"; or any number of similar yes/no questions. A reasonable response to any of these questions is: "Who are you, and why do you want to know?""

Comment Re:The speed of light isn't constant (Score 1) 139

Because of dispersion (different frequencies) inside dynamically polarizable materials. Not in a vacuum. In a vacuum, the speed of light is predicted to be -- the speed of light.

Light can be bent by gravitational fields, but the thought is that the bent trajectories are geodesics in bent spacetime, not actual lenses which bend light by slowing it down due to the susceptibility of space.

Comment Mod parent up as insightful on battery subsidies (Score 1) 333

"Rather than spend $billions on the US war machine to ensure the reliable supply of oil to the country, the US government should be subsidizing the production of batteries to store solar energy."

Mod parent up as insightful! Makes sense now that solar panels are so cheap to focus on other areas -- batteries (or similar energy storage devices like creating liquid fuels from air) being the major limiting factor now (even with many innovations in the pipeline).

Also related: https://en.wikipedia.org/wiki/...

Still, another way to approach this is to make all energy sources pay their true costs up front. For example, Trump talks about millions of jobs to be created by burning more coal, but ignores all the people who will suffer and die from the pollution as an externality. So, by taxing fossil fuels so they are priced correctly in the market up-front (and ideally distributing that tax revenue equally to all citizens) indirectly subsidizes renewables, efficiency, and batteries.

Comment Re:I give the best chance to beat google to YacY (Score 1) 210

Interesting: https://en.wikipedia.org/wiki/...
"YaCy (pronounced "ya see") is a free distributed search engine, built on principles of peer-to-peer (P2P) networks.[1][2] Its core is a computer program written in Java distributed on several hundred computers, as of September 2006, so-called YaCy-peers. Each YaCy-peer independently crawls through the Internet, analyzes and indexes found web pages, and stores indexing results in a common database (so called index) which is shared with other YaCy-peers using principles of P2P networks. It is a free search engine that everyone can use to build a search portal for their intranet and to help search the public internet clearly.
    Compared to semi-distributed search engines, the YaCy-network has a decentralised architecture. All YaCy-peers are equal and no central server exists. It can be run either in a crawling mode or as a local proxy server, indexing web pages visited by the person running YaCy on his or her computer. (Several mechanisms are provided to protect the user's privacy). Access to the search functions is made by a locally running web server which provides a search box to enter search terms, and returns search results in a similar format to other popular search engines.
    YaCy is available on Windows, Mac and GNU/Linux. ..."

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