throwaway_yy2Di

It's easy to tell computer engines aren't analyzing perfectly, because when we tell to them to play themselves, they lose a large fraction of their games, as both colors. Perfect play would always force at least a draw from at least one side.

There's no known tractable way to solve chess. There's something like 10^120 move orders [0], and no known way to find perfect play without brute-forcing (almost) all of them. Chess engines can't solve to to the end of a game to see which moves are certain to win; they can only explore to a very shallow depth, and evaluate the horizon nodes by very human-like [1] approximate heuristics.

It looks perfect from a human PoV (the best human players have no chance of winning); but there's still an unimaginably large gulf between chess engines and mathematically perfect chess.

[0] https://en.wikipedia.org/wiki/Shannon_number

[1] https://github.com/official-stockfish/Stockfish/blob/master/...

Apropos, to anyone who wants to watch the live moves, with expert commentary, they are here (this is the defendant from the Reuters story):

https://chess24.com/en/read/news/chess24-win-moscow-case-ann...

https://www.youtube.com/channel/UCkTCNuQ2mGfW6-SpHpaze_g (direct link to livestream)

If you're looking for live computer engine lines, Steinar Gunderson offers that here, with 38 cores running Stockfish:

http://analysis.sesse.net/

As well as PGN files (live-updated):

http://pgn.sesse.net/

Not my workaround:

http://spectrum.ieee.org/aerospace/space-flight/titan-callin...

http://descanso.jpl.nasa.gov/seminars/abstracts/viewgraphs/H...

This was an extremely serious bug in NASA/ESA's Cassini-Huygens probe, in the S-band link between Huygens (landing on Saturn's moon Titan) and Cassini (acting as radio relay).

It was a timing bug. There'd be a very high relative velocity between Cassini and Huygens, creating a significant (~2e-5) Doppler shift in the link. This shifted the frequency of the 2 GHz carrier (by 38 kHz). Likewise, it shifted the symbol rate of the 16 kbps bit stream (by 0.3 bps). The second effect was overlooked. On the demodulating end (Cassini), the bit-synchronizer expected the nominal bit rate, not the Doppler-shifted bit rate. Since its bandwidth was narrower than the 0.3 bps Doppler shift, it was unable to recognize frame syncs; this was proven in experiments post-launch. The parameter that set the bitrate was stored in non-modifiable firmware.

As it was when launched, Huygens would be unable to return any instrument data. For some context, this was the only probe that's ever visited Titan, at a cost of about $400 million.

The workaround

[spoiler]

The workaround was a major change in the orbit trajectory of Cassini (a $3 billion probe). Details aside, it set up an orbit geometry with this feature: at the time Huygens was descending in Titan's atmosphere, Cassini would be flying at a ~90° angle to their separation. The relative velocity was still 20,000 kph, but tangential velocity doesn't contribute to Doppler shift.

Apropos, the Gaia space telescope's first data release is next week. It's an extremely large dataset of the kinematics (3d position + velocity) of Milky Way stars.

http://www.cosmos.esa.int/web/gaia/dr1

    ...tidally locked, possibly losing their water and
    atmosphere in tens or hundreds of millions of years.

Here's a better answer on /r/askscience:

    Can we directly image the planet from earth?

    1. "The planet/star contrast is 10^-7 " This basically means
    for every 10,000,000 photons from the star, we would measure
    ~ one from the planet.
    
    2. "Current instrumentation using adaptive optics and
    coronography on 10 m class telescopes (like Sphere on VLT or
    Gemini Planetary Imager) aims at achieving a contrast of
    10^-6 to 10^-7 at an angular resolution of 100-200 mas"
    
    3. "The planet has a separation of 38 mas".
    
    4. Therefore with the best planet imagers we cannot
    currently directly image the planet. Our best hope is the
    E-ELT which should have first light in 2024.

To piggyback on this, the Nature paper (which is paywalled) has a free preprint version here:

http://www.eso.org/public/archives/releases/sciencepapers/es...

(PDF)

    However, there is reason to hope that the even larger
    European Extremely Large Telescope will have enough
    resolution (about 5e-8 radians? hard to tell from their
    official publications)

[0] https://www.eso.org/public/usa/teles-instr/e-elt/e-elt-instr...

[1] https://www.eso.org/sci/facilities/eelt/fp7-elt-pub/wfi_work...

You're exactly right; good catch.

Yes, because the lifespan of low-powered red dwarfs is vastly longer than the sun's. The wiki page cites a figure of 4 trillion years (!) for Proxima:

https://en.wikipedia.org/wiki/Proxima_Centauri

    The planet is about 0.05 AU from Proxima Centauri, meaning
    we need an angular resolution of about 1.9e-7 radians to
    even distinguish it from its host star. Is that realistic?

This is why coronagraphs will be so useful.

[0] https://en.wikipedia.org/wiki/Airy_disk#Mathematical_details

[1] a log-log graph shows the envelope is close to inverse-cubic (x^-3)

[2] http://nexsci.caltech.edu/workshop/2016/NIRCam_Planets_and_B...

I don't think JWST could even resolve it from its parent star, judging by [0]. They're too close together.

Proxima Centauri has a luminosity of 0.0017 suns [1], so Earth-like conditions would occur at ~sqrt(0.0017) au = 0.04 au, an apparent angular separation of arcsin(0.04 au / 4.2 light years) = 0.03". JWST wants star-planet separations at least an order of magnitude larger [0], ideally with very hot, infrared-bright planets.

E-ELT should be able to resolve them, according to [2]. Page 7 gives values for a very similar scenario: an Earth-like planet around an M dwarf (like Proxima), 6 pc away (5 times farther), at an angular separation of 0.015" (half as wide). In this scenario, E-ELT could image the star and planet as separate points, and take useful spectroscopic measurements of the planet's light. For it example it could detect a spectral line of oxygen (O2) in 4 hours of exposure time.

[0] http://nexsci.caltech.edu/workshop/2016/NIRCam_Planets_and_B...

[1] https://en.wikipedia.org/wiki/Proxima_Centauri

[2] https://www.eso.org/sci/meetings/2014/exoelt2014/presentatio...

    can it be easily ruled out?

At 2 light years for instance, that spacecraft would trace an apparent ellipse 3.3" in diameter, while Tabby's star (1,480 ly) would be stationary (0.004" parallax). In comparison, the star's apparent disk is just 30 μas wide (0.00003").

That can't physically work: for one because the parallaxes would be different and almost never line up. If something's colinear with a star today, it won't be colinear 6 months later, when the Earth's on the other side of the sun.

At 2 light years for instance, that spacecraft would trace an apparent ellipse 3.3" in diameter, while Tabby's star (1,480 ly) would be stationary (0.004" parallax). In comparison, the star's apparent disk is just 30 μas wide (0.00003").

Which program are you referring to? LSST is fully funded.

https://www.lsst.org/science/solar-system/potentially-hazard...

https://en.wikipedia.org/wiki/Large_Synoptic_Survey_Telescop...

Mathematica is one the most useful tools for this kind of experimental programming. A minimum implementation can be a single REPL line (if you prefer FP style). That's one line from blank page to "play audio"; it's hard to understand how enabling it is to have such shallow barriers to experimenting, it's like cheating.

    ListPlay@ Flatten@ NestList[
       0.996*#& /@ MovingAverage[# ~Join~ {First[#]}, 2]&,
       RandomReal[1.0, {80}], 100]

    If you are the first almost live form, you have plenty of
    time, and can evolved in an environment that has plenty of
    food. Something like the brown goo of Titan, with lots of
    hydrocarbons and other small molecules that you can pick up
    for free.

That's likely generic for pre-biotic environments. Planets don't naturally form redox gradients; if there's a large redox potential, that's reactive chemistry, which will react away to equilibrium over geologic time. It takes work to maintain such a gradient; for example, Earth's oxidizing atmosphere is actively maintained by life. Oxygen is geologically removed from atmospheres, reacting with exposed rock surfaces (oxygen weathering). It takes active expenditure of work (solar energy) to keep it existing.

There is some chemical energy in abiotic planets, but only small amounts, at very low power levels compared to Earth's aerobic biosphere (which eats something like 10^14 watts!). There's photochemistry caused by solar UV light, and there's atmospheric lightning (which is a major player in the Earth's N2 cycle). Most important is geochemical energy; i.e. primordial chemical gradients that aren't yet at equilibrium, because the two reactants are physically separated by rock layers. On Europa for example, a very slow process brings rocks into contact with the ocean, where slow serpentinization reactions can occur: oxidation of Fe++ to Fe+++ by water, with the production of H2. This would be the food source of Europa life, if it's there.

    I think what will really help us to get at a better estimate
    is to answer the question whether there exists life in our
    solar system that evolved independently of that on Earth.

There's no hard reason why another, orthogonal family of life couldn't coexist with DNA/RNA life. We have 10^7 extant species of DNA/RNA life; that's an existence proof that hostile, competing "types" of life can coexist. Suppose we found terrestrial "XNA life" with a biochemistry totally unrelated to anything else, with no possible common origin or lateral gene transfer. Then we would know life on Earth developed independently N >= 2 times, instead of N >= 1. That would change a lot; we could update P(life | Earth-like planet) from the subjective probability range [10^-Graham's number, 1) to something more like [10^-4, 1).

What's really surprising is that this is completely untested! We genuinely don't know if there's "alien" life on Earth, because we don't know how to look for it. There's no black-box tool to approach unknown biochemistry:

    Some have postulated the existence of a 'shadow biosphere'
    on Earth, teeming with life that has gone undiscovered
    because scientists simply don't know where to look. It could
    contain life that relies on a fundamentally different
    biochemistry, using different forms of amino acids or even
    entirely novel ways of storing, replicating and executing
    inherited information that do not rely on DNA or
    proteins. [...] The trick is deciding what to look for and
    how to detect it. The usual way that researchers search for
    new organisms — by sequencing DNA or RNA — will not pick up
    life that does not depend on them.

    ...We could even be oblivious to unfamiliar forms of life
    right under our noses...

"One in 10 billion trillion" sounds like a very large number, and it's put in italics for emphasis,"

And the author even asserts it's "irrational" to think real-world probabilities are this small!

It's easy to construct "unreasonably" small probabilities: take a few small ones and multiply them. If you path-sum all the evolutionary state transitions summing to P(intelligent life|planet), is it a shallow graph with many alternatives (additive probabilities), or a deep graph dominated by long, conjunctive sequences (probabilities multiply)?

If you parse the article carefully, the entire argument is summarized as

"There are more than 10^22 planets, therefore ETI probably exists[ed] if P(intelligent life|planet) > 10^-22".

    Specifically, unless the probability for evolving a
    civilization on a habitable-zone planet is less than one in
    10 billion trillion, then we are not the first. [...] In
    other words, given what we now know about the number and
    orbital positions of the galaxy’s planets, the degree of
    pessimism required to doubt the existence, at some point in
    time, of an advanced extraterrestrial civilization borders
    on the irrational.

There's more than a dozen solar system objects predicted to have liquid water:

http://www.planetary.org/blogs/emily-lakdawalla/2015/0312171...

The article neglects to mention that the Congressional Act which forces (?) the FDA's hand, was one that Phillip Morris sponsored and lobbied for. I think this is key to understanding why the FDA is acting like this, seemingly against public health, while benefiting incumbent cigarette makers.

    Passage, if it comes, may be politically impossible without
    the negotiated support of Philip Morris, whose Marlboro
    brand helps make it the American tobacco industry’s biggest
    player.
    
    The company’s central role, in fact, is a reason that some
    antismoking activists worry that the bill is a deal with the
    devil. Philip Morris’s support is also why other major
    tobacco companies — none of which back the legislation — see
    a cunning ploy by Marlboro’s maker to seal the company’s
    dominant position.

Here's the discovery paper:

http://hubblesite.org/pubinfo/pdf/2016/18/pdf.pdf

Ah, thanks for the update.

Tangentially, there's even larger public datasets coming out of astronomy. PanSTARRS' imaging survey will make 2 PB available online. They even have a picture [0] of the completed dataset in transit, if you wondered what 2 PB of HDD's on a flatbed looks like.

[0] https://archive.stsci.edu/mug/mug_2016/PS1_MUG_2016jan14.pdf...

    "For a 4m sail, for example, the diffraction limit spot size
    on Earth would be on order of 1000m."

https://www.google.com/search?q=4+light+years+*+1+micron+%2F...

https://en.wikipedia.org/wiki/Airy_disk#Size

The general idea is to draw n uniform samples from [1..N] and return them in sorted order. You can generate these incrementally, in order (no sort needed). The mean difference between successive samples is ~N/n. If the samples are uniformly distributed, their differences should have roughly an exponential [0] distribution (if N, n are large).

So the inductive step is: given k'th sample a[k], let a[k+1] = a[k] + S, where S is drawn from a discrete exponential distribution with mean 1/λ = N/n. That's the `exp(log(rand()) * stuff)' part of the code.

This almost works; there's more details [1] if you want it to actually work, and have accurate statistics, not overflow N, etc.

[0] https://en.wikipedia.org/wiki/Exponential_distribution

[1] https://hal.archives-ouvertes.fr/file/index/docid/75929/file...

This works, and is so much simpler.

It's not quite the same problem though; the algorithm described returns samples in sequential order. They mention performance reasons for this (C-f "tape sampling"). It also has the limitation that you need to know the sample size in advance.

Japan's space agency had earlier reported they had lost contact,

http://www.japantimes.co.jp/news/2016/03/27/national/science...

I'm sort of asking if EFF's argument is legally sound. Is code-signing expressive in this case, or merely functional? Is it rather Apple's intent to communicate endorsement that transforms code-signing into an expressive act, that when it's compelled, it's not expressive?