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  1. Nethack needs an upgrade on NetHack: Still One of the Greatest Games Ever Written · · Score: 1

    alt dot org slash nethack

    watch the ttyrecs

    choose the name that's right for you

    dare to compare

  2. Beware overly optimistic forecasts on Tapping Shale Reserves, US Would Become World's Top Oil Producer By 2017 · · Score: 2

    The headline is based on the latest IEA (International Energy Agency) forecast called the "2012 World Energy Outlook"

    Follow the link to a graph of what is being forecast and to the report in question:

    http://earlywarn.blogspot.fr/2012/11/iea-us-to-be-worlds-largest-oil-producer.html

    Look at the graph: conventional oil and natgas are in decline.
    Note the super optimistic growth assumptions for unconventional gas and oil.
    What is the methodology behind this extrapolation? That's the question people should be asking themselves.

    Natgas price is at historic lows. Low prices mean small profits mean decreasing investment.
    These days the unconventional gas industry is facing something of a bust:

    http://www.nytimes.com/2012/10/21/business/energy-environment/in-a-natural-gas-glut-big-winners-and-losers.html?pagewanted=all&_r=0

    How well does that fit with the optimistic growth scenario?

    Also, the IEA does not exactly have a sterling reputation for balanced impartial forecasts:

    http://www.guardian.co.uk/environment/2009/nov/09/peak-oil-international-energy-agency

    Just because something is a headline, doesn't mean it's true. Time will tell, of course.

  3. Re:The equation itself? on 17-Year-Old Wins Intel's $100K Science Prize · · Score: 1

    Here is a calculation to illustrate the main idea

    Define the function f(x) = (x+2)/(x+1)
    a function of this type is called a fractional linear transformation

    Set
    x0=1
    and iterate using f(x)
    x1=f(x0) = 3/2=1.5
    x2=f(x1)= 7/5=1.4
    x3=f(x2) = 17/12 ~ 1.4167
    x4=f(x3)=41/29 ~ 1.4138
    x5=f(x4)=99/70 ~ 1.4143
    x6=f(x5) =239/169 ~ 1.4142

    These fractions approximate, indeed converge to the square root of 2

    It turns out that in this particular case these fractions are the best possible approximations for sqrt(2)

    We know that 1.4142 are the 1st 6 digits of sqrt(2)

    sqrt(2) ~ 1+f1 where
    f1=0.4142....
    1/f1 = 2+f2 where
    f2=0.41421...
    1/f2 = 2+f3 where
    f3=0.41421...

    actually f1=f2=f3=.... ad infinitum

    This means that
    sqrt(2) = 1+ 1/(2+1/(2+1/(2+...))))
    The last expression is called a continued fraction

    the numbers in it are obtained by subtracting away the whole part taking the reciprocal, subtracting away the whole part, etc

    The amazing thing is that for square roots this process isn't random but repeats cyclically. For sqrt(2) the cycle is particularly simple
    we start with 1 and after that all the #s we get are 2

    The numbers
    1
    1+1/2=3/2
    1+1/(2+1/2) = 7/5
    1+1/(2+1/(2+1/2)) = 17/12
    are the fractions that result from truncating the continued fractions
    These fractions are the best possible approximations for sqrt(2) ("best possible" has a precise meaning that we don't need to get into here)

    Now here is the punchline.

    Notice how we get the same fractions by iterating f(x) and by doing the continued fraction expansion

    This doesn't happen for all square roots.
    More interestingly, there can be an infinite overlap in the two sequences of approximations
    O'Dorney figured out when this happens

    http://www.maa.org/abstracts/mf2010-abstracts.pdf

    See page 13

  4. Easy to understand on 60 Years of Hamming Codes · · Score: 2, Interesting

    Hamming codes are practical things, while Shannon's analyses of codes were more abstract (though still hugely useful and important)
    Consider the checksum bit. It helps to catch errors but there are 2 problems. First, if there is a double error (more likely if the checksum is on a longer string), then the error isn't caught Second, even if we know there is an error, we can't recover, but have to resend.
    The easiest error-correcting code is to replace every bit with a triple copy of itself. So
    101 becomes 111000111
    This way, we can recover from any single error, but the scheme is very inefficient.
    Hamming's simplest code takes a 4 bit message and adds 3 very special parity bits (think partial checksums) arranged in a clever way so that any one bit error can be isolated and corrected.
    That's the basic idea. The details are many places, such as http://en.wikipedia.org/wiki/Hamming(7,4)

  5. Re:Great news! on Scientists Cut Greenland Ice Loss Estimate By Half · · Score: 5, Informative

    > We all know that the ice is still melting (but slower than we thought).
    This year we are going to see a new record low for arctic sea ice --- surpassing even the dramatic 2007 decline.
    http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seaice.recent.arctic.png
    What's really startling is that this year, both the NE and the NW passages are completely open. This animation tells the story
    http://arctic.atmos.uiuc.edu/CT/animate.arctic.color.0.html
    Typically, shipping through the NE passage relies on Russian icebreakers. Judging by the satellite photos, at this point the icebreakers aren't needed
    Source: cryosphere today http://arctic.atmos.uiuc.edu/cryosphere/

  6. More information available on Sci-Fi Writer Peter Watts Convicted of Assault · · Score: 2
    A recent posting on Watts' blog has clarified a number of issues http://www.rifters.com/crawl/?p=1193 Questions regarding the video tape, the exact timeline, the allegation of a previous police record (he has none) are addressed in the post. The following excerpt deserves to be highlighted IMO

    2. The Coverage
    The Times-Herald reporter sat in the courtroom throughout the case. She knows there was no assault. She knows the choking incident never occurred. She knows that the only violence was committed by the border guards. These facts are no longer in dispute. And yet, the Times-Herald continues to report that I was found guilty of “assault”, and continues to repeat Beaudry’s allegation that I “choked” him without mentioning that an independent witness utterly discredited his testimony. Unfortunately, while the story has been picked up by numerous other newspapers, most of them simply seem to have cut-and-pasted the Times-Herald reportage. I find this discouraging. As does at least one juror, who opined:

    “The Times Herald continues to print that Mr. Watts was found guilty of assault. HE WAS NOT!!! He was found guilty of obstructing/resisting, and that was due to the time that transpired between him being ordered to do something and him actually complying with the order. We were forced to decide what was a reasonable amount of time for him to comply with an order. Mr. Watts, in my opinion, was treated unfairly by Customs and Border Protection. But, unfortunately, they were not on trial.”

  7. the facts of the case on Sci-Fi Writer Peter Watts Convicted of Assault · · Score: 5, Informative
    The following points were established during the trial. http://www.rifters.com/crawl/?p=1186
    • 1. The incident occured as Watts was exiting the US. He was stopped by US border patrol for a random "exit inspection"
    • 2. Watts initially got out of the car and requested an explanation. At that point, one of the border patrol officers told him to get back in the car. He did so
    • 3. An officer named Beaudry rushed over to the scene, got into the car with Watts, struck him in the face and told him to get out.
    • 4. Watts exited the car and Beaudry ordered him to get to the ground.
    • 5. Watts did not comply, but rather demanded an explanation.
    • 6. Beaudry pepper-spayed watts and threatened him with a baton. At that point Watts lay down, was handcuffed, and placed under arrest.

    At no point did Watts engage in a physical confrontation with the CBP officers. Upon cross-examination the "choking" accusation and the "aggressive stance" accusations were shown to have been fabricated.
    The conviction stemmed solely from point #5 Here are a couple of post-trial juror statements. One was posted on Watts own site. The other was posted as a comment to the Port Huron report on the verdict; see
    http://www.thetimesherald.com/article/20100319/NEWS01/3190308/Jury-remains-out-in-Watts-trial?plckFindCommentKey=CommentKey:e3d49247-c265-47a6-9721-5713e32cc7ed



    As a member of the jury that convicted Mr. Watts today, I have a few comments to make. The jury’s task was not to decide who we liked better. The job of the jury was to decide whether Mr. Watts “obstructed/resisted” the custom officials. Assault was not one of the charges. What it boiled down to was Mr. Watts did not follow the instructions of the customs agents. Period. He was not violent, he was not intimidating, he was not stopping them from searching his car. He did, however, refuse to follow the commands by his non compliance. He’s not a bad man by any stretch of the imagination. The customs agents escalted the situation with sarcasm and miscommunication. Unfortunately, we were not asked to convict those agents with a crime, although, in my opinion, they did commit offenses against Mr. Watts. Two wrongs don’t make a right, so we had to follow the instructions as set forth to us by the judge.



    Peter,

    I believe your description of the trial and deliberations is more accurate than you could know. As a non-conformist and “libertarian” (who has had some experiences not unlike yours) I was not comfortable with my vote, but felt deep inside that it was consistent with the oath we took as jurors. I believe nearly all the jurors searched for a legitimate reason to vote differently. In the end it came down to the question “Was the law broken?”. While I would much rather have a beer and discussion with you than Officer B. I never the less felt obligated to vote my conscience. I also believe most, if not all, the jurors sincerely hope that you are handled with a great degree of leniency, we, unfortunately have no say in that matter.

  8. braneworlds: mass = extra dimension on Scientists Weigh Smallest Mass Ever · · Score: 1

    classical physics = 3 space dimensions relativistic physics = 4 dimensions (space+time) braneworld physics = 5 dimension (space+time+mass) http://superstringtheory.com/experm/exper51.html The holy grail of modern theoretical physics is the unification of quantum and relativistic theory. A key idea here is the possibility that there might be extra, hard-to-perceive dimensions. The braneworld theory say that the extra dimension is mass, so the mass of elementary particles might actually be fluctuating, if ever so slightly. Mass dynamics! Who knows, these ultra fine mass experiments may give us a way to test some of these crazy theories.

  9. Cut the knot: the best Mathematics site on Math Awareness Month · · Score: 3, Informative

    The best hands-on mathematics experience, hands down, is at

    http://www.cut-the-knot.org/

    The topics are accessible, and often accompanied with applets.

    I've used this material to give math talks to high school kids - they love it.

    Here is a real favourite:

    Make a polygon by picking a bunch of points on graph paper (just the grid intersection points) and connecting these points by straight lines. The spiky looking thing is technically called a lattice polygon. A really cool way to calculate the area is to (A) count the grid points strictly inside the polygon (B) count the grid points lying exactly on the edges and vertices, then do (A)+(B)/2-1 Voila!

    The applet and explanation is here:
    http://www.cut-the-knot.org/ctk/Pick.shtml

    (However, the so-inclined may prefer to fool around with this by themselves, first!)

    There are many^(many) phenomena out there like pick's theorem. Call them math paradoxes, or theorems, or whatever, but there's lots of mathematics that is easy to perceive and is mysterious as anything. Mathematics awareness can begin by first learning about and experiencing these brain bending phenomena, and then SEEKING an explanation.

  10. Re:universal ratio: YOU are too a part of the plan on The Golden Ratio · · Score: 1

    This is well know for the Fibonacci sequence F(n+1)/F(n) tends in the limit to the golden ratio