mspringer

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January 11, 2014
Probably not. All right, now that you know my conclusion, let's see how to get there with data. First, some background. Let me give very quick overview of Bitcoin in this context. (There are many comprehensive overviews elsewhere.) Bitcoin is an ongoing ledger of transactions of along the lines of…
November 27, 2013
I had an interesting question posed to me recently: how frequently does the sun emit photons with an energy greater than 1 TeV? All of you know about the experiments going on at the LHC, where particles are accelerated to an energy which is equivalent to an electron being accelerated through a…
April 12, 2013
George Takei posted the following thing to Facebook recently: It got reposted by a bunch of people and provoked a tremendous amount of discussion (for a math topic, anyway), much of which was somewhere in the continuum between merely wrong and psychedelically incoherent. It's not a new subject - a…
April 1, 2013
Why is the sky blue? It's a classic question - probably the classic question of the genre of explanatory popular physics. The famous short version of the answer is that Rayleigh scattering by air molecules affects short-waveength light more than long-wavelength light, and so blue light tends to get…
March 15, 2013
Question from a reader: Pick up a comb, rub it with your hair and you have got some electric charge. Now shake it and you are generating an electromagnetic wave. Am I right? Yes indeed. So why don't we see light emitted when we brush our hair? Let's run some numbers. If you wiggle around an…
February 27, 2013
A reader emailed me a fun question from a physics exam he took, along these lines: A car driver going at some speed v suddenly finds a wide wall at a distance r. Should he apply brakes or turn the car in a circle of radius r to avoid hitting the wall? My first thought was that surely the question…
February 12, 2013
The Theoretical Minimum: What You Need to Know to Start Doing Physics When this book appeared in my mailbox I judged it by its cover and was a little concerned. The problem with the cover is the name of one of the authors: Leonard Susskind. He's an extremely talented physicist and writer, to be…
January 29, 2013
The human eye is sensitive to a portion of the electromagnetic spectrum that we call visible light, which extends from around 400 to 700 nanometer wavelength, peaking in the general vicinity of greenish light at 560 nanometers: Here's the intensity (formally: power per area per unit solid angle per…
January 28, 2013
This post is political. As always, physics readers who don't care about politics are encouraged to skip it. I've got an actual physics post going up tomorrow. Mark and I have been conducting a debate/discussion over gun control in the United States. For the first round, here's his post and my…
January 22, 2013
The first major computer-animated film was Toy Story. It had a few human characters, most prominently Andy (who spends most of the film wearing a hat) and Sid (who sports a buzz cut). The focus of the film is on the plastic toys. One of the major reasons for this is the fact that toys are pretty…
January 16, 2013
Ok, so this isn't really physics as such, but it's pretty fascinating. There's a very large online community called Reddit in which users submit links which interest them. These links come with two little arrows beside them, and the users can vote the link up or down. Here's a screenshot of how the…
January 14, 2013
Recently a number of ScienceBloggers including Mark Hoofnagle of Denialism and myself have written posts about guns and gun control in the United States. While the internet tends to generate more heat than light, we decided that it might be worth having a discussion and debate about the subject.…
January 8, 2013
I'm sitting in a hotel in Utah at the PQE 2013 conference.  As I write this, the temperature is a rather brisk 19F. (For everyone else in the world, -7.2C) That's not cold at all to some of you, but some of you didn't grow up in south Louisiana. Once a year they let us grad students out of the…
January 3, 2013
Over the Christmas break I traveled to Louisiana to visit my family and to Georgia to visit my wife's family. In both cases (especially in the Georgia case!) the overarching theme was the consumption of delicious homemade food in quantities which were somewhere between preposterous and superhuman.…
December 18, 2012
My last post was political, and to be quite honest I sort of hate it when my favorite non-political writers decide to break out the soapbox and flog their views in public. Since I have just done so, let's at least partially make up for it by another post talking about something near and dear to my…
December 17, 2012
The shootings in Connecticut are a monstrous act of incomprehensible horror. For all the atrocities visited upon the world in the last hundred years, this is still without doubt among the most appallingly evil acts ever performed by a single person. And he is dead, and beyond the reach of human…
December 12, 2012
Wow, lots of moon posts these days.  This one is going to talk about a question left by commenter ppnl a couple posts back: ppnl: So could you use a pair of one meter telescopes a kilometer apart to create a point of constructive interference on the moon as small as what would have been created by…
December 3, 2012
This wonderful headline showed up in my Facebook feed: U.S. 'planned to blow up Moon' with nuke during Cold War era to show Soviets might. This was a bit eyebrow-raising. Dr. Strangelove was a slightly unfair caricature, but the Cold War really did have a better-than-average share of nuttiness.…
November 26, 2012
My post about seeing a laser from the moon mentioned  the fact that the beam from a laser spreads as it propagates. We're used to seeing this from a flashlight - the beam from a flashlight across a room is much smaller than the beam from a flashlight across an open field. Lasers spread too, though…
November 7, 2012
If you're one of the probably four people who haven't heard about Nate Silver, you've missed out. He's a statistics guy who runs the always interesting 538 Blog at the New York Times. He made his name in baseball statistics, Moneyball style, and moved into politics where he made state-by-state…
October 30, 2012
There was an xkcd feature a while back which asked the question "If everyone in the world shined a laser pointer at the moon at the same time, would we be able to see it?" The answer was no. A laser pointer doesn't put out much light, and even seven billion of them doesn't represent a whole lot…
October 16, 2012
By now everyone's heard of Felix Baumgartner and his record-breaking leap out of a balloon some 24 miles over the New Mexico desert. While the "official" definition of outer space is generally considered to start at either 60 miles or 100 kilometers, Felix's leap of some 39,045 meters is in many…
October 10, 2012
Over the last two days we've talked about hash functions and their uses in cryptography and elsewhere. Remember that an ideal hash function is basically what cryptographers call a random oracle - given an input, it produces a random number in some range. (In practice this range is always [0,2^(2^n…
October 9, 2012
Yesterday we looked at hash functions. As you recall, they're functions which take an input and generate a random-seeming output. As a quick example, here's the output of the SHA-256 hash function for the name of the Scottish physicist James Maxwell and a misspelling thereof: SHA256("James Clerk…
October 8, 2012
Last week NIST anounced the winner of its Cryptographic Hash Function Competition. After five years of review and many rounds of discussion and elimination, the winner is a hash function called Keccak, and its developers deserve many congratulations. It's a shame hash functions aren't better known…
October 1, 2012
Hey, how about that! Three people in our optics group here at Texas A&M (Professor Alexei Sokolov, postdoc Miaochan Zhi, and grad student Kai Wang) had a photograph from one of their optics experiments make the Optics and Photonics News Image of the Week: Image of the Week: Raman sidebands…
September 24, 2012
There's this grim and affecting scene in both X-Men and X-Men: First Class - a young Erik Lehnsherr watches his family hauled away by Nazis through the gates of a concentration camp. He's being dragged away by the Nazi guards, and he uses his magnetic powers for the first time to grab the gates…
September 17, 2012
In most books or articles that talk about lasers, you'll see a definition of laser light in terms of "coherence". But coherence is sort of a term of art, and the books will go on to explain coherence in terms of the waves being in sync with each other, or the emitted light being very monochromatic…
September 14, 2012
Back before my now-ended blogging hiatus, the server machinery that keeps ScienceBlogs running was not so snazzy as it is now. Now it's running a WordPress implementation that includes LaTeX support. LaTeX is a free environment for (among other things) typesetting mathematics. Let's give it a test…
September 10, 2012
If you've been reading ScienceBlogs for a while, you might remember this little physics blog I used to write. It and I sort of vanished off the internet for a long while. More than a year, I'm sad to say. Long story short, being a grad student takes up a huge amount of time. While I sort of thought…