Built on Facts

Seeing a laser from the moon

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…

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 respect a drop from…

Hash Week! (Part 3)

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)], with n usually equal to…

Hash Week! (Part 2)

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 Maxwell”) = 2667629603913530690117759428994407894024237387971995154086108064226397\ 5353322 SHA256(“James Clark Maxwell”) =…

Hash Week! (Part 1)

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 in the general public, because not only are they…

A Raman Rainbow

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: The crystal in the foreground is being hit by two pulses…

Magneto and Momentum

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 with…

How Single-Colored Is A Laser?

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…

Some Cute Math

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 run: I actually came across the above expression…

Armstrong in Orbit

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…