KaTeX, Khan Academy’s Math Typesetting Library

Khan Academy has published the fastest typesetting library for the web. IntMath’s KaTeX and MathJax comparison demo shows some impressive performance improvements. The demo page took 177 ms to process on my laptop. The MathJax version on the other hand took 4777 ms. The performance comes at a price that not everything is supported in KaTeX (yet). I wish aligned equations were supported, but I can live with it. Until I run across more serious problems I’ll happily use KaTeX instead of MathJax.

KaTeX and MathJax Comparison Demo
by Murray Bourne, IntMath.com

KaTeX – The fastest math typesetting library for the web.

Gravitational Waves Detected

An exciting announcement last week marked another milestone in our understanding of the universe. Almost 100 years ago Albert Einstein predicted the existence of gravitational waves, or ripples in the fabric of space-time. In the late 1970s the existence of gravitational waves had been confirmed for the first time, but they were not able to detect them and prove their existence here on Earth. Not until last week – scientists were finally able to directly observe ripples of gravitational waves. They also decoded the signal and determined its source. The wave was created by a collision of two massive black holes 1.3 billion light years away.

This was done at LIGO (Laser Interferometer Gravitational-wave Observatory). LIGO watches for a minuscule stretching of space with laser light sent through an L-shaped contraption that stretches 4 kilometers in two directions. LIGO is so precise, they were able to compare lengths to within 1/10,000 the width of a proton.

The radius of a proton is about 0.84–0.87 fm. 1 femtometer is a millionth of a nanometer. And 1 nanometer is a billionth of a meter. 1 femtometer is 1 x 10-15 meters. This number already is mind-boggling. I can’t even begin to imagine a device that can measure with a precision of 1/10,000 of a femtometer. What an amazing achievement.

Here are a few good articles for further reading:

Gravitational waves, Einstein’s ripples in spacetime, spotted for first time
by Adrian Cho, Science, published 2/11/2016

Scientists make first direct detection of gravitational waves
by Jennifer Chu, MIT News Office, published 2/11/2016

New insights emerge from LIGO’s gravitational-wave data
by Tushna Commissariat, Physics World, published 2/15/2016

Gravitational wave
Wikipedia

How to stop a hanging Windows service

Windows processes and services can be controlled with the task manager, but occasionally I encountered hung processes that required a reboot or other tools like the Process Explorer. But it looks like Windows has some useful command line tools that can save a lot of time.

1) Open command line prompt (cmd) as Admin

2) Find process id with sc queryex {servicename}, e.g. sc queryex Apache2.4. You can also use tasklist|find "{executable}", e.g. tasklist|find "httpd"

3) Kill the process with taskkill /f /pid {PID}, e.g. taskkill /f /pid 1712

Anywhere Out of the World

I remembered one of my favorite songs by Dead Can Dance ‘Anywhere Out of the World’, and ran across the poem of the same name by Charles Baudelaire:

Anywhere Out of the World

Charles Baudelaire, “Anywhere Out of the World,” translated by Arthur Symons, Baudelaire: His Prose and Poetry (New York: Boni and Liveright, 1919), pp. 51-53

Life is a hospital, in which every patient is possessed by the desire of changing his bed. One would prefer to suffer near the fire, and another is certain that he would get well if he were by the window. It seems to me that I should always be happy if I were somewhere else, and this question of moving house is one that I am continually talking over with my soul.

“Tell me, my soul, poor chilly soul, what do you say to living in Lisbon? It must be very warm there, and you would bask merrily, like a lizard. It is by the sea; they say that it is built of marble, and that the people have such a horror of vegetation that they tear up all the trees. There is a country after your own soul; a country made up of light and mineral, and with liquid to reflect them.”

My soul makes no answer.

“Since you love rest, and to see moving things, will you come and live in that heavenly land, Holland? Perhaps you would be happy in a country which you have so often admired in pictures. What do you say to Rotterdam, you who love forests of masts, and ships anchored at the doors of houses?”

My soul remains silent.

“Or perhaps Java seems to you more attractive? Well, there we shall find the mind of Europe married to tropical beauty.”

Not a word. Can my soul be dead?

“Have you sunk then into so deep a stupor that only your own pain gives you pleasure? If that be so, let us go to the lands that are made in the likeness of Death. I know exactly the place for us, poor soul! We will book our passage to Torneo. We will go still further, to the last limits of the Baltic; and, if it be possible, further still from life; we will make our abode at the Pole. There the sun only grazes the earth, and the slow alternations of light and night put out variety and bring in the half of nothingness, monotony. There we can take great baths of darkness, while, from time to time, for our pleasure, the Aurora Borealis shall scatter its rosy sheaves before us, like reflections of fireworks in hell!”

At last my soul bursts into speech, and wisely she cries to me: “Anywhere, anywhere, out of the world!”

Bill Callahan – Live at Sixth and I

Very excited that npr music shared a full length recording of Bill Callahan’s concert back on October 2nd.

It took place at the beautiful Sixth & I historical synagogue in Washington DC. I was there! And I loved this concert. So much I’m still spellbound weeks later as if I’d just been there.

Very happy I can keep my memory alive with this little keepsake. It was the first time I’ve seen him live in concert.

Bill Callahan’s music career dates back to the early 90s, but I discovered him just about two years ago with his album Apocalypse. I hope he’ll continue to make music for many years to come. Can’t wait to see him and his friends again. I also hope I’ll get to see the Apocalypse tour film one day!

Bill Callahan performed with Matt Kinsey on guitar, Jamie Zuverza on bass, and Adam Jones on drums a beautiful, nearly 2 hour lasting set with

  • The Sing
  • Javelin Unlanding
  • Sycamore
  • Spring
  • Small Plane
  • Drover
  • Seagull
  • Baby’s Breath
  • Ride My Arrow
  • Summer Painter
  • Please Send Me Someone To Love
  • America!
  • Winter Road
  • Rock-Bottom Riser
  • Say Valley Maker

But wait, there’s more Bill Callahan: A Window That Isn’t There: The Elusive Art of Bill Callahan is a great Pitchfork article by Mark Richardson. I enjoyed reading about his impressions meeting Bill Callahan, and learning a bit more about him.

The first time I saw Bill Callahan was not in concert, but when he introduced a movie at the Maryland Film Festival. I didn’t know anything about him, and I didn’t have the best first impression of him because he just seemed annoyed to be there.

Very much like Mark Richardson wrote: “He’s been known to comport himself as if he doesn’t want to be there, and he doesn’t necessarily have much to say.”

While this may not give the best first impression, it soon changed when I started to listen to his music. All was forgiven very soon. The concert chased away any last doubts I may have had. I enjoyed his music prior to the concert. But after the concert I knew that his music will follow me around for years to come.

Franz Kafka is 130

On the occasion of Franz Kafka’s 130th birthday (yesterday), here are two of my favorite short stories!

Rejection

Translated by Willa and Edwin Muir

When I meet a pretty girl and beg her: ‘Be so good as to come with me,’ and she walks past without a word, this is what she means to say:

‘You are no Duke with a famous name, no broad American with a Red Indian figure, level, brooding eyes and a skin tempered by the air of the prairies and the rivers that flow through them, you have never journeyed to the seven seas and voyaged on them wherever they may be, I don’t know where. So why, pray, should a pretty girl like myself go with you?’

‘You forget that no automobile swings you through the street in long thrusts; I see no gentlemen escorting you in a close half-circle, pressing on your skirts from behind and murmuring blessings on your head; your breasts are well laced into your bodice, but your thighs and hips make up for that restraint; you are wearing a taffeta dress with a pleated skirt such as delighted all of us last autumn, and yet you smile – inviting mortal danger – from time to time.’

‘Yes, we’re both in the right, and to keep us from being irrevocably aware of it, hadn’t we better just go our separate ways home?’

On the Tram

Translated by Willa and Edwin Muir

I stand on the end platform of the tram and am completely unsure of my footing in this world, in this town, in my family. Not even casually could I indicate any claims that I might rightly advance in any direction. I have not even any defense to offer for standing on this platform, holding on to this strap, letting myself be carried along by this tram, nor for the people who give way to the tram or walk quietly along or stand gazing into shop windows. Nobody asks me to put up a defense, indeed, but that is irrelevant.

The tram approaches a stopping place and a girl takes up her position near the step, ready to alight. She is as distinct to me as if I had run my hands over her. She is dressed in black, the pleats of her skirt hang almost still, her blouse is tight and has a collar of white fine-meshed lace, her left hand is braced flat against the side of the tram, the umbrella in her right hand rests on the second top step. Her face is brown, her nose, slightly pinched at the sides, has a broad round tip. She has a lot of brown hair and stray little tendrils on the right temple. Her small ear is close-set, but since I am near her I can see the whole ridge of the whorl of her right ear and the shadow at the root of it.

At that point I asked myself: How is it that she is not amazed at herself, that she keeps her lips closed and makes no such remark?

More of Kafka’s short stories can be found at franzkafkastories.com.

Celephaïs

My first website used to be hosted on celephais.com, named after a short story by H.P. Lovecraft. I can’t believe it’s been 15 years now since I walked my first baby-steps on the web. I used the domain for a site dedicated to my favorite artists, musicians, authors, and movies – well, it was pretty much the unfinished sandbox of a site you’re looking at now, but made of static html files and a lot of graphics in a golden/brass 3d-look with some photo image maps.

Lovecraft’s story has always been special to me. It wasn’t about evil creatures, but an outsider who withdrew from the world around him, dreamed and wrote about his dreams. 15 years ago I was drawn to the protagonist and Lovecraft’s own biography, and who knows — maybe it hasn’t changed all that much. If you’re interested, here’s the opening… Continue reading “Celephaïs”

Zequals and the Art of Estimation

This Numberphile video is about Zequals which can be useful if you need to compute a quick estimate, for example to find out if your calculation is on the right track. The idea is to ruthlessly round every number to just one significant digit. For example:

3 * 7 = 21 zz 20
7 * 8 = 56 zz 60
436 * 68 zz 400 * 70 = 28000 zz 30000

The actual answer is 29648 and surprisingly close to the zequal-result. Not all numbers turn out to be that close, but this method works really well for some ranges as this graph illustrates. There’s also extra footage and more to read about zequals on Brady Haran’s Blog.