29 September, 2008

Bloggers given new Ten Commandments by church leaders

Christian bloggers have been given a new set of 'Ten Commandments' aimed at delivering them from the temptations of online arguments. Here it is:

1) You shall not put your blog before your integrity.
2) You shall not make an idol of your blog.
3) You shall not misuse your screen name by using your anonymity to sin.
4) Remember the Sabbath day by taking one day off a week from your blog.
5) Honour your fellow-bloggers above yourselves and do not give undue significance to their mistakes.
6) You shall not murder someone else's honour, reputation or feelings.
7) You shall not use the web to commit or permit adultery in your mind.
8) You shall not steal another person's content.
9) You shall not give false testimony against your fellow-blogger.
10) You shall not covet your neighbour's blog ranking. Be content with your own content.

14 September, 2008

Links for 14.09.08



The Monte-Carlo method

I was actually not aware of the fact that the Monte-Carlo method of integration was proposed by Stan Ulam working on Manhattan project at Los Alamos. I also like his aphorism, which I came across of here:

"My late friend Stan Ulam used to remark that his life was sharply divided into two halves. In the first half, he was always the youngest person in the group; in the second half, he was always the oldest. There was no transitional period."

Secret History of Quantum Physics

An interesting post by Chad Orzel, about the great discoveries made during vacations:

"Erwin Schrödinger famously discovered the equation that bears his name while on a skiing holiday in 1925. He was accompanied on this vacation by one of his many girlfriends, but which of them went on the fateful trip has been lost to history-- Schrödinger kept exceedingly detailed diaries, but the volume covering the relevant period has been lost."

I'm eager to know, who was his girlfriend...

Ten Lessons I wish I had been Taught

I came across these advices of Gian-Carlo Rota in the blog of Alexandre Borovik. Among them there is the following one:

"6) Do not worry about your mistakes.
Once more let me begin with Hilbert. When the Germans were planning to publish Hilbert’s collected papers and to present him with a set on the occasion of one of his later birthdays, they realized that they could not publish the papers in their original versions because they were full of errors, some of them quite serious. Thereupon they hired a young unemployed mathematician, Olga Taussky-Todd, to go over Hilbert’s papers and correct all mistakes. Olga labored for three years; it turned out that all mistake scould be corrected without any major changes in the statement of the theorems. There was one exception, a paper Hilbert wrote in his old age, which could not be fixed; it was a purported proof of the continuum hypothesis, you will find it in a volume of the Mathematische Annalen of the early thirties. At last, on Hilbert’s birthday, a freshly printed set of Hilbert’s collected papers was presented to the Geheimrat. Hilbert leafed through them carefully and did not notice anything."

12 September, 2008

Fermat's last theorem

I was often thinking about "whether Fermat really had a proof of his famous theorem":

Theorem. There are no positive integers x, y, z, and n > 2 such that x^n + y^n = z^n.

Today I found an answer in the mathematical FAQ:

"Did Fermat prove this theorem? No he did not. Fermat claimed to have found a proof of the theorem at an early stage in his career. Much later he spent time and effort proving the cases n = 4 and n = 5. Had he had a proof to his theorem earlier, there would have been no need for him to study specific cases."

This is followed by an interesting discussion about different mistakes that Fermat may have done (see section 3.1.4 of FAQ).

But, anyway, Pierre de Fermat never had his theorem proven.

11 September, 2008

Wolfram support

I was surprised by fast and friendly support that Wolfram offers to Mathematica users. The last two days I was bothering with a problem, which occurs when you try to calculate an alternating sum consisting of big numbers - the precision was not high enough and I always obtained a "noisy" curve instead of the smooth one. I played with accuracy and precision, but nothing helped. Finally, I've sent my notebook to Wolfram support, and have got an answer within a few hours, with a correct notebook attached. Now it seems to work - it is a bit tricky, though. 

10 September, 2008

The LHC switches on this morning

Sincerely, I don't want to contribute in the worldwide discussion about the "black hole consisting of antimatter" (c) which will destroy the Universe, but there is a nice picture from Google today:

09 September, 2008

How to learn any language?

Some time ago I came across a very interesting website by a Swiss amateur linguist François Micheloud. He presents an interesting table for those people who want to learn a foreign language, but don't know from which one to start (or which should be the next). François compares difficulty, popularity, transparency, the number of countries speaking the language etc. For instance he rates Russian to be the easiest languages among the "languages usually considered as hard".

07 September, 2008

Links for 07.09.2008


Useful stuff:
  • Scribd - a "YouTube for documents", supports a variety of formats.
  • Chrome - a new browser from Google. Only for Windows yet.
  • FriendFeed - probably everyone knows this, but I came across it only today. Using friendfeed.com you can share everything you produce in one place. It supports blog, youtube, google reader, picasa, and probably everything else you may need. My account there is lemeshko.


Why is mercury liquid?

The answer is clearly presented here. I find very interesting that mercury does not crystallizes at the room temperature not only due to the filled atomic shells (the Hg configuration is [Xe] 4f14 5d10 6s2), but also because of relativistic effects, which decrease the radius of the 6s orbital.

Mercury is a liquid at room temperature because the "relativistic contraction" of its atomic orbitals makes it behave chemically almost like a noble gas, not wanting to share electrons with other atoms, even other mercury atoms! Note that mercury is monatomic in the gas phase, just like a noble gas. Of course this should not be pushed too far; mercury is not a noble gas. There are enough outer-electron interactions for mercury to remain a liquid (radon, 22 amu heavier, is a gas), to conduct electricity, and to participate in ordinary chemical reactions...

Citations for 07.09.2008

Probably it might be a good idea to make something like bash.org, but for aphorisms and interesting citations... Here there are a few I came across this week:

  • Young man, in mathematics you don't understand things. You just get used to them. John von Neumann
  • There are three rules for writing the novel. Unfortunately, no one knows what they are.  W. Somerset Maugham
  •  Teach the Students You Have - not the ones you wish you had. If you get annoyed at students for being insufficiently prepared, or not as smart as you, you'll become a grumpy old fart, just like some of the lousy teachers you had. John Baez

06 September, 2008

The Most Alien-Looking Place on Earth

An article about a unique island, with a lot of pictures...

Imagine waking up on the Socotra Island and taking a good look around you (let's say your buddies pulled a prank on you and delivered you there, and lets also assume that you don't have any hangover from abuse of any substances). After a yelp of disbelief, you'd be inclined to think you were transported to another planet - or traveled to another era of Earth's history.

The second would be closer to the truth for this island, which is part of a group of 4 islands, has been geographically isolated from mainland Africa for the last 6 or 7 million years. Like the Galapagos Islands, this island is teeming with 700 endemic species of flora and fauna, a full 1/3 of which are found nowhere else on Earth.

03 September, 2008

I was laughing very loud...

Sociologists want to be psychologists, because if you understand the brain you can understand society.

Psychologists want to be biologists, because if you understand life you can understand the brain.

Biologists want to be chemists, because if you understand matter you understand life.

Chemists want to be physicists, because if you understand the universe you understand matter.

Physicists want to be God.

God wants to be a mathematician.

Found here.

02 September, 2008

Terence Tao

A 33 years old professor of math from University of California, 2006 Fields medal winner Terence Tao has a blog. It is extremely interesting as a whole, but here are some links to Terry's advices: Advices on career, On writing papers, Talk to your advisorTake the initiative, and tons of references to older posts therein.

How to write consistently boring scientific literature

An excellent article about writing, which is accessible at Scribd (youtube for docs).

A Scandinavian professor has told me an interesting story. The first English manuscript prepared by one of his PhD students had been written in a personal style, slightly verbose but with a humoristic tone and thoughtful side-tracks. There was absolutely no chance, however, that it would meet the strict demands of brevity, clarity and impersonality of a standard article. With great difficulty, this student eventually learned the standard style of producing technical, boring and impersonal scientific writing, thus enabling him to write and defend his thesis successfully (Fig. 1).

Dunning-Kruger effect

Today I came across some interesting stuff:

The Dunning-Kruger effect is the phenomenon wherein people who have little knowledge (or skill) tend to think they know more (or have more skill) than they do, while others who have much more knowledge tend to think that they know less. Dunning and Kruger were awarded a 2000 Ig Nobel prize for their work.

01 September, 2008

Why the h-index is little use

Two interesting posts by Michael Nilsen about the Hirsch index: the first and the second. Michael notes that the h-index can be calculated to a good approximation from the formula:

h ~ sqrt(T) / 2,

where T is the total number of citations. Therefore it provides no new information beyond the total number of citations, and can not be properly regarded as a new measure of impact at all. Earlier I wrote a little post about Hirsch index (in Russian).

Einstein Versus the Physical Review

A nice story from Physics Today. When Einstein moved to the US, he began to publish his work in American journals, but was not used to the peer-review procedure. After submitting his work "Do gravitational waves exist?" (with Rosen as coauthor) to Physical Review, Einstein received a critically reviewed manuscript with a comment of editor that it "would be great to have [Einstein's] reaction to the various comments and criticisms the referee has made". He was shocked by it and withdrew the article with the following letter to the editor:

Dear Sir,
We (Mr. Rosen and I) had sent you our manuscript for publication and had not authorized you to show it to specialists before it is printed. I see no reason to address the—in any case erroneous—comments of your anonymous expert. On the basis of this incident I prefer to publish the paper elsewhere.
P.S. Mr. Rosen, who has left for the Soviet Union, has authorized me to represent him in this matter.

The paper was finally published in Journal of the Franklin Institute in Philadelphia.

Abstruse Goose - another terrific comics

Here it is.