## Wednesday, February 08, 2006

### Physics as Danish enterprise

Physics, in the usual sense, started with the refined models of the Solar system, and it can be interpreted - with a slight stretch of imagination - as a Danish science.

First of all, some math had to be known before physics could smoothly develop. The letters "Dan" sound almost like "Tan". Who discovered the tangent? Yes, it was Thomas Fincke who was Danish.

Classical mechanics was the first successful discipline of physics as we know it today. Newton's equations could only be found because Kepler's laws of planetary motion were already known. Why were they known?

As Einstein always emphasized, Kepler could only find his laws because of huge Excel files describing the planetary motion and produced by Tycho de Brahe. Although Tycho de Brahe did his important work in Prague under Rudolph II, a great sponsor of arts, sciences, and alchemy, he was born in Copenhagen. Although his Tychonic model was kind of geocentric, it combined the Ptolemaic model with the virtues of the Copernican one and agreed with the available high-precision data.

With Tycho's accurate data, it was straightforward to discover Kepler's laws and Newton's laws, and the rest of classical mechanics quickly followed.

At this point, it should be clear that the rest of the world was just helping to complete some Danish discoveries that initiated classical mechanics. What is the next important milestone in the history of physics? Yes, you're right, it's field theory - especially electromagnetism.

Electromagnetism - the relation between electricity and magnetism - was discovered by Hans Christian Ørsted. Needless to say, he was Danish, too. In 1820 he observed that the needle of his compass was moving whenever the battery was turned on or off. Electromagnetism was born and several other physicists completed the details. As Wikipedia explains, Ørsted never hesitated to promote radical views. For example, he encouraged the greatest writer of fairy-tales, Hans Christian Andersen of Denmark, to write more stuff. :-) Quite a radical set of books.

The rest of electromagnetism was straightforward and it had many obvious implications such as the discovery of special relativity (and consequently also general relativity).

You may think that I am skimming over a lot of other physics to create a false impression that physics is mostly a Danish science. For example, there is also optics. Who discovered the relations between the index of refraction and the density of a gas? Yes, it was Ludwig Lorenz from the University of Copenhagen in 1869. The Dutchman Hendrik Lorentz discovered it independently in 1870, which is why we often call it the Lorentz-Lorenz formula.

I guess that 92% of the readers have not been able to distinguish Lorentz from Lorenz and the Dutchmen from Danes before they read this article. ;-) Do you think that the figure 92% is exaggerated? Do you think that I am incorrectly assuming that all the readers have the IQ of Quantoken? No, I am not! Do you remember the gauge invariance in the theory of Ørsted's electromagnetism? We can fix the ambiguity, can't we? For example, the most natural relativistic gauge-fixing requires that

• partial A^mu / partial x^mu = 0

Do you know whose condition it is and what was his nationality? It's the Lorentz's condition and Lorentz was Dutch, 92% of the readers will say. Nope! It is actually the Lorenz condition and the author was Danish. The Danes are so modest (or ignorant) that they never protest against the typo.

Do you still think that 92% was an exaggeration? Not at all. At scholar.google.com, you will find 3,620 wrong papers :-) that describe the Lorentz gauge. The list of the authors who are wrong includes Schwinger, Guralnik, Kibble, as well as most other physicists you know. On the other hand, only 295 papers talk about the correct Lorenz gauge. You can do the math.

There are two more revolutions in the 20th century physics waiting for us.

The more important one - so far - seems to be quantum mechanics. After introducing the old quantum mechanics, Niels Bohr of Copenhagen became the spiritual leader of the young generation of quantum mechanicians. The orthodox interpretation or quantum mechanics was called the Copenhagen interpretation, to emphasize Bohr's key contributions to the community.

What is the final revolution of the 20th century physics? Yes, it is string theory. Who discovered that there were any strings to talk about in particle physics? You may have seen the TV program about our friend who got drunk when his paper was rejected. But he was not the only one. One of the two other co-discoverers of string theory was Holger Nielsen. We are pretty much near the current state of theoretical physics.

Once again, many readers may protest that I only focused on a single line of reasoning in physics and that there are many other disciplines in physics. For example, self-organized criticality. Well, yes, you're right. Self-organized criticality was invented by Per Bak, another Dane. At this moment, some people will become a bit nervous and argue that biochemistry can't be Danish. Someone had to discover things like the vitamin K and get a Nobel prize for it. Yes, it was Henrik Dam of Denmark.

The feminists will object that all the physicists above were male and the ratio should have been 50:50. Well, I can't offer you this number. But I can tell you that one of the Nobel prize candidates may be Denmark's Lene Hau of Harvard University who was able to stop the light. She may become the first female physics Nobel prize winner after more than 40 years.

Dear Muslim friends, it is now up to you to multiply the discoveries above by a factor of 250 in order to give the humankind the same contribution per person as the Danes. If you can't do it, then we will have to conclude that at least at the level of natural science, neither Allah nor Mohammed (PBUH) works right.

And that's the memo.

1. Well, talking about bragging rights I guess the Dannish really do not have much to say. First thing first, the Arabs improved something they learned from the Indians and invented the ten numerical symbols we use today. Without them you can not do any calculation of any kind. That alone is many times more significant than any little things the Dannish have discovered. All european written languages also had an origin in Arab.

Second, the Chinese have a right to brag about the invention of paper, without which you can't publish any paper. More importantly, without the stuff, not only that you can not write any thing or publish a paper, you don't even know what to do when you shit! So each time when you have to wipe you ass clean, make sure you thank the Chinese! Too bad it took a little over a thousand years before the invention of paper was spreaded to Europe. During that time period the savages must have been wiping their butts with dusty dirts.

After saying that, granted that the Dannish did make some great contributions to modern science. But that is no reason to use cartoon to insult on a different culture or a different religion.

Quantoken

2. Dear Quantoken,

fair enough, but let me mention that today, we are usually using semiconductors instead of paper and they store the hexadecimal numbers instead of the decimal ones. Some discoveries, however precious, are less lasting than others. ;-) Quantum mechanics will survive, however.

Best
LM

3. Lubos:
Nothing lasts forever. But the invension of paper can probably last another few thousand years, or maybe forever because it uses a sustainable natural resource: trees. At least you still can't wipe your ass with semiconductors. Numerical symbols will last a few million more years for as long as a thing called language still exists.

Mean while, the greatest discovery in physics, the Newton Classical Mechanics, lasted no more than three hundred years before it was replaced by Quantum Mechanics. Do you think QM will out live the longevity of classical mechanics? One would reasonably believe that in another 50 or 100 years it will be replaced by something better. If my developing GUITAR theory can be completed in the next few years then there may be just 20 more years lifetime for QM befoe it is replaced.

Quantoken

4. Es gab zwei weltstürzende Angriffe gegen das Göttliche Existenzgefüge, die von deutschem Boden ausgingen. Der eine war Marx, der andere war Nietzsche. Beide waren zum Scheitern verurteilt. Doch beider Scheitern erbrachte ein Unmaß von Erkenntnis zum Status menschlicher Existenz im Kosmos.
Nach meiner Einschätzung sind uns die Moslems um Längen voraus in der Erkenntnis ihres Koran.
The World needs Islam!

5. A few additions to the list of eminent Danish scientists:

Ole Rømer (1644-1710) made the first (viable) calculation of the speed of light.

Inge Lehmann (1888-1993), seismologist; in 1930 she discovered the earth's solid core. If there had been a Nobel prize for the earth sciences she would surely have won it! The Lehman discontinuity is named after her. The American Geophysical Union awards the Inge Lehmann Medal in her honour. And no, her dates are no typo. She lived to the ripe old age of 105.

Valdemar Poulsen (1869-1942), inventor of magnetic recording of sound and other information. In essence every tape recorder, floppy or hard disk is based on his invention. Poulsen also invented the arc transmitter, a milestone in the history of radio.

Aage Bohr, like his father Niels, a Nobel laureate in physics.

Nicolas Steno (in Danish: Niels Steensen or Niels Stensen; latinized to Nicolaus Stenonis), anatomist and geologist. He pretty much founded the science of geology.

So far Denmark has produced six Nobel laureates in medicine: Jens C. Skou, Niels Finsen, Johannes Fibiger, Henrik Dam, Niels K. Jerne, and August Krogh; the latter is one of the greatest physiologists of all time.

A few internationally renowned Danish mathematicians:

Erasmus Bartholin (1625-1698).
Hans Frederick Blichfeldt (1873-1945).
Harald Bohr (1887-1951; brother of Niels Bohr).
Thomas Clausen (1801-1885).
Agner Erlang (1878-1929).
Jørgen Pedersen Gram (1850-1916).
Poul Heegaard (1871-1948).
Johan Ludwig William Valdemar Jensen (1859-1925).
Sophus Christian Juel (1855-1935).
Georg Mohr (1640-1697).
Niels Nielsen (1865-1931).
Jakob Nielsen (1890-1959).
Julius Peter Christian Petersen (1839-1910).
Thorvald Nicolai Thiele (1838-1910).
Ernst Witt (1911-1991).
Hieronymous Georg Zeuthen (1839-1920).
For these mathematicians see http://www-history.mcs.st-andrews.ac.uk/~history/Countries/Denmark.html .

And while we are at it...

Christian Jürgensen Thomsen (1788-1865), Danish archaeologist. When Jürgensen Thomsen entered the field, the study of prehistory was hopelessly confused; he divided prehistory into the three now well-known epochs: Stone Age, Bronze Age, and Iron Age.

Danes have also made significant contributions to linguistics. The great names include Louis Hjelmslev (1899-1955), Otto Jespersen (1866-1943), Karl Verner, and in particular Rasmus Rask (1787-1832); the latter is one of the founders of indo-european comparative philology.

Finally, programming is, if anything, a Danish enterprise:

Peter Naur (of 'Backus-Naur' fame) created the Algol 60 language.

Per Brinch Hansen created the Concurrent Pascal language.

Jakob Nielsen is the world's leading usability expert.

Rasmus Lerdorf created PHP, the most widely used scripting language for web pages.

Anders Hejlsberg created the Turbo Pascal programming language.

Anders Hejlsberg (!) created or masterminded the Delphi programming language/environment.

Anders Hejlsberg (!) created or masterminded Microsoft's C# programming language.

Bjarne Stroustrup created C++, the language in which Windows is written.

Not a bad record when you think about it: PHP, Turbo Pascal, Delphi, C#, and C++.