Thursday, November 01, 2007

Alfred Wegener: 127th birthday

Today, Robert Laughlin celebrates his 57th birthday. Congratulations.

However, we want to talk about a guy who was born 127 years ago, Alfred Wegener. Trained as an astronomer and getting mature as a famous meteorologist, he became the most important geologist of the 20th century.

Yes, Alfred Wegener is the father of continental drift. His discovery has been humiliated for decades even though every other child must surely be able to re-discover the theory. Why did so many people oppose him so frantically?

Well, some of them just found it impossible for continents to move. Continents are big and physics based on intuition makes any motion of such large solid objects extremely hard. However, most people humiliated Wegener mainly because pretty much everyone else, especially in America, was doing the same thing. And let's admit it: the American geologists before the pre-war and post-war continental brain drift were just not too good. ;-)

Evidence

It may look hard for continents to move but a scientist must avoid too fast conclusions here. The continents are big but the forces that act or may act on them are probably big, too, and there is a lot of time when the drift could occur. There was never any solid no-go theorem and Wegener had a lot of evidence that they had to move. For example,

• the shapes of continents fit together
• mountain ranges seemed to be lined up, too
• coal fields in Europe and America matched
• the same fossils of reptiles were found in places that should have been close in the past
• several climate anomalies: coal deposits in Antarctica, glacial deposits in South Africa, dinosaurs in Australia seemingly adapted to much colder weather

Figure 1: Lystrosaurus, of dog's size, was found at all continents as a fossil. This model is real, thanks to the CEO of the Jurassic Park. ;-) Mesosaurus was another example: it was found exactly in Southern Africa and eastern South America.

I do think that the evidence Wegener offered was so powerful and diverse that it was extremely unreasonable to think that they were just a collection of coincidences. See Wegener's book, The Origin of Continents and Oceans: it is not trivial to find too many dramatic problems with it. And what about the mechanism? Well, it had to be true that the continents had to be flowing or "plowing" through the crust in some way: the material beneath the continents had to behave as a kind of liquid.

The only task was to determine the forces and other details. The only indisputable major error that Wegener made was to assume, at least at some point, that the motion was due to centrifugal force. However, Wegener understood in the 1920s that shallower oceans were geologically younger. I think he would instantly understand seafloor spreading if someone told him about this concept - he could have also found it theoretically if he were a supergenius - but he didn't have enough time. He died in 1930, thirty years before his theory became acceptable for his slower colleagues.

I would say that the very invention of a new term, plate tectonics, in the 1960s was a method for the "mainstream" geologists to hide their gigantic blunder and pretend that the new science is something different than what Wegener taught us. The term "theory of continental drift" should have been used for plate tectonics instead.

Supercontinents

The present description of the history of supercontinents and other ancient continents may have some errors in it but it is fascinating anyway.

Vaalbara may have been created 3.1 gigayears ago by merging previous smaller, unknown continents. This oldest known supercontinent may have existed for 0.3 gigayears. Another supercontinent, Kenorland, was formed 2.7 gigayears ago. About 0.2 gigayears later, it broke to Laurentia (today: U.S. and Canadian Northeast), Baltica (today: Northwestern Eurasia), Australia (Yilgarn craton covers present Western Australia), and Kalahari (today: Southern Africa).

Columbia existed between 1.8 and 1.5 gigayears ago and this continent included Laurentia, Baltica, Ukraine, Amazonia, Australia, and perhaps Siberia, North China, and Kalahari. Quite a cool geography. ;-)

"Recent" era

The last gigayear may be a bit more familiar. Rodinia (from Slavic "rodina" which means "family" in Czech but "motherland" in Russian) broke 750 megayears ago. The components were reunified in a different way in the Paleozoic era, between 542 and 251 megayears ago, but we no longer call them Rodinia. They became Pangaea, the most famous supercontinent.

Figure 2: Pangaea

Our present continents are drawn on it. Pangaea broke to Laurasia (present NATO sphere of influence) and Gondwana (the poor ancient supercontinent) with the Saharan Sea in it:

Figure 3: Pangaea splits up

If you have a special weakness for the recent evolution, look at this animation showing how Pangaea split. Notice that Saudi Arabia has only recently become close to Iraq. ;-) The Tethys Sea in between them became the dry headquarters of OPEC. :-) I don't have a consistent story but I suppose that the existence of oil in this "squeezed" region is no coincidence.

Analogously, India drifted from Madagascar before it collided with Asia. You may also see a lot of reconstructions in various eras, including the future supercontinents, on the linked website. In 50 megayears, Mexican California will move to Alaska, Chinese wing of Asia will approach Australia, the Mediterranean will squeeze and dry up. The Eurasiafrica will keep on turning clockwise and North America will eventually sit into Africa where South America was earlier. Unless Amasia is formed so that the Pacific Ocean diminishes for the first time, the U.N. will unify the world again into Pangaea Ultima in 250 megayears or so. ;-)

Lessons

One obvious lesson is that consensus doesn't mean anything in science. Another, more technical but still general lesson is that whenever we observe some patterns that include far too many arbitrary choices, we should always ask whether this complexity has been evolving. Things change, even without any intervention from us humans. ;-) Wegener's wisdom about continents was very analogous to Darwin's wisdom about evolving species that was formulated half a century earlier. Nevertheless, it was still hard for most people to swallow. Are we doing a similar error in another discipline today?

Well, it is probably obvious where I am going. The convoluted properties of the particle spectrum we observe may also be a result of some historical evolution, as eternal inflation combined with the landscape may suggest. But it doesn't have to be so. And even if it is so, the mathematics that controls such an evolution might be much more unique and calculable than its genetic and continental counterparts.

And that's the memo.