Friday, January 13, 2012

Cosmic simulations and bad history

Brian Hayes writes A Box of Universe in the current American Scientist, and gives a good explanation of large-scale cosmological simulations.
A History of the History of the Universe
Our view of the universe — and of our own place in it — was famously upset by the Copernican revolution of the 16th century. But the past 100 years have seen even more radical upheavals in cosmology. ...

Edwin P. Hubble, examining the spectra of galaxies, ... Hubble showed that their velocity is proportional to their distance. The whole universe is expanding. ...

Bruno’s Legacy
Four hundred years ago, the idea that the Earth goes around the Sun rather than vice versa was not just a scientific breakthrough but also a cultural bombshell. People were asked to reimagine the world they were living in. Not everyone welcomed the opportunity. Books were burned. In the case of Giordano Bruno, an author was burned.

In the modern world, cosmological revolutions seem to cause hardly a ripple in public consciousness. Inflation, dark matter, dark energy — these ideas also call for a reimagining of the world we live in, but they have provoked very little fuss outside the community of science. It’s certainly a relief that no one will be burned at the stake over matters of cosmological doctrine. But are we really more liberal and open-minded, or just not paying attention?
His history is bad. No books or cosmologists were burned. Giordano Bruno was burned by the Romans in 1600 for denying the divinity of Jesus Christ. The Catholic Church never censored a scientific publication. The expansion was discovered by Lemaitre, not Hubble.

The modern equivalent of the Galileo Affair is when a scientist submits an article with a conclusion that is not justified by the data and reasoning in the article. That happens every day, of course, and the journal editor either rejects the article or makes the author revise his conclusions. Galileo only got into trouble when he stubbornly refused to restrict his conclusions to what could be justified from his evidence.

I don't know why public consciousness should care so much about inflation, dark matter, and dark energy. Inflation has not been verified. Dark matter makes the spiral galaxies look prettier, and that's about all. Dark energy is mainly surprising because physicists have been telling us for a century that there was no aether.

Saying that baryonic matter is only 5% of the universe is supposed to impress us, but we have always heard stories like that. It is like saying stars are only 10% of the baryonic matter, or that Sun-like stars are only 5% of the stars, or that planets are only 5% of the solar system, or that rocky planets are only 5% of the planets, or that the Earth's crust is only 5% of the Earth, or that people live on only 5% of the land on Earth, or that we only use 5% of our brains, etc.

Hayes has written a lot of good articles, but he has fallen for some overly dramatic historical myths.

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