Glenn McDavid

Alessandra Celletti and Ettore Perozzi, Celestial Mechanics: The Waltz of the Planets. This is a semi-popular look at one of my old and persistent interests. Very little math, but a lot of graphs and terminology. It includes the traditional subjects, e.g. tidal forces, the discovery of Neptune, Delaunay's lunar theory, and the stability of the solar system. but the emphasis is on modern developments, e.g.

• Modern dynamical systems theory and chaotic motion.
• Trojan satellites and Lagrange Points--L1 can actually be useful, even though it is unstable.
• Artificial satellites and space travel, including Hohmann transfer orbits.
• Planetary ring systems.
• The Kuiper belt, the outer solar system, and the demotion of Pluto from planetary status (correct, IMHO).
• Planets around other stars.

A unifying theme is the importance of resonant orbits. For example, Neptune makes three orbits around the Sun in about the same number of years as Pluto makes two. This is not a coincidence.

Recommended for those with some general knowledge of astronomy.

From the Daily Mail: Family holidays ruined by earliest Easter in 90 years

God Plays Dice refers to this column, introducing a nice discussion of how the date of Easter is calculated. At the end of it she refers back to it, commenting

And I have no sympathy for the people quoted in that article. They've known this was coming since 1752, when the UK changed over to the Gregorian calendar.

Via Slashdot

Via John Baez.

Mythbustin’ the Moon Hoax…

From The Astrological Magazine

We regret to announce that due to unforeseen circumstances beyond our control, the publication of The Astrological Magazine will cease with the December 2007 issue.

(Emphasis mine). Via Bad Astronomy.

Huge Hole Found in the Universe. Via Slashdot.

( picture behind cut )

From "Kevin & Kell" via Bad Astronomy.

Eris is more massive than Pluto. After being reclassified from planet to "Kuiper Belt Object", Astronomers have now determined that Pluto is not even the largest such object. Eris, being heavier and further away from the Sun, has the bragging rights, at least for now.

Looking at it the other way, if you insist that Pluto really is a planet, you now have to admit that Eris is as well.

Why is the Past Different from the Future?

Cosmologists Predict A Static Universe In 3 Trillion Years

"When Dutch astronomer Willem de Sitter proposed a static model of the universe in the early 1900s, he was some 3 trillion years ahead of his time."

Via Slashdot.

The de Sitter universe was one of the first cosmological models devised using General Relativity, and is widely discussed in Gen Rel textbooks--I have several in the basement. Nice to see the classics are still relevant :-)>

6000 years of Republican debates. Is there anybody around who can channel H.L. Mencken???

HUGE NEWS: first possibly Earthlike extrasolar planet found!

See 1300 black holes

Blast of Giant Atom Created Our Universe, from the December, 1932 issue of Popular Science. From the (2007) introduction:

This is a pretty amazing article. It’s a concise summary of the big bang theory published only 3 years after Edwin Hubble made his famous observations about the redshifts of distant galaxies. Yet it’s pretty much identical to one you’d see today. Only a few details like the size of the initial “atom” and the age of the universe seem off. Keep in mind it took another 35 years or so before the scientific community came to accept that the big bang really happened.

Found via a post at Cosmic Variance, which emphasizes the work of Father Georges-Henri Lemaître, and concludes

Lemaître passed away in 1966, a year after Penzias and Wilson detected the microwave radiation leftover from the Primeval Atom.

I.e, Lemaître lived long enough to see his work confirmed by observation.

More on geocentrism linked to a note at Talking Points Memo. There Joshua Micah Marshall laments that Molly Ivins is no longer around to write about the story. Personally, I would like to see H.L. Mencken's comments.

From Cosmic Variance

The spheroidal distribution of stars in the centers of rotating disk galaxies is called the “bulge”. Now, introduce a bunch of bored and horny 19 year olds into the mix, and you have a dangerous cocktail. One of my colleagues lost complete control of a 250 person lecture class when she had two male students hold up pictures of different galaxies, while she expounded on how “This guy over here has a small bulge, but the bulge of this guy is quite prominent.” The titters started as she forged ahead unknowing, until the entire class collapsed in hysterics. At that point, you just have to put down your laser pointer, send the class home, and head for the bar. Learning is over.

This reminded me of how my classes in quantum mechanics taught me about the mathematics of bras.

See Approaching the Sun.

Paint the Moon via Bad Astronomy.

From Neo-con twist on Xena Eris:( Read more... )