Yep, looks like he's gone off walkabout again.

No posts for 30 days.

I've finally got around to replacing Haloscan's commenting system with one of my own. Currently it's still pretty basic and doesn't allow HTML yet but it appends the comments to the end of the post instead of popping up one of those tedious little windows.

The motivation for making this change has been the need to implement a generic annotation system for a number of applications. Some of them you'll be seeing shortly.

OK, I'm back. Lot's to talk about, not enough time. So let me bulletpoint you.

• Tim May blogs up a storm in the comments section of this post about the Titan landing. He also points to this helpful summary.
• Speaking of comments, Laputan Logic got its first comment spam. Time to write a new commenting system methinks.
• My Nahkla Dog article "A Dog's Life" now graces the pages of the nakhladogmeteorites.com website - with permission as part of a high-powered digital rights licensing deal.
  
• Still tinkering with the format. Finding columns a bit too constraining.
• Had lot's of fun playing around with Javascript on the notebook computer. Will have something to show for it eventually.
  
• Eating masala thosai is like kissing the face of God - better actually.
• Old news but popular brand "Darkie" toothpaste is now called "Darlie" toothpaste. Cover picture of a smiling negro inverted and now somewhat racially ambiguous. Still in killer peppermint.
  
• Actually stood on a tsunami beach. Not a lot to report beyond that simple fact. Didn't swim.
  
• The true legacy of 911? The plastic steak knife.
• What stands between Malaysia and total food nirvana? Chicken "ham" and beef "salami".
  
• Move over Chicxulub. It wasn't some meteorite that killed the dinosaurs. It was us mammals - we ate their babies.
  

The other side of the argument which says that all these hominim skeletons found so far, including those of the Neanderthals and Homo floresiensis may all, in fact, be examples of one species - our own.

Tandem repeats anyone?

Yes, it's official. Jesus of Nazareth was in reality a German backpacker on an overland trip to India who accidentally got mixed up in local politics. This we can infer from the face reconstructed from the Shroud of Turin by an Italian forensic police unit. This should come as a warning to all parents who worry about letting their kids have passports.

Indonesia 80,428
Sri Lanka 28,627
India 12,709
Thailand 4,800
East Africa 137
Maldives 67
Malaysia 66
Burma 53
Bangladesh 2

Total 126,889

Also here's an interesting article from 1999 about tsunamis in which I learn amongst other things that Katsushika Hokusai never intended his Great Wave image to represent a tsunami. In fact tsunamis do not even disturb the surface until they reach the shore, instead being transmitted through the entire depth of the ocean. Fleets of fishermen have been known to sail right over them without noticing, only to discover on returning to port that homes and families have been swept away.

A survivor who works as a masseuse on a beach in Penang looked up and saw the wave. He wasn't certain what it was he was looking at but his customer, a Japanese tourist looked up and shouted "Tsunami! Run! Run for your life!"
The Malay language now has a new word. Well, not really, of course the word has been part of the international lexicon for many years but, at least with regard to the Malay peninsula, nobody had an actual use for it until now.

The LA Times is currently running the best popular account of the Pioneer Anomaly that I have read so far.

The Anomaly refers to a strange force which is apparently being experienced by the three-decade-old Pioneer space-probes which has been causing them to slow down in a way contrary to what would be predicted by Newton's theory of gravitation (or Einstein's modification).

Five hundred years older than the Great Pyramids of Giza and a thousand years older that Stone Henge, the passage tomb of Newgrange in Ireland is the oldest roofed structure in the world.

It's purpose was to act as a gnomon to mark the Northern winter solstice, the shortest day of the year. At dawn on that day every year (either December 21st or 22nd), the sun rises from its most Southern point and shines directly onto the dazzling white quartz outer wall of Newgrange asd well as passing through a hole and illuminating its inner chamber. The construction of Newgrange was a remarkable feat of engineering demonstrating an advanced knowledge of astronomy and geometry on the part of its Neolithic builders.

Okay, I did kind of imply that I would still be posting from time to time.

The Planetary Society has a great article up on its site about the current state of knowledge about Titan and what it means for the Huygens space probe descent into its atmosphere. I thought this method of ascertaining the structure of Titan's atmospher by looking at star light shining though it was rather neat.

But the most important result to come out of the second Titan encounter was the result of two occultation experiments performed by the UVIS team. An occultation experiment involves staring at a bright light source -- in this case, the bright stars Spica and Shaula -- and watching how the intensity of their light varies as they appear to cross behind a semitransparent target. Occultation experiments will be performed throughout the mission on the atmospheres of Titan and Saturn, as well as on Saturn's rings. UVIS is sensitive to ultraviolet wavelengths, so it probes the uppermost atmosphere, the region in which Huygens will be relying upon the friction between her heat shield and the atmosphere to brake.

Once the data came down from the spacecraft on Monday afternoon, Pacific time, the UVIS team worked around the clock in order to analyze what the flashes of light from Spica and Shaula meant for the vertical structure of the atmosphere. Early Thursday morning was a critical event for the Huygens mission, a "GO / NO-GO" meeting for the Probe Targeting Maneuver, a burst of Cassini's engines that will set the spacecraft on a collision course for Titan. If the atmospheric models proved wrong, the mission would be forced to scuttle the plans for a January descent for Huygens.

Fortunately, the calculated values for the density of Titan's atmosphere -- the most critical number -- came "within three percent of predictions," reported UVIS Principal Investigator Larry Esposito. Because of the near-perfect match between predictions and observations, "We got the green light to proceed for the next step," said Jean-Pierre Lebreton, Project Scientist for Huygens. "The UVIS team did a great job in analyzing the data within 24 hours. In a sense it's almost disappointing -- we did not have to change anything."

It seems as though the computer models have got Titan's atmosphere just about right so the big mystery reamins: Where are those big sloshing hydrocarbon oceans that should have been raining down on Titan's surface? Something definitely has been raining down because Titan appears to be geologically new but currently there is no sign of anything actually wet down there.

It's showing, I'm sure. It's been a little more than just a slow news week around here, frankly I'm running out of steam. Time to take one of those breaks again. I'm off to Malaysia and, although I'll be taking a laptop with me, blogging is likely to be very light indeed.

It might even end up being totally non-existent.

Apologies to my new friends who have just discovered this blog and allow me to allay the fears of longer term readers (who will tell you that I'm a bit prone to disappear for months on end), blogging will be back to normal in a month or so.

An event of note that will be missed by this blog, unfortunately, will be the Huygens space probe descent. Alas, I'll be way too busy eating roti and curry to worry much about it so I'm relying on you to keep an eye on that one.

Finally, in the spirit of the season, I hope you all have good one and, while I have you're all gathered and cozy around the warmth of the barbecue, let me leave you with this heart-warming tale about the true meaning of Christmas.

Purebred bull terrier snouts have changed dramatically over a short period. Photo shows specimens from 1931, 1950 and 1976 (by Fondon and M. Nussbaumer).

One problem with our current understanding about how evolution works is that the main mechanism we think of when it comes to genetic modification, the single-point mutation, is a comparatively rare and generally detrimental event. The changing of a single nucleotide only occurs at a rate of 1 in a 100 million nucleotides per generation so it is hard to see how species depending solely on this mechanism would be able to adapt very quickly to changes in their environments. And yet, as the fossil record demonstrates, new species emerge and diversify quite rapidly in geological terms and for species to be able adapt and evolve as quickly as they clearly do, other mechanisms for genetic modification must also be in play.

One such mechanism which has been suggested but only recently shown to be significant, at least in land animals, is a DNA copying error which causes tandem repeats. The term tandem repeat refers to a region of DNA which repeats a sequence over and over again. The repeat sequence might be a simple alternation of two nucleotides or it could be a pattern of dozens or even thousands of nucleotides repeated over and over. These mutations occur at a rate 100,000 times more frequently than single-point mutations do but, unlike the latter, their effect are generally be quite subtle and normally not detrimental the organism. Single-point mutations, on the other hand, are usually either neutral or fatal and only a tiny number of these mutations bestow any benefit at all on the organism.

Tandem repeats in DNA have recently been identified as the main mutation type responsible for astonishing variety of shapes and sizes in domesticated dogs. This variation in dogs, ranging from Chihuahuas to Great Danes, has emerged very rapidly - in the space of a only a few thousand years. Dog breeding is an extreme case when viewed in evolutionary terms because even dogs with particularly unfavourable mutations can be kept alive by their owners and this enables their genotypes to vary quite considerably in ways that would not be possible in the wild. Consequently, domesticated dogs have much higher incidences of tandem repeats in the genes that affect their shape and size than wild dog strains. In other words - and this should come as no surprise - they have been bred to be highly adaptable to human whim and fancy. Wild dogs, on the other hand, have had to face much stricter selection for fitness and this has, presumably, kept this kind of variability in check and ensured morphological stability for long periods of time.

It's interesting to ponder one of the implications of a tandem repeat driven theory of evolution, that our genomes may be considerably more adaptable and in a state of flux to a greater extent than we have previously recognised.

OK, so I'm up to page 68 of Leonardo's Notebooks, only another 1497 to go.

Continuing on with the subject of the eye, vision and light, Leonardo in this note dated 1492, contrasts the notion that light falls upon the eye with another theory popular at the time that the eye projects rays outwards to the object that it is seeing:

It is impossible that the eye should project from itself, by visual rays, the visual virtue, since, as soon as it opens, that front portion [of the eye] which would give rise to this emanation would have to go forth to the object and this it could not do without time.

Naturally, one's mind turns, from time to time, to wonder about what actually happened to the lost tribes of Israel. Similarly, one can't help pondering the fate of the lost Viking colonies of Greenland and North America.

It has long been known that the Earth is hollow and that there are, in fact, enormous openings at each of the poles.