Monday, January 26, 2009

9.14 Galileo's eyes

(Galileo Galilei [1564-1642], circa 1630)

Well, it is only inevitable in this age of TV CSI shows: Scientists from both UK and Italy are now seeking the Vatican's approval to exhume Galileo's body, so that they can do some DNA analysis to figure out what had ailed Galileo's eyes.

This news has been widely reported, see for example, here and here. The scientists' interest is to explain why Galileo described Saturn as having "lateral ears" rather than rings around the planet. And the theory is that poor eyesight was behind the error.

Galileo's drawings of Saturn are shown on the left:

The one on top was sketched in 1610, and the bottom, 1616.

These "arms" were clarified by Dutch astronomer, Christiaan Huygens, in 1659, as a ring system. He was able to do so because of improved telescope optics. [Note: Huygens also discovered Saturn's moon, Titan, and for this reason, the probe exploring Titan is named after him. And a few years later, Jean-Dominique Cassini discovered 4 other major moons of Saturn: Iapetus, Rhea, Tethys, and Dione.]

So what was wrong with Galileo's eyes and vision? It was actually quite well-documented. According to this site, for example:

"Galileo’s sight began to deteriorate in the middle of 1636 when he was 68 years old, and by the end of June 1637 he had lost the use of his right eye while his left eye was affected by a constant discharge. He described seeing a 'luminous halo' around candle flames. To date there has been little speculation by modern optometrists or physicians about the possible causes of Galileo’s blindness. In July 1636 he wrote to his friend, an Italian lawyer living in France, Elia Diodati, 'I have been in bed for five weeks oppressed with weakness and other infirmities. Added to the (proh dolor!) the sight of my right eye - that eye whose labours (I have no hesitation in saying) have had such glorious results, is lost forever. That of the left, which was and is imperfect, is rendered null by a continual running’. He became totally blind early in December 1637, a few months after using the telescope to discover that the moon wobbles on its axis ('lunar libration') which was quite a remarkable observation to make with only one useful eye. At this point he wrote to Father Castelli noting that 'The noblest eye is darkened which nature ever made, an eye so privileged and so gifted with rare qualities that it may with truth be said to have seen more than the eyes of all those who are gone, and to have opened the eyes of all those who are to come'."

The keywords are shown in red. The symptom/sign suggests active keratitis [discharge] accompanied by corneal edema [halo]. And since both eyes eventually lost vision, it would imply a chronic retinal problem, perhaps posterior uveitis. The left eye was probably further complicated by band keratopathy in his last years. His 20X telescope was actually a low-vision device - at least by 1616, Galilio appeared to still have retained enough vision (at least 20/400) to allow somewhat accurate observation of Saturn's rings/arms.

What the proposed DNA analysis can prove? Probably not much. The project is expected to cost around £282,000, by the way.