Friday, June 05, 2009


Here is a recent APOD (Astronomy Picture of the Day), an image of the Sun made with the orbiting SOHO (Solar and Heliospheric Observatory) in September 1999, showing a huge solar prominence, a mass of twisted plasma arching high above the solar limb. These violent storms can hurl winds of charged particles into space, disrupting terrestrial communications and causing spectacular auroras. Click to enlarge.

To the image I have added a black dot representing the size of the Earth on the same scale. There it is, nestled minutely in the center of this great firestorm.

Yes, that black dot is the Earth, our magnificent planet, in all of its natural wonder, with nearly seven billion of us seeking love, and security, and purpose, and meaning -- lost, dwarfed, in this local manifestation of cosmic violence.

More than two thousand years ago, Aristarchus devised a clever way to measure the sizes and distances of the Sun and Moon, and told his contemporaries that the Sun was six or seven times bigger than the Earth (I tell how he did it in Walking Zero). Apparently, only a handful of Aristarchus's' contemporaries had the technical know-how to appreciate his method or the imagination to embrace his result. Aristarchus was a skilled mathematician and a careful observer, but his true greatness lies in his willingness to accept what was so counterintuitive to "common sense."

We now know that Aristarchus's method was correct, but he lacked the technical ability to make one crucial quantitative observation with sufficient accuracy. The Sun is not six or seven times bigger than the Earth; it is more than one hundred times bigger! Perhaps it is just as well he didn't get it right. Would even Aristarchus have had the courage to accept what we now know to be true?

Look at the image above again, with that tiny black dot. Even today, how many of us are psychologically prepared to live in a universe of such arching grandeur? There was a time when cosmology reinforced our sense of cosmic centrality. How do we reconcile the scale of the cosmos as we now understand it with our sense of being central and important in the lesser circle of our daily lives?