The shortest day of the year is known as the winter solstice, and it falls on (or very close to) December 21. (For those in the southern hemisphere, the shortest day comes on or near June 21.)

But anyone who keeps a close eye on the time at which the sun rises and sets will notice something a bit perplexing: Neither the earliest sunset nor the latest sunrise falls on the day of the winter solstice. In fact, the earliest sunset can fall more than a week before the solstice, and the latest sunrise can fall more than a week after the solstice.

What a year for science! And a good year to be a science journalist, too, as we marked not only the 150th anniversary of Darwin’s Origin of Species (along with Darwin’s own 200th birthday), but also the 400th anniversary of Galileo’s first use of the telescope. Although I’m a big fan of Darwin, astronomy and physics have long been my bread and butter, so it was Galileo who captured my attention through much of 2009. This spring I toured through Galileo’s Italy, and paid a visit to a world-class observatory on an Arizona mountaintop.

This entry – the first in my “Quarks to Quasars” blog – is adapted from an essay I originally wrote for the website of Pages Books in Toronto earlier this month.