Our neighbourhood as a system

Long ago the present writer as a child paid a visit to the Dominion Astrophysical Observatory on its mountaintop site near Victoria, British Columbia. I remember my overwhelming first impression as if it had occurred only a week ago: the silver-painted dome rising among dark fir trees, the cold cavernous interior and the towering framework of the 72-inch (183-cm) telescope directed upward toward a ribbon of starry sky glimpsed between shutters overhead. In the huge silent dome that opened onto a silent Universe I discovered the mystique of a great observatory.

Yet that evening's greatest revelation came by way of a simple graphic display on a wall in the observatory's foyer. It was a comparative view of our solar system's principal members, very similar to the drawing presented here in Figure 2.1. I stood for half an hour in front of the little backlighted panel of glass on which it was painted, stunned by my first realization of our Earth's minuscule size relative to its parent body the Sun, and by my discovery that our local system included planets as gigantic as Saturn or Jupiter, and as tiny as little Ceres.

That evening's visit spawned a frenzy of telescope building and nightly planetary observation. Very soon I knew the experience of viewing the shimmering, banded disc of giant Jupiter through lenses that I had assembled in a cardboard tube.