Saturday, December 03, 2005

Into the blue

Joel -- who you will know from Comments -- reports seeing Venus with the unaided eye in broad daylight from San Antonio, at 2:30 in the afternoon on December 1. This is no mean feat.

He had a couple of things in his favor. He lives further south than most of us here in the States, and therefore Venus was higher in his sky. And right now Venus is as bright as it ever gets, about magnitude - 4.7. A waning, growing crescent.

To pull this off, you'd need a perfectly clear sky and know exactly where to look. Getting your eyes to focus at infinity can be a problem; try looking at the horizon first, then up into the sky. It can also help to dilate your pupils. And so on.

But why, Joel, why? What's the point? Why all that trouble to see a dot of light against the blue?

Well, we both know the answer to that, but I suppose it isn't easy to explain. It's not just the dot of light. It's making ourselves part of the intricate machinery of the world. It's having the solar system turning in our brain, as a kind of mental orrery. It means knowing why that dot of light is where it is, and as bright as it is, and why a whole universe of celestial objects is there swimming in the blue.

And, by the way, this evening offers a chance to see a very young crescent Moon, about 56 hours old and eyelash thin, perhaps the youngest Moon you have ever seen (anything younger than 30 hours is an achievement). Just as the sky gets dark, low in the southwest, to the lower right of Venus (about a fist-width at arm's length). Not the best time of the year for young Moon spotting, but doable. Venus will be easy to spot in the gathering dusk. Don't wait too long or the Moon will have set.

Tomorrow evening, ABSOLUTELY NOT TO BE MISSED, a lovely crescent Moon will join Venus in the twilight sky. As the sky gets dark, look for Earthshine on the part of the Moon not lit by sunlight.

Way to go, Joel!