Solar eclipse envy
So Africa and parts of the Middle East were today treated to a total solar eclipse, where the moon lines up perfectly between the Earth and the Sun. Although total solar eclipses generally occur every 18 months or so, we’re in a bit of a dry season at the moment - the last eclipse was in 2003, and the next won’t be until 2008 - so you can bet that the true eclipse junkies would have been out in force.
Indeed, in Libya, normally a hard place for tourists to gain entry, special visas and permission to bring in telescopes were made widely avaiable, giving amateur and professional astronomers alike the chance to experience the eclipse under Libya’s clear and calm skies.
There’s only been one total eclipse in Australia recently, and that was Ceduna in South Australia a few years ago. As much as I would have liked to have gone, I didn’t really have anyone to go with and wasn’t comfortable going by myself. So, I missed out on my best chance for several years - not until 2012 does another eclipse come my way, although by my luck I’ll have moved somewhere else and still miss out!!! Hopefully, though I’ll make it eventually - it really sounds like one of the most breathtaking things.
Oh, and finally, I love this line from the ABC news story:
Eclipses should never be viewed without proper optical filters or glasses specially designed to filter out ultraviolet light, which is invisible to the human eye but can burn the retina even when the sun is covered.
Yes, that’s true up to a point - the UV light from the sun can burn your retina, possibly doing permanent damage. Even when only a sliver of the sun is visible it might be enough to do damage. The exact timing is unclear - the Straight Dope estimates up to 30 seconds of exposure might be safe, whereas Dr. Karl says anything more than a “brief glimpse” is going to blind you - even if 99% of the sun is covered. I find this hard to believe - I’ve looked at the sun before, the whole sun albeit briefly, and don’t seem to have suffered ill effects. Sure that’s not a proof, or even remotely scientific, but it seems a little extreme. (That said, don’t look at the sun. This is pure conjecture, not legal advice!)
In any case, a very important point (at least from the enjoyment perspective) is that when the sun is completely covered (as in, totality) it is completely safe. The sun is covered, that’s what totality means, and so the moon blocks all of the harmful light. Yes, there’s probably still some leaking around the edge, particularly if the eclipse is such that the moon appears slightly smaller than the sun rather than larger, but it’s not going to do any damage - it will be the weakest part of the UV emission anyway (think cross sections).
So if you ever get the opportunity to look at a solar eclipse, bring your pinhole projector or your special glasses, wait for totality, then enjoy the most amazing astronomical site. But as soon as that first crescent of light re-appears, cover up again! And if you can’t wait for or can’t reach a solar eclipse, there’s always a couple of lunar eclipses each year - there’s one coming to a location near you!