Tomorrow afternoon, you could have a front row seat to one of the most visually stunning of celestial events: a total solar eclipse. It’s happening over the southern Pacific Ocean and northern Australia, but no worries, mate: There are plenty of places you can watch it live online! It starts at 20:35 UTC (2:35 p.m. CST) on Tuesday.
Folks here on Earth are fortunate to be the benefactors of a cosmic roll of the dice : The Moon and Sun appear to be the same size in the sky. It really is a coincidence. As it happens, the Sun, at 1.4 million kilometers, is about 400 times the diameter of the Moon at 3470 km, but is also about 400 times farther away (It is 150 million km to the Sun and 380,000 km to the Moon). These two numbers very nearly cancel each other out, leaving the Sun and Moon nearly apparently equal in size.
Additionally, the Moon’s monthly orbital path sometimes brings it directly between the Earth and the Sun. When that happens, the Moon blocks the disk of the Sun, eclipsing it. It doesn’t happen every month because the Moon’s orbit is slightly tilted with respect to the Earth and Sun, so things have to line up just right. It generally happens about once a year or so somewhere on Earth.
In the case of tomorrow’s eclipse, Australia has the best seat in the house. Now, thanks to the Internet, so do you.
Time and Space
The dark blue line crossing Australia into the Pacific is the line of totality; the place where you see the entire disk of the Sun blocked. It starts on the left (west) side and sweeps eastward, to the right. The shadow will take about 3 hours to move across the Earth, but for any one location the eclipse lasts only a few minutes as the Moon’s shadow passes over. The biggest population center in the path is Cairns, Australia.
Tomorrow’s eclipse is mostly over the ocean, so very few people will be able to see it in person. But, thanks to the Internet, many sites are broadcasting the event live and you can watch it as if you were there.
You can find lists of live webcasts at UniverseToday.com. Some of the better views will be at the Cairns Eclipse 2012 UStream channel, and at SLOOH. I would be remiss if I didn’t point out that weather is critical here; if it’s cloudy then there won’t be much of a view. But you should tune in just in case.
You should take advantage of this opportunity while you can: The next total eclipse won’t happen for nearly a year. That one will be on November 3, 2013, over the Atlantic Ocean and equatorial Africa.