A solar eclipse happens when the moon, as it orbits Earth, passes directly in front of the sun, obscuring its rays and casting a shadow on Earth's surface. Sometimes referred to as a "happy accident of nature," a total solar eclipse occurs when the moon is perfectly aligned with both the sun and Earth, so it appears from our perspective that the sun is completely blocked.
The total solar eclipse became visible in the far north of Australia about an hour after sunrise local time on November 14 (afternoon of November 13 in the United States and evening of November 13 in Europe).
A total eclipse of the sun can only be seen from within what's known as the path of totality, a narrow path the moon's inner shadow travels as it glides across the Earth. The most populated areas within that path are in the Cairns and Great Barrier Reef region.
It estimated to take about three hours for the moon's shadow to travel the entire path of totality. What time total darkness occurred, and how long it lasted, depended on location. Totality was expected to begin in Cairns at 0638 local time and was to last nearly two minutes. By contrast, totality was estimated to only last just about 20 seconds in the small town of Innisfail.
According to NASA, a full solar eclipse happens, on average, every 18 months. The last one happened in July 2010, crossing Chile's Easter Island, and one will occur over equatorial Africa in November 2014. But for any given region, a total solar eclipse only happens, on average, once every 375 years.
Solar eclipses were shrouded in superstition in ancient times -- in China, for example, viewing total solar eclipses was important for divining the future success of an emperor. However, as scientific knowledge deepened, these events became opportunities for conducting important experiments. It was during a total solar eclipse in 1919 that Einstein's theory of general relativity was tested and confirmed for the first time.
A solar eclipse is often described as one of nature's most awe-inspiring events. Some people are so moved by the experience of watching an eclipse that they travel around the world chasing them.
About an hour leading up to totality, all sorts of things begin to happen. There are changes in the color of the sky, the temperature drops, birds and animals behave in a peculiar manner and shadows sharpen, according to Rick Brown, an eclipse chaser from New York who is viewing his 14th total solar eclipse. "I never really expected to be moved the way I was. It's a phenomenal thing to see," he said, recalling his first experience.
As the moon's shadow sweeps across the Earth, the sun turns into a crescent in the sky. Just before totality, so-called Baily's beads - bright spots of sunlight shining through the moon's craggy surface - can appear around the moon. Then the moon completely blots out the sun, leaving only a halo of light visible. After the brief period of darkness, Baily's beads might appear again as the sun comes back into view.