Billions of fish in the Pacific Ocean will be treated to an awe-inspiring celestial event on July 2. That's because a total solar eclipse will be visible over a huge swath of the southern Pacific.
Land animals including humans in Chile and Argentina will also get to observe the total spectacle, as will anybody connected to the Internet. And most parts of South America will be able to see a partial eclipse.
A total solar eclipse occurs when the moon passes in front of the sun. In an amazing cosmic coincidence, even though the moon is 400 times smaller than the sun, it's also 400 times closer — so from Earth they appear to be the same size.
Astronomers treasure solar eclipses because it gives them an opportunity to study the solar corona, a layer of extremely hot gases extending out thousands of miles from the sun's surface. The corona is actually hotter than the sun's surface, something that remains a bit of a mystery.
Eclipses have also been important to physicists. In 1919, an astronomer named Arthur Stanley Eddington set out to test Albert Einstein's theory of general relativity. One of the predictions was that the sun's gravity could bend light from a star more than traditional theories of gravity predicted. Eddington helped organize two expeditions — to Sobral in Brazil and to the island of Príncipe off the coast of West Africa — to watch the total solar eclipse on May 29, 1919. Their measurements confirmed Einstein's theory was correct.
A team of astronomers from National Optical Astronomy Observatory in Arizona and students from the University of La Serena in Chile will attempt to repeat Eddington's observations. The eclipse will pass directly over the National Science Foundation's Cerro Tololo Inter-American Observatory located near La Serena.
By the way, there won't be solar eclipses in perpetuity. The moon's orbit is taking it slightly farther from the Earth each year. Very slightly. But in 600 million years, it will be appear too small to completely cover the sun.
Procrastinators, you are warned.