By now many of you will have had the pleasure of witnessing first hand the great solar eclipse of August 21st. Here, outside the Springfield Museums, I was part of a crowd of several hundred who watched in awe as the Moon partially obscured the Sun. Whether you viewed a partial or total eclipse, no doubt the eerie experience is something that will stay with you for a long time. I remember, as a child, watching the eclipse of January, 1963 as it passed over Cape Town, my home town in South Africa, while my sister and I were having a swimming lesson. I can still see the color of the darkened pool water as the Sun disappeared.
If you think about it, though, from a scientific point of view, an eclipse is not really such a complicated event. As explained in a recent XKCD comic strip, “It’s a thing going in front of another thing,” or more specifically, the Moon passing in front of the Sun, casting a shadow on the Earth as it does so.
What’s really neat, however, is the strange coincidence that makes it possible for humans on Earth to view a total solar eclipse: The Sun is 400 times larger than the Moon, but it just happens to be 400 times farther away, which, to the observer on Earth, makes these two heavenly bodies appear almost exactly the same size. So if you are standing in the path of totality, you will experience the Moon totally blocking the Sun. Among all the billions of star systems in our galaxy, the chances of such perfect alignment are rare. However, it won’t always be this way here on Earth, as the Moon is gradually moving away from our home planet at about one and a half inches per year. Eventually, in a few hundred million years, there will be no more total eclipses visible from Earth.
While eclipse science is fairly straightforward, it has helped provide proof of a rather more complicated scientific concept. Einstein’s 1915 Theory of General Relativity held that gravity was not a force, as Newton had understood it, but rather the warping of space-time. The more mass a body has, the greater the distortion that occurs. Einstein therefore predicted that the trajectory of objects moving through space would be distorted by the gravity of any massive body they pass by. According to his theory, such distortion would apply to light rays too.
During the solar eclipse of May 1919, an experiment performed by British astronomer, Sir Arthur Eddington, proved him right. Eddington was able to show that during the eclipse, stars close to the Sun appeared to have changed their positions slightly. What had in fact happened was that the Sun’s gravity had distorted their light. Normally, when the Sun is shining, you can’t observe this effect because the stars, other than our Sun, are not visible in daylight. However, an eclipse provides a unique opportunity to see the light from stars pass close to the Sun without being obscured by its light. Eddington’s observations provided the first validation of Einstein’s theory, which has been similarly confirmed many times during subsequent eclipses.
There are many things we can learn from an eclipse, among them, how animals react to the unusual dip in sunlight, and how the power provided by solar panels drops as the Sun is obscured, and then surges immediately afterwards. And then there’s the experience itself, the pure wonder of the moment – nature at her finest.
Join the Springfield Stars Club on Tuesday, September 26th at 7:00pm at the Springfield Science Museum for a group discussion led by Stars Club president, Alan Rifkin, on “Reliving the Great American Eclipse.” Come and share your eclipse experience and learn more about these extraordinary events. Refreshments will be served, and the public is welcome. The meeting is free of charge for members, with a suggested donation of $2 per non-member.
Also, on Friday, October 6th at 7:30pm, the Stars Club and the Springfield Science Museum will host “Stars over Springfield,” an astronomy adventure for the whole family. Meteorite expert Peter Scherff will give a talk on meteorites, and will exhibit specimens from his vast collection. A fee of $3 for adults and $2 for children under 18 will be charged.
Copyright © Amanda Jermyn