Those lucky enough to be in Indonesia this past week, or to have visited there last week, were treated to a total solar eclipse. On the program was the eclipse itself (as seen through UV-protective glasses), the corona of the Sun (which looks a bit like a lion’s mane), and even the ‘diamond ring’ effect near the close of this spectacular event.
A solar eclipse is caused by the physical obstruction of the Sun by the Moon. While the Moon passes very close to the Sun every new Moon, eclipses do not happen every new moon. This is because the Moon is not orbiting exactly in the same plane as the Earth. Instead, there is an offset of about 5 degrees, which amounts to separation that is just large enough for the Moon to clear the path of the Sun on most months.
What is perhaps even more interesting is that the angular size that the Moon subtends on the sky is more or less equal to the angular size of the disk of the Sun. If the Moon were just a bit farther away then it would appear smaller to us on the sky and would not obstruct the whole disk. In turn, if the Moon were closer its apparent size would be larger than it is at present. In this case it would cover up the entire disk plus the corona.
The origin of the Moon is still a much debated topic. We do know the Moon started out closer to the Earth than it is now, and is slowly moving away from the Earth over time, all to conserve angular momentum. This universal principle says that the mass times the velocity times the distance is conserved in any system. What does this mean?
It means that millions of years ago neither the corona nor diamond ring effect could be seen. Likewise, far into the future the amplitude of the solar eclipses will go down, making them a less dramatic spectacle than they are today. We are living in an interesting time! Has anyone out there in our extensive worldwide readership seen this most recent solar eclipse? Has anyone out there seen any solar eclipse? It would be great to compile your stories.
