Monday, 17 July 2017

Eclipse 2017 - the big one!

I was talking with a reporter who asked how I felt about the "big eclipse" coming in August. I had to snicker. It isn't a big one. Let me explain.

Just how Big?

In terms of "big eclipses", the August eclipse isn't all that big. Eclipses are measured in time. The time that the Sun is completely blocked by the Moon is called totality and we measure the duration of totality.

From the perspective of duration the August 2017 will not be a particularly long eclipse. The maximum duration does not even crack three minutes. Eclipses can last up to seven minutes (for ground observers) so this one does not even make it to the middle of the scale. It is below average.

I suppose another way to measure eclipses is how many people may get a chance to see it. From that perspective, the August 2017 eclipse ranks up near the top. A lot of people could potentially see it, many with a relatively easy drive (under normal circumstances) to the central path.

In comparison, the eclipse of July 2009 was a really big one. Not only was that eclipse a long one in terms of duration (longest in the 21st century) it crossed heavily populated areas like Shanghai in China. The eclipse path started in India (also a highly populated place) before crossing the mountains into China and then out to the ocean.

An American Eclipse

This eclipse is unique in one big aspect. It crosses the lower continental USA and no other countries. That is a lot of land mass (an entire continental width) to cover and still only be one country. Of course, that is partly because the USA is a big country.

The USA has 50 states,  two of which are not directly connected (Alaska and Hawaii). The other 48 states are sometimes called the lower 48. They make up the familiar shape of the USA. This eclipse crosses the lower 48.

There has not been an eclipse path in the lower 48 since 1979. That makes it a big thing, especially if you are American. Hawaii did get to see a total, a rather long one at that, in 1991. By comparison that is a small population and land fall amount compared to the August 2017 eclipse. Still, that has been a long wait for many.

For people who reside outside the USA, this eclipse is a bit of a hassle. Especially if you come from countries under travel restriction or quotas. The USA is not always an easy place to visit for some. Visa application fees expensive (about $160 each time you apply) and he process can be difficult. An embassy visit might be required and so forth. Thus the "Big One" is not as attractive for some eclipse chasers that live outside the country.

Solar Minimum

The August 2017 eclipse is occurring at solar minimum. That means that the Sun has fewer sunspots than at Solar Maximum. Sunspots are storms or disturbances on the surface of the Sun. During a total solar eclipse they are seen along the edge in the form of prominences. Plus they can cause interesting shapes and twists in the solar corona.
1983 Corona shape near sunspot minimum - Bill Kramer
1991 Corona shape near sunspot maximum - Bill Kramer

Is solar minimum a bad thing for solar eclipses? No, it just means that the corona might not be as bright and rounded. In fact, the shape of the corona will most likely be quite interesting with short polar brushes and coronal wings extended out along the equatorial directions. The eclipse in 1983 (see image above) was nearer to minimum and it appeared as a butterfly in the sky. For comparison a very active corona can be seen in the 1991 eclipse. Eclipses at solar minimum often exhibit very complex coronas so it will be interesting to see what we get.

For a preview of the coronal shape, see the SOHO web site.

So it will NOT be big and great?

It is going to be great, don't get me wrong. All eclipses are great. It just won't be a particularly long eclipse. And there will be a big audience to see it. It is summer time and the chances of good weather along the path are quite high.

Trust me, it will be Great! It will be Big! You are gonna love it!


However I tend to think of this eclipse as the "Easy One". Since I am America I have no travel issues other than getting to the central path and finding a hotel. We booked a hotel quite a while ago that would be easy to reach for us and family and friends. That was easy. There were a lot of choices. By getting a hotel in advance we avoided the increased costs others are finding as they look now, nearer to the big event. So not only was it easy, we got a good discount by booking a block of rooms for our friends and family. This one was relatively cheap.

It was not like trying to find a hotel or lodge in the middle of some jungle or out in the ocean. No exotic transportation is needed, we can drive a car. This one is EASY! That makes it a Great American Eclipse indeed!

Now then, as to the name "The Big Eclipse" - it is a book for kids. A well done book at that! Check it out at https://www.amazon.com/Big-Eclipse-Nancy-Coffelt/dp/1945170859




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