Get ready for a total solar eclipse of 2017

Translation of the post Get Ready for the Total Solar Eclipse of 2017 by Jeffrey Bryant, Research Programmer, Wolfram | Alpha Scientific Content.
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On August 21, 2017, an event will occur in some parts of the western hemisphere that has not been observed by most people before throughout their lives. A total eclipse of the Sun will cover the surface of the United States and nearby oceans. Although eclipses of this type are not uncommon around the world, the likelihood that this will happen next to you is rather small - and often happens only once in a lifetime, unless, of course, you travel around the world regularly. This year, the total eclipse will be at a reasonable distance for car travel for most people in 48 continental states.
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The total eclipse of the Sun is the result of the motion of the Moon in front of the Sun, from the point of view of the observer on Earth. The shadow of the moon is rather small and only comes into contact with the earth’s surface in a small area, as shown in the following illustration.



We can use the Wolfram 3D graphics to create a more realistic visualization of this event. First, we use texture to make the Earth more realistic.



Apply the texture to a rotated spherical surface as follows.



We will present the shadow of the earth as a cone.



The moon can be represented by a simple sphere ( Sphere ), offset from the center of the model, and its orbit is a simple dotted 3D path. Both objects are specified through the model parameters, since the moon's orbit will experience a precessional motion in time. It is useful to be able to betray the values ​​of these functions in order to make the shadow align to the line we need.




As well as the shadow of the earth, we represent the shadow of the moon as a cone.



Finally, we create some additional model elements for use as annotations.




Now we just need to build a model. We want the Moon to be on the same axis with the Sun, so to achieve this we use the value 0 ° for one of the parameters. To take into account the precession of the orbit so that the shadow falls on North America, we use the value of 70 ° for the second parameter. The rest is just information about the style.




This means that due to deviations from the circular orbit path, the moon is sometimes farther from the Earth than at other times; it also means that, due to the inclination of the orbit, it may be higher or lower than the Earth-Sun orbit plane. Usually, when the moon passes “between” the Earth and the Sun, it is “above” or “below” the Sun from the point of view of the observer on the surface of the Earth. Geometry is influenced by other effects, but the geometry is lined up from time to time successfully, and the Moon actually blocks some or all of the Sun's disk. On August 21, 2017, the geometry will be “just right”, and in some places on Earth, the Moon will cover at least part of the Sun.

In addition to illustrating the eclipse geometry, we can also use the Wolfram language, namely the GeoGraphics function to create various maps showing where the eclipse will be visible. By writing some code, you can get detailed results. For example, we can combine the features of SolarEclipse with GeoGraphics to show where you can see the path of the 2017 total solar eclipse. The total eclipse phase will be visible in a narrow strip that crosses the central part of the United States.



So which states will see a total solar eclipse? The following example can be used to determine this. First we extract the polygon corresponding to the full phase of the upcoming eclipse.





Suppose you want to zoom in on a particular state to look at it in more detail. At this level, we are only interested in the path of the total solar eclipse and the axial line. Once again, we use SolarEclipse to get the necessary elements.




Then simply use GeoGraphics to generate a map of the state in question - in this case, Wyoming.



We can use the Wolfram Data Repository for more eclipse information, for example, eclipse time in various places.




We can use this data to build annotated time stamps for various points along the eclipse path.



Then we simply combine the elements.



Of course, even if an eclipse occurs, there is no guarantee that you will be able to witness it. If the weather is bad, you just notice that it will be dark in the middle of the day. Using WeatherData , we can try to predict which regions are expected to be cloudy on August 21. The following example is based on a similar publication by the Wolfram community .

The following code retrieves all counties that intersect with the boundaries of the eclipse polygon.



Most of the work is related to estimating the values ​​of “ CloudCoverFraction ” for each district on August 21 for each year from 2001 to 2016 and finding the average value for each district.




Then use GeoRegionValuePlot to build these values. In general, it appears that most areas along this path have a relatively low probability of cloudy weather on August 21 based on historical data.



The total solar eclipse of August 21, 2017 is not a joke - because the path passes through a large territory of the United States. Do your best to see it! Take the necessary precautions and wear glasses to view eclipses. If your children are already in school, find out if they are planning any activities on this. Plan ahead, as traffic jams can be very heavy in places close to a total eclipse. Have a good time!

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Also read the Double Eclipse blog ! Or why Carbondale, Illinois, is special