On Monday, August 21, 2017, a total solar eclipse will be visible in some areas of the United States. This is now less than 1,000 days away. The event has been a long time coming. While the last total solar eclipse to be seen in the United States occurred in 1991, that event was limited to Hawaii. Before that, the last solar eclipse visible from the continental United States was on February 26, 1979.
While the 1979 event tracked across Oregon, Washington and Montana, people in 12 states will see the 2017 event. Both eclipses started in Oregon. The earlier one then tracked up into Canada. The 2017 eclipse starts in Oregon, travels across the central United States before finishing far out to sea beyond South Carolina.
A total solar eclipse is a rather rare occurrence. Estimates place the likelihood of any point on Earth experiencing one only every 400 years. This is not absolute, however. Several Oregon locations saw the 1979 eclipse and they will see the 2017 event as well. For them, experiencing two solar eclipses in a little more than 35 years is quite unusual. Closer yet are the cities of Carbondale, Illinois, and Cape Girardeau, Missouri. Residents there will see the 2017 eclipse as well as another in April, 2024. This separation of less than seven years for these two eclipses is very unusual. Of course, it may be hundreds of years before these cities see another.
To be a total eclipse, the moon must completely obscure the sun, for an observer standing on Earth. This can occur monthly, at New Moon. Ordinarily, however, the moon passes either above, or below, the sun’s position, as viewed from Earth. As a result, the moon’s shadow normally sweeps across open space. On rare occasions, as the moon passes directly in front of the sun, a shadow is cast upon the surface of the Earth. If the sun is partially obscured, a partial eclipse results. If the sun is completely obscured, a total solar eclipse occurs. The moon is much smaller than the sun, of course. In fact, the moon is some 400 times smaller. In an astronomical twist, the moon is also 400 times closer to the Earth. This makes the apparent size of the moon very close to the apparent size of the sun. When the moon passes directly in front of the sun, it is able to completely eclipse the sun, for some viewers on Earth.
The shadow cast by the moon, however, is very small. Depending on the distance between the Earth and the moon, which varies somewhat, the moon’s shadow will darken a strip of Earth about 70 miles wide. This strip is called the Zone of Totality. Those people located within this zone will experience a total solar eclipse. Those near, but outside, will see a partial solar eclipse.
On August 21, 2017, the sun is eclipsed for as much as 2 minutes and 40 seconds at the maximum point. Hopkinsville, Kentucky happens to be located at this point. People not located there may see a shorter eclipse duration. Those located outside the zone of totality will only see a partial eclipse. Some cities that will experience totality include Nashville, Tennessee, Kansas City and St. Louis, Missouri. The 2017 eclipse will potentially be seen by millions of people located across the United States.
Each total solar eclipse is unique, but there are similarities. The Earth will darken over time as the moon obscures more and more of the sun. This is the partial eclipse phase. As totality approaches, the amount of sunlight striking the Earth will be greatly diminished. The sky will become similar to twilight. Colors normally seen at sunset will be visible during the day. Birds, animals and insects will be fooled into believing that night is falling. Some will return to their nests or roosts. Nocturnal creatures will begin to emerge. These effects often happen even if a total solar eclipse occurs early in the morning. After totality ends, another partial eclipse phase occurs until the moon passes beyond the sun’s location.
The biggest factor that cannot be predicted with certainty is the weather on August 21, 2017. Cloudy weather could obscure the eclipse for interested observers. As a result, many people examine historical weather patterns in order to determine prime eclipse viewing locations. Since the 2017 event occurs in August, there are some rather promising weather possibilities. In Oregon, the August weather tends to be sunny and dry, perfect eclipse conditions. Morning fog, storms, or clouds, could thwart eclipse viewers, however.
Idaho and Wyoming residents will also experience the 2017 eclipse. The weather in these states could allow a very good eclipse viewing experience. The eclipse occurs fairly early in the day, lessening the possibility of localized thunderstorms.
As the total solar eclipse tracks across more states, from Nebraska to South Carolina, the possibility of inclement weather increases. These locations will experience the eclipse later in the day. Afternoon storms, or hazy weather, could be encountered. Such weather could limit the eclipse experience.
Many US cities have already begun planning for the August 21, 2017 total solar eclipse. The event represents an opportunity to entertain tens of thousands of visitors to cities located within the zone of totality. With proper attention to details, cities can provide a favorable eclipse experience that also highlights the attractions of the local area. Weather permitting, of course.
– the distance from the Earth to the moon increases each year. In less than 1.5 billion years, the moon will not be close enough to produce total solar eclipses. After that, only partial or annular eclipses will occur.
– when the moon eclipses the sun, the sky darkens enough to allow planets and bright stars to be seen in the daytime. On August 21, 2017, the bright star Rigel should be visible low in the south. – Albert Einstein predicted that a total solar eclipse could provide direct proof of the General Theory of Relativity. He postulated that the eclipsed sun would cause light to be bent, for an observer on Earth. This would be proved as stars located behind the sun would appear to be shifted in location. This visual evidence was demonstrated during an eclipse in 1919.
– as the moon passes in front of the sun, it blocks enough sunlight that the solar corona, the super heated atmosphere, becomes visible to people on Earth. The shape of the corona is different during each eclipse as it is influenced by the level of magnetic solar storms, which constantly changes.
– ancient civilizations did not understand the science responsible for total solar eclipses. Eclipses were attributed to supernatural causes and thought to be bad omens.
– the theoretical maximum duration of a total solar eclipse is about 7 minutes. The 2017 eclipse is less than half this duration, at 2 minutes, 40 seconds for those located in Hopkinsville, Kentucky.
– the sun is not safe to view during any portion of the partial eclipse phase. Even if only 1% of the sun is visible, observers risk damage to their eyes through direct observation. At this eclipse stage, the sun appears to be dim enough to view. Unfortunately, the lit portion still transmits full force sunlight to the optic nerve. Because the level of light is so much lower than normal, the observer feels no urge to avert their gaze. Moreover, the optic nerve does not contain pain receptors so victims are unaware that their eyesight is being damaged. Proper eye protection is vital for all observers of the partial solar eclipse phase.