A rare natural spectacle: A total eclipse of the sun
dpa Friday, August 18, 2017, 7:56 am TWN
Washington (dpa) - Eighteen years ago, Spanish fashion designer Paco Rabanne, 83, predicted catastrophe: On August 11, 1999, the day of a total solar eclipse over Europe, the Russian space station Mir would break apart under the "black sun" and destroy a number of cities.
As we know, this didn't happen. Scientists, on the other hand, can predict with a fair degree of accuracy what will occur during a solar eclipse.
Question: How does a total solar eclipse occur?
Answer: It occurs when the moon comes between the Earth and sun, completely obscuring the sun in the process. It is only observable during a new moon, when the Earth, moon and sun come into direct alignment. In broad daylight it becomes dark for a few minutes, and stars are visible in the sky.
Only in a narrow swath of the Earth's surface, a maximum of 270 kilometres wide, will the total eclipse be visible - where the core shadow of the moon falls onto the planet. Those finding themselves in the half shadow will experience a partial eclipse in which the moon blocks only part of the sun.
Q: Why doesn't it happen every month?
A: Because the moon's orbit is tilted slightly toward Earth's orbit. Therefore the new moon wanders away from the Earth, either above or below the sun. Only when the sun, moon and Earth are aligned in a straight line will the moon cast its shadow upon the Earth, and only then do we experience a solar eclipse.
Q: But the sun is much larger than the moon, correct?
A: That's true, the sun is approximately 400 times the size of the moon, but it is also about 400 times farther away from Earth. Therefore they appear roughly the same size when viewed from Earth.
Q: Where is the total solar eclipse visible on August 21?
A: It will be visible in 14 US states - from Oregon in the north-west to South Carolina in the south-east. It will be experienced as a partial eclipse in parts of Europe, Africa and South America.
Q: How long is the total eclipse visible?
A: In the individual US regions, the total solar eclipse will last a maximum of 2 minutes and 40 seconds.
An eclipse can, depending on the circumstances, last up to seven and a half minutes. For example, on July 22, 2009, a total eclipse over China and the western Pacific Ocean lasted 6 minutes and 39 seconds.
The duration of an eclipse is influenced, among other things, by the apparent diameters of the moon and the sun combined with the distance of each from Earth during their respective orbits.
Q: Why is a total eclipse something special?
A: It is quite rare for a human to experience the phenomenon more than once in the same place. The next total solar eclipse is expected on July 2, 2019, and will be visible over the Pacific Ocean, including some cities in Argentina and Chile.
Q: Where in Europe will it be possible to witness the phenomenon on August 21?
A: In Western Europe, including Portugal, Spain, western France and Great Britain, a partial eclipse will be visible. In Lisbon, for example, barely a fifth of the sun will be obscured.
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