In less than a week, the Moon will pass in front of the Sun in the middle of the day blocking between 20 to 100% of the Sun’s light across the continental United States as it does.
How much of an eclipse will I see?
The geographic region that will see a total solar eclipse, known as the path of totality, is 70 miles wide, hitting land westward of Salem, Oregon (just south of Portland) around 10:15am and moving out over the Atlantic Ocean around 2:50pm just after passing through Columbia, South Carolina. Other cities in the path of totality include Salem, Oregon, Nashville, Tennessee, and parts of both Kansas City and St Louis. For detailed maps of the path of totality, check out the website eclipse2017.org.
How long will the eclipse last?
The eclipse will take just 1 hour and 33 minutes to move across the United States. Those in Oregon will see a shorter eclipse as the shadow will hit the Earth at an angle there causing it to cover a larger portion of its path than when viewed straight on. In western Oregon, the shadow will clock speeds around 2410 miles per hour compared to speeds as low as 1462 miles per hour in western Kentucky. At a given location, the Sun will be at least partially eclipsed up to 2-3 hours with totality lasting between 2-3 minutes.
NASA has an extremely informative interactive map that allows you to click on your location to learn the amount of obscuration you will see, the duration of totality you will experience, as well as the precise time you should head outside to look. Vox also has a cool tool that allows you to enter your zip code to get an idea of how the eclipse will look from your perspective.
What else will I see during the eclipse?
If you are in the path of totality or close to it, you should be able to see phenomena that are usually otherwise overpowered by the Sun’s light. The Sun’s corona, a wispy layer of plasma surrounding our star, for example, is visible during totality as a ring around the black disk that is the obscured Sun. In fact, scientists have several experiments planned to study the corona while the Moon conveniently blocks the rest of the Sun’s light.
You should also see other stars! There are always stars in the sky during the day – we just usually cannot see them as they outshone by a much closer star, the Sun.
While the Moon and the Sun have conveniently placed themselves so that the smaller yet closer Moon appears precisely the same size as the larger but more distant Sun from our perspective, the Moon does not have a smooth surface. Our Moon has hundreds of craters that, without erosion, plate tectonics, or volcanism, have stood the test of time. As the Moon obscures the Sun, the bumpy lunar surface will allow spots of light to appear along the edge of the eclipse known as Bailey’s beads.
You don’t need to look up to see something out of the ordinary. The Sun’s image projected on the ground will appear as crescent shapes covering the Earth’s surface. A good place to catch this phenomenon is under a tree, as the light passes through different gaps in the leaves and branches.
How can I safely view the eclipse?
We all know not to stare at the Sun on an ordinary day, but even at 99% obscuration, looking directly at the Sun can be damaging to your vision. Even looking at those Bailey’s beads without protection could be harmful. NASA warns that the amount of light that passes through ordinary sunglasses is on the order of thousands too much to be considered safe.
Instead you will need special eclipse glasses or hand-held solar viewers that filter all but 0.003% of optical, ultraviolet, and infrared light usually through a thin layer of aluminum, chromium or silver. Look for glasses that meet ISO safety standards although there are reports of counterfeit glasses falsely claiming ISO compliance. The American Astronomical Society offers a list of reputable vendors. You shouldn’t see anything through proper eclipse glasses except the Sun which should not hurt your eyes. Your local library, planetarium, or astronomical society may even have free ones to share.
Will I see another eclipse in my lifetime?
There are between 2 to 4 solar eclipses per year but a total solar eclipse is less common – roughly once every 1.5 years somewhere on Earth. For a total solar eclipse to occur, the Moon has to be in its new moon phase, its path has to cross the orbital plane of the Earth around the Sun, and it has to be at the right distance to the Earth to match the size of the Sun. And all of these things have to happen at the same time!
We’ll only have to wait until July of 2019 to see the next total solar eclipse. That one will pass over the South Pacific and then Chile and Argentina. The next total solar eclipse in the US will be in April of 2024: it will span from Mexico then Texas and move up through Indiana and Ohio. After that, those in the US will have to wait until 2045 to see another one.
So next week’s solar eclipse may not be the only one you see in your lifetime, especially if you are willing and able to travel. But eclipses, especially when seen in totality, represent an unusual opportunity to gain perspective on our place in the universe, to collectively take a break, even if just for a few minutes, and marvel at the fact that we are all hurtling through space together on a ball of rock as it orbits a glowing star.
Until next time, this is Sabrina Stierwalt with Everyday Einstein’s Quick and Dirty Tips for helping you make sense of science. You can become a fan of Everyday Einstein on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at everydayeinstein@quickanddirtytips.com.
Image courtesy of shutterstock.
Tidak ada komentar:
Posting Komentar