Photo: The total phase of the November 3, 2013, solar eclipse as seen from Gabon, Africa. Credit: Jay Pasachoff / Allen Davis / Vojtech Rusin / Miloslav Druckmüller. Photo resized for the Rotary Web site. Original and license can be viewed at: https://eclipse.aas.org/resources/images-videos
“If you don’t have plans to see the eclipse I hope you will after this talk.” This opening remark by Jim Todd, OMSI director of space science education, was sure to peak everyone’s interest. The upcoming event has been in the news every day for weeks, and most would have difficulty escaping the excitement and anticipation.
A total solar eclipse takes place when the moon is close enough to the earth to completely cover the sun. This bit of magic occurs rarely somewhere in the world, and even more rarely does it extend across the entirety of the US. That it can happen at all is a result of size and distance: the sun is 400 times larger than the moon but the moon is 400 times closer to the earth than the sun. For comparison, the moon is as wide as the U.S. Mr. Todd explained that the sun and moon and earth have to line up in order for an eclipse to occur. What’s more, the moon’s phase has to be a new or full. A lunar eclipse occurs during a full moon; a solar eclipse occurs during a new moon.
The path for this Great American Eclipse extends from Oregon to South Carolina, and it is the first total eclipse to sweep the entire U.S. since 1918. The area is 60 miles wide, and totality—when the sun is completely blocked out by the moon and only the corona is visible–can be glimpsed for about two minutes near the center line of the path. The last total eclipse in Oregon was in 1979 but cloud cover made it invisible to folks in Portland. “It’s a magical moment to see it, and there won’t be another total eclipse in Oregon for 124 years.” The next eclipse in world will be in 2024. If this statement wasn’t enough, Mr. Todd’s claim that it will be the “greatest show on earth,” is sure to get people running to the store to buy protective eye glasses. There will be an eerie twilight, stars will come out, and the temperature will drop 10 degrees. According to Mr. Todd, a total eclipse is so spectacular that “you will remember where you were and who you were with, the same way you remember a wedding” or similarly momentous event.
The Great American Eclipse will happen on August 21 beginning just after 9 AM and will last 2 1/2 hours. It will take only 9 minutes for the moon’s shadow to cross Oregon but totality will last only two, brief minutes. The longest totality on record was just over 7 minutes long. Go early, (over 1 million visitors are expected in Oregon!), find a place with a clear view of the horizon, and plan to stay there for the entire event. The sun will be visible at about 40 degrees above the southeastern horizon.
The next annular, partial, eclipse in Oregon will take place in 2023 over Crater Lake.
A bit of caution: you must wearprotective solar glasses during the entire eclipse. Sunglasses will not work. You can permanently damage your eyes in 10 seconds, and even though you will not feel anything or notice any difference right away, in a few days your vision will begin to deteriorate. You can take the glasses off during totality, but only during totality. In fact, you won’t see totality at all while wearing solar glasses.
For more information, visit
https://eclipse2017.nasa.gov/sites/default/files/interactive_map/index.html
Jim Todd has worked at OMSI for 32 years. He manages the Kendall planetarium, trains teachers in astronomy and science, and coordinates astronomy nights at OMSI. He has a BS in secondary education and teaches part time at PCC.