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Science Briefing: Viewing eclipses from space and other totally awesome wonders

FILE -- NASA astronaut Don Pettit snapped this image from the International Space Station of the moon's shadow racing across the earth during an annular eclipse May 20, 2012. (Photo: Don Pettit/NASA)

NASA astronaut Don Pettit has gone where few have gone before: to space. That means he’s one of the few people to have ever observed solar eclipses from such a vantage point.

The Oregon native from Silverton has come back to the state to be a part of the Oregon Museum of Science and Industry’s total solar eclipse viewing event at the state fairgrounds Monday. The path of totality will rip through the state capital at about 2,000 mph, allowing viewers here to bathe in almost two minutes of the darkest part of the moon’s shadow.

Pettit said during a press event at the L.B. Amphitheatre Sunday afternoon that he’s ready and willing to go back to space and live on the International Space Station again. He’s already made three trips to space, and has lived on the space station for more than six months.

“I train, and I do everything that they tell me to do. And I keep my head down low. I hope to get another trip to go to station,” he said.

From the windows of the space station, he can not only get great views of earth, but of solar eclipses.

“You see this black spot, and then it gets closer and closer,” he said, explaining how the moon’s umbral and penumbral shadows race across the surface of the earth.

The umbra is the darkest part of the moon’s shadow. For earthbound observers of a total solar eclipse, that’s the part of the shadow they want to be under to experience totality. For those outside of it and in the penumbra, they’ll see a partial solar eclipse.

Pettit said he’s seen solar eclipses from space, but never has he seen one from the surface of planet earth. He’s excited about Monday, for sure.

Eclipses happen in patterns

Humans are good at noticing patterns. And at some point in human history, they started noticing that solar eclipses followed a cycle: Every 18 years, 11 days and 8 hours, an identical eclipse would occur. This was named the saros cycle, and it was the early way humans predicted eclipses.

“Throughout antiquity, without knowing why these occurred, observers would note that these occurred, and with some level of precision, make predictions about when they might occur next,” said Jim Brau, a physicist at the University of Oregon, who is also part of OMSI’s event.

He also noted that back in those days some predictors of eclipses who got it wrong were met with “a very bloody demise.”

After Johannes Kepler and Isaac Newton came along in the 1600s with their detailed understandings of planetary motion and gravity, scientists these days can predict eclipses down to the second.

One of those people include Fred Espenak, a retired NASA astrophysicist, who said in an interview earlier this month that he would be in Casper, Wyoming for Monday’s total solar eclipse. He doesn’t use the saros cycle to predict eclipses; instead, he uses high-level spherical trigonometry and sophisticated computer programs to predict eclipses with high precision. He’s worked out predictions to at least the year 3,000.

Why does the eclipse happen from west to east?

Some people have called or written into the KATU newsroom wondering why the sun moves from east to west while the eclipse will go from west to east. Well, here’s the answer: The moon moves. In fact, the moon orbits the earth counterclockwise -- or west to east.

“The moon rising in the east and setting in the west is really an illusion created by the rotation of the earth,” said Brau, explaining also that the earth rotates in a counterclockwise direction. “So that means that the shadow that the moon carries across the surface of the earth is dominated by the motion of the moon – this counterclockwise direction, means (the eclipse goes) from west to east.”

What science will be conducted during this eclipse?

All kinds of science experiments will be conducted during Monday’s eclipse by professionals and by citizen scientists – including studying the sun’s outer atmosphere, called the corona, measuring how much the temperature will drop during the eclipse and how animals react to totality. But Brau also said scientists will be studying how part of the earth’s atmosphere, called the ionosphere, will behave when the sun’s light no longer shines on it. The earth’s atmosphere becomes ionized when the atoms in it have had their electrons ripped away by solar radiation.

And the state of the ionosphere matters, because it can determine how far radio waves travel.

“The recombination of electrons with the ions will take place (during the eclipse), and we’re expecting that radio communication for a certain period of time will be extended over long distances,” Brau said.

For Pettit, the eclipse, and all that goes into making one happen and happen the way it does, creates an interest in science.

“It gets people thinking about all these little technical details, and I think that’s good,” he said.

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