Total Solar Eclipse 2017: What Scientists Can Learn From The Spectacular Blackout

Total solar eclipse
A total solar eclipse seen from the beach on Ternate island, Indonesia, on March 9, 2016. Beawiharta/Reuters

For most Americans, the total solar eclipse on August 21 will be a piece of celestial entertainment. Impressive, even awe-inspiring, but perhaps also a welcome distraction from work, or something to bring the family together for a few brief minutes.

For scientists across the nation, however, the event will be an unmissable opportunity to learn about aspects of space and the sun they can't study properly at any other time. Here are some of the experiments that will be taking place during the brief blackout.

The fringes of the Sun

The sun's outer atmosphere—known as the corona—is a pretty exciting place.

"This is a region where all the action happens," Alex Young, an Associate Director for Science at NASA, said in a video interview on the agency's website. Studying the corona can help predict the behavior of solar winds, charged particles released by the sun, and "coronal mass ejections," where it fires out a quick burst of solar material, both of which can affect the Earth and other planets.

These phenomena are known as space weather, and scientists would love to know more about them. But there's a problem: when the sun is at its full brightness, it's very hard to study the corona. The outer region of the corona is, "millions of times dimmer than the solar disk," according to Young.

Astronomers can use instruments called coronagraphs, in which metal disks blot out the Sun. But these tools also obscure part of the lower corona to prevent light from the main body of the sun diffracting around them and ruining the image.

So scientists are seizing this opportunity to take a look at the mysterious region. NASA is funding six experiments studying the corona during the eclipse, according to a statement.

Among them, a team led by Philip Judge of the High Altitude Observatory in Boulder, Colorado, will observe the corona's magnetic field structure with new instruments in the hope of gaining a better understanding of how the sun generates space weather.

Meanwhile, Shadia Habbal of the University of Hawaii's Institute for Astronomy in Honolulu wants to learn more about why the corona is much hotter than the surface of the sun—a counterintuitive fact, given that it is further away from the sun's heat source.

Her team will image the sun from five sites across four states 600 miles apart, using spectrometers to analyze light emitted by different ionized elements in the corona, and selective filters to capture it using different colors. They hope the the data they gather will improve their understanding of how the corona is heated.

Changes in the Earth's atmosphere

When the sun isn't shining on the Earth, it isn't just the amount of light our planet is exposed to that changes. The ultraviolet radiation issued by the sun will also suddenly drop away, meaning sudden changes in the ionosphere, the ionized layers of the Earth's atmosphere that the radiation creates.

The levels of ultraviolet radiation released by the sun in normal conditions can fluctuate in unpredictable ways. But during the eclipse, scientists will have a clear period of time in which the radiation is blocked, before returning quickly. That temporary barrier makes testing exactly how the ionosphere responds to changes in radiation easier than usual.

One experiment, by a team called EclipseMob, aims to be "the largest-ever low-frequency radio wave propagation experiment." The team has recruited between 170 and 200 amateur "citizen scientists" across the U.S. to help out. Volunteers around the nation have built their own radio receivers, and will take readings of a signal transmitted by EclipseMob from Colorado before, during and after the eclipse.

By reviewing data from around the country, the team hopes to see how the eclipse affects the way radio waves travel through the atmosphere, while controlling for any effect that location relative to the transmitter might have on a reading.

Jill Nelson, from the EclipseMob team, tells Newsweek that, as well as creating unique conditions for experiments, an eclipse provides a great opportunity to engage non-scientists with large scale projects like theirs. "We get drawn into [science] when we have a chance to observe a phenomenon," she says. "This is something we can't re-create in a lab, but it's conveniently being created for us across the U.S. And so I think there's lots of people who, now that they'll be able to observe it, are excited about what's happening and understanding the science."

Proving relativity

Eclipses also provide a unique opportunity to test the theories of Albert Einstein. According to Einstein's general theory of relativity, a huge object like the sun should have such a strong gravitational pull that it will bend light passing around it.

In 1919, during another eclipse, the astrophysicist Arthur Eddington and his team took measurements from Brazil and Africa simultaneously. They noticed that the observable position of stars near the sun differed from their recorded position, suggesting their light was bending in the way Einstein had predicted.

Eddington's data were later disputed, leading others to try and repeat the experiment. It was last attempted in 1973, but, according to Livescience, the University of Texas team that carried out the redo ran into difficulties and produced results that could not conclusively confirm Eddington's.

Now physicist and amateur astronomer Donald Bruns and others are hoping to repeat the experiment during America's eclipse, using modern instruments to get a more certain result. "All these experiments, and the best they could get was maybe 10 percent error," Bruns told Livescience. "I think I can get 2 percent." He'll be heading to a high-altitude location in Wyoming, and laying down a fresh concrete slab to stabilize his telescope.

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