A total solar eclipse reveals a cosmic truth

The writer Annie Dillard, in a famous 1982 essay in the Atlantic, perceived in an eclipse a mind-blowing derangement of human existence, with intimations of the end of the world.

“Seeing a partial eclipse bears the same relation to seeing a total eclipse as kissing a man does to marrying him, or as flying in an airplane does to falling out of an airplane,” Dillard wrote.

Totality’s power comes from how strange it is, how unlike anything else. This entirely natural event has a supernatural vibe.

When the moon fully blocks the sun, darkness descends with stunning swiftness. The air temperature plummets. Birds and insects might start acting strangely. And in place of the normally incandescent sun, you see only a black disk surrounded by a glowing, shimmering, entrancing ring of light. It’s the corona — the sun’s atmosphere.

Seeing the corona is rare enough. But look around, and you’ll also notice the eclipsed sun surrounded by bright stars and planets. For the April 8 eclipse, Venus and Jupiter will bracket the sun, and Mars and Saturn may be faintly visible, according to NASA.

The sun and the stars and the planets do not, under normal circumstances, share the same sky. You could say the sun is diurnal, the stars nocturnal.

It is only during totality that the eclipse reveals a simple if profound truth: The sun lives among the stars, and the planets live with the sun. The five planets that may be visible on April 8 — counting the planet at your feet — will be lined up, along with the sun and moon, on the ecliptic of the solar system.

These are the kinds of ho-hum facts we learn in elementary school but that become gasp inducing during totality.

“We can literally see our place in the universe,” NASA astrophysicist Michael Kirk said.

“At totality, when you look at the sun, you actually realize that it is a star,” said Nicola “Nicky” Fox, the top science administrator at NASA. “It looks more like it’s a living, breathing thing rather than just a bright light.”

A ‘mind blowing’ experience

Totality has the paradoxical quality of hiding the sun but also revealing its nature — what it is, what it’s made of, how it works.

Copernicus explained the motion of the planets in a heliocentric solar system in 1543, but nearly a century later, the idea that Earth is not the center of Creation was still getting Galileo in deep trouble.

Not until the second half of the 19th century did scientists have evidence that the sun is the same thing as the stars of the night sky. The breakthrough came through spectroscopy, the technique of analyzing wavelengths of light for the signatures of different elements. It took decades more for anyone to understand how the sun works. That mystery was entangled with the greatest unknown of all: the age of the sun.

Right up to the 20th century, some scientists estimated that the sun and Earth might be only a few tens of millions of years old. But Charles Darwin’s most famous theory, critics were quick to point out, required a very old Earth in which life could slowly evolve into a great diversity of forms.

British mathematician William Thomson, known as Lord Kelvin, argued for a much younger sun, based on calculations that assumed the sun produced energy through gravitational interactions as matter fell toward the core. The debate was resolved only with the development of atomic physics.

During an 1868 eclipse in India, French astronomer Pierre Jules Janssen detected a previously unknown element in the atmosphere of the sun using spectroscopy. English astronomer Joseph Norman Lockyer independently confirmed the discovery and gave the element its name: helium.

Now we know that hydrogen atoms fuse into helium atoms in the sun’s core. This reaction converts a small percentage of mass into energy in a process that is extremely efficient, fitting neatly with estimates that the solar system is a whopping 4.6 billion years old. The energy migrates outward from the core and eventually reaches Earth, making life possible.

Many other types of stars burn hydrogen as fuel. But our sun is a mature, relatively calm, reliable star. Look around the universe, and you will see a lot of stars that are comparatively unfriendly. They explode in their youth or spew radiation promiscuously. Red dwarf stars, the most common kind in our galaxy, are capable of blowing away the atmospheres of nearby planets.

“Different stars burn at different rates, liberating their free energy over millions to trillions of years,” physicist Michael Turner said in an email. “Long-lived stars like our sun do so over billions of years, making a rich biological evolution possible.”

The total solar eclipse on April 8 will be unusually convenient for Americans who want to witness this cosmic truth. The Texas-to-Maine path of totality — the narrow ribbon where the moon will cast its shadow — crosses many sizable cities, including Dallas, Indianapolis, Cleveland, Buffalo and Rochester.

According to NASA, about 31 million people in the United States don’t have to go far from home to experience totality. They just have to look up.

“Even though intellectually you know what it’s going to look like,” NASA’s Fox said, “it’s just mind-blowing.”