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Summer’s Spectacular Solar Series, Part I: Hello, Sun.
published during a waxing gibbous moon.
03/09/2017

Summer’s Spectacular Solar Series is a recurring column on NOW.SPACE that answers all the questions you’ve ever had about our magnificent Sun but were too afraid to ask.


When you look up at the night sky, wherever you are on Earth, and whatever the viewing conditions, there is always one star missing, one star that you never see. Our star, the Sun.

It’s easy to forget that the Sun is a star, a common and ordinary one at that. It dominates our days, defines them even. We alternately seek it out and actively try to escape it. It’s the reason we are here in the first place, yet it is also a danger to us. We’ve had to invent so many things to allow us to be in its presence: sunglasses, sun shades, sun block.

Summer's Spectacular Solar Series

Astronomers estimate there are approximately 100,000,000 stars in our galaxy and roughly 2,000,000,000 galaxies in the Universe. That’s a ridiculous amount of stars. In our lifetime, and in our species’ lifetime, we have no hope of studying all the stars in our galaxy, let alone all the stars in the Universe. The best we can do is study the ones within reach and extrapolate from there. And what better star to start with than the one in our front/back/side yard?

We didn’t always know that that the Sun was the same as those tiny points of light in the celestial sphere. In classical times, the Greek philosopher Anaxagoras was one of the first to suggest that our Sun was also a star, just a heck of a lot closer. But like many whose ideas came before their time, he was ridiculed and dismissed by his peers. Two thousand years later, Italian philosopher Giordano Bruno came to the same conclusion and was not only persecuted by the Roman Church but also burned at the stake for contradicting ideas upheld by the Church at the time.

Once we understood the Sun was a star, the next hurdle was determining what powered it. In antiquity, some thought that the Sun was a flaming ball of metal, but no one could explain why it never flickered or went out, like fires on Earth. Aristotle argued that objects in the sky couldn’t possibly be made from the same substance as objects on the base, imperfect Earth. As the Sun was in the heavens, it had to be made of something purer. He proposed a new substance he named “ether,” after the Greek word for ‘glowing,’ and proclaimed it everlasting thereby enabling the Sun and the stars to glow forever, thereby accounting for why they never went out.

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Galileo was the first to challenge this idea of perfection when he turned his telescope on the Sun and discovered its face was marred by black spots. Over time he observed these spots to appear and disappear, grow and shrink, and rotate in and out of view. Clearly, the Sun was not pure as Aristotle proposed. Later the same century, Italian and French astronomer, Giovanni Cassini, was the first to estimate the distance to the Sun, enabling Isaac Newton to determine its mass, using his newly derived laws of gravitation. These calculations gave credence to the idea that the laws of math and science as formulated on Earth governed the heavens as well. Therefore the Sun and the stars were one in the same. Not only that, but the laws of physics and chemistry had to be the same for the Earth, the Sun, and the stars. So what we observed here also applied to what we observed out there.

The question of why the Sun shines is important not only for physics and astronomy but geology and biology as well. As John Herschel said in his 1833 Treatise on Astronomy:

“The sun’s rays are the ultimate source of almost every motion which takes place on the surface of the earth. By its heat are produced all winds … By their vivifying action vegetables are elaborated from inorganic matter, and become, in their turn, the support of animals and of man, and the sources of those great deposits of dynamical efficiency which are laid up for human use in our coal strata.”

Summer's Spectacular Solar Series

Many early theories could produce the required amount of heat from the Sun, but they implied ages for the Earth and the Sun far too young to account for observed effects such as erosion and natural selection. By the early 1900’s, physicists had considered several energy sources as promising solutions: gravitational energy, radioactivity, and nuclear energy. But each hypothesis had its own problems with trying to account for the massive scale of the Sun’s power.

That all began to change after Albert Einstein announced his famous finding of the relationship between mass and energy. This kicked off a chain reaction of insights in the physics community, especially in quantum mechanics, which indicated that the conditions in the center of the Sun were hotter and denser than previously imagined. Not only could nuclear fusion take place there, but it could also be sustained for billions of years. Like much of science, this paradigm shift didn’t take place overnight. It was the result of a chain of discoveries by many different scientists; each building on the findings of those that came before them. Pierre Currie, Ernest Rutherford, Albert Einstein, Arthur Eddington, George Gamow, Hans Bethe, and likely many more lesser-known (dare I say hidden) figures all had a hand in solving this mystery.

So maybe next time you step outside on a sunny day and look up, you’ll appreciate our solar power source just a little bit more.