--- title: What Solar Eclipses Have Taught Us About the Universe description: Total solar eclipses like the one that will cross the US on August 21 have taught us about how the universe works. Here's what we've learned canonical: https://time.com/4889158/solar-eclipse-astronomy-universe/ author: Amy Shira Teitel article:opinion: false article:content_tier: free article:published_time: 2017-08-09T12:58:12.000Z article:modified_time: 2026-10-08T09:27:53.053Z article:section: Science og:title: What Solar Eclipses Have Taught Us About the Universe og:description: Thank eclipses for these scientific discoveries og:url: https://time.com/4889158/solar-eclipse-astronomy-universe/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt27e5c8b99e1b0b0b/6988d89b86f68e54886e5e2a/western-science1.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 4256 og:image:height: 2394 og:image:alt: NORWAY-ASTRONOMY-ECLIPSE og:type: article twitter:card: summary_large_image twitter:title: What Solar Eclipses Have Taught Us About the Universe twitter:description: Thank eclipses for these scientific discoveries twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt27e5c8b99e1b0b0b/6988d89b86f68e54886e5e2a/western-science1.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # What Solar Eclipses Have Taught Us About the Universe > Sponsored content. 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Future Proof is free at time.com/newsletters. ### Sources * TIME Newsletters: [time.com/newsletters](/c/time-nl-futureproof-2026q3/newsletters?i=090208a7-968c-4419-b29e-05f367c91913&cr=time-nl-futureproof-2026q3-v1) ## Video: Here's How Astronomers Used Eclipses to Understand the Universe [Watch (HLS stream): Here's How Astronomers Used Eclipses to Understand the Universe](https://cdn.jwplayer.com/manifests/Lav03yn1.m3u8) (7:02)  _Published 2017-08-09. Eclipses, what happens when one body in space passes in front of another, are very common. The key is being in the right place at the right time to see it. Throughout human history astronomers have used eclipses to understand the universe._ by [Amy Shira Teitel](https://time.com/author/amy-shira-teitel/) ## Amy Shira Teitel Aug 9, 2017 12:58 PM UTC by [Amy Shira Teitel](https://time.com/author/amy-shira-teitel/) ## Amy Shira Teitel Aug 9, 2017 12:58 PM UTC [Total solar eclipses](http://new.time.com/4750899/total-solar-eclipse/) like the one that will cross the U.S. on Aug. 21 have captured the attention of astronomers throughout history — and have often led to advances in our understanding of how the universe works. Astronomers have been studying[ solar eclipses](http://new.time.com/4834676/total-solar-eclipse-2017-rare/) for centuries. In the late 16th and early 17th centuries, Danish astronomer Tycho Brahe and his apprentice German astronomer Johannes Kepler studied eclipses to try to arrive at a rough estimate of the moon’s diameter. In the 19th century, eclipse observations got even more interesting, thanks in large part to advances in scientific instruments like [telescopes](http://new.time.com/4881471/solar-eclipse-2017-telescopes/) and spectrometers, devices that let scientists analyze the chemistry of stars and distant planets. In 1868, French astronomer Jules Janssen and English astronomer Norman Lockyer were observing separate solar eclipses when they discovered a new element, which they named _helios_, after the Greek word for “sun.” Today, it’s known as [helium](https://www.universetoday.com/53563/who-discovered-helium/). During an eclipse in 1879, American astronomer Charles Augustus Young and Scotland-born astronomer William Harkness both thought they had discovered [another new element](https://www.space.com/36785-solar-eclipse-science-throughout-history.html). But they had actually observed exceptionally hot iron in the sun’s corona, the sun’s outer atmosphere. This was the first indication that the corona is millions of degrees hotter than the sun’s surface, a mystery that puzzles astronomers to this day. Perhaps the most interesting eclipse-based discovery came in 1919\. Albert Einstein’s theory of general relativity was still being met with skepticism. Under this theory, big gravitational masses like stars and planets warp the fabric of space-time, bending light as it travels through the universe. Einstein didn’t have a way of proving it, but luckily, Sir Frank Watson Dyson, the Astronomer Royal of Britain at the time, a senior post in the Royal Households of the U.K., came up with a solution. He plotted the positions of stars that would be near the sun’s limb, or edge, before a solar eclipse, then measured their positions again during the eclipse. He found that the stars’ positions had changed. The only explanation was that the mass of the sun was bending space-time and curving the stars’ light. They _looked_ to be in different positions, but it was really an effect of the sun’s mass. It was proof Einstein was right. So when you watch the eclipse on Aug. 21, which will be visible in [parts of 14 states](http://new.time.com/4884482/total-solar-eclipse-2017-map/) as a total solar solar eclipse and in the rest of the country as a partial solar eclipse, it’s a good moment to remember the cosmic event’s history of illuminating our place in space. _Amy Shira Teitel is a spaceflight historian who will co-host TIME’s livestream of the solar eclipse on Aug. 21_ ## Transcript I'm spaceflight historian, Amy Shira Teitel. And let me tell you the upcoming total solary clips on August twenty first is definitely a once in a lifetime event not to be missed. And if you can get anywhere to see whom person, why not tune in to times live stream coverage. We're going to be talking the people in the field in the path of totality and sharing their views. It's going to be an incredibly event Hosted by yours truly. And not only are eclipses just beautiful cool things to see. They're also scientifically very important. In fact, almost thru out most of human history, scientist had been using eclipses to study space and really understand the universe that we life in Eclipses happen all the time. Technically speaking, an eclipse is just when one body in space is obscured by another body crossing in front of it. So they happen all the time. But what's rare is being in the right place at the right time to see it. Like a solar eclipse, the moon passes between the sun and the earth every month. That's what we see as a new moon. It's rare that the 3 bodies actually line up so perfectly such that the moon obscure the sun at any given point on earth. Ancient civilizations knew this. They study the sky the way some of us study our favorite tv program and that included eclipses. The earliest recorded sighting of a solar eclipse was by [ UNKNOWN ] philosopher Thales of Mylades. He predicted a total solar eclipse would happen sometime during the year 585 BCE and he was right. It happened on May 28th of that year. [ UNKNOWN ] astronomers have worked backwards to confirm that yes, a total eclipse did happen where Thales would have seen it. On that date. No one is entirely sure how Thales was able to predict that eclipse, but it's possible he had an understanding of two solar cycles that let him understand that it would be happening that year. The Saros Cycle and the Exeligmos Cycle. Another solar eclipse was seen by Plutarch on March 20th of the year 71. He wrote, of the event, that even when the moon, covers the sun entirely, a kind of light is visible around the rim which keeps the shadow from being profound and absolute. It's possible, that his observations, were the first time that anyone in recorded history, actually saw the solar corona. So ancient astronomers studied eclipses and they knew what was happening. They understood that it was the moon blocking the light of the sun. They also studied the phases of the moon to understand that the earth and the moon were both spherical, not flat. And interestingly, all of this still worked within the geocentric universe. The Aristotelian cosmos that had the Earth at the center with all of the planets orbiting around it. When we're talking about eclipses, it's easy to explain it, whether the Earth is orbiting the sun or whether the sun is orbiting the Earth. It helped, too, that eclipses happen at relatively regular intervals. This all fit within Aristotle's model of the cosmos, wherein everything is perfect and unchanging. Of course, all of that fell apart with Copernicus in 1543, when he published in De Rev that the sun is actually the center of the solar system, not the earth. In addition to de- centering the earth from our understanding of the cosmos, Copernicus was also a fan of eclipses. The [ UNKNOWN ] used to [ UNKNOWN ] camera to absorb four partial eclipses i 1530, 1536, 1540 and 1541. [ UNKNOWN ] also studied eclipses to try and measure the moon's diameter. As to his apprentice Johannes Kepler Of course using pinhole cameras and even with Kepler's revelation that orbits are actually elliptical and not perfectly circular. Their measurements of the moon's diameter were an estimation at best. Eclipse observations got more interesting in 19th century, when astronomers are using telescopes. Not unlike those that Galileo Galilei used to discover the moons of Jupiter. They also started using secondary instruments like prisms to study the sun during an eclipse. French astronomer Jules Janssen traveled to India to view a solar eclipse on August 18th of 1868. Using a telescope and a prism, he noticed there was a bright spectral line from right around the sun's corona, The discovery was independently duplicated on October 20th of that year by English astronomer Norman Lockyer. Together with English chemist Edward Frankland, they named the element helios, after the Greek word for the Sun. Studying a solar eclipse is how we discovered the element helium. A little more than a decade later, during the 1879 eclipse, another pair of astronomers independently discovered what they thought was a new element called Coronium. What it turned out, this wasn't a new element at all. But rather exceptionally hot iron in the solar corona. It was studying a solar eclipse that astronomers learned that the sun's corona is unbelievably hot Millions of degrees hotter that the Sun's surface. But perhaps the most interesting thing we've learned about the universe from a solar eclipse is that Einstein was right with his theory of general relativity. Hundreds of years before Einstein, Isaac Newton published the Principia and laid out his view of the universe. It was a neat and orderly one governed by forces and laws. But Einstein's work on relativity in the early 1900s went against Newton in many ways. Namely he argued that space is not static. For Newton space was inert and unchanging. For Einstein objects can change structures and space. Einstein used the fourth dimension of time to create what he called the fabric of spacetime. Whereas Newton held that light traveled from say the sun to the Earth By photons moving through the vacuum. Einstein said that they traveled on a straight line, but could be warped along the fabric of space- time by the gravity of a larger body. It's almost as if space- time is a trampoline's surface, and a planet is a bowling ball. A photon is a marble rolling along it, and while it might bend its path around the bowling ball to the photon, it's still traveling in a straight line. For Einstein, gravity was infect of the warping of the fabric of space time whereas, for Newton, it was a direct attraction. The problem for Einstein was he needed some way to prove it and an eclipse was the answer. Sir Frank Watson Dyson, the astronomer royal of Britain at the time came with a way to test Einstein's theory. He measured the position of stars that would be near the sun's [ UNKNOWN ] eclipse then measured their position again during an eclipse in 1919. He found that the stars' positions have changed. There is a pronounced whipping by the sun's mass destroying once and for all Newton's idea of inert space And of course, this eclipse will be no different. Will most people just go outside to look at something incredible, to see darkness in the middle of the day? Scientist will be doing various experiments to try to learn a little bit more about the sun and our universe By studying that solar eclipse. Thank you guys so much watching and I hope that's got you a little bit more excited about the upcoming eclipse. And speaking of, be sure to subscribe to times table so you don't miss out on our live streaming event August 21. And if you are fascinated by space flight history specifically the Apollo era. 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