Why total solar eclipses are so special

Legend has it that a savage battle between the Lydians and Medes came to a sudden standstill. Weapons dropped to the ground as the men looked up to the sky in terror and awe. The sun, which only moments before shone high above them, had vanished. This omen caused both sides to lay down their arms and declare a truce. What the Lydians and Medes experienced that day was a total solar eclipse. Eclipses occur when astronomical objects align. The alignment of the sun, moon, and earth creates a solar or lunar eclipse. But even though the moon orbits the earth every month, solar eclipses don't happen that often. That's because the moon's orbit is tilted by about 5 degrees compared to the earth's path around the sun. Most of the time, it passes slightly above or below the sun in our sky. Twice a year, the moon's orbit crosses the sun-earth line. These are called lunar nodes. When a new or full moon occurs near one of these nodes, we get an eclipse. A lunar eclipse happens when earth moves between the sun and the moon, casting its shadow on the moon's surface. Sunlight passing through earth's atmosphere scatters and turns red, creating a blood moon. Lunar eclipses can be seen from the entire night side of earth. Solar eclipses are a rarer sight, with people traveling across the world to witness them. But how can the moon perfectly cover the sun at all? Although the sun is about 400 times larger than the moon, it's also roughly 400 times farther away. This makes them appear the same size in the sky, allowing the moon to perfectly cover the sun. There are three types of solar eclipse. A partial eclipse, when the moon covers only part of the sun. An annular eclipse, when the moon is farther from the earth, leaving a bright ring of light, also called the ring of fire. And the most spectacular of all, the total solar eclipse. Totality can last anywhere from a few seconds to a few minutes. It's only visible along a narrow path called the path of totality, the track of the moon's shadow across earth. Totality can only be seen from within the moon's full shadow, called the umbra. From the partial shadow, called the penumbra, we can see a partial eclipse. The path of totality is incredibly narrow. Even though total solar eclipses happen anywhere on earth about every 18 months, it can take centuries before one returns to the same place. Which is why witnessing totality is so extraordinary. Little by little, the world begins to change. Trees project tiny crescent suns onto the ground and shadows grow sharper. The temperature drops and the colors of the sunset appear across the horizon. The moon covers more of the sun until only a thin string of lights is revealed. These are called Bailey's beads, shaped by the moon's valleys. Then a flash of light, the diamond ring, and suddenly a total solar eclipse. For a few minutes, day turns into night. Birds stop chirping and return to their nests. Night creatures begin to stir. It's daytime, but we're able to see bright planets and stars. Look up and you'll see the sun's outer atmosphere, the wispy, glowing corona. For most of human history, total solar eclipses were the only way we could observe it. Today, we've found ways to extend this moment. Missions from the European Space Agency can recreate eclipse-like conditions in space, allowing us to study the corona beyond the few minutes of totality. Since 1995, ESA and NASA's Solar and Heliospheric Observatory, or SOHO, has used an instrument called a coronagraph, which revealed massive solar eruptions and uncovered thousands of comets flying close to the sun. PROBA-3 uses two spacecraft flying in precise formation so that one blocks the sun for the other, creating an artificial eclipse that allows scientists to observe the inner corona for hours at a time. Meanwhile, Solar Orbiter studies the sun from closer distances. It has provided some of the first close-up views of the sun's polar regions and is helping scientists understand the origin of the solar wind. Earth observation satellites in space can capture the moon's shadow as it races across Earth. Today, scientists can predict eclipses with extraordinary precision, mapping their paths centuries into the future and into the past. Which is how we know that on May 28, 585 BC, a total solar eclipse likely brought a truce between rival nations. And just as the Lydians and the Medes froze more than two millennia ago, we still stop everything to look up. Because eclipses bridge together the past and the present. They connect legend to science. They remind us that even in moments of darkness, there is always something to discover. From ancient myths to modern science, we've come to understand eclipses like never before. And still, when the sky goes dark during the middle of the day, it feels like magic.