A total solar eclipse is not only a notable astronomical event but also plays a major role in leading to many important discoveries.
On April 8, millions of people across the United States had the opportunity to observe the solar eclipse. At noon local time, the sky will darken as a total solar eclipse appears in 15 states. Over the decades, total solar eclipses have become less mysterious and have become an opportunity to test scientific hypotheses and lead to many new discoveries, according to Business Insider. Here are 7 total solar eclipse events that help advance human scientific understanding.
1. Measure the Earth’s rotation
Some of the earliest records of eclipses date back thousands of years. Some experts believe that a stone carving on a monument in Ireland describes the eclipse that occurred on November 30, 3340 BC. Human-made traces on turtle shells from China and Babylonian clay tablets from more than 3,000 years ago also mention solar eclipses. Through historical descriptions of solar eclipses, 18th-century astronomer Edmond Halley first noticed that Earth’s rotation had slowed over millennia.
2. Discover the cause of a solar eclipse
Two modern scholars believe that the Greek philosopher Anaxagoras of Clazomenae recognized the Moon’s role in eclipses. Most likely, he developed the hypothesis after witnessing the annular solar eclipse on February 17, 478 BC.
Anaxagoras believed that air pressure caused the flat Earth to float in the center with the Sun, Moon and stars rotating around it. Despite that error, he still discovered the basic mechanism behind a solar eclipse. Anaxagoras believed that the Moon reflected sunlight. His hypothesis also correctly states that when the Moon moves in front of the Sun, it creates a solar eclipse. Similarly, when the Earth is between the Sun and the Moon, a lunar eclipse will take place. Anaxagoras also used the Moon’s shadow during a solar eclipse to estimate its size, but his calculations were much smaller than it actually was.
3. Estimate the distance from Earth to the Moon
On March 14, 189 BC, a total solar eclipse passed over northern Türkiye. Greek astronomer Hipparchus was just a child at the time, but he may have witnessed the event. Years later, Hipparchus was able to use someone else’s description of that eclipse to create one of the most accurate mathematical estimates of the distance from the Earth to the Moon. Although Hipparchus’s direct account is lost, a 4th-century scholar details how he used the information.
The astronomer estimated the distance between the total eclipse location in what is now Türkiye and Alexandria, Egypt (where 1/5 of the Sun was exposed) to calculate. Based on calculations, Hipparchus made several estimates, including a figure of 452,848 km, which is not too far from the exact distance of 384,400 km.
4. Predict the path of the eclipse
In the 11th or 12th century, Mayan astronomers made a remarkable prediction of their time. They calculated a total solar eclipse would take place in 1991 and their prediction was within a day of each other. It was not until many centuries later that humanity was able to make more accurate predictions. In the 18th century, Edmond Halley, famous for his discovery of the comet that bears his name, created a map predicting the path of the solar eclipse on March 5, 1715 with extremely high accuracy (with only a difference of 4 minutes), based on Isaac Newton’s law of universal gravitation.
5. Discovery of helium
Helium is abundant in the universe but very rare on Earth. A solar eclipse helped astronomers discover the element. French astronomer Pierre Jules César Janssen came to India to observe a solar eclipse on August 18, 1868. He used spectroscopy to separate sunlight into spectra.
Janssen saw a yellow line with a wavelength unlike any other element. At the same time, British astronomer Norman Lockyer developed a device to observe the Sun even without an eclipse. He also saw the same colored line. Lockyer called the mysterious element helium. It took scientists two decades to see it on Earth, in experiments with Mount Vesuvius lava and uranium.
6. Prove Einstein’s theory of relativity
Astronomer James Craig Watson was certain he found evidence of a new planet in the 1878 solar eclipse. Located between the Sun and Mercury, Vulcan was only visible when the Moon was obscured by the giant star. giant. Several more eclipses passed but no one found evidence of Vulcan. In 1915, Albert Einstein explained Mercury’s unusual orbit using the general theory of relativity. This explanation fits the data better than a mysterious planet that is difficult to observe.
However, Einstein’s theory of relativity had no scientific evidence until the solar eclipse on May 29, 1919. The physicist said the Sun’s gravity bends light from nearby stars. In 1919, there were several expeditions to Principe, an island off the coast of Africa, and Brazil. When the Moon obscures the Sun, astronomers take pictures. The stars appear to shift in position relative to the reference image. The new position shows that the Sun bends light as Einstein predicted.
7. Research eclipses from space
The Gemini 12 crew of Jim Lovell and Buzz Aldrin were the first to witness a total solar eclipse from space. On November 12, 1966, a solar eclipse moved from Peru to Brazil and the two astronauts flew near the band of totality. It was a coincidental event. Aldrin’s photos are somewhat less clear. Four years later, television channels reported on the solar eclipse of the century that took place on March 7, 1970. NASA also launched more than 20 rockets to study ultraviolet radiation and X-rays from the Sun during the phenomenon. They will continue to use rockets to collect data about the solar eclipse on April 8.