Total solar eclipse sequence

Science in the shadow of the 2024 solar eclipse

On April 8th 2024, millions of people across the United States, Canada and Mexico were left spellbound by a total solar eclipse, as eerie darkness descended in the daytime. 

Total eclipses happen somewhere on Earth about every 18 months due to a peculiarity of the cosmos- the sun is 400 times farther away than the moon but also appears 400 times smaller than it. The path of totality, however, seldom passes over such highly populated areas. The craze for viewing the total eclipse was undeniable. Many flocked to the narrow band of the US where it was visible, with some even booking flights or skydiving during the eclipse for a once-in-a-lifetime experience.

Eclipses have played a crucial role in advancing the sciences, helping to prove Einstein’s theory of general relativity and aiding in the discovery of helium. They also present a unique opportunity for scientists to study certain aspects of the sun which are otherwise difficult to observe, such as the solar atmosphere, or corona. With the sun headed towards a peak in its 11-year cycle of activity, this was a particularly opportune moment to learn more about its behaviour and understand its inner workings. 

NASA supported citizen scientists across the US through various projects to study not only the sun, but also its impact on earth during the eclipse. Hundreds of photographers lining the path of totality helped in making an eclipse megamovie, while 35 teams of citizen scientists captured video clips to display the magnetic structure of the sun’s middle corona. NASA also launched high-altitude planes and balloons to get a clearer view of the eclipse and gather data.

Radio stations and amateur radio operators across the country were encouraged to send and receive as many radio signals as possible, measuring their strength and reach, to understand the effect of the eclipse on the ionosphere, a layer of our atmosphere crucial for radio communication. In fact, subtly shifted ‘time signals’ were observed coming out of a government station in Colorado, due to a Doppler shift caused by the rapid expansion and contraction of the ionosphere during the eclipse. This indicated rapid shifts in the ionosphere during the total eclipse as compared to those observed during sunrise and sunset, as if a switch were flipped off and on again. 

The effect of the eclipse on animal behaviour was also of interest, with past reports indicating widespread confusion. Some animals such as horses and cattle begin to turn in for the night, and crickets and cicadas might start chirping their evening song as the sky darkens and temperatures drop. Unusual animal behaviour has also been reported, with giraffes becoming more active and galloping around, and Galapagos tortoises apparently taking it as a sign to begin mating. While tortoises did not breed at an Ohio Zoo in the path of the eclipse, heightened activity was observed. Some of these behaviours are not understood, so scientists observed animals in zoos across the country and asked people to watch out for strange behaviour.

There is much that isn’t known about eclipses and their effect on our planet. From unravelling mysteries of solar physics to advancing our understanding of our own world, each eclipse fuels curiosity and drives breakthroughs in science. 

Image Credit: Ian Parker from Unsplash

Image Description: Total solar eclipse sequence