Strange phenomenon appears during a total solar eclipse

According to CNN, the total solar eclipse occurring on the night of August 12 and early morning of August 13 (Hanoi time) will provide scientists with a rare opportunity to study the mysterious phenomenon called shadow band. These are strange gray ripples that glide across the ground in the minutes just before and after totality, when the Moon completely obscures the Sun, making the sky dark.

Nature describes that, initially, the shadow bands appear faint and haphazard, but as the total phase approaches, they become more orderly and clear, the distance between the bands decreasing to 2.5-5 cm. After the total phase ends, this pattern reverses: the shadow band reappears, gradually fading and cluttering until it disappears completely.

During a solar eclipse, observers at different locations along the eclipse's path will see different shadow banding effects, with some being almost unable to see them while others can see them clearly.

According to Space, the shadow band is very difficult to photograph because it often occurs when only nearly 1% of sunlight is left unobscured by the Moon, so the contrast is extremely low. The normal speed of the shadow strip on the ground is about 3 m/s and the width is only about 2.5-5 cm, so they are very faint and blurred when taking photos or videos. Another reason is that the shadow bands are more visible when they are moving than when they are still.

For the past 175 years, researchers have tried to explain the shadow band phenomenon. One theory is that these bands are higher order interference fringes of a narrow slit diffraction pattern, formed when light waves pass through a narrow slit on a solid surface, creating a dark band in the middle and more bright bands on each side. Then, in 1924, Italian astronomer Guido Horn-D'Arturo suggested that the shadow band was the image of a pinhole of the Sun overlapping due to a gap in the Earth's upper atmosphere.

However, the most likely explanation for the shadow band is a meteorological effect from the last rays of sunlight being distorted by the Earth's turbulent atmosphere. During a solar eclipse, the Sun's disk is reduced to a very narrow "thread" of light, each point along this thread sparkling like a star. Therefore, the shadow band may be the combined result of the light coming from each glitter point.

David Turnshek, a professor of physics and astronomy at the University of Pittsburgh, first saw the shadow band as a teenager. This time he will fly to León, Spain, to observe the eclipse with some colleagues. Turnshek hopes to be able to detect and record video of the shadow band using ground-based equipment.

Turnshek is not the only researcher looking to record the shadow band on August 12. Gordon Telepun, a solar eclipse hunter who once served as a NASA ambassador, will be on the Spanish island of Mallorca to watch the event. He has seen the shadow bands in 5 out of 7 solar eclipses and emphasized that the shadow bands are easy to miss because they occur right before the total eclipse. Joe Conti, an independent researcher with a passion for physics in Massachusetts, is calling on eclipse observers across Iceland and Spain to record the mysterious phenomenon and hopes the data collected can help the scientific community find out exactly what causes the shadow band.

A total solar eclipse occurs when the Moon is between the Earth and the Sun, temporarily obscuring the Sun's surface from view from the ground. This creates a dark disk in the sky, surrounded by a faint halo of light from the Sun's outer atmosphere, called the corona. The Moon is about 400 times smaller than the Sun, but also about 400 times closer to Earth, making both appear the same size in the sky. For a total solar eclipse to occur, the Sun, Moon and Earth must be perfectly aligned in space.

According to Sky News, places in the path of totality will be in darkness. This band is 100 to 200 km wide on Earth's surface where the Moon's shadow sweeps across, turning day into twilight when the Moon completely obscures the Sun. Specifically, people in northern Russia, Greenland, Iceland, Spain and a small corner of Portugal will have the opportunity to admire the total solar eclipse. Britain and Ireland will experience a partial solar eclipse, when the Moon obscures between 90% and 96% of the Sun, creating a deep twilight effect rather than complete darkness. Meanwhile, people in the northern US from Alaska to North Carolina will see a partial eclipse.