Shadow bands

Shadowbands

Shadow bands are thin, wavy lines of alternating light and dark that can be seen moving and undulating in parallel on plain-coloured surfaces immediately before and after a total solar eclipse.

- Shadow bands
Shadowbands

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In the lower picture, the light has been collimated.

Collimated beam

A collimated beam of light or other electromagnetic radiation has parallel rays, and therefore will spread minimally as it propagates.

A collimated beam of light or other electromagnetic radiation has parallel rays, and therefore will spread minimally as it propagates.

In the lower picture, the light has been collimated.
An example of an optical collimating lens.
Diagram of a collimated-light display system, as seen from the side of a flight simulator
Diagram of display system that uses collimated light and a real flight simulator

During a solar eclipse, the Sun's light becomes increasingly collimated as the visible surface shrinks to a thin crescent and ultimately a small point, producing the phenomena of distinct shadows and shadow bands.

English: Portrait of Hermann Goldschmidt, 1866

Hermann Goldschmidt

German-French astronomer and painter who spent much of his life in France.

German-French astronomer and painter who spent much of his life in France.

English: Portrait of Hermann Goldschmidt, 1866
Royal Medal to commemorate the 100th Asteroid, showing Astronomers John Russel Hind, Hermann Goldschmidt and Robert Luther, 1869
Portrait of Christ by Goldschmidt. Ink on paper. Date unknown

In 1820, Goldschmidt discovered shadow bands in total solar eclipses.

Partial and annular phases of the solar eclipse of May 20, 2012

Solar eclipse

A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring Earth's view of the Sun, totally or partially.

A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring Earth's view of the Sun, totally or partially.

Partial and annular phases of the solar eclipse of May 20, 2012
Comparison of minimum and maximum apparent sizes of the Sun and Moon (and planets). An annular eclipse can occur when the Sun has a larger apparent size than the Moon, whereas a total eclipse can occur when the Moon has a larger apparent size.
Geometry of a total solar eclipse (not to scale)
Fraction of the Sun's disc covered, f, when the same-sized discs are offset a fraction t of their diameter.
Total solar eclipse paths: 1001–2000, showing that total solar eclipses occur almost everywhere on Earth. This image was merged from 50 separate images from NASA.
Astronomers Studying an Eclipse painted by Antoine Caron in 1571
Records of the solar eclipses of 993 and 1004 as well as the lunar eclipses of 1001 and 1002 by Ibn Yunus of Cairo (c. 1005).
Erhard Weigel, predicted course of moon shadow on 12 August 1654 (O.S. 2 August)
Illustration from De magna eclipsi solari, quae continget anno 1764 published in Acta Eruditorum, 1762
The progression of a solar eclipse on August 1, 2008 in Novosibirsk, Russia. All times UTC (local time was UTC+7). The time span between shots is three minutes.
Eddington's original photograph of the 1919 eclipse, which provided evidence for Einstein's theory of general relativity.
The Moon's shadow over Turkey and Cyprus, seen from the ISS during a 2006 total solar eclipse.
A composite image showing the ISS transit of the Sun while the 2017 solar eclipse was in progress.
Eclipse path for total and hybrid eclipses from 2021 to 2040.

Phenomena associated with eclipses include shadow bands (also known as flying shadows), which are similar to shadows on the bottom of a swimming pool.