Kids ASK! about Science & Technology
[Editor speaks: I'm sure most of you have heard the phrase "once in a blue moon", which is used to describe an usual occurrence. But has this "blue moon" ever been seen or witnessed by anyone? Does it even exist? Read on to find out...]
“The time was 1883, the year an Indonesian volcano named Krakatoa exploded. Scientists liken the blast to a 100-megaton nuclear bomb. Fully 600 km away, people heard the noise as loud as a cannon shot. Plumes of ash rose to the very top of Earth’s atmosphere. And the moon turned blue.
Krakatoa’s ash is the reason. Some of the ash-clouds were filled with particles about 1 micron (one millionth of a meter) wide–the right size to strongly scatter red light, while allowing other colors to pass. White moonbeams shining through the clouds emerged blue, and sometimes green.
Blue moons persisted for years after the eruption. People also saw lavender suns and, for the first time, noctilucent clouds. The ash caused “such vivid red sunsets that fire engines were called out in New York, Poughkeepsie, and New Haven to quench the apparent conflagration,” according to volcanologist Scott Rowland at the University of Hawaii.
Other less potent volcanos have turned the moon blue, too. People saw blue moons in 1983, for instance, after the eruption of the El Chichon volcano in Mexico. And there are reports of blue moons caused by Mt. St. Helens in 1980 and Mount Pinatubo in 1991.
The key to a blue moon is having in the air lots of particles slightly wider than the wavelength of red light (0.7 micron)–and no other sizes present. This is rare, but volcanoes sometimes spit out such clouds, as do forest fires.”
Source: Phillips, M. (2004, July 7). Blue moon. Retrieved July 29, 2008, from NASA – Science@NASA Web site: http://science.nasa.gov/headlines/y2004/
So, blue moons really do exist occasionally and the reason why blue moons can be seen is because the air has lots of particles that can scatter light into different colours. And when the white moonbeams shine through this air, the moon may appear blue or green.
You can also read the article, “Once in a blue moon” by Science@NASA here, http://science.nasa.gov/newhome/
headlines/ast26feb99_1.htm, for more interesting information about blue moons.
For more information, here are some recommended library books on the moon:
The moon by Elaine Landau
Publisher: New York: Children’s Press, 2008
Call No.: J 523.3 LAN
Exploring the moon by Peter Grego
Publisher: London : QED, 2007
Call No.: J 523.3 GRE
The moon exposed by Allison Lassieur
Publisher: Oxford : Raintree, 2007
Call No.: J 523.3 LAS
The Earth and its moon by Chris Oxlade
Publisher: London : Wayland, 2007
Call No.: J 523.3 OXL
If you would like to visit more websites on solar systems, here are some good sites to check out as well:
1) Solar System Exploration: Kids – http://solarsystem.nasa.gov/kids/index.cfm
2) StarChild: A Learning Centre for Young Astronomers – http://starchild.gsfc.nasa.gov/docs/
3) Astronomy For Kids – http://www.kidsastronomy.com/index.htm
All websites were last accessed on 3 August 2008. Please check the websites’ homepages for the terms and conditions of use. All book summaries were taken from the book descriptions. All images were extracted from www.amazon.com.
For the availability of the above book titles, please check the library catalogue.
Answered and posted by Ms Elizabeth Lee
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