06-10-2007 The Blue Marble (Article 106)

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Simon Kenny
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Location: Shannon, Co. Clare, Ireland

06-10-2007 The Blue Marble (Article 106)

Post by Simon Kenny » Wed Feb 04, 2009 11:27 am

The Blue Marble (Article 106)

This photograph of the Earth from space is one of the most powerful images ever taken. Astronauts on board the Apollo XVII spacecraft took it on their voyage to the Moon, the last humans to walk on its surface. It was taken about two hours after the spacecraft left Earth orbit, about 45,000 kilometres away. One astronaut compared the image to a child’s glass marble, which inspired its title.

The photo was taken about 10.30am, GMT, on December 7th 1972. Africa is clearly visible as it begins to straddle the midday meridian. The Sun was directly behind the camera, so the full hemisphere of the Earth is visible. Since it is December, the snowy expanses of Antarctica are clearly visible in sunlight, surrounded by great swirls of cloud over the Southern Ocean. Africa’s many climates are detectable in the cloud cover. Over Northern Africa, a cloudless atmosphere reveals the red sands of the Sahara and the arid deserts of Arabia to the East, with the narrow channel of the Red Sea dividing both. Mottled rain clouds form over equatorial Central Africa, while to the South is the cloudless Namibian desert. To the East, the island of Madagascar stands clear, its green tints suggesting a more benign climate.

The image has a profound emotional effect, encapsulating as it does the end of a process of understanding our place in the cosmos. Not very long ago, we thought we were the centre of all things, around which everything else revolved. First Copernicus, then Galileo and Kepler realised the Earth is a satellite of the Sun. Later discoveries showed the Sun itself resides in an outer suburb of an average galaxy, itself a member of a group of galaxies, which are gravitationally attached to a much bigger group, and so on. This picture brought home to us visually, as dry facts could never do, that we are very lucky to inhabit such a beautiful gem of a planet, the only one we know in the universe that supports life, and supports it in such vigorous variety. Clear skies!

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