Earth Day Science

Earth, the marvellous blue orb

The Earth as seen from space. Photo: AP  

Sometimes, you have to leave a place to appreciate it.

Humans have not exactly left Earth. It has been 40 years or so, in fact, since representatives of this erstwhile spacefaring species have been more than a few hundred miles from our planets surface.

Today, human spaceflight, such as it is, is centred on the International Space Station. It lumbers around Earth about 250 miles out. It is staffed by six astronauts conducting scientific and medical experiments.

One of the little-known benefits of the space station is that it is at just the right altitude to photograph things on Earth. Every week, the astronauts aboard the space station record images of things that would spew headlines if we saw them on any one of the thousands of planets that we now know circle other stars.

Earth Day is today, and so it’s worth taking a look.

From above, we can see how geology has become destiny. This is the one place we know in the universe where primordial forces the ones that gave rise to our wrinkled mountain ranges, gouges of canyons, winding ribbons of water and mud, circus spirals of clouds, volcanoes, continents slipping under one another, a crust that splits and belches fire have conspired to bring about life.

“Earth has been habitable for 4 billion years,” geologists say, “regulated by the ebb and flow of carbon dioxide in the atmosphere and the crust.” Washed out of the atmosphere by rain, that greenhouse gas weathers rocks, carrying silica, calcium and carbon compounds into the ocean and eventually under the ocean floor. Millions of years later, carbon dioxide is disgorged in volcanoes, replenishing the atmosphere.

The thermostat is self-regulating. The more carbon dioxide in the atmosphere, the more violent the weather, and the faster the gas is rained out. When it cools off, there is less rain and carbon dioxide builds back up.

Seems like one organism

Given a chance in the form of a stable environment, life thrives in unexpected ways. From above, the entire world seems like one organism, one market exchange for genes and, as demonstrated by lights seen from above, an increasingly complicated and gaudy nervous system more and more apparent to the rest of the cosmos.

The glory of the Earth is its blue oceans, the cradle of life as we know it. Someday, we might find another one Out There Earth 2.0, it is sometimes called.

Our planet’s marine blue is so striking that it showed up in Voyager 1s camera from 4 billion miles away on Feb. 14, 1990, and again posing in the far distance beyond Saturns rings for the Cassini spacecrafts camera on July 19, 2013.

The third rock from the sun is a pale blue dot, the only one we know.


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Printable version | Dec 1, 2021 10:54:54 PM | https://www.thehindu.com/in-school/sh-science/earth-the-marvellous-blue-orb/article7126399.ece

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