Earlier this week NASA released a photograph taken from the Cassini probe as it completed an orbit around Saturn. In the background, close to a billion miles away, a careful observer can make out a small dot, barely noticeable in the surrounding dark, that is home to six billion humans and uncountable forms of plant, animal and microbial life.
The photograph itself is a minor miracle, composed of 141 separate shots taken over a four-hour period in which Saturn experienced a solar eclipse. The image was also digitally enhanced to make Earth, Mars, Venus, and Saturn’s moons more noticeable. (Cassini is so far away from the earth that each pixel of the image represents roughly 45 miles.)
The Cassini probe was launched in 1997 and has been in orbit around Saturn since July 2004. The photograph that NASA published was taken four months ago, on July 19, a day when people were encouraged to wave at Saturn as Cassini began taking pictures of its former home. The probe will continue to gather data until 2017, at which point it is expected to burn up in Saturn’s atmosphere.
While it is one of the most spectacular images of the earth taken from deep space, the Cassini photograph is still much closer to home than the Voyager 1 photograph that NASA retrieved in 1990 from some 4 billion miles, an image that famously prompted the American astronomer Carl Sagan to refer to Earth as “a pale blue dot.” Sagan noted that this image confounded the “delusion that we have some sort of privileged position in the Universe.”
Far from condemning humanity to irrelevance, however, Sagan and many other scientists felt that the photographs inspired a deeper appreciation of the planet’s fragile beauty. Indeed, Carolyn Porco, who leads the Cassini imaging team at the Space Science Institute in Boulder, Colorado has said that a 2006 sighting of Earth among the rings of Saturn had left her eager to make another image that would allow “everyone around the globe to savor the uniqueness of our planet and the preciousness of the life on it.”
Living in an age of rapid technological progress, we often forget how long it has taken us to come to terms with the scales on which life as a whole can be understood, not to mention the truly baffling dimensions of interstellar space. Shortly before the French Revolution a Scot called James Hutton, the father of modern geology, recalibrated our sense of Earth’s age ‒ which Bishop James Ussher had, infamously, declared to be around 4,000 years ‒ when he realized that the rock strata in an “angular unconformity” in southern Scotland showed the true figure to be several degrees of magnitude beyond contemporary estimates.
As James Hutton decoded the “annals of a former world” and understood that Earth was millions rather than thousands of years old, he wrote that his “mind seemed to grow giddy by looking so far into the abyss of time.” Twenty years later the prodigious astronomer William Herschel came to a similar conclusion about the night sky when he concluded that ‘deep space’ must also imply ‘deep time.’ In a similarly unsettling moment, Herschel realized that his telescope’s power of “penetrating space” was also a way of “penetrating into time past” and that some of the light that he was observing must have been travelling for close to two million years.”
In the short time that Cassini has been travelling towards Saturn, a great deal seems to have happened on Earth, much of it far from inspirational. A war barely noticed outside Africa has quietly consumed more than 4,000,000 lives; trillions of dollars have been squandered on military conflicts and other geopolitical follies, and thanks to rampant greed and corruption, the global financial system has faltered and nearly ground to a halt twice. During this brief time, taken in our entirety, it is far from clear that we are making any progress at all.
Cassini’s images invite us to alter our perspective radically, and to remember in Sagan’s memorable words that “everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives” has lived on this pale blue dot; “every saint and sinner in the history of our species [has] lived there-on a mote of dust suspended in a sunbeam.” Space photographs moved Sagan to write that “Earth is the only world known so far to harbour life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.”
