Sunday, December 20, 2009

carl sagan and the interstellar adventures of the voyager mission

i contributed today's podcast to the excellent 365 days of astronomy project! go have a listen to carl sagan and the interstellar adventures of the voyager missions, or read the trascript below! (i like that they published the trasnscipt in the same lowercase form that i submitted it!)


hello everyone! i'm amanda bauer, a postdoctoral research fellow in astronomy at the university of Nottingham in england. today is december 20th, 2009, the 13th anniversary of astronomer carl sagan's death.

my first memory of carl sagan is from my first year as an undergraduate at the university of cincinnati. i was majoring in french and taking the university's only undergraduate astronomy course as my one science requirement. my professor played a few episodes of the COSMOS mini-series in class. eventhough this tv series was written in the late 1970s by carl sagan, ann druyan, and steven soter, the episodes made a memorable impression on me! i wondered why i had never seen anything explaining the universe so simply and understandably before. remember, this was back before youtube allowed us immediate access to all the good, and the bad, video information humans had to offer each other.

i'd like to mention an online video project i've been involved with at the university of nottingham, called sixty symbols. filmmaker brady haran, has worked in collaboration with scientists here to create 5-10 minute youtube videos about the various funny little letters and squiggles used by physicists and astronomers to explain concepts about the physical universe. you can find videos at

so a couple months after first being exposed to the COSMOS tv series, the movie contact was released, proving to be a huge inspiration in my thoughts about the future. in fact, just a few weeks later, i decided to change my course and switch my college major to physics, dedicated to the idea of studying astronomy as much as i could! i only found out many years later that the movie contact was actually based on a novel by carl sagan!

My student days are long gone now, but I regularly hear colleagues claim that he was a huge influence in their decision to study astrophysics.

In addition to communicating astronomy and critical thinking to the public, i admire carl sagan because he actively applied science to public welfare, he was a skeptic who fought against pseudo science, he wrote about the virtues of cannabis under the pseuonymn "Mr. X," he won a pulitzer prize for his book "The Dragons of Eden," and he contributed hugely to the scientific discoveries about our solar system made by space probes sent out in the 1970s and 80s.

One project in particular seems to have left a lasting impression on human beings: the twin voyager missions. in 1977, NASA launched the voyager 1 and voyager 2 spacecraft, which were intended for 4 year missions to explore the outer regions of our solar system! Both voyagers have completely exceeded all expectations for their missions and continue to explore the the farthest reaches of our solar system!

traveling aboard each voyager spacecraft is an ambitious time capsule, intended to communicate the story of humity to any being that might find them! referred to as a 'golden record,' each time capsule is a phonographic 12-inch gold-plated copper disk. carl sagan chaired the committee that determined what message should be sent out into space on the voyager spacecrafts to portray the uniqueness of life on earth. imagine how exciting it must have felt to lead the group of people who designed, created, and found what images, symbols, and sounds to use to explain to a potential distant unknown creature... who we are, where we are, and *what* we are!

in the end, the team included 115 images, nature sounds of earth, 90 minutes of music, and spoken greetings from 55 different languages, among other things.

voyager 1 remains the most distant human made object we have sent to space, having passed the distance of pioneer 10 on february 17, 1998. As of November 20th, 2009, voyager 1 is over 111 times the farther from the sun than the earth! that's 111 astronomical units. thats more than 16,000 million kilometers and about 4 times as far from the sun as pluto's orbit!

these little chunks of synthetic machinery have been traveling away from earth for 32 years, and continue to travel outward, well beyond the confines of our solar system, making them the first spacecraft in interstellar space! the nearest star to our sun, Proxima Centauri, is 4.2 light-years away. at its current speed (about 38,000 miles per hour!), it will take 56,000 years for voyager 1 to reach the next star!!

it will have lost power, and all interactive capabilities, long before that time. NASA scientists estimate that in 2025, the spacecraft will lose electrical power, because the Radio-isotope Thermo-electric Generators will run out of their plutonium fuel sources, due to natural radioactive decay. The voyagers will lose power well before they reach another star system.

but the good news is that the 'golden record' has a shelf life of 1 billion years!

it's actually impossible to predict the exact trajectory of the voyager spacecraft as they will get gravitationally bumped along their journeys. but they could pass nearby several thousands of stars during the next billion years, while the golden records will still be playable. and they will possibly pass out into intergalactic space! voyager 1 is traveling 35 degrees out of the ecliptic plane to the north. Voyager 2 is traveling 48 degrees out of the ecliptic plane to the south and will pass 4.3 light years (25 trillion miles) from Sirius, the brightest star in earth's night sky.

it's amazing how far these spacecraft will travel away from earth. and it reminds me just how incredible it is that the light from the distant galaxies that i study everyday, has traveled for over 10 billions years, across spacetime, without running into any obstacles, only to crash into the primary mirror of a telescope we happen to have sitting on the surface of earth. amazing!

relatively early on in the voyager missions, the voyager 1 spacecraft turned around to take an image of the earth on february 14, 1990. in that photo, earth appeared as a tiny dot, encompassing one single pixel of that entire image. carl sagan was inspired to call our home planet the "pale blue dot" based on that image, and i'd like to leave you with some of his words. thank you for listening:

"Consider again that dot. That's here. That's home. That's us. On it, everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another and to preserve and cherish that pale blue dot, the only home we've ever known."

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