TechTV – Foundations of the Second Law. Brian Cox: Why we need the explorers. Pale Blue Dot. Seen from about 6 billion kilometers (3.7 billion miles, 40 astronomical units), Earth appears as a tiny dot (the blueish-white speck approximately halfway down the brown band to the right) within the darkness of deep space. Background The Voyager 1 spacecraft is a 722-kilogram (1,592 lb) robotic American space probe launched by NASA on September 5, 1977, to study the outer solar system and eventually interstellar space. Operating for 36 years, 7 months and 8 days as of today (15 April 2014), the spacecraft receives routine commands and transmits data back to the Deep Space Network.
It is the first probe to leave the solar system and is the farthest man-made object from Earth. A Universe From Nothing' by Lawrence Krauss, AAI 2009 Sustainable Energy - Without the Hot Air with David MacKay