by GREG CLERKX
Flight Engineer Chris Cassidy replaces a pump controller box, leaking ammonia coolant on the International Space Station, May 11, 2013. PHOTO/NASA
Any time we embark upon a journey, be it a morning commute or a leisurely day trip, we engage in transition. We are a travelling species, which means transitions are commonplace for us, mundane even. But there are some trips that can still fire the human imagination, and none more so than the journey, experienced only by a lucky few, from the surface of Earth to the beginning of space.
On his 108-minute flight in 1961, the Soviet cosmonaut Yuri Gagarin, the first human being in space, reached a peak altitude of 327 kilometres (203 miles), after blasting off the planet atop a mighty Vostok rocket. After launch shook his tiny capsule violently, Gagarin experienced the feeling of weightlessness, and saw the curvature of the Earth first-hand. By all accounts, he crossed the mysterious border between the Earth and space. Or did he? It has been more than half a century since Gagarin’s historic journey, but there is still no universally accepted definition of where space begins.
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Recent scientific discoveries have further muddled our terrestrial-celestial border confusion. In 2009, an instrument called the Suprathermal Ion Imager (SII) pinpointed 118 kilometres as the point at which charged particles from space begin to overwhelm the relatively mild particle flow of the Earth’s upper atmosphere. That was the point, researchers argued, where space really begins. Headlines hailing the discovery of the ‘edge of space’ briefly splashed across the media, but the attendant stories were hesitant, bracketing any notions of finality with alternative edge-of-space definitions.
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