Great Expeditions: 50 Journeys that changed our world. Levison Wood

Чтение книги онлайн.

       Saturn’s rings. The colour variations indicate different chemical compositions.

      The orbit around Jupiter accelerated both spacecraft towards their next destination, Saturn. In November 1980, and just 7.5 km (12 miles) off course, Voyager 1 sent back beautiful close-ups of Saturn’s rings, revealing incredible structures within them. The rings are composed of billions of particles, ranging from dust-size to much larger rocks the size of houses. One of the most memorable images of the entire Voyager mission was that of the spinning rings, backlit by the sun like giant spokes on a wheel. Voyager 1 then flew within 1,500 km (2,500 miles) of Titan, Saturn’s largest moon. It is one of only three moons known to have an atmosphere, made up mainly of nitrogen as well as methane. As a result, the photochemistry is thought to be similar to that of an early Earth, before life took hold.

      After this close up view of Titan, Voyager 1 then moved out of the plane of the Solar System towards interstellar space, its main mission complete.

      The world in a twist

      By 1986, Voyager 2 was now approaching Uranus. It found that the planet spins like the other planets but is tipped on its side. Scientists believe this was caused by a collision with a planet-sized body early in the history of the Solar System. As a consequence, its magnetic field is twisted by Uranus’ unusual rotation into a long corkscrew shape behind the planet. Uranus was also found to be the coldest planet in the Solar System. It is not the furthest planet from the sun but it has no internal heat source.

      Voyager 2 also discovered ten additional moons to add to the five that were already known. The most interesting of Uranus’ moons was Miranda, one of the most bizarre objects in the Solar System with 19-km (12-mile) deep canyons and giant escarpments. Its surface is an assortment of terrains and looks as though it has been glued together. Not surprisingly therefore, astronomers once believed that Miranda was smashed to pieces and re-assembled under its own gravitational pull. This could explain its bizarre configuration but the actual reason is still something of a mystery.

      More mind-bending discoveries

      Travelling at 64,000 km/h (40,000 mph), Voyager 2 made its rendezvous with Neptune, the last of the outer planets, in August 1989. It was just 35 km (22 miles) off its charted course and 1 second off its projected flyby time. The encounter revealed a storm the size of Earth with the fastest winds ever measured in the Solar System of nearly 1,600 km/h (1,000 mph). This astonished NASA scientists as Neptune is very far from the sun and it was thought that solar energy usually drives atmospheric activity. Having discovered six new moons, Voyager 2 then flew by the last solid body it would encounter in the Solar System, Triton, Neptune’s largest moon and the coldest known object in the Solar System. It orbits in an opposite rotation from the planet and it’s thought that it may have once been an independent object orbiting around the sun before a cataclysmic collision with another moon smashed Triton into the well of Neptune’s gravity. Voyager 2 revealed jagged mountains, high cliffs, frozen lakes and active geysers.

      The Pale Blue Dot

      The Voyager spacecraft are powered by plutonium radioisotope thermoelectric generators, but to preserve energy NASA have had to systemically shut down Voyager’s instruments. In 1990, its cameras were switched off but before doing so, one final image was taken by Voyager 1, the ‘Solar System Family Portrait’. It was dubbed ‘Pale Blue Dot’ by the astronomer Carl Sagan as Earth appears as no more than a fraction of a pixel in the image.

      With the main mission objectives complete but both spacecraft still functioning, albeit with fewer instruments still operational, the mission now became the Voyager Interstellar Mission. Its objective was to explore the edges of the Solar System beyond the outer planets to the outer limits of the Sun’s sphere of influence, and potentially beyond.

      Deep space traveller

      In 2012, Voyager 1 reached the outer edges of the Solar System and entered the transition into interstellar space. This is the space between star systems within our galaxy. As the ships move further into deep space the effects of the solar wind from our sun decrease and the interstellar galactic wind increases. When the ships’ sensors finally detect only a background reading of particles originating from within the Solar bubble, and detect that the direction of the magnetic field has changed, NASA will finally announce that Voyager 1 has fully entered interstellar space.

      Around 2025, power will finally run out on the spacecraft but they will continue to travel through space long after everything mankind has, or will ever build has gone. Currently, they are 4 light years away from Sirius, the brightest star in the heavens. In just 290,000 years, they will arrive there!

      ‘Look again at 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 … on a mote of dust suspended in a sunbeam.’

       Carl Sagan, in his book ‘Pale Blue Dot’

      Timeline for Voyager 1 and 2.

The American Frontier

       Lewis and Clark’s Corps of Discovery expedition

      “They collect the wild fruits and roots, attend to the horses or assist in that duty, cook, dress the skins and make all the apparel, collect wood and make their fires, arrange and form their teepees, and when they travel, pack the horses and take charge of all the baggage; in short the man does little else except attend his horses hunt and fish.

       Meriwether Lewis on the role of the Shoshone woman, August 19 1805.

       WHEN

      1804–6

       ENDEAVOUR

      To explore the huge and unknown new territory recently gained by the United States.

       HARDSHIPS & DANGERS

      The explorers faced an ever-present threat of violence from native tribes. They also experienced severe hunger, exhaustion and frostbite.

       LEGACY

      The expedition realized the moral right of United States to extend across the continent to the Pacific. It brought back hundreds of previously unknown species, as well as detailed maps of previously uncharted areas.

       The men could go no further.

      Frostbitten, lame and hungry beyond reason, they stood at the apex of a continent. Behind them lay the full length of the mighty river that they had spent sixteen exhausting months paddling, trekking, and rowing up. Ahead of them, they had expected to see another river, one that would give them food and a gentle ride down to the ocean. Instead, they saw a monstrous range of icy mountains. They would need horses and many days’ supplies to cross them and the only natives they had found were refusing to offer them anything. This, truly, was the end of their journey. They would never reach their destination.

      Then СКАЧАТЬ