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Technology to the rescue 00:00:04:25,00:00:08:20, Just as modern cars don't look like|a Model T Ford anymore, so are present 00:00:08:21,00:00:12:07, day telescopes radically different|from their classic predecessors 00:00:12:08,00:00:14:17, like the five metre Hale telescope. 00:00:14:18,00:00:17:22, For one thing, their|mounts are much smaller. 00:00:17:23,00:00:21:21, The old-style mount is an equatorial|one where one of the axis 00:00:21:22,00:00:25:18, is always mounted parallel|to the Earth's rotation axis. 00:00:25:19,00:00:29:12, In order to keep track of the sky's|motion, the telescope simply 00:00:29:13,00:00:34:05, has to rotate around this axis at the|same speed with which the Earth rotates. 00:00:34:06,00:00:37:04, Easy, but space-hungry. 00:00:37:05,00:00:42:01, The modern day altitude azimuth|mounts are much more compact. 00:00:42:02,00:00:46:11, With a mount like that, the telescope|is pointed much like a cannon. 00:00:46:12,00:00:51:06, One simply chooses the bearing,|chooses the altitude, and off you go. 00:00:51:07,00:00:54:16, The problem is to keep|track of the sky's motion. 00:00:54:17,00:01:00:06, The telescope pretty much has to rotate|around both axis, and at varying speeds. 00:01:00:07,00:01:06:18, Essentially this only became possible once|telescopes were computer controlled. 00:01:06:19,00:01:08:21, A smaller mount is cheaper to build. 00:01:08:22,00:01:13:13, Moreover, it fits into a smaller dome|which reduces the cost even further 00:01:13:14,00:01:16:08, and it improves the image quality. 00:01:16:09,00:01:19:20, Take the twin Keck Telescopes|on Hawaii, for example. 00:01:19:21,00:01:22:15, Although their 10 metre mirrors|are twice as large as the one 00:01:22:16,00:01:26:11, of the Hale telescope, they|nevertheless fit into smaller domes 00:01:26:12,00:01:29:06, than the one on Palomar Mountain. 00:01:31:01,00:01:33:11, Telescope mirrors have evolved too. 00:01:33:12,00:01:35:03, They used to be thick and heavy. 00:01:35:04,00:01:37:21, Now they're thin and lightweight. 00:01:37:22,00:01:42:20, Mirror shells that can be many metres|wide are cast in giant, rotating ovens. 00:01:42:21,00:01:46:08, And they are still less|than 20 centimetres thick. 00:01:46:09,00:01:48:25, An intricate support structure|prevents the thin mirror 00:01:49:01,00:01:51:05, from cracking under its own weight. 00:01:51:06,00:01:55:03, Computer controlled pistons and actuators|also help to keep the mirror 00:01:55:04,00:01:56:21, in perfect shape. 00:01:59:09,00:02:01:13, This system is called active optics. 00:02:01:14,00:02:05:21, The idea is to compensate and to correct|any deformations of the main mirror 00:02:05:22,00:02:10:14, caused by gravity, the wind,|or temperature changes. 00:02:10:15,00:02:14:06, Now, a thin mirror also|weighs much less. 00:02:14:07,00:02:17:11, That means that its whole supporting|structure, including the mount 00:02:17:13,00:02:19:11, can also be a lot trimmer and lighter. 00:02:19:12,00:02:21:14, And cheaper! 00:02:21:15,00:02:24:09, Now here's the 3.6 metre|New Technology Telescope 00:02:24:10,00:02:27:19, built by European astronomers|in the late 1980s. 00:02:27:20,00:02:30:21, It served as a testbed for|many of the new technologies 00:02:30:22,00:02:32:03, in telescope building. 00:02:32:04,00:02:36:25, And even its enclosure has nothing in|common with traditional telescope domes. 00:02:37:01,00:02:40:06, The New Technology Telescope|was a great success. 00:02:40:07,00:02:43:07, It was time to break|the six metre barrier. 00:02:43:14,00:02:47:10, Mauna Kea Observatory sits on|the highest point in the Pacific 00:02:47:11,00:02:50:24, 4200 metres above sea level. 00:02:52:24,00:02:57:03, On the beaches of Hawaii, tourists|enjoy the Sun and the surf. 00:02:57:04,00:03:00:13, But high above them astronomers|face chilling temperatures 00:03:00:14,00:03:07:04, and altitude sickness in their quest to|unravel the mysteries of the Universe. 00:03:07:05,00:03:10:03, The Keck Telescopes are among|the largest in the world. 00:03:10:04,00:03:15:03, Their mirrors are 10 metres|across, and wafer-thin. 00:03:15:04,00:03:20:01, Tiled like a bathroom floor, they|consist of 36 hexagonal segments 00:03:20:02,00:03:23:12, each controlled to nanometre precision. 00:03:23:13,00:03:27:05, These are true giants, devoted|to observing the heavens. 00:03:27:06,00:03:30:03, The cathedrals of science. 00:03:30:04,00:03:32:15, Nightfall on Mauna Kea. 00:03:32:16,00:03:37:18, The Keck Telescopes begin collecting|photons from the far reaches of the cosmos. 00:03:37:19,00:03:40:13, Their twin mirrors combining|to be effectively larger 00:03:40:14,00:03:43:11, than all earlier telescopes. 00:03:43:12,00:03:46:09, What will be tonight's catch? 00:03:50:16,00:03:55:13, A pair of colliding galaxies,|billions of light-years away? 00:03:55:14,00:04:01:08, A dying star, gasping its last|breath into a planetary nebula? 00:04:01:09,00:04:07:01, Or maybe an extrasolar planet|that might harbour life? 00:04:07:02,00:04:11:23, On Cerro Paranal in the Chilean Atacama|Desert - the driest place on Earth - 00:04:11:24,00:04:16:01, we find by far the biggest|astronomy machine ever built: 00:04:16:02,00:04:19:14, the European Very Large Telescope. 00:04:32:04,00:04:35:13, The VLT is really four telescopes in one. 00:04:35:14,00:04:38:19, Each sporting an 8.2 metre mirror. 00:04:38:20,00:04:40:03, Antu. 00:04:40:04,00:04:41:06, Kueyen. 00:04:41:07,00:04:42:08, Melipal. 00:04:42:09,00:04:43:19, Yepun. 00:04:43:20,00:04:49:11, Native Mapuche names for the Sun,|the Moon, the Southern Cross and Venus. 00:04:49:12,00:04:53:20, The huge mirrors were cast in Germany,|polished in France, shipped to Chile 00:04:53:21,00:04:57:06, and then slowly transported|across the desert. 00:04:57:07,00:05:00:24, At sunset, the telescope|enclosures open up. 00:05:01:00,00:05:04:14, Starlight rains down on|the VLT mirrors. 00:05:05:06,00:05:08:02, New discoveries are made. 00:05:11:22,00:05:14:04, A laser pierces the night sky. 00:05:14:05,00:05:16:17, It projects an artificial star|into the atmosphere 00:05:16:18,00:05:19:21, 90 kilometres above our heads. 00:05:19:22,00:05:22:23, Wavefront sensors measure how|the star's image is distorted 00:05:22:24,00:05:25:03, by the atmospheric turbulence. 00:05:25:04,00:05:28:24, Then, fast computers tell a|flexible mirror how it has to 00:05:29:00,00:05:31:20, deform itself in order to|correct the distortion. 00:05:31:21,00:05:34:24, In effect untwinkling the stars. 00:05:35:00,00:05:38:15, This is called adaptive optics|and it's the big magic trick 00:05:38:16,00:05:40:08, of present day astronomy. 00:05:40:09,00:05:44:21, Without it, our view of the Universe|would look blurred by the atmosphere. 00:05:44:22,00:05:48:22, But with it, our images|are razor-sharp. 00:05:51:11,00:05:55:12, The other piece of optical wizardry|is known as interferometry. 00:05:55:13,00:05:59:09, The idea is to take the light from two|separate telescopes and to 00:05:59:10,00:06:02:16, bring it together in a single point,|while preserving the 00:06:02:17,00:06:05:08, relative shifts between|the lightwaves. 00:06:05:09,00:06:09:04, If it is done precisely enough the|result is that the two telescopes 00:06:09:05,00:06:12:15, act as if they were part of|a single, colossal mirror 00:06:12:16,00:06:15:23, as large as the distance|between them. 00:06:15:24,00:06:20:01, In effect, interferometry gives|your telescope eagle-like vision. 00:06:20:02,00:06:23:15, It allows smaller telescopes|to reveal a level of detail that 00:06:23:16,00:06:28:11, would otherwise only be visible|with a much larger telescope. 00:06:28:12,00:06:31:15, The twin Keck Telescopes on|Mauna Kea regularly team up 00:06:31:16,00:06:33:13, as an interferometer. 00:06:33:14,00:06:37:11, In the case of the VLT, all four|telescopes can work together. 00:06:37:12,00:06:40:19, In addition, several smaller|auxiliary telescopes can also 00:06:40:20,00:06:44:22, join the ranks in order to|sharpen up the view even more. 00:06:45:20,00:06:49:10, Other big telescopes can|be found all over the globe. 00:06:49:11,00:06:53:12, Subaru and Gemini North|on Mauna Kea. 00:06:53:13,00:06:58:06, Gemini South and the|Magellan Telescopes in Chile. 00:06:58:07,00:07:02:07, The Large Binocular Telescope|in Arizona. 00:07:04:04,00:07:06:20, They are constructed at|the best available sites. 00:07:06:20,00:07:09:18, High and dry, clear and dark. 00:07:09:20,00:07:12:16, Their eyes are as large|as swimming pools. 00:07:12:18,00:07:16:10, All kitted out with adaptive optics|to counteract the blurring 00:07:16:10,00:07:18:02, effects of the atmosphere. 00:07:18:04,00:07:21:24, And sometimes they can have the|resolution of a virtual behemoth 00:07:22:00,00:07:24:16, thanks to interferometry. 00:07:25:16,00:07:27:20, Here's what they've shown us. 00:07:27:22,00:07:29:10, Planets. 00:07:32:14,00:07:34:06, Nebulae. 00:07:35:08,00:07:39:24, The actual sizes - and squashed|shapes - of some stars. 00:07:39:24,00:07:43:04, A cool planet orbiting|a brown dwarf. 00:07:43:04,00:07:47:12, And giant stars whirling around|the core of our Milky Way Galaxy 00:07:47:14,00:07:52:18, governed by the gravity of|a supermassive black hole. 00:07:52:20,00:07:56:10, We've come quite a|way since Galileo's day.