1 00:00:00,000 --> 00:00:05,000 Understanding the vast scale of the Universe is no mean feat 2 00:00:05,000 --> 00:00:10,000 but Hubble has helped us to understand the skies around us. 3 00:00:10,000 --> 00:00:15,000 It has peered far away to the very edges of the visible Universe 4 00:00:15,000 --> 00:00:23,000 and taken snapshots of space as it appeared deep in the cosmic past, billions of years ago. 5 00:00:40,000 --> 00:00:44,000 Episode 68: The Hubble time machine 6 00:00:47,000 --> 00:00:52,000 Presented by Dr. J, aka Dr Joe Liske 7 00:00:54,000 --> 00:00:58,000 The Universe is a very big and very old place 8 00:00:58,000 --> 00:01:04,000 The distances and timescales involved in astronomy are sometimes difficult to wrap your head around 9 00:01:04,000 --> 00:01:09,000 For example, we usually think of the Solar System as being a pretty big place 10 00:01:09,000 --> 00:01:16,000 after all, it would take nearly 600 years to travel out to Neptune at the speed of an average passenger jet. 11 00:01:16,000 --> 00:01:22,000 But on a cosmic scale, the entire Solar System is just a tiny, tiny speck. 12 00:01:24,000 --> 00:01:30,000 As we can't travel to other galaxies or star systems and view them for ourselves 13 00:01:30,000 --> 00:01:33,000 we rely on telescopes like Hubble. 14 00:01:34,000 --> 00:01:38,000 One of the main scientific justifications for building Hubble 15 00:01:38,000 --> 00:01:43,000 was to measure the size and age of the Universe. 16 00:01:43,000 --> 00:01:48,000 This task has produced some of the telescope's most iconic images, 17 00:01:48,000 --> 00:01:55,000 taken as Hubble peered into the faraway Universe to see what galaxies looked like in the past. 18 00:01:58,000 --> 00:02:02,000 So how is it possible that Hubble can look into the past? 19 00:02:02,000 --> 00:02:09,000 Well, that's because, just like a spacecraft, light also travels at a finite speed. 20 00:02:09,000 --> 00:02:15,000 At 300,000 kilometres per second, this speed is very high, but it is still finite. 21 00:02:15,000 --> 00:02:20,000 That means that, in principle, everything we see is a thing of the past. 22 00:02:20,000 --> 00:02:27,000 Now normally, in our everyday lives, it doesn't matter, because the distances are just too small. 23 00:02:27,000 --> 00:02:32,000 But when we look at the Moon, we see it as it was about one second ago. 24 00:02:38,000 --> 00:02:42,000 The Sun we see as it was about eight minutes ago. 25 00:02:43,000 --> 00:02:45,000 For the nearest star it's about four years, 26 00:02:45,000 --> 00:02:53,000 and the edge of our galaxy we see as it was about 100,000 years ago. 27 00:02:54,000 --> 00:03:02,000 As we look further, these thousands of years turn into millions, and even billions, 28 00:03:02,000 --> 00:03:05,000 right back to when the Universe was very young. 29 00:03:05,000 --> 00:03:10,000 We see these galaxies as they were in the very distant past 30 00:03:11,000 --> 00:03:18,000 Galaxies near to us are fully-formed, seen as sleek spirals and smooth ellipticals 31 00:03:18,000 --> 00:03:28,000 As we travel further back we see toddlers that are rough around the edges, still in the middle of evolving into fully-grown galaxies. 32 00:03:32,000 --> 00:03:36,000 Nowhere is these seen better than in the Hubble Deep Field images. 33 00:03:36,000 --> 00:03:43,000 To create these images, Hubble gazed at the same patches of sky for very long periods of time 34 00:03:43,000 --> 00:03:49,000 gathering enough light to see extremely faint and very far away objects. 35 00:03:50,000 --> 00:03:55,000 These images show some of the most distant galaxies that have ever been observed, 36 00:03:55,000 --> 00:04:04,000 going back an incredible 13.2 billion years to a time when the Universe was only about half a billion years old. 37 00:04:05,000 --> 00:04:11,000 This far back in time, our Milky Way may have just formed 38 00:04:11,000 --> 00:04:18,000 However, the Earth only made an appearance just under 8.5 billion years later 39 00:04:18,000 --> 00:04:25,000 The entire history of the Earth has taken place over just a third of the Universe's lifetime 40 00:04:25,000 --> 00:04:29,000 from the Earth's formation, to the emergence of dinosaurs, 41 00:04:29,000 --> 00:04:32,000 early life, and humans, 42 00:04:32,000 --> 00:04:43,000 to the present day, where astronomers use Hubble to view some of the Universe's earliest inhabitants and explore our origins. 43 00:04:45,000 --> 00:04:49,000 So how do we know what these very distant galaxies look like today? 44 00:04:49,000 --> 00:04:51,000 Well, we can't know for sure. 45 00:04:51,000 --> 00:04:58,000 We do know, however, that the Universe on very large scales pretty much looks the same everywhere. 46 00:04:58,000 --> 00:05:08,000 That means that, today, these very distant galaxies will look very similar to the galaxies we observe in our local patch of the Universe around us. 47 00:05:08,000 --> 00:05:15,000 Vice versa, by looking at these distant galaxies we are also, in a way, observing our own past. 48 00:05:17,000 --> 00:05:26,000 Hubble is still searching the distant Universe for clues about how the Universe formed, and how it has evolved. 49 00:05:26,000 --> 00:05:35,000 Several of Hubble’s surveys, for example CANDELS, CLASH, and GOODS, are scanning for distant supernova explosions, 50 00:05:35,000 --> 00:05:38,000 objects that are good celestial distance markers. 51 00:05:40,000 --> 00:05:48,000 Observations of distant supernovae led to the discovery that the expansion of the Universe is accelerating, 52 00:05:48,000 --> 00:05:55,000 which earned three astronomers a Nobel Prize in Physics in 2011. 53 00:05:56,000 --> 00:06:06,000 Using Hubble, we can observe the Universe as it once was — going back to a time before the Sun, and perhaps even the Milky Way, had even formed. 54 00:06:06,000 --> 00:06:15,000 Hubble’s successor, the James Webb Space Telescope, due to be launched in 2018, will push this frontier even further, 55 00:06:15,000 --> 00:06:21,000 and will perhaps even allow us to observe the very first generation of galaxies to have formed in the Universe. 56 00:06:22,000 --> 00:06:29,000 This is Dr J, signing off for the Hubblecast. Once again, nature has surprised us beyond our wildest imagination. 57 00:06:33,000 --> 00:06:38,000 The Hubblecast is produced by ESA/Hubble at the European Southern Observatory in Germany. 58 00:06:38,000 --> 00:06:43,000 The Hubble mission is a project of international cooperation between NASA and the European Space Agency. 59 00:06:43,000 --> 00:06:46,000 www.spacetelescope.org 60 00:06:50,000 --> 00:06:54,000 Transcribed by ESA/Hubble. Translation --