WEBVTT Kind: captions Language: en 1 00:00:00.130 --> 00:00:02.310 I’m at the Arecibo Observatory in Puerto Rico. 2 00:00:02.310 --> 00:00:06.970 It is one of the world’s largest radio telescopes, with a dish 300 metres across. 3 00:00:06.970 --> 00:00:11.220 And I had seen pictures and video of this before I came here, 4 00:00:11.220 --> 00:00:15.860 but, honestly, the sheer scale is impossible to get across on camera. 5 00:00:15.860 --> 00:00:16.860 It is massive. 6 00:00:16.860 --> 00:00:20.539 For 50 years, it’s been listening to the sky, and one day, 7 00:00:20.539 --> 00:00:22.130 it might just save the world. 8 00:00:22.130 --> 00:00:26.140 Arecibo’s been part of discovering the large-scale structure of the universe. 9 00:00:26.140 --> 00:00:29.710 We’ve discovered pre-biotic molecules in distant galaxies, 10 00:00:29.710 --> 00:00:33.200 the first millisecond pulsar, the first exoplanets. 11 00:00:33.200 --> 00:00:34.660 The big one, which everyone knows about, 12 00:00:34.660 --> 00:00:38.020 is the Nobel Prize for the discovery of the binary pulsar 13 00:00:38.020 --> 00:00:41.230 and the way that its orbit decayed exactly as predicted by general relativity. 14 00:00:41.230 --> 00:00:43.110 There's 50 years of discoveries here, 15 00:00:43.110 --> 00:00:46.050 I could talk for 50 years on discoveries of Arecibo. 16 00:00:46.050 --> 00:00:48.970 One of the most incredible things about the observatory is this, 17 00:00:48.970 --> 00:00:51.610 the suspended platform that I’m standing on right now. 18 00:00:51.610 --> 00:00:56.080 This entire colossal structure is suspended in the air on cables, 19 00:00:56.080 --> 00:00:58.870 like a suspension bridge, there are no pillars underneath 20 00:00:58.870 --> 00:01:00.829 holding this up and getting in the way. 21 00:01:00.829 --> 00:01:05.579 All this weight is being carried by the three concrete towers around the dish. 22 00:01:05.579 --> 00:01:09.479 And this platform isn’t static: big parts of it move. 23 00:01:09.479 --> 00:01:12.729 The telescope, by going a short way north and south, 24 00:01:12.729 --> 00:01:15.450 can actually see about a third of the total sky from here. 25 00:01:15.450 --> 00:01:17.649 The main bowl of this dish is spherical. 26 00:01:17.649 --> 00:01:18.979 The complication, though, is: 27 00:01:18.979 --> 00:01:22.649 a spherical mirror doesn’t have a point of focus, like a hyperbolic mirror, 28 00:01:22.649 --> 00:01:26.579 which we’re used to with big optical telescopes and most big radio telescopes. 29 00:01:26.579 --> 00:01:28.900 And so, in order to get the signal to a focus, 30 00:01:28.900 --> 00:01:32.399 the Gregorian dome contains two smaller reflectors. 31 00:01:32.399 --> 00:01:34.829 These smaller reflectors actually bring everything to a point focus. 32 00:01:34.829 --> 00:01:38.719 That means, in the Gregorian dome, we can have much wider band receivers 33 00:01:38.719 --> 00:01:42.869 and cover from 0.3GHz to 10GHz in frequency. 34 00:01:42.869 --> 00:01:47.469 Arecibo can do something that most radio telescopes can’t: it can transmit. 35 00:01:47.469 --> 00:01:51.700 Famously, in 1974, it beamed the Arecibo message out to the stars, 36 00:01:51.700 --> 00:01:53.759 but there are also some more practical uses 37 00:01:53.759 --> 00:01:56.990 for sending big pulses of energy into space: radar. 38 00:01:56.990 --> 00:02:02.000 Arecibo can bounce radar signals off planets, asteroids and, well, 39 00:02:02.000 --> 00:02:03.799 anything nearby in the solar system. 40 00:02:03.800 --> 00:02:07.700 And it can build up clear pictures of what's out there in the dark. 41 00:02:07.700 --> 00:02:10.660 The advantage of using the radar imaging is 42 00:02:10.670 --> 00:02:15.540 you can actually see the shape much better compared to optical imaging. 43 00:02:15.540 --> 00:02:19.450 We can actually see boulders on the surface if they are close enough, 44 00:02:19.450 --> 00:02:23.130 if it looks like a bone or if it looks like a... sweet potato! 45 00:02:23.130 --> 00:02:25.970 The S-band transmitter is a high-powered transmitter 46 00:02:25.970 --> 00:02:30.070 that works at 2380MHz of frequency, that’s the S-band. 47 00:02:30.070 --> 00:02:32.900 The whole transmitter's a megawatt of power. 48 00:02:32.900 --> 00:02:35.630 This transmitter produces a beam of power, 49 00:02:35.630 --> 00:02:38.570 and if you put your hand right through it you could get burned. 50 00:02:38.570 --> 00:02:41.570 We mostly observe near-Earth asteroids. 51 00:02:41.570 --> 00:02:45.820 When new asteroids are found their orbit is not very well defined yet, 52 00:02:45.820 --> 00:02:50.070 the main thing that we can do is really enhance the orbit information. 53 00:02:50.070 --> 00:02:54.810 You transmit a signal and when it hits a moving object 54 00:02:54.810 --> 00:02:58.400 the wavelength of the signal changes depending on 55 00:02:58.400 --> 00:03:02.790 if the asteroid is moving towards the observer or away from the observer. 56 00:03:02.790 --> 00:03:08.710 In that way we can actually get an estimate, to millimetres per second, 57 00:03:08.710 --> 00:03:10.540 of the velocity of the asteroid. 58 00:03:10.540 --> 00:03:13.930 When new asteroids are found the distance can be determined 59 00:03:13.930 --> 00:03:16.940 to hundreds of metres, even tens of metres. 60 00:03:16.940 --> 00:03:21.100 We can get very accurate information of where the asteroid will be 61 00:03:21.100 --> 00:03:26.560 from now to a decade forward, or even a century forward. 62 00:03:26.560 --> 00:03:29.820 Asteroid Apophis, the preliminary orbiting information showed 63 00:03:29.820 --> 00:03:32.120 that it actually might hit the Earth. 64 00:03:32.120 --> 00:03:38.700 After it was observed with radar they could determine it will come super-close, 65 00:03:38.700 --> 00:03:43.690 it will probably disturb some of the satellites that are orbiting Earth, 66 00:03:43.690 --> 00:03:45.310 but it doesn’t hit the Earth. 67 00:03:45.310 --> 00:03:48.740 That’s very important to know, because now 68 00:03:48.740 --> 00:03:54.290 we know we don’t have to send Bruce Willis to deflect the asteroid(!) 69 00:03:54.290 --> 00:03:56.500 Of all natural catastrophes, 70 00:03:56.500 --> 00:04:00.100 impacts are the one thing that we can actually avoid. 71 00:04:00.100 --> 00:04:05.430 Earthquakes, volcanoes, they just happen and we can’t actually help that. 72 00:04:05.430 --> 00:04:09.260 But if we can observe an asteroid early enough 73 00:04:09.260 --> 00:04:14.840 we have an opportunity to deflect it. 74 00:04:14.840 --> 00:04:17.970 Thank you so much to everyone at the Arecibo Observatory. 75 00:04:17.970 --> 00:04:20.040 If you’d like to know more about them and their discoveries 76 00:04:20.040 --> 00:04:21.639 pull down the description for lots of links, 77 00:04:21.639 --> 00:04:23.910 and if you want to see behind the scenes on this video 78 00:04:23.910 --> 00:04:27.160 then Matt, who’s on camera, has been taking a load of footage 79 00:04:27.160 --> 00:04:29.010 and has put it together for the second channel.