1 00:00:00,000 --> 00:00:04,000 We all know that black things get hot. Just look at these 2 00:00:04,000 --> 00:00:08,000 two identical cars. They’re made out of the same materials 3 00:00:08,000 --> 00:00:12,000 and yet the black one is going to be a lot hotter than the white one. 4 00:00:12,000 --> 00:00:16,000 And that is because it is absorbing a lot of those beautiful sun rays. 5 00:00:16,000 --> 00:00:20,000 Why is Webb’s Radiator Super Black? 6 00:00:20,000 --> 00:00:24,000 Now the James Webb Space 7 00:00:24,000 --> 00:00:28,000 Telescope has two important sides. A hot side and a cool side. 8 00:00:28,000 --> 00:00:32,000 The sunshield blocks the heat on the one side and the mirror observes 9 00:00:32,000 --> 00:00:36,000 on the cool side. It even has a radiator to keep it extra cool. 10 00:00:36,000 --> 00:00:40,000 But everything except the mirrors are black on the side 11 00:00:40,000 --> 00:00:44,000 that needs to be cool? So I was questioning why 12 00:00:44,000 --> 00:00:48,000 are Webb’s radiators coated in this super dark paint? 13 00:00:48,000 --> 00:00:52,000 This paint is made by Ball Aerospace and it’s called Ball Infrared 14 00:00:52,000 --> 00:00:56,000 Black or BIRB. And it’s somehow vital to regulating 15 00:00:56,000 --> 00:01:00,000 Webb’s temperature. So the reason temperature control is 16 00:01:00,000 --> 00:01:04,000 on this telescope is that the telescope observes in the infrared 17 00:01:04,000 --> 00:01:08,000 spectrum of light. Now we may not 18 00:01:08,000 --> 00:01:12,000 but we do perceive it as heat. 19 00:01:12,000 --> 00:01:16,000 And so to get data without any interference from Webb’s instruments 20 00:01:16,000 --> 00:01:20,000 they have to be cooled. I am so ready for this! 21 00:01:20,000 --> 00:01:24,000 To well below -400 degrees Fahrenheit. 22 00:01:24,000 --> 00:01:28,000 Webb’s instruments naturally 23 00:01:28,000 --> 00:01:32,000 create heat as they work, so the radiator 24 00:01:32,000 --> 00:01:36,000 radiates that heat out of it. I’m going to look 25 00:01:36,000 --> 00:01:40,000 and show you here. I’ve got a flashlight we use for inspections. 26 00:01:40,000 --> 00:01:44,000 If you look at it that shiny thing 27 00:01:44,000 --> 00:01:48,000 over here and then look how black that is. 28 00:01:48,000 --> 00:01:52,000 music 29 00:01:52,000 --> 00:01:56,000 So why are these radiators black? 30 00:01:56,000 --> 00:02:00,000 Well, as it turns out, things that absorb heat 31 00:02:00,000 --> 00:02:04,000 also emit heat well. 32 00:02:04,000 --> 00:02:08,000 Now the reason black objects absorb and emit heat well involves a lot of math 33 00:02:08,000 --> 00:02:12,000 and a thing called the Stephan-Boltzmann Law. But what it comes down to is that they are 34 00:02:12,000 --> 00:02:16,000 highly emissive. Emissivity is a measure of how 35 00:02:16,000 --> 00:02:20,000 well something radiates heat. And according to physics, 36 00:02:20,000 --> 00:02:24,000 and ideal radiator is an ideal absorber. 37 00:02:24,000 --> 00:02:28,000 I left this board outside for an hour and the side with the black paint 38 00:02:28,000 --> 00:02:32,000 absorbed a lot more solar radiation. And then I went back 39 00:02:32,000 --> 00:02:36,000 at night with the FLIR camera. The black side of the wood 40 00:02:36,000 --> 00:02:40,000 is cooler than the white paint. It is acting like a small radiator. 41 00:02:40,000 --> 00:02:44,000 So it released its energy from earlier in the day much more 42 00:02:44,000 --> 00:02:48,000 efficiently than side with the white paint. 43 00:02:48,000 --> 00:02:52,000 The more emissive a material, the more it can transfer heat. 44 00:02:52,000 --> 00:02:56,000 The Ball Infrared Black paint on Webb’s radiators 45 00:02:56,000 --> 00:03:00,000 happens to be one of the most emissive substances ever 46 00:03:00,000 --> 00:03:05,640 sent to space! 47 00:03:05,640 --> 00:03:05,643 music