0:08:09.317,0:08:14.298 (Birds chirping) 0:00:00.595,0:00:03.746 We're here at the University[br]of California, Santa Barbara 0:00:03.770,0:00:06.357 to discuss a dream of humanity: 0:00:06.381,0:00:09.363 the ability to exit our solar system 0:00:09.387,0:00:11.569 and enter another solar system. 0:00:11.593,0:00:15.177 And the solution is literally[br]before your eyes. 0:00:15.621,0:00:18.383 So I have two things on me[br]that you have -- I have a watch, 0:00:18.407,0:00:19.813 and I have a flashlight, 0:00:19.837,0:00:22.019 which, if it's not on you,[br]it's on your phone. 0:00:22.043,0:00:23.926 So the watch keeps time, 0:00:23.950,0:00:27.195 and my flashlight[br]just illuminates my environment. 0:00:27.219,0:00:30.456 So like art, to me,[br]science is illuminating. 0:00:30.480,0:00:32.877 I want to see reality in a different way. 0:00:32.901,0:00:34.410 When I turn on the flashlight, 0:00:34.434,0:00:37.304 suddenly the dark becomes bright,[br]and I suddenly see. 0:00:37.328,0:00:38.963 The flashlight and its light, 0:00:38.987,0:00:40.464 which you can see coming out -- 0:00:40.488,0:00:43.042 the light on my hand[br]is not only illuminating my hand, 0:00:43.066,0:00:44.768 it's actually pushing on my hand. 0:00:44.792,0:00:47.101 Light carries energy and momentum. 0:00:47.125,0:00:50.201 So the answer is not to make a spacecraft[br]out of a flashlight, 0:00:50.225,0:00:52.154 by having the exhaust come out this way 0:00:52.178,0:00:53.845 and the spacecraft goes that way -- 0:00:53.869,0:00:55.741 that's what we do today with chemistry. 0:00:55.765,0:00:56.947 The answer is this: 0:00:56.971,0:00:59.515 Take the flashlight and put it[br]somewhere on the Earth, 0:00:59.539,0:01:00.774 in orbit or on the Moon, 0:01:00.798,0:01:02.571 and then shine it on a reflector, 0:01:02.595,0:01:06.903 which propels the reflector to speeds[br]which can approach the speed of light. 0:01:06.927,0:01:09.411 Well, how do you make a flashlight[br]that's big enough? 0:01:09.435,0:01:10.752 This isn't going to do it, 0:01:10.776,0:01:12.855 my hand doesn't seem to be going anywhere. 0:01:12.879,0:01:15.101 And that's because the force[br]is very, very low. 0:01:15.125,0:01:17.125 So the way that you can solve this problem 0:01:17.149,0:01:19.964 is taking many, many flashlights,[br]which are actually lasers, 0:01:19.988,0:01:21.472 and synchronizing them in time, 0:01:21.496,0:01:25.100 and when you gang them all together[br]into a gigantic array, 0:01:25.124,0:01:27.344 which we call a phased array, 0:01:27.368,0:01:30.241 you then have a sufficiently[br]powerful system, 0:01:30.265,0:01:32.760 which, if you make it roughly[br]the size of a city, 0:01:32.784,0:01:36.910 it can push a spacecraft,[br]which is roughly the size of your hand, 0:01:36.934,0:01:41.161 to speeds which are roughly[br]25 percent the speed of light. 0:01:41.185,0:01:44.979 That would enable us to get[br]to the nearest star, Proxima Centauri, 0:01:45.003,0:01:47.450 which is a little over[br]four light years away, 0:01:47.474,0:01:49.474 in less than 20 years. 0:01:50.019,0:01:52.947 Initial probes would be[br]roughly the size of your hand, 0:01:52.971,0:01:55.577 and the size of the reflector[br]that you're going to use 0:01:55.601,0:01:57.490 is going to be roughly human size, 0:01:57.514,0:01:59.529 so not a whole lot larger than myself, 0:01:59.553,0:02:01.466 but a few meters in size. 0:02:01.490,0:02:07.561 It only uses the reflection of light[br]from this very large laser array 0:02:07.585,0:02:09.379 to propel the spacecraft. 0:02:09.403,0:02:11.378 So let's talk about this. 0:02:11.402,0:02:14.583 This is a lot like sailing on the ocean. 0:02:14.607,0:02:17.822 When you sail on the ocean,[br]you're pushed by the wind. 0:02:17.846,0:02:20.679 And the wind then drives the sail[br]forward through the water. 0:02:20.703,0:02:24.398 In our case, we're creating[br]an artificial wind in space 0:02:24.422,0:02:25.699 from this laser array, 0:02:25.723,0:02:29.049 except the wind is actually the photons[br]from the laser itself, 0:02:29.073,0:02:32.196 the light from the laser becomes the wind 0:02:32.220,0:02:33.545 upon which we sail. 0:02:33.569,0:02:35.100 It is a very directed light -- 0:02:35.124,0:02:37.248 it's often called directed energy. 0:02:37.272,0:02:38.702 So why is this possible today, 0:02:38.726,0:02:41.268 why can we talk about[br]going to the stars today, 0:02:41.292,0:02:42.971 when 60 years ago, 0:02:42.995,0:02:45.514 when the space program began in earnest, 0:02:45.538,0:02:47.728 people would have said,[br]"That's not possible"? 0:02:47.752,0:02:52.212 Well, the reason it's possible today[br]has a lot to do with the consumer, 0:02:52.236,0:02:54.236 and the very fact that you're watching me. 0:02:54.569,0:02:56.855 You're watching me[br]over a high-speed internet, 0:02:56.879,0:03:02.307 which is dominated by the photonics[br]of sending data over fiber optics. 0:03:02.776,0:03:06.501 Photonics essentially allow[br]the internet to exist 0:03:06.525,0:03:07.799 in the way it does today. 0:03:07.823,0:03:10.978 The ability to send vast amounts[br]of data very quickly 0:03:11.002,0:03:13.820 is the same technology[br]that we're going to use 0:03:13.844,0:03:16.958 to send spacecraft[br]very quickly to the stars. 0:03:16.982,0:03:19.530 You effectively have an infinite[br]supply of propellent, 0:03:19.554,0:03:21.403 you can turn it on and off as needed. 0:03:21.427,0:03:26.772 You do not leave the laser array[br]that produces the light on 0:03:26.796,0:03:28.201 for the entire journey. 0:03:28.225,0:03:30.757 For small spacecraft,[br]it's only on for a few minutes, 0:03:30.781,0:03:34.299 and then it's like shooting a gun. 0:03:34.323,0:03:38.363 You have a projectile[br]which just moves ballistically. 0:03:38.387,0:03:41.847 Even if we, as humans,[br]are not on the spacecraft, 0:03:41.871,0:03:44.667 at least we have the ability[br]to send out such spacecraft. 0:03:45.133,0:03:47.320 You want to remotely view, 0:03:47.344,0:03:50.844 or have remote imaging and remote sensing, 0:03:50.868,0:03:52.264 of an object. 0:03:52.288,0:03:54.887 So when we go to Jupiter, for example, 0:03:54.911,0:03:56.950 with a flyby mission, 0:03:56.974,0:03:58.609 we are taking pictures of Jupiter, 0:03:58.633,0:04:00.316 we're measuring the magnetic field, 0:04:00.340,0:04:01.514 the particle density, 0:04:01.538,0:04:03.529 and we're basically exploring remotely. 0:04:03.553,0:04:05.482 The same way that you are looking at me. 0:04:05.506,0:04:08.823 And all of the current missions[br]that are beyond the Moon 0:04:08.847,0:04:10.887 are remote-sensing missions. 0:04:10.911,0:04:13.744 What would we hope to find[br]if we visited an exoplanet? 0:04:13.768,0:04:16.141 Perhaps there's life on an exoplanet, 0:04:16.165,0:04:18.744 and we would be able to see[br]evidence of life, 0:04:18.768,0:04:21.029 either through atmospheric biosignatures 0:04:21.053,0:04:23.168 or through, you know, a dramatic picture, 0:04:23.192,0:04:25.958 we would be able to see something[br]actually on the surface. 0:04:25.982,0:04:28.681 We don't know if there's life[br]elsewhere in the universe. 0:04:28.705,0:04:32.379 Perhaps on the missions that we send out,[br]we will find evidence for life, 0:04:32.403,0:04:33.855 perhaps we will not. 0:04:34.196,0:04:37.076 And while economics may seem[br]like an inappropriate thing 0:04:37.100,0:04:40.868 to bring into a talk[br]on interstellar capability, 0:04:40.892,0:04:45.812 it is in fact one of the driving issues[br]in achieving interstellar capability. 0:04:46.479,0:04:50.620 You have to get things to the point[br]where they're economically affordable 0:04:50.644,0:04:51.914 to do what we want to do. 0:04:51.938,0:04:53.359 So currently, 0:04:53.383,0:04:54.909 we have systems in the lab 0:04:54.933,0:04:59.864 which have achieved the ability[br]to synchronize over very large scales, 0:04:59.888,0:05:03.618 out to about 10 kilometers[br]or roughly six miles. 0:05:04.367,0:05:07.234 We've been able to achieve[br]synchronization of laser systems, 0:05:07.258,0:05:08.869 and it's worked beautifully. 0:05:08.893,0:05:13.266 We've known how to build lasers[br]for many decades, 0:05:13.290,0:05:17.160 but it's only now that the technology[br]has gotten inexpensive enough, 0:05:17.184,0:05:18.755 and become mature enough 0:05:18.779,0:05:23.649 that we can imagine[br]having huge arrays, literally, 0:05:23.673,0:05:27.299 kilometer-scale arrays,[br]much like solar farms, 0:05:27.323,0:05:31.685 but instead of receiving light,[br]they transmit light. 0:05:31.709,0:05:37.522 The beauty of this type of technology[br]is it enables many applications, 0:05:37.546,0:05:40.490 not just relativistic flight[br]for small spacecraft, 0:05:40.514,0:05:43.172 but enables high-speed spacecraft, 0:05:43.196,0:05:45.601 high-speed flight in our solar system, 0:05:45.625,0:05:47.458 it enables planetary defense, 0:05:47.482,0:05:49.950 it enables space debris removal, 0:05:49.974,0:05:55.617 it enables powering of distant assets[br]that we may want to send power to, 0:05:55.641,0:05:59.426 such as spacecraft or bases[br]on the Moon or other places. 0:05:59.450,0:06:01.633 It's an extremely versatile technology, 0:06:01.657,0:06:04.315 it's something that humanity[br]would want to develop 0:06:04.339,0:06:07.466 even if they didn't want[br]to send spacecraft to the stars, 0:06:07.490,0:06:10.076 because that technology[br]allows so many applications 0:06:10.100,0:06:12.601 that are currently not feasible. 0:06:12.625,0:06:15.267 And therefore, I feel[br]it's an inevitable technology, 0:06:15.291,0:06:17.355 because we have the ability, 0:06:17.379,0:06:20.195 we just need to fine-tune the technology 0:06:20.219,0:06:23.426 and in a sense, wait for economics[br]to catch up with us 0:06:23.450,0:06:26.649 so that it becomes cheap enough[br]to build the large systems. 0:06:26.673,0:06:29.244 The smaller systems are affordable now. 0:06:29.268,0:06:32.704 And we've already started building[br]prototype systems in our lab. 0:06:33.284,0:06:35.291 So while it's not[br]going to happen tomorrow, 0:06:35.315,0:06:36.871 we've already begun the process, 0:06:36.895,0:06:38.990 and so far, it's looking good. 0:06:39.014,0:06:42.868 This is both a revolutionary program, 0:06:42.892,0:06:46.177 in terms of being[br]a transformative technology, 0:06:46.201,0:06:49.137 but it's also an evolutionary program. 0:06:49.161,0:06:52.808 So personally,[br]I do not expect to be around 0:06:52.832,0:06:56.698 when the first[br]relativistic flight happens. 0:06:56.722,0:07:00.117 I think that's probably 30-plus years off[br]before we get to that point, 0:07:00.141,0:07:01.712 and perhaps more. 0:07:01.736,0:07:02.910 But what inspires me 0:07:02.934,0:07:06.117 is to look at the ability[br]to achieve the final goal. 0:07:06.141,0:07:08.649 Even if it does not happen in my lifetime, 0:07:08.673,0:07:11.537 it can happen in the lifetime[br]of the next generation 0:07:11.561,0:07:12.998 or the generation beyond that. 0:07:13.022,0:07:16.099 The consequences are so transformative 0:07:16.123,0:07:19.568 that we literally, in my opinion,[br]must go down this path, 0:07:19.592,0:07:21.900 and must explore what the limitations are, 0:07:21.924,0:07:24.117 and then how do we overcome[br]the limitations. 0:07:24.141,0:07:25.895 The search for life on other planets 0:07:25.919,0:07:30.100 would be one of humanity's[br]foremost explorations, 0:07:30.124,0:07:32.225 and if we're able to do so, 0:07:32.249,0:07:34.645 and actually find life on another planet, 0:07:34.669,0:07:36.756 it would change humanity forever. 0:07:36.780,0:07:38.304 Everything is profound in life. 0:07:38.328,0:07:39.522 If you look deep enough, 0:07:39.546,0:07:44.427 you'll find something incredibly complex[br]and interesting and beautiful in life. 0:07:45.019,0:07:47.566 And the same is true[br]with the lowly photon 0:07:47.590,0:07:50.970 that we use to see every day. 0:07:51.352,0:07:56.071 But when we look outside[br]and we imagine something vastly greater, 0:07:56.095,0:07:59.309 an array of lasers that are synchronized, 0:07:59.333,0:08:03.472 we could imagine things[br]which are just extraordinary in life. 0:08:03.496,0:08:05.456 And the ability to go to another star 0:08:05.480,0:08:08.107 is one of those[br]extraordinary capabilities.