1 00:00:00,240 --> 00:00:10,839 [Music] 2 00:00:16,970 --> 00:00:14,749 hi everyone my name is Sophia and I am a 3 00:00:20,660 --> 00:00:16,980 third year grad student at Penn State 4 00:00:23,960 --> 00:00:20,670 and astronomy in astrobiology and I am 5 00:00:26,900 --> 00:00:23,970 doing my PhD in say which is search for 6 00:00:30,620 --> 00:00:26,910 extraterrestrial intelligence and this 7 00:00:32,930 --> 00:00:30,630 is a pretty uncommon choice SETI has 8 00:00:35,150 --> 00:00:32,940 often had kind of the perception of 9 00:00:38,739 --> 00:00:35,160 being kind of kooky fringe out of the 10 00:00:41,450 --> 00:00:38,749 mainstream and it doesn't actually get 11 00:00:44,810 --> 00:00:41,460 almost any government funding so it's a 12 00:00:46,459 --> 00:00:44,820 difficult discipline to do a PhD in but 13 00:00:48,439 --> 00:00:46,469 I think it's very important and we're 14 00:00:50,509 --> 00:00:48,449 sort of experiencing resurgence now and 15 00:00:52,880 --> 00:00:50,519 interest in the search for techno 16 00:00:54,559 --> 00:00:52,890 signatures which is this kind of new 17 00:00:56,959 --> 00:00:54,569 brand that talks about the same thing 18 00:00:59,630 --> 00:00:56,969 and so before I started I wanted to give 19 00:01:02,869 --> 00:00:59,640 a little bit of background on why I 20 00:01:05,870 --> 00:01:02,879 think study is a fruitful contribution 21 00:01:10,250 --> 00:01:05,880 to the field of astrobiology and why I 22 00:01:12,980 --> 00:01:10,260 personally have chosen to do it so for 23 00:01:15,170 --> 00:01:12,990 me there are two reasons that techno 24 00:01:17,720 --> 00:01:15,180 signatures tie very well into bio 25 00:01:19,640 --> 00:01:17,730 signatures one of these is that techno 26 00:01:22,250 --> 00:01:19,650 signatures could be more detectable than 27 00:01:25,700 --> 00:01:22,260 bio signatures if we're looking for life 28 00:01:27,290 --> 00:01:25,710 elsewhere in the universe it might be 29 00:01:29,180 --> 00:01:27,300 that we can find more detectable 30 00:01:30,770 --> 00:01:29,190 signatures by looking for something that 31 00:01:33,830 --> 00:01:30,780 intelligent or technological life is 32 00:01:36,830 --> 00:01:33,840 doing them by trying to maximize the 33 00:01:38,870 --> 00:01:36,840 signal-to-noise with instruments such as 34 00:01:41,300 --> 00:01:38,880 levar looking for say atmospheric bio 35 00:01:43,550 --> 00:01:41,310 signatures and another nice thing about 36 00:01:47,290 --> 00:01:43,560 techno signatures is in a lot of cases 37 00:01:49,070 --> 00:01:47,300 they have fewer natural confounders so 38 00:01:52,190 --> 00:01:49,080 specifically what I do is radio 39 00:01:54,020 --> 00:01:52,200 astronomy so if you see a very very 40 00:01:56,210 --> 00:01:54,030 narrow band radio signal coming from 41 00:01:58,520 --> 00:01:56,220 somewhere in the galaxy boom you've done 42 00:02:00,470 --> 00:01:58,530 it there's no natural Astrophysical 43 00:02:02,300 --> 00:02:00,480 phenomenon that we know of that could 44 00:02:03,820 --> 00:02:02,310 produce such a signal it has to be 45 00:02:08,109 --> 00:02:03,830 produced by some sort of synthetic 46 00:02:10,789 --> 00:02:08,119 synthesizer from a another intelligence 47 00:02:12,870 --> 00:02:10,799 whereas you have a lot of problems with 48 00:02:15,390 --> 00:02:12,880 a possible abiotic confounders 49 00:02:20,130 --> 00:02:15,400 or astrobiological systems atmospheres 50 00:02:23,430 --> 00:02:20,140 and that sort of thing so and I guess as 51 00:02:25,640 --> 00:02:23,440 a photo point i I see bio signatures and 52 00:02:27,870 --> 00:02:25,650 techno signatures is sort of a continuum 53 00:02:30,600 --> 00:02:27,880 we're talking a lot about say 54 00:02:32,970 --> 00:02:30,610 atmospheric bio signatures now if you 55 00:02:35,190 --> 00:02:32,980 don't see oxygen but you see a huge 56 00:02:37,080 --> 00:02:35,200 amount of chlorofluorocarbons or 57 00:02:38,340 --> 00:02:37,090 something like that suddenly your bio 58 00:02:40,170 --> 00:02:38,350 signature techno signature your line 59 00:02:41,730 --> 00:02:40,180 gets a little bit messy and so I think 60 00:02:44,000 --> 00:02:41,740 this is a really good time for the 61 00:02:45,660 --> 00:02:44,010 resurgence of this field and 62 00:02:47,640 --> 00:02:45,670 specifically what I'm going to be 63 00:02:49,650 --> 00:02:47,650 talking about is kind of the more 64 00:02:51,960 --> 00:02:49,660 traditional setting where we're looking 65 00:02:54,780 --> 00:02:51,970 for these radio signatures coming from 66 00:02:58,230 --> 00:02:54,790 somewhere else in the galaxy so with 67 00:02:59,970 --> 00:02:58,240 that background I'm going to start with 68 00:03:01,470 --> 00:02:59,980 my acknowledgments because science is a 69 00:03:04,020 --> 00:03:01,480 human endeavor and I could not have done 70 00:03:05,790 --> 00:03:04,030 this project without these humans Jason 71 00:03:08,400 --> 00:03:05,800 right my advisor at Penn State and 72 00:03:10,200 --> 00:03:08,410 Emilio Enriquez and Andrew Semien who 73 00:03:12,030 --> 00:03:10,210 are both part of the breakthrough listen 74 00:03:15,300 --> 00:03:12,040 initiative at the Berkeley City Research 75 00:03:18,270 --> 00:03:15,310 Center and this work that I'm presenting 76 00:03:21,140 --> 00:03:18,280 is currently in review and so hopefully 77 00:03:25,230 --> 00:03:21,150 will be published in say a month or so 78 00:03:28,200 --> 00:03:25,240 so I'm actually here going to show an 79 00:03:31,230 --> 00:03:28,210 edited version of a figure you saw a 80 00:03:33,030 --> 00:03:31,240 couple talks ago to point out but when 81 00:03:34,140 --> 00:03:33,040 we're looking for signals from radio 82 00:03:36,240 --> 00:03:34,150 transmitters somewhere else in the 83 00:03:39,600 --> 00:03:36,250 galaxy we have to think about how 84 00:03:41,580 --> 00:03:39,610 they're moving relative to us so because 85 00:03:43,470 --> 00:03:41,590 of the Doppler effect a transmitter 86 00:03:45,330 --> 00:03:43,480 that's moving towards us is going to 87 00:03:47,010 --> 00:03:45,340 appear at a higher frequency than it's 88 00:03:48,480 --> 00:03:47,020 actually transmitted I got and if it's 89 00:03:51,570 --> 00:03:48,490 moving away from us it's going to appear 90 00:03:53,580 --> 00:03:51,580 to lower frequency and this is important 91 00:03:55,170 --> 00:03:53,590 because when we think about where life 92 00:03:57,600 --> 00:03:55,180 is going to originate where intelligent 93 00:03:59,210 --> 00:03:57,610 life might be in the galaxy we usually 94 00:04:02,730 --> 00:03:59,220 think about planetary systems and 95 00:04:05,580 --> 00:04:02,740 planetary systems have orbits and they 96 00:04:07,199 --> 00:04:05,590 have bodies that are rotating and so 97 00:04:08,970 --> 00:04:07,209 these orbits and rotations are going to 98 00:04:12,330 --> 00:04:08,980 act movements toward and away from us 99 00:04:14,490 --> 00:04:12,340 and well the nice thing so we don't fit 100 00:04:16,500 --> 00:04:14,500 in SETI as we don't know what frequency 101 00:04:19,830 --> 00:04:16,510 this is going to be at inherently so 102 00:04:21,780 --> 00:04:19,840 whether it shows up at say 10 gigahertz 103 00:04:22,879 --> 00:04:21,790 or 4 gigahertz like we don't know what 104 00:04:25,070 --> 00:04:22,889 they're transmitting at 105 00:04:28,670 --> 00:04:25,080 so the actual Doppler shift doesn't 106 00:04:32,119 --> 00:04:28,680 matter too much but what does matter is 107 00:04:34,369 --> 00:04:32,129 if that velocity towards our way from us 108 00:04:37,010 --> 00:04:34,379 is changing over time then there's going 109 00:04:39,260 --> 00:04:37,020 to be some change in the frequency over 110 00:04:43,129 --> 00:04:39,270 time and that actually does matter 111 00:04:44,839 --> 00:04:43,139 ah so this here is an exoplanet radial 112 00:04:47,119 --> 00:04:44,849 velocity plot actually from one of the 113 00:04:49,670 --> 00:04:47,129 first exoplanets ever discovered and 114 00:04:51,529 --> 00:04:49,680 what you'll notice is think of this 115 00:04:53,570 --> 00:04:51,539 radial velocity as a frequency so this 116 00:04:55,580 --> 00:04:53,580 is your frequency axis it gets higher in 117 00:04:57,230 --> 00:04:55,590 frequency and then it gets lower in 118 00:05:00,350 --> 00:04:57,240 frequency over time and then it gets 119 00:05:01,610 --> 00:05:00,360 higher in frequency again and like I 120 00:05:03,890 --> 00:05:01,620 said in SETI we don't care what the 121 00:05:05,689 --> 00:05:03,900 actual frequency is but we do care about 122 00:05:08,570 --> 00:05:05,699 how quickly it's changing over time and 123 00:05:10,399 --> 00:05:08,580 that's called the drift rate so I've 124 00:05:12,769 --> 00:05:10,409 highlighted this region here in the 125 00:05:15,110 --> 00:05:12,779 yellow box this part of the radial 126 00:05:17,629 --> 00:05:15,120 velocity curve is where the frequency is 127 00:05:20,480 --> 00:05:17,639 changing the fastest over time so that's 128 00:05:21,800 --> 00:05:20,490 where the relative motion between us and 129 00:05:23,659 --> 00:05:21,810 the transmitter has the biggest effect 130 00:05:28,700 --> 00:05:23,669 on our signal and so that's what I want 131 00:05:31,689 --> 00:05:28,710 to think about so this plot is has a lot 132 00:05:34,459 --> 00:05:31,699 of stuff going on so I'll build it up so 133 00:05:37,159 --> 00:05:34,469 this is actually a plot of some data 134 00:05:39,969 --> 00:05:37,169 from a known extraterrestrial 135 00:05:41,809 --> 00:05:39,979 transmitter which is Voyager 136 00:05:45,499 --> 00:05:41,819 extraterrestrial in the literal sense of 137 00:05:47,689 --> 00:05:45,509 the word and what you're seeing here in 138 00:05:49,640 --> 00:05:47,699 these three panels are waterfall plots 139 00:05:51,279 --> 00:05:49,650 and we use these a lot in radio 140 00:05:55,339 --> 00:05:51,289 astronomy and what they show is 141 00:05:57,829 --> 00:05:55,349 frequency here on the x axis and time on 142 00:06:00,290 --> 00:05:57,839 the y axis and then the color shows you 143 00:06:02,360 --> 00:06:00,300 the intensity so this middle panel is 144 00:06:03,679 --> 00:06:02,370 the carrier wave of a Voyager and what I 145 00:06:05,899 --> 00:06:03,689 want you to get out of this is this is 146 00:06:09,110 --> 00:06:05,909 not a vertical one this line is sloped 147 00:06:10,999 --> 00:06:09,120 so this is the start of the observation 148 00:06:13,459 --> 00:06:11,009 and over time instead of going straight 149 00:06:16,040 --> 00:06:13,469 down staying at the same frequency you 150 00:06:18,140 --> 00:06:16,050 see it changing in frequency and this is 151 00:06:20,390 --> 00:06:18,150 important because luckily this 152 00:06:22,640 --> 00:06:20,400 particular slope is caused by the front 153 00:06:23,990 --> 00:06:22,650 rotation we know the Earth's rotation we 154 00:06:26,659 --> 00:06:24,000 can characterize that we can normalize 155 00:06:30,110 --> 00:06:26,669 it up and if we do that we get this nice 156 00:06:32,149 --> 00:06:30,120 sharp blue peak so yay we detected it at 157 00:06:35,300 --> 00:06:32,159 full signal-to-noise we know voyagers 158 00:06:35,800 --> 00:06:35,310 there that's great if you instead assume 159 00:06:36,730 --> 00:06:35,810 that 160 00:06:38,379 --> 00:06:36,740 it's gonna stay at the same frequency 161 00:06:40,330 --> 00:06:38,389 all the time and you don't account for 162 00:06:42,940 --> 00:06:40,340 the direct rate you get this red line 163 00:06:45,340 --> 00:06:42,950 and you notice suddenly you've lost a 164 00:06:46,629 --> 00:06:45,350 whole bunch of signal-to-noise it might 165 00:06:49,270 --> 00:06:46,639 be hard to tell that something's there 166 00:06:50,980 --> 00:06:49,280 you've lost the structure and so if 167 00:06:52,900 --> 00:06:50,990 you're not checking for all of these 168 00:06:56,440 --> 00:06:52,910 drift rates you might throw the baby out 169 00:06:59,080 --> 00:06:56,450 with the bathwater so how do we deal 170 00:07:00,490 --> 00:06:59,090 with that well like I said we don't know 171 00:07:02,650 --> 00:07:00,500 what frequency the signal is going to 172 00:07:05,230 --> 00:07:02,660 come at and we don't know what it's 173 00:07:06,520 --> 00:07:05,240 strict rates gonna be so the solution is 174 00:07:08,290 --> 00:07:06,530 we have to search all the frequencies 175 00:07:10,600 --> 00:07:08,300 and all the dearth traits in any data we 176 00:07:14,140 --> 00:07:10,610 get and if that sounds computationally 177 00:07:15,280 --> 00:07:14,150 expensive it is so unfortunately we 178 00:07:16,780 --> 00:07:15,290 can't go through all these waterfall 179 00:07:19,330 --> 00:07:16,790 plots by eye at this point we're just 180 00:07:21,520 --> 00:07:19,340 getting too many so we have to rely on 181 00:07:23,710 --> 00:07:21,530 algorithms and those algorithms have 182 00:07:27,909 --> 00:07:23,720 computation time and memory constraints 183 00:07:29,770 --> 00:07:27,919 so my first question when I ran into 184 00:07:31,210 --> 00:07:29,780 this problem was why don't you just 185 00:07:33,490 --> 00:07:31,220 search all the directories and the 186 00:07:34,810 --> 00:07:33,500 answer is it's just too expensive you 187 00:07:36,820 --> 00:07:34,820 don't want to waste time searching drift 188 00:07:38,140 --> 00:07:36,830 rates but aren't physical at all because 189 00:07:43,469 --> 00:07:38,150 they correspond to accelerations that 190 00:07:50,350 --> 00:07:47,200 basically the algorithms that we use to 191 00:07:52,450 --> 00:07:50,360 go through images and search for sloping 192 00:07:55,150 --> 00:07:52,460 lines searching for these drifting 193 00:07:56,740 --> 00:07:55,160 signals scale order n if you want to 194 00:08:00,130 --> 00:07:56,750 search twice as many drift rates it's 195 00:08:02,409 --> 00:08:00,140 gonna take you twice as long so how can 196 00:08:03,730 --> 00:08:02,419 we put reasonable bounds on the range of 197 00:08:06,520 --> 00:08:03,740 just rates who want our algorithms to 198 00:08:10,240 --> 00:08:06,530 search this question has been tackled 199 00:08:12,640 --> 00:08:10,250 before in 1971 and this was actually 200 00:08:14,620 --> 00:08:12,650 back when NASA was doing sunny so this 201 00:08:18,219 --> 00:08:14,630 was from the NASA project Cyclops report 202 00:08:20,980 --> 00:08:18,229 and there's this paragraph that I've 203 00:08:24,010 --> 00:08:20,990 highlighted some quotes out of that says 204 00:08:26,950 --> 00:08:24,020 okay well it's 1971 we don't know about 205 00:08:28,140 --> 00:08:26,960 any exoplanets so what do we know in our 206 00:08:31,450 --> 00:08:28,150 own solar system 207 00:08:34,329 --> 00:08:31,460 well Earth's rotation causes a dearth 208 00:08:36,579 --> 00:08:34,339 rate Jupiter has an eight-hour day which 209 00:08:39,339 --> 00:08:36,589 is the fastest rotation period in the 210 00:08:40,269 --> 00:08:39,349 solar system if an earth-like planet had 211 00:08:42,459 --> 00:08:40,279 an eight-hour day 212 00:08:45,010 --> 00:08:42,469 what drift rate would we get and so 213 00:08:47,130 --> 00:08:45,020 that's the math they did in 1971 and 214 00:08:50,850 --> 00:08:47,140 they said oh we get a drift rate 215 00:08:52,380 --> 00:08:50,860 10 to the negative 9 Nana hurts so it 216 00:08:54,900 --> 00:08:52,390 doesn't matter too much for this talk 217 00:08:57,090 --> 00:08:54,910 what those units are but it's drifting 1 218 00:08:59,400 --> 00:08:57,100 Hertz in frequency every second if 219 00:09:03,660 --> 00:08:59,410 you're observing it 1 gigahertz is what 220 00:09:05,280 --> 00:09:03,670 that means so they did that and then 221 00:09:07,290 --> 00:09:05,290 everybody in the community started using 222 00:09:09,000 --> 00:09:07,300 this as their standard they search for 223 00:09:14,040 --> 00:09:09,010 slopes up to 1 Nana Hertz and they're 224 00:09:15,750 --> 00:09:14,050 done cool now we know of exoplanets we 225 00:09:17,639 --> 00:09:15,760 know of a lot of we have a much larger 226 00:09:19,769 --> 00:09:17,649 sample size we know of a lot more that 227 00:09:22,230 --> 00:09:19,779 we could do to physically motivate that 228 00:09:24,300 --> 00:09:22,240 number but no one had done it so my 229 00:09:25,920 --> 00:09:24,310 question was could we take what we know 230 00:09:28,139 --> 00:09:25,930 about exoplanets I'm physically motivate 231 00:09:33,630 --> 00:09:28,149 that to see if we're choosing reasonable 232 00:09:35,400 --> 00:09:33,640 grades so you can break this problem 233 00:09:38,610 --> 00:09:35,410 down into pieces because they add 234 00:09:40,259 --> 00:09:38,620 linearly which is really nice so some of 235 00:09:41,639 --> 00:09:40,269 this we already know and this is the 236 00:09:44,009 --> 00:09:41,649 part that Oliver and Billingham kind of 237 00:09:45,750 --> 00:09:44,019 did where you say ok we know what the 238 00:09:47,579 --> 00:09:45,760 Earth's rotation is we can characterize 239 00:09:49,710 --> 00:09:47,589 that and we know what our orbit around 240 00:09:51,990 --> 00:09:49,720 the Sun is and so any relative motion 241 00:09:54,329 --> 00:09:52,000 from that we can correct out well we 242 00:09:56,220 --> 00:09:54,339 don't know is if we have a transmitter 243 00:09:58,740 --> 00:09:56,230 say sitting on a planet or in orbit 244 00:10:00,329 --> 00:09:58,750 around the star what's its rotation 245 00:10:02,519 --> 00:10:00,339 gonna be on that planet could even be on 246 00:10:04,410 --> 00:10:02,529 a moon with a rotation around a planet 247 00:10:06,030 --> 00:10:04,420 that's orbiting a star like you can make 248 00:10:10,290 --> 00:10:06,040 these systems arbitrarily complicated 249 00:10:12,269 --> 00:10:10,300 but there's some amount of terms there 250 00:10:14,460 --> 00:10:12,279 that you need to add into this side and 251 00:10:16,100 --> 00:10:14,470 that gives you your total relative 252 00:10:19,740 --> 00:10:16,110 acceleration so your total drift right 253 00:10:22,319 --> 00:10:19,750 so you can make this into an equation if 254 00:10:24,660 --> 00:10:22,329 you want and I've kind of color-coded 255 00:10:26,639 --> 00:10:24,670 the important terms here which is the 256 00:10:29,250 --> 00:10:26,649 yellow part is Earth's rotation and 257 00:10:31,319 --> 00:10:29,260 orbital motion cool we know that the 258 00:10:33,420 --> 00:10:31,329 pink part on the end here is all the 259 00:10:36,230 --> 00:10:33,430 radial accelerations which I included 260 00:10:38,280 --> 00:10:36,240 for completeness but that's say if 261 00:10:39,870 --> 00:10:38,290 someone out there made a even 262 00:10:41,340 --> 00:10:39,880 breakthrough starshot but the alien 263 00:10:43,710 --> 00:10:41,350 version have had something that was 264 00:10:45,900 --> 00:10:43,720 accelerating and transmitting it might 265 00:10:47,280 --> 00:10:45,910 have another term but we don't know 266 00:10:49,710 --> 00:10:47,290 anything about that so let's set that to 267 00:10:52,740 --> 00:10:49,720 zero so these are the two I focused on 268 00:10:54,780 --> 00:10:52,750 the rotation of whatever body is hosting 269 00:10:56,519 --> 00:10:54,790 the transmitter and then the orbital 270 00:10:56,910 --> 00:10:56,529 motion of whatever body so seeing the 271 00:11:01,049 --> 00:10:56,920 transfer 272 00:11:04,319 --> 00:11:01,059 and so what I did was I applied this to 273 00:11:06,419 --> 00:11:04,329 a bunch of different systems so I looked 274 00:11:07,619 --> 00:11:06,429 in the solar system basically doing what 275 00:11:09,929 --> 00:11:07,629 Oliver and Billingham did but with 276 00:11:12,689 --> 00:11:09,939 updated numbers solar system planets 277 00:11:14,069 --> 00:11:12,699 moons minor bodies so if there was a 278 00:11:14,519 --> 00:11:14,079 transmitter on a comment in our solar 279 00:11:16,139 --> 00:11:14,529 system 280 00:11:19,769 --> 00:11:16,149 what drift rate would that produce would 281 00:11:22,259 --> 00:11:19,779 we see that then I looked at rotation 282 00:11:24,059 --> 00:11:22,269 rates for exoplanets which unfortunately 283 00:11:27,329 --> 00:11:24,069 we don't have that much literature on 284 00:11:29,939 --> 00:11:27,339 right now but I did my best we looked at 285 00:11:32,400 --> 00:11:29,949 orbits from planets moons and exoplanets 286 00:11:34,079 --> 00:11:32,410 that are in very tight orbits around 287 00:11:36,119 --> 00:11:34,089 their host bodies which would maximize 288 00:11:38,909 --> 00:11:36,129 your acceleration and therefore maximize 289 00:11:41,009 --> 00:11:38,919 your drift rate we looked at orbits from 290 00:11:44,579 --> 00:11:41,019 minor bodies and exoplanets that are 291 00:11:47,129 --> 00:11:44,589 eccentric so when I say eccentric I mean 292 00:11:48,689 --> 00:11:47,139 really elliptical orbits and that the 293 00:11:49,829 --> 00:11:48,699 key with these is most of the time they 294 00:11:51,780 --> 00:11:49,839 won't give you very high dressed rates 295 00:11:53,699 --> 00:11:51,790 cuz they're going slow when they packed 296 00:11:56,340 --> 00:11:53,709 by the central body they're going really 297 00:11:58,889 --> 00:11:56,350 fast so I said what if you happen to 298 00:11:59,669 --> 00:11:58,899 catch it at this point from just the 299 00:12:02,720 --> 00:11:59,679 wrong angle 300 00:12:05,100 --> 00:12:02,730 what drift rate would you get and then 301 00:12:08,129 --> 00:12:05,110 so that included a little more because 302 00:12:10,470 --> 00:12:08,139 we wanted to do that for fun and finally 303 00:12:11,579 --> 00:12:10,480 we looked at orbits from okay what if 304 00:12:13,049 --> 00:12:11,589 the transmitter was around the black 305 00:12:14,609 --> 00:12:13,059 hole what if it was around a neutron 306 00:12:16,799 --> 00:12:14,619 star just trying to get kind of the most 307 00:12:19,650 --> 00:12:16,809 absurd scenarios to make sure all our 308 00:12:24,079 --> 00:12:19,660 bases were covered and at the same time 309 00:12:27,059 --> 00:12:24,089 we did some more theoretical work so 310 00:12:29,309 --> 00:12:27,069 what could our maximum upper limits be 311 00:12:30,479 --> 00:12:29,319 in different scenarios so one of them 312 00:12:33,090 --> 00:12:30,489 that we looked at was the break-up 313 00:12:34,859 --> 00:12:33,100 rotation rate for a spherical body so if 314 00:12:37,350 --> 00:12:34,869 you have a spherical body that's 315 00:12:39,960 --> 00:12:37,360 gravitationally bound and it's spinning 316 00:12:42,359 --> 00:12:39,970 really really fast eventually if you 317 00:12:44,429 --> 00:12:42,369 keep upping the velocity it'll throw 318 00:12:46,019 --> 00:12:44,439 itself apart where the centrifugal force 319 00:12:49,109 --> 00:12:46,029 on the equator is equal to the 320 00:12:50,609 --> 00:12:49,119 gravitational force so you can't have 321 00:12:52,409 --> 00:12:50,619 any rotation faster than that 322 00:12:54,650 --> 00:12:52,419 so we said that is our upper limit for 323 00:12:57,779 --> 00:12:54,660 rotation and tried some of those systems 324 00:13:01,199 --> 00:12:57,789 we tried theoretical systems that were 325 00:13:02,549 --> 00:13:01,209 doing surface grazing orbits so if your 326 00:13:04,349 --> 00:13:02,559 planet was literally touching the 327 00:13:07,300 --> 00:13:04,359 surface of the star you can't get much 328 00:13:10,480 --> 00:13:07,310 much faster than that 329 00:13:12,460 --> 00:13:10,490 and then we also looked at if you have 330 00:13:13,720 --> 00:13:12,470 one of those waterfall plots what's the 331 00:13:15,489 --> 00:13:13,730 maximum drift rate you could even 332 00:13:17,379 --> 00:13:15,499 observe so that would be the ultimate 333 00:13:20,800 --> 00:13:17,389 upper limit your instrumentation can't 334 00:13:22,749 --> 00:13:20,810 catch anything faster and we looked at 335 00:13:25,059 --> 00:13:22,759 people who have simulated planet 336 00:13:26,949 --> 00:13:25,069 formation and tracked rotation which is 337 00:13:29,920 --> 00:13:26,959 not very common but some people have 338 00:13:33,579 --> 00:13:29,930 done it and added those into our work as 339 00:13:36,670 --> 00:13:33,589 well so this is like the beautiful 340 00:13:39,999 --> 00:13:36,680 output of this project which is a table 341 00:13:41,439 --> 00:13:40,009 sorted by drift rate for all of these 342 00:13:43,900 --> 00:13:41,449 different systems so that I talked about 343 00:13:45,220 --> 00:13:43,910 in the past couple slides and there are 344 00:13:48,340 --> 00:13:45,230 a few things I want you to notice here 345 00:13:51,040 --> 00:13:48,350 the first one is this yellow bar at the 346 00:13:53,319 --> 00:13:51,050 top and that is the project cyclops 347 00:13:56,259 --> 00:13:53,329 recommendation that was the one Hertz 348 00:14:00,129 --> 00:13:56,269 per second at 1 gigahertz recommendation 349 00:14:01,480 --> 00:14:00,139 from NASA in 1971 and this table sorted 350 00:14:03,670 --> 00:14:01,490 by drift rate so you'll notice that 351 00:14:08,079 --> 00:14:03,680 anything above that line it would have 352 00:14:09,309 --> 00:14:08,089 caught if you used that cutoff and you 353 00:14:11,019 --> 00:14:09,319 took your data and ran it through one of 354 00:14:12,639 --> 00:14:11,029 those algorithms I mentioned you would 355 00:14:16,119 --> 00:14:12,649 get the signal at full signal-to-noise 356 00:14:18,400 --> 00:14:16,129 awesome anything below that line would 357 00:14:20,619 --> 00:14:18,410 not be caught including you'll notice a 358 00:14:25,689 --> 00:14:20,629 transmitter on i/o in our own solar 359 00:14:27,850 --> 00:14:25,699 system so that's no good and I wanted to 360 00:14:30,879 --> 00:14:27,860 show here breakthrough listen which is 361 00:14:33,340 --> 00:14:30,889 the biggest SETI search ever done is 362 00:14:35,650 --> 00:14:33,350 using something they were like a couple 363 00:14:38,699 --> 00:14:35,660 times the project Cyclops recommendation 364 00:14:41,590 --> 00:14:38,709 why not so they would catch everything 365 00:14:43,660 --> 00:14:41,600 here in the solar system but then they 366 00:14:45,100 --> 00:14:43,670 would miss some if there were 367 00:14:48,129 --> 00:14:45,110 transmitters on some of the exoplanets 368 00:14:52,179 --> 00:14:48,139 we knew ah they could be missed by 369 00:14:54,850 --> 00:14:52,189 breakthrough listens cutoff so with all 370 00:14:57,160 --> 00:14:54,860 that in mind we decided to recommend in 371 00:15:00,490 --> 00:14:57,170 this work the blue line here which is 372 00:15:03,910 --> 00:15:00,500 209 Hertz so 200 times what people were 373 00:15:06,790 --> 00:15:03,920 searching before to make sure that every 374 00:15:08,949 --> 00:15:06,800 observed system exoplanet system 375 00:15:11,679 --> 00:15:08,959 anything in the solar system would be 376 00:15:13,379 --> 00:15:11,689 caught by that recommendation and below 377 00:15:16,299 --> 00:15:13,389 that line I mean you can get up to 378 00:15:18,090 --> 00:15:16,309 ridiculous kind of arbitrarily high 379 00:15:20,340 --> 00:15:18,100 values here 380 00:15:21,689 --> 00:15:20,350 and basically what this tells you is if 381 00:15:23,400 --> 00:15:21,699 you want to look for transmitters around 382 00:15:25,079 --> 00:15:23,410 black holes you need a totally different 383 00:15:29,850 --> 00:15:25,089 survey design you can't keep using these 384 00:15:31,350 --> 00:15:29,860 same algorithms so I just kind of wanted 385 00:15:36,569 --> 00:15:31,360 to finish up with another view of that 386 00:15:37,860 --> 00:15:36,579 data so this is your frequency again so 387 00:15:39,900 --> 00:15:37,870 this is how much your frequency has 388 00:15:42,319 --> 00:15:39,910 changed over a 5-minute observation 389 00:15:46,079 --> 00:15:42,329 which is kind of standard for SETI and 390 00:15:49,019 --> 00:15:46,089 the pink line is project Cyclops so it 391 00:15:51,420 --> 00:15:49,029 catch anything kind of within this area 392 00:15:53,490 --> 00:15:51,430 but any higher slopes would be state 393 00:15:56,370 --> 00:15:53,500 so here's breakthrough listen with its 394 00:15:57,749 --> 00:15:56,380 grey line which does a lot better but 395 00:15:59,850 --> 00:15:57,759 would still miss if there was a 396 00:16:01,980 --> 00:15:59,860 transmitter on beta pick V which is a 397 00:16:03,920 --> 00:16:01,990 large gas giant exoplanet which is one 398 00:16:07,379 --> 00:16:03,930 of the few we have rotation rates for uh 399 00:16:08,850 --> 00:16:07,389 and I'm also showing this figure I'm 400 00:16:12,509 --> 00:16:08,860 sure you will notice this wonderful 401 00:16:14,160 --> 00:16:12,519 sinusoidal curve here and that's just a 402 00:16:16,710 --> 00:16:14,170 warning kind of warning to the audience 403 00:16:18,360 --> 00:16:16,720 that all of this only works if you can 404 00:16:20,819 --> 00:16:18,370 approximately direct rate is linear and 405 00:16:23,370 --> 00:16:20,829 if your observation time is really short 406 00:16:25,740 --> 00:16:23,380 compared to the orbital period or the 407 00:16:27,090 --> 00:16:25,750 rotational period you can do that but if 408 00:16:29,430 --> 00:16:27,100 you have something that's rotating 409 00:16:31,199 --> 00:16:29,440 really really fast for example like this 410 00:16:34,079 --> 00:16:31,209 particular asteroid in our solar system 411 00:16:35,970 --> 00:16:34,089 it had a transmitter on it your linear 412 00:16:38,009 --> 00:16:35,980 fits don't work anymore and so you have 413 00:16:39,480 --> 00:16:38,019 to keep that in mind that that's kind of 414 00:16:43,379 --> 00:16:39,490 a flaw in this method when you're using 415 00:16:45,900 --> 00:16:43,389 it so with that I just wanted to go 416 00:16:47,280 --> 00:16:45,910 through some takeaways the drift rates 417 00:16:49,290 --> 00:16:47,290 that could be produced by known 418 00:16:50,819 --> 00:16:49,300 Astrophysical systems greatly exceed the 419 00:16:52,439 --> 00:16:50,829 maximum drift rate that's been chosen by 420 00:16:55,590 --> 00:16:52,449 many SETI searches in the past which is 421 00:16:57,449 --> 00:16:55,600 not good we recommend using a maximum 422 00:16:59,009 --> 00:16:57,459 drift rate of 200 nano Hertz which is 423 00:17:00,689 --> 00:16:59,019 large enough to catch all of those known 424 00:17:04,169 --> 00:17:00,699 solar system objects and all known 425 00:17:06,299 --> 00:17:04,179 exoplanets and drift right scale 426 00:17:08,730 --> 00:17:06,309 linearly so using this more physically 427 00:17:10,860 --> 00:17:08,740 motivated maximum it's 200 times the 428 00:17:14,429 --> 00:17:10,870 computation time which is a lot but also 429 00:17:16,980 --> 00:17:14,439 it's easily parallelizable and so if you 430 00:17:19,530 --> 00:17:16,990 have the resources to go up to 200 it's 431 00:17:21,240 --> 00:17:19,540 a pretty reasonable proposition to it at 432 00:17:24,299 --> 00:17:21,250 least try going higher than this one 433 00:17:27,449 --> 00:17:24,309 Nana Hertz guideline that was proposed 434 00:17:29,260 --> 00:17:27,459 in the past so with that I will take any 435 00:17:36,970 --> 00:17:29,270 questions I'll leave these up and 436 00:17:46,060 --> 00:17:36,980 you for attention thank you very much 437 00:17:53,290 --> 00:17:51,460 hello little closer okay hi um so I have 438 00:17:55,060 --> 00:17:53,300 kind of a philosophical question for you 439 00:18:01,480 --> 00:17:55,070 I'm interested to hear your thoughts on 440 00:18:04,630 --> 00:18:01,490 like Dyson spheres and transitioning 441 00:18:06,040 --> 00:18:04,640 study into photometry and do you think 442 00:18:10,690 --> 00:18:06,050 that's a good idea 443 00:18:12,900 --> 00:18:10,700 or yeah just one any thoughts my thought 444 00:18:15,250 --> 00:18:12,910 is that it's an excellent idea and that 445 00:18:17,050 --> 00:18:15,260 broadening what techno signature means 446 00:18:20,620 --> 00:18:17,060 and I'm having that new label helps a 447 00:18:21,520 --> 00:18:20,630 lot to is very important and thinking 448 00:18:23,380 --> 00:18:21,530 about all of the different ways that 449 00:18:25,390 --> 00:18:23,390 technology impacts its environment so 450 00:18:27,100 --> 00:18:25,400 kind of like I was saying thinking about 451 00:18:28,840 --> 00:18:27,110 it in a spectral way when you're looking 452 00:18:30,040 --> 00:18:28,850 at exoplanet atmospheres what signatures 453 00:18:34,780 --> 00:18:30,050 could technology leave 454 00:18:36,250 --> 00:18:34,790 their ideas like looking for belts of 455 00:18:38,410 --> 00:18:36,260 satellites around planets the way we 456 00:18:40,890 --> 00:18:38,420 look for two moons automatically or 457 00:18:44,230 --> 00:18:40,900 Dyson spheres and I think they're all 458 00:18:45,580 --> 00:18:44,240 pieces in this larger puzzle and none of 459 00:18:47,350 --> 00:18:45,590 them have been explored very well in the 460 00:18:49,750 --> 00:18:47,360 past so there's a lot of work yet to do 461 00:18:52,660 --> 00:18:49,760 and we should be using all of the tools 462 00:18:54,550 --> 00:18:52,670 that we have so I do radio SETI because 463 00:18:56,080 --> 00:18:54,560 that's where I started I'm a radio 464 00:18:58,840 --> 00:18:56,090 astronomer but I do want to branch out 465 00:18:59,830 --> 00:18:58,850 into more types of techno signatures 466 00:19:05,610 --> 00:18:59,840 because I think they're all very