1 00:00:12,770 --> 00:00:08,540 I'm going to talk to you a bit today 2 00:00:15,320 --> 00:00:12,780 about the isotopic record of the geo 3 00:00:18,019 --> 00:00:15,330 biological record or the geochemical 4 00:00:21,620 --> 00:00:18,029 record somewhat what Lucy was talking 5 00:00:23,749 --> 00:00:21,630 about and I will preface this that I am 6 00:00:25,819 --> 00:00:23,759 by no means an expert in ice topic 7 00:00:28,580 --> 00:00:25,829 chemistry but I'm the best you've got 8 00:00:29,870 --> 00:00:28,590 for this one I'm talking so I will try 9 00:00:32,269 --> 00:00:29,880 to answer any questions that you have 10 00:00:35,330 --> 00:00:32,279 after this but some of the questions 11 00:00:37,069 --> 00:00:35,340 might best be kept for the speakers so 12 00:00:40,189 --> 00:00:37,079 this is actually going to be just a 13 00:00:43,189 --> 00:00:40,199 short talk since this is a huge sort of 14 00:00:44,930 --> 00:00:43,199 topic and it's essentially a detective 15 00:00:46,549 --> 00:00:44,940 story where you look at a signal and 16 00:00:49,610 --> 00:00:46,559 then you try to interpret it and figure 17 00:00:51,349 --> 00:00:49,620 out the best that you can make of it so 18 00:00:53,060 --> 00:00:51,359 I'm just going to familiarize you with 19 00:00:55,340 --> 00:00:53,070 the different types of isotopic 20 00:00:58,189 --> 00:00:55,350 fractionation and the terminology that 21 00:01:02,360 --> 00:00:58,199 she says it's quite often times foreign 22 00:01:05,870 --> 00:01:02,370 from what we are used to seeing so first 23 00:01:08,090 --> 00:01:05,880 things first just in case as sarah has 24 00:01:12,649 --> 00:01:08,100 pointed out earlier oh i guess i should 25 00:01:14,120 --> 00:01:12,659 be doing this to ya not everybody never 26 00:01:15,889 --> 00:01:14,130 assume that your audience knows exactly 27 00:01:19,639 --> 00:01:15,899 what you're talking about for the most 28 00:01:21,830 --> 00:01:19,649 basic stuff so just in case you don't 29 00:01:26,179 --> 00:01:21,840 know what an isotope is i'm just going 30 00:01:28,399 --> 00:01:26,189 to cover that quickly so when atoms are 31 00:01:30,679 --> 00:01:28,409 formed either through decay of other 32 00:01:34,370 --> 00:01:30,689 atoms or initially form that the 33 00:01:38,870 --> 00:01:34,380 creation of the atom back in the stellar 34 00:01:41,420 --> 00:01:38,880 day is of matter you can form atoms with 35 00:01:44,109 --> 00:01:41,430 the same number of protons but different 36 00:01:50,480 --> 00:01:44,119 neutrons and so here's an example of 37 00:01:52,399 --> 00:01:50,490 carbon all of these have six protons but 38 00:01:54,080 --> 00:01:52,409 they have different various numbers of 39 00:01:57,830 --> 00:01:54,090 neutrons and so you can get a carbon of 40 00:02:00,499 --> 00:01:57,840 a wait of 1208 of 13 or a mass of 14 and 41 00:02:02,649 --> 00:02:00,509 so you have three different Prime forms 42 00:02:06,910 --> 00:02:02,659 of carbon out there for example and 43 00:02:11,210 --> 00:02:06,920 carbon-12 and carbon-14 are stable as in 44 00:02:13,520 --> 00:02:11,220 they don't decay to other forms of atoms 45 00:02:17,420 --> 00:02:13,530 to lesser atoms on an appreciable time 46 00:02:19,880 --> 00:02:17,430 scale but carbon-14 is radioactive has a 47 00:02:22,960 --> 00:02:19,890 half-life of 5,700 48 00:02:28,130 --> 00:02:22,970 years so after if you have like a a 49 00:02:30,199 --> 00:02:28,140 pound or a mole of carbon 14 after fifty 50 00:02:32,059 --> 00:02:30,209 seven hundred and fifteen years you will 51 00:02:33,920 --> 00:02:32,069 have half a pound or half a mole of 52 00:02:36,830 --> 00:02:33,930 carbon as it will have degraded to other 53 00:02:39,410 --> 00:02:36,840 products so primarily in the geochemical 54 00:02:42,260 --> 00:02:39,420 record since we're looking at timescales 55 00:02:44,720 --> 00:02:42,270 of 4 billion years and 3 billion years 56 00:02:48,680 --> 00:02:44,730 we're typically focused on the stable 57 00:02:50,840 --> 00:02:48,690 form of isotopes that we have the 58 00:02:52,400 --> 00:02:50,850 heavier isotopes are typically the less 59 00:02:55,699 --> 00:02:52,410 stable one so you're looking for the 60 00:03:02,660 --> 00:02:55,709 ones that mostly are near the mass of 61 00:03:04,880 --> 00:03:02,670 the the base Adam and the differences in 62 00:03:06,920 --> 00:03:04,890 the geologic record between the ratios 63 00:03:08,590 --> 00:03:06,930 of the assessee topes tells a lot about 64 00:03:13,250 --> 00:03:08,600 the environmental and biological 65 00:03:16,460 --> 00:03:13,260 conditions that we have so before we get 66 00:03:18,620 --> 00:03:16,470 into the talk I have to address this so 67 00:03:21,199 --> 00:03:18,630 there is a special sort of terminology 68 00:03:24,620 --> 00:03:21,209 that ice topic scientists use and it is 69 00:03:26,360 --> 00:03:24,630 this Delta notation and so if you look 70 00:03:28,670 --> 00:03:26,370 at any isotopic paper they're going to 71 00:03:31,580 --> 00:03:28,680 refer to the Delta values for their 72 00:03:34,610 --> 00:03:31,590 scopes and that is essentially you take 73 00:03:37,759 --> 00:03:34,620 however much of the heavier element is 74 00:03:40,130 --> 00:03:37,769 in this case carbon 13 and you find a 75 00:03:43,430 --> 00:03:40,140 ratio between carbon 13 and carbon to 76 00:03:46,610 --> 00:03:43,440 sample and then you subtract it from a 77 00:03:50,300 --> 00:03:46,620 ratio in a standard sample that has been 78 00:03:51,890 --> 00:03:50,310 established unilaterally so you always 79 00:03:53,720 --> 00:03:51,900 are comparing to the same value in the 80 00:03:56,270 --> 00:03:53,730 literature and then you divide that 81 00:03:59,030 --> 00:03:56,280 difference over that standard reference 82 00:04:02,560 --> 00:03:59,040 again and so you multiply it times a 83 00:04:06,110 --> 00:04:02,570 thousand and you get this Delta value 84 00:04:09,740 --> 00:04:06,120 and so this is reported as either Delta 85 00:04:12,560 --> 00:04:09,750 or per mil using this symbol which looks 86 00:04:14,020 --> 00:04:12,570 like a typo of a percentage symbol but 87 00:04:17,560 --> 00:04:14,030 that's actually what it looks like and 88 00:04:21,949 --> 00:04:17,570 so one percent of a composition of 89 00:04:25,010 --> 00:04:21,959 something is equal to 10 Delta or 10 per 90 00:04:27,230 --> 00:04:25,020 mil and apparently this is a a point of 91 00:04:29,089 --> 00:04:27,240 contention among isotopic scientists 92 00:04:30,460 --> 00:04:29,099 that you refer to it as Delta or per 93 00:04:32,350 --> 00:04:30,470 meal instead of del 94 00:04:34,450 --> 00:04:32,360 apparently that's like nails on the 95 00:04:36,130 --> 00:04:34,460 chalkboard for a lot of people so 96 00:04:38,890 --> 00:04:36,140 they've actually I found this in my 97 00:04:41,440 --> 00:04:38,900 studies they have a they have this poem 98 00:04:43,900 --> 00:04:41,450 there once was a man from Cornell who 99 00:04:46,320 --> 00:04:43,910 pronounced every Delta as del but the 100 00:04:50,910 --> 00:04:46,330 spirit of Erie returned in a fury and 101 00:04:56,740 --> 00:04:50,920 transferred that fellow to hell so 102 00:04:58,540 --> 00:04:56,750 remember that Delta and per meal so the 103 00:05:00,340 --> 00:04:58,550 reference standards that I pointed out 104 00:05:02,470 --> 00:05:00,350 before this is what's been established 105 00:05:04,540 --> 00:05:02,480 in the geochemical community and if I 106 00:05:08,230 --> 00:05:04,550 mistaken you can take it up with the 107 00:05:12,160 --> 00:05:08,240 either Wikipedia or the isotope 108 00:05:13,660 --> 00:05:12,170 geochemistry this afternoon but the 109 00:05:18,490 --> 00:05:13,670 reference standards for the carbon 110 00:05:25,500 --> 00:05:18,500 ratios come from this Vienna peedee 111 00:05:27,790 --> 00:05:25,510 belemnite all right from South Carolina 112 00:05:30,130 --> 00:05:27,800 nitrogen they just fixed it to our 113 00:05:34,090 --> 00:05:30,140 current ratio of nitrogen in the 114 00:05:39,550 --> 00:05:34,100 atmosphere hydrogen and oxygen since the 115 00:05:42,159 --> 00:05:39,560 ocean is a great sort of bulk bulk area 116 00:05:44,620 --> 00:05:42,169 its ratio does not change much so they 117 00:05:48,100 --> 00:05:44,630 fixed that standard to the modern mean 118 00:05:49,810 --> 00:05:48,110 ocean water value and sulfur this one's 119 00:05:52,210 --> 00:05:49,820 always a bit intriguing to me and I wish 120 00:05:55,810 --> 00:05:52,220 I knew why they fix it to this meteorite 121 00:05:58,750 --> 00:05:55,820 sample from Canyon Diablo oh it must be 122 00:06:00,730 --> 00:05:58,760 a popular one or there might be some 123 00:06:04,750 --> 00:06:00,740 legitimate scientific reason for it but 124 00:06:06,219 --> 00:06:04,760 that is what that is fixed to so there 125 00:06:07,960 --> 00:06:06,229 are three different types of 126 00:06:11,140 --> 00:06:07,970 fractionation that I'm going to touch 127 00:06:13,120 --> 00:06:11,150 upon here the first one is equilibrium 128 00:06:15,100 --> 00:06:13,130 fractionation since when you're looking 129 00:06:17,320 --> 00:06:15,110 at samples in the rock they'll have 130 00:06:18,730 --> 00:06:17,330 different ratios and in order to 131 00:06:20,290 --> 00:06:18,740 understand how they get to that ratios 132 00:06:22,420 --> 00:06:20,300 you have to understand the processes 133 00:06:25,240 --> 00:06:22,430 that go into fractionating them between 134 00:06:28,150 --> 00:06:25,250 the heavy and the lighter isotopes so 135 00:06:30,070 --> 00:06:28,160 equilibrium fractionation fractionation 136 00:06:32,860 --> 00:06:30,080 involves separation of the isotopes 137 00:06:35,290 --> 00:06:32,870 based upon an equilibrium process so if 138 00:06:37,480 --> 00:06:35,300 you have a chemical reaction going in 139 00:06:39,730 --> 00:06:37,490 some water in there exchanging atoms 140 00:06:43,029 --> 00:06:39,740 between them there might be a tendency 141 00:06:43,690 --> 00:06:43,039 for one of the size of the equilibrium 142 00:06:45,880 --> 00:06:43,700 reaction to 143 00:06:49,510 --> 00:06:45,890 scavenge up the heavier isotopes for 144 00:06:51,280 --> 00:06:49,520 example and so you will see a definite 145 00:06:55,690 --> 00:06:51,290 signature between the heavy and the 146 00:06:57,460 --> 00:06:55,700 light products and reactants in this 147 00:07:00,240 --> 00:06:57,470 reaction based upon just equilibrium 148 00:07:02,670 --> 00:07:00,250 processes and this is dependent upon 149 00:07:04,690 --> 00:07:02,680 larger atoms the heavier isotopes 150 00:07:07,360 --> 00:07:04,700 typically have a decrease in the 151 00:07:09,070 --> 00:07:07,370 vibrational energy and so that affects 152 00:07:11,350 --> 00:07:09,080 what side of the equilibrium equation 153 00:07:14,980 --> 00:07:11,360 they'll show up a pond and so an example 154 00:07:16,750 --> 00:07:14,990 of this not one hundred percent of the 155 00:07:19,900 --> 00:07:16,760 time but a lot of the time is water 156 00:07:22,450 --> 00:07:19,910 condensation so if you have a room at 157 00:07:24,400 --> 00:07:22,460 one hundred percent humidity and juror 158 00:07:26,980 --> 00:07:24,410 and you have some water droplets that 159 00:07:29,200 --> 00:07:26,990 form it is freely exchanging between the 160 00:07:31,960 --> 00:07:29,210 water moisture in the atmosphere and the 161 00:07:33,670 --> 00:07:31,970 water moisture on the surface and so the 162 00:07:35,380 --> 00:07:33,680 heavy isotopes in the drops that are 163 00:07:37,510 --> 00:07:35,390 forming as long as that one hundred 164 00:07:39,970 --> 00:07:37,520 percent humidity is maintained will 165 00:07:41,890 --> 00:07:39,980 precipitate more readily and so the 166 00:07:46,630 --> 00:07:41,900 water and those droplets will be heavier 167 00:07:48,430 --> 00:07:46,640 than the water in the air a second type 168 00:07:51,730 --> 00:07:48,440 of fractionation is kinetic 169 00:07:53,890 --> 00:07:51,740 fractionation and so this is the other 170 00:07:56,920 --> 00:07:53,900 type of processes that occur during non 171 00:08:01,120 --> 00:07:56,930 equilibrium conditions and so that would 172 00:08:03,970 --> 00:08:01,130 be if you had wind blowing through that 173 00:08:08,200 --> 00:08:03,980 previous experiment and it wasn't 100% 174 00:08:11,190 --> 00:08:08,210 heute humid anymore and you're going to 175 00:08:13,210 --> 00:08:11,200 get still some water condensation or 176 00:08:15,550 --> 00:08:13,220 actually let's look at this in the 177 00:08:18,580 --> 00:08:15,560 reverse manner sorry as I have done here 178 00:08:20,770 --> 00:08:18,590 evaporation is typically a process so 179 00:08:23,530 --> 00:08:20,780 you'll have water that has reached a 180 00:08:27,120 --> 00:08:23,540 high enough temperature to kick up some 181 00:08:30,220 --> 00:08:27,130 of the water into water vapor and that 182 00:08:32,260 --> 00:08:30,230 the heavier elements will be left behind 183 00:08:34,480 --> 00:08:32,270 and the lighter elements are 184 00:08:37,990 --> 00:08:34,490 preferentially kicked into the water 185 00:08:40,330 --> 00:08:38,000 vapor and then wind blows through and it 186 00:08:42,550 --> 00:08:40,340 blows out those lighter elements making 187 00:08:44,350 --> 00:08:42,560 it a non equilibrium condition which 188 00:08:46,450 --> 00:08:44,360 then encourages more of the lighter 189 00:08:49,440 --> 00:08:46,460 elements to come into the air and then 190 00:08:51,880 --> 00:08:49,450 pulled away so that's an example of a 191 00:08:55,240 --> 00:08:51,890 kinetic fractionation process and 192 00:08:55,710 --> 00:08:55,250 another major thing here is biological 193 00:08:57,540 --> 00:08:55,720 process 194 00:08:59,400 --> 00:08:57,550 these are typically not at equilibrium 195 00:09:01,259 --> 00:08:59,410 so they're driven in one direction and 196 00:09:04,710 --> 00:09:01,269 have a very hard time going backwards 197 00:09:10,259 --> 00:09:04,720 and so you see a large preference for 198 00:09:12,300 --> 00:09:10,269 lighter isotopes in biological processes 199 00:09:16,259 --> 00:09:12,310 and this is one of the major line of 200 00:09:18,480 --> 00:09:16,269 evidence that they look at for the bio 201 00:09:20,280 --> 00:09:18,490 signatures that Lucy was talking about 202 00:09:23,059 --> 00:09:20,290 before if you see something that looks 203 00:09:26,610 --> 00:09:23,069 like life you can take an ice etobicoke 204 00:09:29,309 --> 00:09:26,620 from it and see if it's if it 205 00:09:31,550 --> 00:09:29,319 corresponds to the environment of what 206 00:09:34,769 --> 00:09:31,560 you would expect or if it's enriched in 207 00:09:38,569 --> 00:09:34,779 light isotopes or if it's enriched in 208 00:09:41,069 --> 00:09:38,579 one direction then it's indicative of a 209 00:09:43,230 --> 00:09:41,079 biological process and so that's some of 210 00:09:46,860 --> 00:09:43,240 the things that they've used for some of 211 00:09:49,590 --> 00:09:46,870 the rock samples from Greenland from 3.6 212 00:09:51,210 --> 00:09:49,600 billion years ago as to try to support 213 00:09:54,840 --> 00:09:51,220 the evidence that the samples they're 214 00:09:57,809 --> 00:09:54,850 looking at our from living matter and so 215 00:10:01,100 --> 00:09:57,819 all of this together in a nice pretty 216 00:10:05,040 --> 00:10:01,110 diagram so if you look at the ocean as a 217 00:10:06,840 --> 00:10:05,050 base value of zero percent so that's our 218 00:10:09,420 --> 00:10:06,850 reference material and you're looking at 219 00:10:13,129 --> 00:10:09,430 the oxygen the heavy oxygen as it goes 220 00:10:16,470 --> 00:10:13,139 throughout the year environmental system 221 00:10:19,019 --> 00:10:16,480 it first starts with the evaporation 222 00:10:20,670 --> 00:10:19,029 lighter isotopes evaporate and so 223 00:10:23,759 --> 00:10:20,680 suddenly you have the clouds up there 224 00:10:26,269 --> 00:10:23,769 that are at negative ten Delta or 225 00:10:29,639 --> 00:10:26,279 negative 10 per mil and so you now have 226 00:10:32,910 --> 00:10:29,649 clouds that are isotopically lighter 227 00:10:36,660 --> 00:10:32,920 than the ocean then when they head over 228 00:10:38,879 --> 00:10:36,670 the land you it starts to rain you 229 00:10:44,460 --> 00:10:38,889 preferentially rain the heavier isotopes 230 00:10:48,150 --> 00:10:44,470 and so now you get it's only negative 231 00:10:52,730 --> 00:10:48,160 three per mil now and the water vapor up 232 00:10:56,549 --> 00:10:52,740 here is then negative 15 per mil and so 233 00:11:00,480 --> 00:10:56,559 you get lighter elements down here which 234 00:11:03,119 --> 00:11:00,490 is at the same time enhancing the water 235 00:11:05,189 --> 00:11:03,129 that's left behind then you can get 236 00:11:08,129 --> 00:11:05,199 evaporation returning it to the system 237 00:11:09,300 --> 00:11:08,139 which helps to make it lighter again in 238 00:11:10,860 --> 00:11:09,310 the vapor passes 239 00:11:14,190 --> 00:11:10,870 I'm you can cross over some mountain 240 00:11:17,700 --> 00:11:14,200 ridges and the subsequent precipitation 241 00:11:21,750 --> 00:11:17,710 then changes the ratio again so you do 242 00:11:23,490 --> 00:11:21,760 get you can track how the fractionation 243 00:11:26,280 --> 00:11:23,500 changes throughout this ecological 244 00:11:28,800 --> 00:11:26,290 system and it tells you some evidence 245 00:11:30,780 --> 00:11:28,810 where the water came from what happened 246 00:11:32,490 --> 00:11:30,790 to it along the way it just leaves them 247 00:11:34,560 --> 00:11:32,500 signal behind that you can put your 248 00:11:37,890 --> 00:11:34,570 detective hat on and help to figure out 249 00:11:39,660 --> 00:11:37,900 what is going on the last type of 250 00:11:42,329 --> 00:11:39,670 isotope fractionation I'm going to talk 251 00:11:45,300 --> 00:11:42,339 about is mass independent and so this is 252 00:11:48,180 --> 00:11:45,310 stuff that's not the the kinetic isotope 253 00:11:52,290 --> 00:11:48,190 of fractionation that I talked about 254 00:11:55,560 --> 00:11:52,300 before or the the unidirectional one so 255 00:12:01,260 --> 00:11:55,570 this is not based upon mass for the 256 00:12:03,150 --> 00:12:01,270 fractionation so this oh it's not based 257 00:12:05,480 --> 00:12:03,160 upon the mass so it doesn't scale 258 00:12:07,710 --> 00:12:05,490 linearly like it did with the 259 00:12:10,950 --> 00:12:07,720 equilibrium and kinetic fractionation 260 00:12:12,960 --> 00:12:10,960 this is based on photochemical and spin 261 00:12:16,530 --> 00:12:12,970 forbidden reactions and so you'll see 262 00:12:18,810 --> 00:12:16,540 some signals that are left behind due to 263 00:12:20,310 --> 00:12:18,820 the isotopic fractionation that is not 264 00:12:21,960 --> 00:12:20,320 covered by the previous forms that i 265 00:12:23,990 --> 00:12:21,970 mentioned and i'll get to a picture in 266 00:12:29,490 --> 00:12:24,000 just a second that will be quite 267 00:12:31,079 --> 00:12:29,500 informative but one of the best things 268 00:12:33,900 --> 00:12:31,089 that they use to track this with is 269 00:12:36,750 --> 00:12:33,910 sulfur isotopes and so when you look at 270 00:12:39,440 --> 00:12:36,760 a graph like this so this is a display 271 00:12:41,850 --> 00:12:39,450 of sulfur isotope fractionation 272 00:12:45,180 --> 00:12:41,860 throughout the Earth's geologic history 273 00:12:48,360 --> 00:12:45,190 and if you look at this you can see a 274 00:12:51,420 --> 00:12:48,370 giant scatter plot over here and then 275 00:12:54,180 --> 00:12:51,430 suddenly it all evens out it is level 276 00:12:57,150 --> 00:12:54,190 for the past two and a half billion 277 00:13:00,090 --> 00:12:57,160 years and see I hope if you're a 278 00:13:02,520 --> 00:13:00,100 scientist or anybody and look at this 279 00:13:05,630 --> 00:13:02,530 you could be like something has happened 280 00:13:08,370 --> 00:13:05,640 there let's figure out what that is and 281 00:13:12,360 --> 00:13:08,380 so this corresponds to the great 282 00:13:14,220 --> 00:13:12,370 oxygenate oxygenation event which the 283 00:13:16,590 --> 00:13:14,230 oxygen reacts with the sulfur in the 284 00:13:18,840 --> 00:13:16,600 isotope to create sulfates and the 285 00:13:21,570 --> 00:13:18,850 sulfate reducing bacteria then 286 00:13:22,240 --> 00:13:21,580 essentially fixes this isotopic ratio 287 00:13:24,760 --> 00:13:22,250 after 288 00:13:26,710 --> 00:13:24,770 but before that it does have the oxygen 289 00:13:29,770 --> 00:13:26,720 to react with and nothing essentially 290 00:13:31,180 --> 00:13:29,780 scavenges out so you see this what 291 00:13:33,550 --> 00:13:31,190 appears to be random sort of 292 00:13:35,980 --> 00:13:33,560 fractionation that's going on so you can 293 00:13:38,020 --> 00:13:35,990 track the isotopic record and see really 294 00:13:39,580 --> 00:13:38,030 great things that help to tell us about 295 00:13:43,330 --> 00:13:39,590 what's happened in the history of the 296 00:13:45,130 --> 00:13:43,340 Earth's geologic record and so the main 297 00:13:48,130 --> 00:13:45,140 take-home point and I will let you 298 00:13:50,170 --> 00:13:48,140 choose your geek of choice whether you 299 00:13:53,290 --> 00:13:50,180 want fringe or buffy the vampire slayer 300 00:13:56,440 --> 00:13:53,300 is you get to put on your detective hat 301 00:13:59,920 --> 00:13:56,450 and use it to figure out what this 302 00:14:02,590 --> 00:13:59,930 record is telling you and so the high 303 00:14:05,560 --> 00:14:02,600 Delta values equal heavy isotope liquid 304 00:14:07,660 --> 00:14:05,570 nourishment and anything else that you 305 00:14:10,480 --> 00:14:07,670 see different with the isotopic record 306 00:14:12,070 --> 00:14:10,490 could be because of the temperature the 307 00:14:14,650 --> 00:14:12,080 different chemical reactions that have 308 00:14:18,370 --> 00:14:14,660 been happening precipitation or other 309 00:14:21,130 --> 00:14:18,380 processes that scientists are currently 310 00:14:22,420 --> 00:14:21,140 discovering but it's a great tool you 311 00:14:25,090 --> 00:14:22,430 just have to spend a lot of time and 312 00:14:28,810 --> 00:14:25,100 figure out why the ratios are the way