1 00:00:04,400 --> 00:00:07,800 Speaker 1: Welcome to tech Stuff, a production from I Heart Radio. 2 00:00:11,840 --> 00:00:14,800 Speaker 1: Hey there, and welcome to tech Stuff. I'm your host 3 00:00:14,880 --> 00:00:17,720 Speaker 1: Jonathan Strickland. I'm an executive producer with I Heart Radio, 4 00:00:17,800 --> 00:00:20,759 Speaker 1: and how the tech are you? It is time for 5 00:00:20,880 --> 00:00:25,959 Speaker 1: a tech Stuff classic episode. This episode originally aired on 6 00:00:26,120 --> 00:00:30,840 Speaker 1: August tenth, two thousand fifteen. It is titled is carbon 7 00:00:30,960 --> 00:00:34,120 Speaker 1: Dating on the Way out? This episode might need to 8 00:00:34,159 --> 00:00:38,320 Speaker 1: be carbon dated. Let's take a listen. This comes from 9 00:00:38,440 --> 00:00:42,440 Speaker 1: nikkil Cardale, and I do apologize that I'm sure I 10 00:00:42,640 --> 00:00:46,440 Speaker 1: mispronounced your name, but uh, the request was could you 11 00:00:46,520 --> 00:00:50,280 Speaker 1: do an episode explaining this carbon dating is pretty useful? 12 00:00:50,320 --> 00:00:56,080 Speaker 1: So this effect seems relevant and uh. Cardale actually uh 13 00:00:56,560 --> 00:01:00,000 Speaker 1: commented on and and included another tweet from real scientists 14 00:01:00,800 --> 00:01:04,600 Speaker 1: that including an article titled will our fossil use ruin 15 00:01:04,760 --> 00:01:07,800 Speaker 1: our ability to use carbon dating as a scientific tool? 16 00:01:08,760 --> 00:01:12,759 Speaker 1: This is really fascinating the idea of using carbon dating, uh, 17 00:01:12,840 --> 00:01:17,839 Speaker 1: and how that that method might be in jeopardy because 18 00:01:18,200 --> 00:01:21,120 Speaker 1: of the use of fossil fuels. So I thought I 19 00:01:21,160 --> 00:01:24,679 Speaker 1: would go into that explain what carbon dating is and 20 00:01:24,840 --> 00:01:28,240 Speaker 1: why it might not be an accurate means of telling 21 00:01:28,280 --> 00:01:32,680 Speaker 1: how old something is after too long So going into 22 00:01:32,760 --> 00:01:35,440 Speaker 1: the article, it's about how the enormous amount of carbon 23 00:01:35,440 --> 00:01:38,720 Speaker 1: emissions we generate could make carbon dating and unreliable means 24 00:01:38,760 --> 00:01:42,120 Speaker 1: to determine the age of certain types of materials. But 25 00:01:42,240 --> 00:01:45,199 Speaker 1: to understand how that's possible, we need to know how 26 00:01:45,319 --> 00:01:49,760 Speaker 1: carbon dating works first, So we're gonna do a carbon 27 00:01:49,880 --> 00:01:52,760 Speaker 1: dating one oh one. Now, the first thing that we 28 00:01:52,800 --> 00:01:57,240 Speaker 1: have to talk about is carbon fourteen. So the fourteen 29 00:01:57,520 --> 00:02:00,760 Speaker 1: in carbon fourteen tells us it's an isotope of carbon. 30 00:02:01,480 --> 00:02:05,520 Speaker 1: This particular isotope must have eight neutrons because carbon has 31 00:02:05,560 --> 00:02:09,040 Speaker 1: six protons. You can change the number of neutrons in 32 00:02:09,080 --> 00:02:12,960 Speaker 1: an atom, that's the different types of isotopes atoms may have, 33 00:02:13,320 --> 00:02:16,080 Speaker 1: but you can't change the number of protons and atom 34 00:02:16,120 --> 00:02:19,600 Speaker 1: has without changing that element. So carbon has six protons, 35 00:02:19,840 --> 00:02:21,840 Speaker 1: and if you change that number of protons, you change 36 00:02:21,880 --> 00:02:26,440 Speaker 1: the element itself. It acts reacts differently in chemical operations, 37 00:02:27,040 --> 00:02:31,840 Speaker 1: and uh is no longer carbon. So carbon twelve is 38 00:02:31,919 --> 00:02:35,600 Speaker 1: the most common form of carbon that we find. It 39 00:02:35,639 --> 00:02:38,920 Speaker 1: has six protons and six neutrons. Then you have carbon thirteen, 40 00:02:38,960 --> 00:02:41,600 Speaker 1: which is six protons and seven neutrons, and both of 41 00:02:41,600 --> 00:02:45,800 Speaker 1: those are stable forms of carbon that means they don't decay. 42 00:02:45,960 --> 00:02:49,080 Speaker 1: So if you have carbon twelve or carbon thirteen, you 43 00:02:49,080 --> 00:02:51,600 Speaker 1: put it in a box and you leave for I 44 00:02:51,639 --> 00:02:54,600 Speaker 1: don't know, two billion years, and you come back, you're 45 00:02:54,639 --> 00:02:57,680 Speaker 1: still gonna have carbon twelve or carbon thirteen because they 46 00:02:57,720 --> 00:03:01,640 Speaker 1: remain stable they do not decay. But carbon fourteen is different. 47 00:03:01,919 --> 00:03:07,280 Speaker 1: It is a radio isotope. Radioisotopes are also known as 48 00:03:07,480 --> 00:03:12,040 Speaker 1: radio nucleides, and these are isotopes of a particular atom 49 00:03:12,200 --> 00:03:16,320 Speaker 1: that have an unstable nucleus. These isotopes undergo what we 50 00:03:16,360 --> 00:03:19,840 Speaker 1: call nuclear decay, and in that process they release some 51 00:03:19,960 --> 00:03:23,720 Speaker 1: excess energy in the form of stuff like gamma rays 52 00:03:23,720 --> 00:03:28,360 Speaker 1: and or subatomic particles. Carbon fourteen undergoes what is called 53 00:03:28,760 --> 00:03:32,840 Speaker 1: beta decay. So when it decays, one of the neutrons 54 00:03:32,880 --> 00:03:37,320 Speaker 1: in the nucleus spontaneously changes into a proton, an electron, 55 00:03:37,680 --> 00:03:41,560 Speaker 1: and an anti neutrino. The nucleus gives the boot to 56 00:03:41,560 --> 00:03:45,440 Speaker 1: the electron and the anti neutrino, but the proton stays behind, 57 00:03:45,520 --> 00:03:48,880 Speaker 1: which means the atom no longer is a carbon atom. 58 00:03:48,920 --> 00:03:52,080 Speaker 1: Since again we mentioned that atoms depend upon the number 59 00:03:52,120 --> 00:03:55,920 Speaker 1: of protons and the nucleus, so the carbon fourteen decays 60 00:03:56,000 --> 00:04:01,720 Speaker 1: into nitrogen fourteen, and nitrogen fourteen has seven protons and 61 00:04:01,840 --> 00:04:04,840 Speaker 1: seven neutrons. Also, by the way, one of the few 62 00:04:05,080 --> 00:04:08,920 Speaker 1: stable elements that has both an odd number of protons 63 00:04:09,000 --> 00:04:13,240 Speaker 1: and an odd number of neutrons uh, and nitrogen fourteen 64 00:04:13,440 --> 00:04:16,640 Speaker 1: is stable. It makes up the vast majority of the 65 00:04:16,720 --> 00:04:21,360 Speaker 1: nitrogen found naturally unearthed, More than of the nitrogen found 66 00:04:21,360 --> 00:04:25,920 Speaker 1: on Earth is nitrogen fourteen. So radioactive decay occurs naturally 67 00:04:26,080 --> 00:04:29,719 Speaker 1: within these isotopes, and it's a spontaneous occurrence. That's really 68 00:04:29,800 --> 00:04:33,520 Speaker 1: important to remember. Carbon fourteen has a radioactive half life 69 00:04:33,560 --> 00:04:38,400 Speaker 1: of about five thousand, seven hundred years. There's some confusion 70 00:04:38,440 --> 00:04:40,880 Speaker 1: about what that means. I find in day to day 71 00:04:40,880 --> 00:04:43,520 Speaker 1: conversations with people who haven't had science in a while. 72 00:04:43,760 --> 00:04:46,800 Speaker 1: You guys who have recently had this in science class, 73 00:04:46,800 --> 00:04:49,520 Speaker 1: you're rolling your eyes right now. But for adults who 74 00:04:49,520 --> 00:04:52,040 Speaker 1: have not taken a science class in a long time, 75 00:04:52,360 --> 00:04:56,800 Speaker 1: this might require some some refreshing. So half life of 76 00:04:56,880 --> 00:05:00,200 Speaker 1: five thousand, seven hundred years, what does that mean? It 77 00:05:00,240 --> 00:05:03,160 Speaker 1: means if you have a given amount of carbon fourteen, 78 00:05:03,760 --> 00:05:07,560 Speaker 1: after five thousand, seven hundred years or so, you'll have 79 00:05:07,920 --> 00:05:11,240 Speaker 1: only half of that carbon fourteen remaining. The other half 80 00:05:11,400 --> 00:05:16,440 Speaker 1: having undergone decay radioactive decay and turning into nitrogen. Now, 81 00:05:16,480 --> 00:05:18,919 Speaker 1: this doesn't mean that all the carbon fourteen will be 82 00:05:18,920 --> 00:05:22,320 Speaker 1: gone after another five thousand, seven hundred years, nor does 83 00:05:22,360 --> 00:05:25,320 Speaker 1: it mean that carbon fourteen has a full life of 84 00:05:25,360 --> 00:05:28,479 Speaker 1: eleven thousand, four hundred years or anything like that. In fact, 85 00:05:28,560 --> 00:05:31,640 Speaker 1: what it really means is that after another five thousand, 86 00:05:31,720 --> 00:05:35,039 Speaker 1: seven hundred years, half of the remaining sample will have decayed, 87 00:05:35,160 --> 00:05:37,479 Speaker 1: leaving you with about a quarter of what you started with. 88 00:05:37,680 --> 00:05:40,000 Speaker 1: And another five thousand, seven hundred years if that means 89 00:05:40,000 --> 00:05:42,120 Speaker 1: you'd be left with about an eighth of that sample, 90 00:05:42,200 --> 00:05:46,680 Speaker 1: and so on. Carbon fourteen exists naturally on Earth in 91 00:05:46,760 --> 00:05:50,400 Speaker 1: trace amounts. Before the nineteen forties, the carbon fourteen on 92 00:05:50,480 --> 00:05:54,599 Speaker 1: Earth was created through a natural process. Once in a while, 93 00:05:54,800 --> 00:05:58,560 Speaker 1: cosmic rays, these very high energy particles in outer space, 94 00:05:58,800 --> 00:06:02,320 Speaker 1: would collide with an atom in our atmosphere or upper atmosphere, 95 00:06:02,680 --> 00:06:05,240 Speaker 1: and this collision would end up emitting a high energy 96 00:06:05,279 --> 00:06:09,200 Speaker 1: neutron that then could collide with nitrogen atoms that are 97 00:06:09,240 --> 00:06:13,000 Speaker 1: also way up there in our atmosphere. Now, cosmic rays 98 00:06:13,040 --> 00:06:16,919 Speaker 1: are high energy sub atomic particles. They originate outside of 99 00:06:16,920 --> 00:06:21,320 Speaker 1: our solar system, usually they're emitted by supernova of massive stars, 100 00:06:21,640 --> 00:06:25,360 Speaker 1: and these subatomic particles are primarily atomic nuclei and high 101 00:06:25,520 --> 00:06:28,760 Speaker 1: energy protons. So this collision of the high energy neutron 102 00:06:28,880 --> 00:06:33,640 Speaker 1: with the nitrogen forces a proton to leave the nucleus 103 00:06:33,680 --> 00:06:36,960 Speaker 1: and the IN fourteen changes to C fourteen, So in 104 00:06:36,960 --> 00:06:39,839 Speaker 1: other words, nitrogen fourteen turns to carbon fourteen. So instead 105 00:06:39,839 --> 00:06:42,479 Speaker 1: of having seven protons and seven neutrons, the new atom 106 00:06:42,520 --> 00:06:46,479 Speaker 1: has six protons and eight neutrons. The proton that was 107 00:06:46,560 --> 00:06:49,640 Speaker 1: broken off from the nucleus zooms off with an electron, 108 00:06:50,120 --> 00:06:52,560 Speaker 1: so you get one proton and one electron. That means 109 00:06:52,600 --> 00:06:56,760 Speaker 1: you have an atom of hydrogen. So again what's happening 110 00:06:56,839 --> 00:07:02,000 Speaker 1: is a high energy neutron collides with hydrogen fourteen, forces 111 00:07:02,080 --> 00:07:06,080 Speaker 1: out a proton. The proton and an electron high tail 112 00:07:06,160 --> 00:07:10,920 Speaker 1: it and honeymoon off as hydrogen, and the incoming neutron 113 00:07:11,560 --> 00:07:14,760 Speaker 1: joins the party, and now you've got carbon fourteen. So 114 00:07:14,880 --> 00:07:18,760 Speaker 1: pre nineties, carbon fourteen is rare because of two reasons. 115 00:07:19,000 --> 00:07:22,960 Speaker 1: It undergoes radioactive decay, so over time it disappears, and 116 00:07:23,040 --> 00:07:25,560 Speaker 1: it's produced by an event that's not super frequent, though 117 00:07:25,600 --> 00:07:29,800 Speaker 1: it's also not uncommon, so it does happen regularly enough 118 00:07:29,880 --> 00:07:36,040 Speaker 1: that carbon fourteen is replenished, but it's a very small 119 00:07:36,160 --> 00:07:40,280 Speaker 1: overall percentage of the carbon here on Earth. We'll be 120 00:07:40,280 --> 00:07:42,880 Speaker 1: back with more of this classic episode of tech stuff 121 00:07:42,920 --> 00:07:54,679 Speaker 1: after this quick break. Now, living things here on Earth 122 00:07:55,160 --> 00:07:59,000 Speaker 1: absorb carbon through various means, and some of that carbon 123 00:07:59,160 --> 00:08:02,920 Speaker 1: is carbon fort So it maybe that you know, you 124 00:08:03,160 --> 00:08:05,120 Speaker 1: eat a plant and that plant has some of the 125 00:08:05,120 --> 00:08:06,920 Speaker 1: carbon fourteen in it. Now you have some of the 126 00:08:06,920 --> 00:08:10,000 Speaker 1: carbon fourteen and you And if we know the ratio 127 00:08:10,120 --> 00:08:13,640 Speaker 1: of carbon fourteen to the stable form of carbon twelve, 128 00:08:14,280 --> 00:08:16,480 Speaker 1: we can look at materials and analyze them to see 129 00:08:16,520 --> 00:08:19,160 Speaker 1: how the ratio of carbon fourteen to carbon twelve in 130 00:08:19,200 --> 00:08:23,559 Speaker 1: the material stacks up to the standard ratio. With living things, 131 00:08:23,600 --> 00:08:25,640 Speaker 1: this becomes a matter of looking at how much carbon 132 00:08:25,680 --> 00:08:30,880 Speaker 1: fourteen is not there? All right, That's it's a little confusing. 133 00:08:31,000 --> 00:08:34,480 Speaker 1: Let me explain. So, when a living thing is still alive, 134 00:08:35,000 --> 00:08:38,280 Speaker 1: it accumulates carbon at about the same rate it loses carbon. 135 00:08:39,200 --> 00:08:43,920 Speaker 1: So carbon cosmic rays produced this carbon fourteen frequently enough 136 00:08:44,000 --> 00:08:48,439 Speaker 1: that the ratio between carbon fourteen and carbon twelve remains steady. 137 00:08:48,480 --> 00:08:51,640 Speaker 1: So the percentage of carbon fourteen to carbon twelve is 138 00:08:51,880 --> 00:08:56,280 Speaker 1: fairly standardized. But when a living thing stops being alive 139 00:08:56,480 --> 00:09:00,600 Speaker 1: and turns into a not living any more or thing, 140 00:09:01,160 --> 00:09:04,960 Speaker 1: it stops accumulating carbon, so it has the carbon that 141 00:09:05,000 --> 00:09:08,800 Speaker 1: it has inside of it stays. That's it. You're not 142 00:09:08,840 --> 00:09:12,760 Speaker 1: losing anymore. You're not gaining any more except for carbon 143 00:09:12,840 --> 00:09:18,360 Speaker 1: fourteen because carbon fourteen undergoes radioactive decay, so over time, 144 00:09:18,840 --> 00:09:22,480 Speaker 1: some of that carbon fourteen starts to convert to nitrogen. 145 00:09:23,520 --> 00:09:28,200 Speaker 1: So that means if you can look at the remains 146 00:09:28,360 --> 00:09:31,920 Speaker 1: of a living thing and detect the ratio of carbon 147 00:09:31,960 --> 00:09:35,520 Speaker 1: fourteen to carbon twelve, you can get an idea of 148 00:09:35,520 --> 00:09:38,680 Speaker 1: how long ago it was that it stopped taking in carbon, 149 00:09:38,880 --> 00:09:41,280 Speaker 1: as in, how long ago was it that this lip 150 00:09:41,440 --> 00:09:45,199 Speaker 1: once living thing died. It gets a little more complicated 151 00:09:45,240 --> 00:09:48,840 Speaker 1: than all that, but here's the basic rule. If we 152 00:09:48,880 --> 00:09:52,000 Speaker 1: want to be really precise, here's the equation we use 153 00:09:52,240 --> 00:09:56,160 Speaker 1: to determine the age of a sample of material. You 154 00:09:56,600 --> 00:10:00,120 Speaker 1: have an equation where you take the natural logarithm of 155 00:10:00,480 --> 00:10:03,880 Speaker 1: NF divided by n o uh that in turn is 156 00:10:03,880 --> 00:10:07,280 Speaker 1: divided by negative point six nine three, and then you 157 00:10:07,360 --> 00:10:12,000 Speaker 1: multiply it by t uh one half, so one half t. 158 00:10:12,800 --> 00:10:17,120 Speaker 1: The natural logarithm is a specific logarithm applied to this 159 00:10:17,160 --> 00:10:20,480 Speaker 1: equation and other things as well. NF divided way n 160 00:10:20,520 --> 00:10:23,880 Speaker 1: O actually refers to the percentage of carbon fourteen and 161 00:10:23,920 --> 00:10:27,319 Speaker 1: the sample compared to the amount found in living stuff today, 162 00:10:28,160 --> 00:10:31,200 Speaker 1: and T times one half is the half life of carbon. 163 00:10:31,360 --> 00:10:34,160 Speaker 1: So that's five thousand, seven hundred years. So it's a 164 00:10:34,200 --> 00:10:37,040 Speaker 1: lot easier to understand this if we take a specific example. 165 00:10:38,000 --> 00:10:41,120 Speaker 1: So let's say you've got a sample of some sort 166 00:10:41,200 --> 00:10:45,400 Speaker 1: of material and you have determined that there is five 167 00:10:45,480 --> 00:10:48,560 Speaker 1: percent of the amount of carbon fourteen in that material 168 00:10:49,160 --> 00:10:51,559 Speaker 1: compared to what you would find in something that is 169 00:10:51,600 --> 00:10:55,000 Speaker 1: alive right now, So you take a sample of a 170 00:10:55,040 --> 00:10:58,439 Speaker 1: living thing, and then you take the sample of the 171 00:10:58,480 --> 00:11:01,280 Speaker 1: thing you're testing. You either the thing you're testing only 172 00:11:01,320 --> 00:11:03,240 Speaker 1: has five percent of the carbon fourteen you would find 173 00:11:03,240 --> 00:11:05,360 Speaker 1: in living things. That means you would fill out the 174 00:11:05,360 --> 00:11:10,000 Speaker 1: equation with the natural logarithm of point zero five divided 175 00:11:10,040 --> 00:11:14,280 Speaker 1: by negative point six nine three, and you multiply that 176 00:11:14,280 --> 00:11:18,000 Speaker 1: that result to with five thousand, seven hundred years the 177 00:11:18,080 --> 00:11:20,080 Speaker 1: natural logorithm at point zero five. By the way, in 178 00:11:20,120 --> 00:11:22,560 Speaker 1: case you don't want to whip out your calculator is 179 00:11:22,679 --> 00:11:26,319 Speaker 1: negative two point nine nine five seven three to two 180 00:11:26,440 --> 00:11:29,720 Speaker 1: seven three five five. If you divide that by negative 181 00:11:30,080 --> 00:11:33,480 Speaker 1: point six nine three, you get four point three to 182 00:11:33,640 --> 00:11:39,640 Speaker 1: two eight four five nine. Don't dial that number. If 183 00:11:39,679 --> 00:11:42,720 Speaker 1: you take that number, the four point three, etcetera, and 184 00:11:42,720 --> 00:11:45,800 Speaker 1: you multiply that by five thousand, seven hundred years, you 185 00:11:45,920 --> 00:11:48,800 Speaker 1: end up with twenty four thousand, six hundred forty point 186 00:11:48,880 --> 00:11:52,079 Speaker 1: two years, meaning the stuff you're looking at died somewhere 187 00:11:52,320 --> 00:11:55,960 Speaker 1: around that time frame, give or take thirty two hundred years. 188 00:11:56,360 --> 00:11:58,760 Speaker 1: So somewhere on twenty four thousand, six hundred forty years 189 00:11:58,800 --> 00:12:03,080 Speaker 1: ago is when that thing no longer breathed or lived, 190 00:12:03,160 --> 00:12:06,760 Speaker 1: or however you wanted to define it. By the way, 191 00:12:06,920 --> 00:12:10,600 Speaker 1: this approach does have a limitation. Anything older than sixty 192 00:12:10,640 --> 00:12:13,720 Speaker 1: thou years is pretty much out of bounds. Carbon fourteen 193 00:12:13,760 --> 00:12:16,040 Speaker 1: just isn't a reliable means of dating that sort of material, 194 00:12:16,080 --> 00:12:19,240 Speaker 1: and we have to rely on other methods. So carbon fourteen, 195 00:12:19,679 --> 00:12:22,959 Speaker 1: because of the decay once against two very small amounts, 196 00:12:23,559 --> 00:12:27,200 Speaker 1: it's very difficult to narrow it down to a specific time, 197 00:12:27,240 --> 00:12:29,640 Speaker 1: and if it's long enough, there won't be any carbon 198 00:12:29,679 --> 00:12:32,720 Speaker 1: fourteen at all. All the carbon fourteen will have decayed 199 00:12:32,720 --> 00:12:35,679 Speaker 1: by then you can't use carbon dating if there's no 200 00:12:35,760 --> 00:12:40,560 Speaker 1: carbon fourteen left. So to actually test the carbon fourteen concentration, 201 00:12:41,280 --> 00:12:44,920 Speaker 1: you first have to take the sample, uh whatever object 202 00:12:45,000 --> 00:12:47,520 Speaker 1: it might be. You have to remove part of it, 203 00:12:48,120 --> 00:12:50,640 Speaker 1: and typically you would apply some chemicals to the material, 204 00:12:51,120 --> 00:12:54,160 Speaker 1: usually a very strong acid wash and a strong base wash. 205 00:12:54,600 --> 00:12:59,240 Speaker 1: That's to remove all the contaminating materials that could end 206 00:12:59,320 --> 00:13:03,079 Speaker 1: up giving you false readings on carbon fourteen. Then you 207 00:13:03,120 --> 00:13:07,199 Speaker 1: would burn the sample within a glass container to capture 208 00:13:07,240 --> 00:13:11,400 Speaker 1: the carbon dioxide that is emitted when you burn the material, 209 00:13:11,920 --> 00:13:15,160 Speaker 1: and then you would analyze the carbon dioxide to find 210 00:13:15,200 --> 00:13:18,600 Speaker 1: out the concentration of carbon fourteen. So you can see 211 00:13:18,600 --> 00:13:21,400 Speaker 1: that this approach has a big drawback. It ends up 212 00:13:21,480 --> 00:13:24,640 Speaker 1: damaging whatever it is you are attempting to date in 213 00:13:24,679 --> 00:13:28,040 Speaker 1: the first place. And that's why some particularly high valued 214 00:13:28,040 --> 00:13:31,360 Speaker 1: items go without being tested, because the perception is that 215 00:13:31,440 --> 00:13:35,280 Speaker 1: even a small sample of that original piece would be 216 00:13:35,320 --> 00:13:39,920 Speaker 1: too much damage to to uh make on this item. 217 00:13:39,960 --> 00:13:43,680 Speaker 1: So certain items are considered very precious and there's a 218 00:13:43,679 --> 00:13:47,360 Speaker 1: big resistance to using carbon dating because by the definition, 219 00:13:47,360 --> 00:13:50,439 Speaker 1: you're going to be damaging the material. Now there's several 220 00:13:50,440 --> 00:13:54,079 Speaker 1: lines of research that are exploring possible non destructive means 221 00:13:54,160 --> 00:13:58,920 Speaker 1: of using radiocarbon dating. There's one that uses plasma oxidation 222 00:13:59,200 --> 00:14:02,640 Speaker 1: and the use of non destructive washes to clean samples 223 00:14:02,760 --> 00:14:07,160 Speaker 1: of those contaminating humic acids, which would lead to errors 224 00:14:07,200 --> 00:14:10,960 Speaker 1: if they remained behind, but those are still largely in 225 00:14:10,960 --> 00:14:14,200 Speaker 1: the testing phase and aren't the common means of using 226 00:14:14,200 --> 00:14:17,040 Speaker 1: carbon dating. Also, keep in mind that we use this 227 00:14:17,160 --> 00:14:20,920 Speaker 1: method to estimate the date of things made from organic materials, 228 00:14:20,960 --> 00:14:24,760 Speaker 1: like the Dead Sea scrolls, but this estimation is based 229 00:14:24,800 --> 00:14:27,880 Speaker 1: upon when the materials were harvested, so, in other words, 230 00:14:28,160 --> 00:14:30,920 Speaker 1: whenever the living thing that the materials came from stopped 231 00:14:30,920 --> 00:14:34,640 Speaker 1: being alive, it doesn't tell us the date of when 232 00:14:34,640 --> 00:14:37,880 Speaker 1: the artifact was actually produced. So it's possible that you 233 00:14:37,880 --> 00:14:41,440 Speaker 1: could come across an artifact like a scroll and you 234 00:14:41,560 --> 00:14:44,160 Speaker 1: use carbon dating on it and find out that the 235 00:14:44,320 --> 00:14:47,800 Speaker 1: scroll material is two thousand years old, meaning two thousand 236 00:14:47,920 --> 00:14:52,360 Speaker 1: years ago whatever the scroll was made out of stopped living, 237 00:14:53,040 --> 00:14:56,320 Speaker 1: but it doesn't tell you about the contents written in 238 00:14:56,360 --> 00:15:00,200 Speaker 1: the scroll. It's possible that the contents were at to 239 00:15:00,240 --> 00:15:04,280 Speaker 1: the scroll much after the living thing stopped being alive. 240 00:15:04,400 --> 00:15:07,320 Speaker 1: Still it's a pretty good bet that the two are 241 00:15:07,320 --> 00:15:10,360 Speaker 1: within the same neighborhood of time, rather than someone held 242 00:15:10,400 --> 00:15:13,720 Speaker 1: onto blank scrolls for a few centuries before finally jotting 243 00:15:13,760 --> 00:15:17,200 Speaker 1: something down. All Right, it's all this is cool, But 244 00:15:17,920 --> 00:15:21,360 Speaker 1: how did we even figure out radio carbon dating would 245 00:15:21,400 --> 00:15:25,560 Speaker 1: be a possible way of figuring out how old something is. Well. 246 00:15:25,560 --> 00:15:27,960 Speaker 1: Some early discoveries were made in the nineteen thirties at 247 00:15:27,960 --> 00:15:31,920 Speaker 1: the Lawrence Radiation Laboratory in Berkeley, and you probably remember 248 00:15:31,920 --> 00:15:34,360 Speaker 1: that if you've been listening to tech stuff. It factored 249 00:15:34,360 --> 00:15:36,760 Speaker 1: heavily into the discussion I had with Ben Bolan about 250 00:15:36,760 --> 00:15:42,840 Speaker 1: the Manhattan Project. So Franz Curry, an American physicist, observed 251 00:15:42,880 --> 00:15:46,080 Speaker 1: something really interesting when he irradiated a cloud of air 252 00:15:46,280 --> 00:15:50,360 Speaker 1: in a cloud chamber. He used neutrons to uh to 253 00:15:50,520 --> 00:15:55,040 Speaker 1: irradiate that cloud, and he saw proton recoil tracks that 254 00:15:55,080 --> 00:15:59,520 Speaker 1: indicated something was losing protons. So he concluded that the 255 00:15:59,600 --> 00:16:02,960 Speaker 1: neutral rons that he was using, we're colliding with nitrogen 256 00:16:03,040 --> 00:16:06,680 Speaker 1: fourteen and producing what was believed to be a form 257 00:16:06,720 --> 00:16:09,880 Speaker 1: of carbon as a result, with hydrogen being the other 258 00:16:09,920 --> 00:16:13,200 Speaker 1: product of this collision. His work was further explored by 259 00:16:13,240 --> 00:16:18,280 Speaker 1: physicists like Tom W. Bonner, W. M. Brubaker, W. J. Bircham, 260 00:16:18,560 --> 00:16:22,680 Speaker 1: and Maurice gold Hauber. Now collectively, this laid the foundation 261 00:16:22,760 --> 00:16:25,760 Speaker 1: for the simple equation of a high energy neutron plus 262 00:16:25,920 --> 00:16:31,040 Speaker 1: nitrogen fourteen produces one hydrogen atom and one carbon fourteen atom. 263 00:16:31,120 --> 00:16:33,920 Speaker 1: Then you had Enrico Fermi. We talked about him in 264 00:16:33,960 --> 00:16:37,240 Speaker 1: the Manhattan Project, and his work showed that the cross 265 00:16:37,280 --> 00:16:40,400 Speaker 1: section of a nitrogen fourteen atom was much larger than 266 00:16:40,400 --> 00:16:45,400 Speaker 1: other materials, and that suggested that neutron and nitrogen collisions 267 00:16:45,440 --> 00:16:48,440 Speaker 1: might happen fairly regularly in nature as long as there 268 00:16:48,480 --> 00:16:52,760 Speaker 1: were a supply of high energy neutrons. Stay tuned for 269 00:16:52,800 --> 00:16:56,760 Speaker 1: the exciting conclusion of this textuff classic episode right after 270 00:16:56,800 --> 00:17:08,600 Speaker 1: we take this break. Then you have a Serge Korf, 271 00:17:09,000 --> 00:17:11,439 Speaker 1: who was a physicist who was born in Finland and 272 00:17:11,440 --> 00:17:13,960 Speaker 1: whose family immigrated to the United States in the early 273 00:17:14,000 --> 00:17:18,880 Speaker 1: twentieth century. He discovered the phenomenon that cosmic rays interact 274 00:17:18,920 --> 00:17:22,399 Speaker 1: with atoms and produce high energy neutrons in the upper atmosphere. 275 00:17:22,680 --> 00:17:28,040 Speaker 1: So Pharem's prediction and corpse observation we're starting to kind 276 00:17:28,080 --> 00:17:31,960 Speaker 1: of coalesce here. The observations convinced scientists that the neutrons 277 00:17:32,000 --> 00:17:35,679 Speaker 1: themselves were not cosmic rays, because the neutrons had a 278 00:17:35,680 --> 00:17:40,080 Speaker 1: lifespan of just eighteen minutes, and therefore a neutron wouldn't 279 00:17:40,080 --> 00:17:42,560 Speaker 1: be able to survive the long trip through space. They 280 00:17:42,640 --> 00:17:45,720 Speaker 1: must have been something else first, so they said the 281 00:17:45,720 --> 00:17:49,280 Speaker 1: neutrons had to be a byproduct of another interaction. A 282 00:17:49,320 --> 00:17:52,480 Speaker 1: cosmic ray must be interacting with something in the atmosphere. 283 00:17:52,880 --> 00:17:56,280 Speaker 1: That interaction caused this high energy neutron to be emitted, 284 00:17:56,560 --> 00:17:59,480 Speaker 1: and Core hypothesized that these neutrons could then interact with 285 00:17:59,600 --> 00:18:04,440 Speaker 1: nitrogen and fourteen to produce carbon fourteen in the upper atmosphere. Now, 286 00:18:04,440 --> 00:18:06,639 Speaker 1: it was Willard F. Libby who came up with the 287 00:18:06,720 --> 00:18:09,760 Speaker 1: idea that since carbon fourteen is generated at a steady 288 00:18:09,880 --> 00:18:12,719 Speaker 1: rate due to cosmic ray interactions in our atmosphere, you 289 00:18:12,760 --> 00:18:16,000 Speaker 1: should be able to use it to measure how long 290 00:18:16,160 --> 00:18:19,200 Speaker 1: something has been dead. Libby would measure the value of 291 00:18:19,240 --> 00:18:22,800 Speaker 1: carbon fourteen's half life at five thousand, five hundred sixty 292 00:18:22,800 --> 00:18:25,840 Speaker 1: eight years, give or take thirty years, which became known 293 00:18:25,920 --> 00:18:29,000 Speaker 1: as the Libby half life, and Libby himself would be 294 00:18:29,000 --> 00:18:32,120 Speaker 1: awarded the Nobel Prize in nineteen sixty for his work 295 00:18:32,160 --> 00:18:35,800 Speaker 1: in radiocarbon dating. All right, So that's the history of 296 00:18:35,880 --> 00:18:39,920 Speaker 1: radiocarbon dating and generally how radiocarbon dating works. So why 297 00:18:40,040 --> 00:18:43,280 Speaker 1: is it in trouble or what could possibly be causing 298 00:18:43,320 --> 00:18:46,800 Speaker 1: confusion with radiocarbon dating. Well, there are two big things 299 00:18:46,800 --> 00:18:49,439 Speaker 1: we need to talk about, and one was one that 300 00:18:49,480 --> 00:18:51,720 Speaker 1: I've alluded to a couple of times. I mentioned that, 301 00:18:52,720 --> 00:18:56,119 Speaker 1: you know, pre nineteen forties, you had a certain level 302 00:18:56,240 --> 00:19:00,440 Speaker 1: of carbon fourteen that was pretty standard, but the nuclear 303 00:19:00,480 --> 00:19:04,119 Speaker 1: age really messed things up for us. They made carbon 304 00:19:04,160 --> 00:19:06,880 Speaker 1: fourteen dating a bit tricky. Starting in the nineteen forties, 305 00:19:06,920 --> 00:19:10,600 Speaker 1: we began testing nuclear bombs. Now, these bombs released a 306 00:19:10,600 --> 00:19:13,520 Speaker 1: lot of energy upon exploding, partly in the form of 307 00:19:13,600 --> 00:19:16,280 Speaker 1: high energy neutrons. You can probably see where this is going. 308 00:19:16,680 --> 00:19:19,760 Speaker 1: Some of those high energy neutrons ended up interacting with 309 00:19:19,920 --> 00:19:23,520 Speaker 1: nitrogen fourteen atoms, which meant that it produced carbon fourteen 310 00:19:23,560 --> 00:19:27,840 Speaker 1: atoms as a result. So the concentration of carbon fourteen 311 00:19:28,280 --> 00:19:33,040 Speaker 1: increased in the wake of nuclear bomb testing. So anything 312 00:19:33,080 --> 00:19:36,080 Speaker 1: that died after the nineteen forties actually has a higher 313 00:19:36,119 --> 00:19:39,800 Speaker 1: concentration of carbon fourteen than the stuff that died before 314 00:19:39,920 --> 00:19:43,440 Speaker 1: the nineteen forties did even know at the time of death. 315 00:19:43,640 --> 00:19:47,840 Speaker 1: According to Professor Nalini no Khannie of the Evergreen State College, 316 00:19:48,040 --> 00:19:51,919 Speaker 1: the nineteen fifties saw a one hundred percent spike in 317 00:19:52,040 --> 00:19:56,160 Speaker 1: carbon fourteen coming into the atmosphere. In nineteen sixty three, 318 00:19:56,560 --> 00:19:59,600 Speaker 1: the United States and Russia agreed to stop above ground 319 00:19:59,720 --> 00:20:02,280 Speaker 1: nucle you're testing, and the levels of carbon fourteen in 320 00:20:02,280 --> 00:20:05,560 Speaker 1: the atmosphere gradually dropped down to their normal levels. But 321 00:20:05,640 --> 00:20:08,679 Speaker 1: that means there's a blip in the carbon fourteen radar 322 00:20:08,760 --> 00:20:11,919 Speaker 1: between the nineteen forties and nineteen sixty three. So if 323 00:20:11,920 --> 00:20:14,720 Speaker 1: you put yourself in the shoes of a future archaeologist, 324 00:20:15,240 --> 00:20:19,320 Speaker 1: radiocarbon dating becomes unreliable because the levels of carbon fourteen 325 00:20:19,400 --> 00:20:22,679 Speaker 1: could be deceptive. If the thing you're measuring died during 326 00:20:22,720 --> 00:20:25,600 Speaker 1: the era of nuclear testing, it might appear to be 327 00:20:25,760 --> 00:20:29,040 Speaker 1: younger than you thought because there's a higher concentration of 328 00:20:29,119 --> 00:20:33,520 Speaker 1: carbon fourteen in its sample than you otherwise would have expected. 329 00:20:33,840 --> 00:20:38,160 Speaker 1: So it may seem that something died in twenty fifteen 330 00:20:38,200 --> 00:20:41,879 Speaker 1: as opposed to nineteen sixty three. That's just an example. 331 00:20:42,440 --> 00:20:44,840 Speaker 1: Now to the article that prompted this episode in the 332 00:20:44,880 --> 00:20:49,040 Speaker 1: first place, that's a different case. Researchers published a study 333 00:20:49,040 --> 00:20:51,960 Speaker 1: in the Proceedings of the National Academy of Sciences about 334 00:20:52,000 --> 00:20:55,639 Speaker 1: how the use of fossil fuels is further making radiocarbon 335 00:20:55,720 --> 00:20:59,560 Speaker 1: dating less reliable, and this time it's not an excess 336 00:20:59,600 --> 00:21:03,000 Speaker 1: of carbon and fourteen. It's actually the opposite problem. Fossil 337 00:21:03,040 --> 00:21:07,120 Speaker 1: fuels have no carbon fourteen in them because they are 338 00:21:07,200 --> 00:21:12,000 Speaker 1: fossil fuels. This is billions of years old, so they're 339 00:21:12,000 --> 00:21:14,679 Speaker 1: far too old for any carbon fourteen to remain. Remember 340 00:21:14,680 --> 00:21:18,720 Speaker 1: that carbon fourteen is decaying over time and turning into nitrogen, 341 00:21:18,840 --> 00:21:23,600 Speaker 1: so eventually all of those carbon fourteen atoms decay. So 342 00:21:23,640 --> 00:21:27,360 Speaker 1: burning a fossil fuel releases carbon dioxide, and the carbon 343 00:21:27,520 --> 00:21:30,120 Speaker 1: in that CEO two has no carbon fourteen and it's 344 00:21:30,160 --> 00:21:33,840 Speaker 1: all carbon toolver carbon thirteen. So the more fossil fuels 345 00:21:33,880 --> 00:21:37,480 Speaker 1: we burn, the more we dilute the concentration of carbon 346 00:21:37,520 --> 00:21:40,800 Speaker 1: fourteen that's in the atmosphere. So stuff from the nuclear 347 00:21:40,840 --> 00:21:44,040 Speaker 1: age tends to look younger than it really is because 348 00:21:44,040 --> 00:21:47,080 Speaker 1: of the higher concentration of carbon fourteen. Stuff from the 349 00:21:47,160 --> 00:21:51,000 Speaker 1: later ages of fossil fuel use will look older than 350 00:21:51,040 --> 00:21:54,439 Speaker 1: they really are because carbon fourteen has been diluted So 351 00:21:54,480 --> 00:21:58,159 Speaker 1: according to the study, fresh organic material in twenty fifty 352 00:21:58,440 --> 00:22:01,280 Speaker 1: would contain the same amount of AREB and fourteen relative 353 00:22:01,359 --> 00:22:06,359 Speaker 1: to carbon twelve as something dating from ten fifty. So 354 00:22:06,480 --> 00:22:11,000 Speaker 1: you have a thousand years of doubt in any radiocarbon 355 00:22:11,119 --> 00:22:14,960 Speaker 1: dated samples. You would be look at the two samples 356 00:22:14,960 --> 00:22:18,280 Speaker 1: if you if all you had were miniscule samples of 357 00:22:18,359 --> 00:22:20,520 Speaker 1: two things and one of them was a T shirt 358 00:22:21,080 --> 00:22:24,119 Speaker 1: that was made in twenty fifty, and another was a 359 00:22:24,160 --> 00:22:28,080 Speaker 1: piece of cloth that dated from ten fifty, and you 360 00:22:28,119 --> 00:22:32,560 Speaker 1: did radiocarbon dating, you'd get the same result. This is 361 00:22:32,560 --> 00:22:35,160 Speaker 1: not good if you are trying to figure out how 362 00:22:35,240 --> 00:22:39,840 Speaker 1: old something is. Heather Graven, who authored the study on 363 00:22:39,880 --> 00:22:43,080 Speaker 1: fossil fuel emissions and the effect on radiocarbon dating, says 364 00:22:43,119 --> 00:22:47,280 Speaker 1: that if we were to reduce carbon dioxide emissions drastically 365 00:22:47,359 --> 00:22:50,919 Speaker 1: in the very near future, the effect on future radiocarbon 366 00:22:51,000 --> 00:22:54,359 Speaker 1: dating would be equivalent to inserting a one year error 367 00:22:54,440 --> 00:22:59,440 Speaker 1: on top of any estimation. If we don't drastically reduce emissions, 368 00:22:59,480 --> 00:23:03,160 Speaker 1: that error age will continue to grow over time. One 369 00:23:03,200 --> 00:23:06,000 Speaker 1: thing that the concentration of carbon fourteen tells us is 370 00:23:06,000 --> 00:23:08,520 Speaker 1: how much carbon dioxide in the atmosphere comes from the 371 00:23:08,520 --> 00:23:12,440 Speaker 1: burning of fossil fuels, So as we see the concentration decrease, 372 00:23:12,760 --> 00:23:16,240 Speaker 1: we know that's because proportionally more carbon twelve is being 373 00:23:16,280 --> 00:23:19,720 Speaker 1: released into the atmosphere, diluting the already tiny concentration of 374 00:23:19,760 --> 00:23:22,639 Speaker 1: carbon fourteen. So that's useful for scientists who are studying 375 00:23:22,680 --> 00:23:27,280 Speaker 1: climate change and pollution. But that's not exactly a happy story, 376 00:23:27,400 --> 00:23:32,000 Speaker 1: is it. So what are our options if carbon dating 377 00:23:32,160 --> 00:23:36,040 Speaker 1: becomes unreliable. Well, that depends on what you're trying to analyze. 378 00:23:36,400 --> 00:23:39,640 Speaker 1: If you're looking at inorganic stuff like rocks, you don't 379 00:23:39,640 --> 00:23:41,639 Speaker 1: need to use carbon fourteen in the first place. That 380 00:23:41,640 --> 00:23:44,520 Speaker 1: would be pretty much useless. You would use something else 381 00:23:44,520 --> 00:23:48,040 Speaker 1: like potassium argon dating, which is useful to estimate the 382 00:23:48,040 --> 00:23:50,400 Speaker 1: age of rocks that are a hundred thousand years old 383 00:23:50,520 --> 00:23:52,920 Speaker 1: or younger. And if that's not a big enough range, 384 00:23:52,960 --> 00:23:56,200 Speaker 1: you can actually use uranium lead dating and that will 385 00:23:56,280 --> 00:23:59,320 Speaker 1: let you estimate rocks between one point four and five 386 00:23:59,480 --> 00:24:03,000 Speaker 1: million years old. There's a lot of different options if 387 00:24:03,000 --> 00:24:05,840 Speaker 1: you're trying to date stuff. When it comes to organic materials, however, 388 00:24:05,880 --> 00:24:09,159 Speaker 1: it's a lot more tricky. Radio carbon was a great tool, 389 00:24:10,119 --> 00:24:13,440 Speaker 1: but if it becomes unreliable. We're gonna have to use 390 00:24:13,520 --> 00:24:19,160 Speaker 1: other methods like contextual clues and other items that are 391 00:24:19,160 --> 00:24:23,960 Speaker 1: helping us connect things to dates. So this is a 392 00:24:24,000 --> 00:24:27,880 Speaker 1: big problem. I guess you could argue that's a big 393 00:24:27,920 --> 00:24:31,800 Speaker 1: problem for future generations. And perhaps the records we leave 394 00:24:31,880 --> 00:24:39,840 Speaker 1: behind now are so uh so complete, they're so voluminous, 395 00:24:39,880 --> 00:24:43,120 Speaker 1: I guess is the best word that future generations will 396 00:24:43,160 --> 00:24:46,840 Speaker 1: likely have more than enough material to determine when something 397 00:24:47,280 --> 00:24:52,040 Speaker 1: originated from our time versus earlier times. But the point 398 00:24:52,080 --> 00:24:56,119 Speaker 1: being that the way we're interacting with our world is 399 00:24:56,240 --> 00:25:01,800 Speaker 1: changing this fundamental ratio of carbon fourteen to carbon twelve, 400 00:25:02,560 --> 00:25:06,920 Speaker 1: and that means that a really brilliant means of determining 401 00:25:06,920 --> 00:25:10,280 Speaker 1: how old something is is not really going to be 402 00:25:10,800 --> 00:25:14,679 Speaker 1: an accurate measure for very much longer. So it's kind 403 00:25:14,680 --> 00:25:18,680 Speaker 1: of a bummer. Obviously, for things that are much, much 404 00:25:18,760 --> 00:25:22,280 Speaker 1: much older, it'll at least in the short term, not 405 00:25:22,440 --> 00:25:24,600 Speaker 1: be that big of a deal, especially if we can 406 00:25:24,680 --> 00:25:28,239 Speaker 1: relate it to other items that we we already know 407 00:25:28,440 --> 00:25:31,880 Speaker 1: the age of those items. It won't be as destructive 408 00:25:31,960 --> 00:25:35,080 Speaker 1: as saying we can never use radio carbon dating again. 409 00:25:35,400 --> 00:25:39,919 Speaker 1: We just have to keep that changing, uh ratio of 410 00:25:39,960 --> 00:25:42,639 Speaker 1: carbon fourteen to carbon twelve in mind, so that we 411 00:25:42,720 --> 00:25:46,560 Speaker 1: make sure we're making accurate measurements. I hope you enjoyed 412 00:25:46,600 --> 00:25:50,080 Speaker 1: that classic episode of tech Stuff about carbon dating. If 413 00:25:50,080 --> 00:25:52,919 Speaker 1: you have suggestions for topics I should cover in future 414 00:25:53,000 --> 00:25:56,119 Speaker 1: episodes of tech Stuff, please reach out to me on Twitter. 415 00:25:56,440 --> 00:25:58,840 Speaker 1: The handle for the show is text Stuff H s 416 00:25:59,040 --> 00:26:04,280 Speaker 1: W and I talked to you again really soon. Yes. 417 00:26:08,440 --> 00:26:11,440 Speaker 1: Text Stuff is an I Heart Radio production. For more 418 00:26:11,520 --> 00:26:14,920 Speaker 1: podcasts from I Heart Radio, visit the I Heart Radio app, 419 00:26:15,040 --> 00:26:18,200 Speaker 1: Apple Podcasts, or wherever you listen to your favorite shows.