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		<id>https://www.explainxkcd.com/wiki/index.php?action=history&amp;feed=atom&amp;title=3205%3A_Carbon_Dating</id>
		<title>3205: Carbon Dating - Revision history</title>
		<link rel="self" type="application/atom+xml" href="https://www.explainxkcd.com/wiki/index.php?action=history&amp;feed=atom&amp;title=3205%3A_Carbon_Dating"/>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;action=history"/>
		<updated>2026-05-23T04:01:25Z</updated>
		<subtitle>Revision history for this page on the wiki</subtitle>
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	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=412620&amp;oldid=prev</id>
		<title>RG: removed incomplete notice</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=412620&amp;oldid=prev"/>
				<updated>2026-05-14T02:24:52Z</updated>
		
		<summary type="html">&lt;p&gt;removed incomplete notice&lt;/p&gt;
&lt;table class=&quot;diff diff-contentalign-left&quot; data-mw=&quot;interface&quot;&gt;
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				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;← Older revision&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;Revision as of 02:24, 14 May 2026&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l10&quot; &gt;Line 10:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 10:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;==Explanation==&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;==Explanation==&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;−&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;{{incomplete|This page was created recently by a SPEAR MADE OF FREE ELECTRONS. Don't remove this notice too soon.}}&lt;/del&gt;&lt;/div&gt;&lt;/td&gt;&lt;td colspan=&quot;2&quot;&gt;&amp;#160;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{w|Carbon dating}} is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of {{w|carbon}}. This method is commonly used by {{w|archaeology|archaeologists}} and is invaluable in terms of estimating the point in time a piece of organic matter (such as a fossil) died. It uses the fact that carbon in Earth's biosphere maintains a known ratio between the isotopes &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C, &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C (irrelevant for carbon dating) and &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C. Its intake by living organisms (by photosynthesis, in the case of plants, or by consumption in the case of non-plants, accounting for known {{w|Fractionation of carbon isotopes in oxygenic photosynthesis|fractionation}} differences) is also relatively stable, until the organism dies and stops taking in carbon compounds. From that point on, the relative concentration of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C in the dead organism can only decrease through radioactive decay. By measuring the relative amount of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C left in the organism's remains, archaeologists can determine how long ago that organism last actively replenished its carbon, and thus how long ago it died.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{w|Carbon dating}} is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of {{w|carbon}}. This method is commonly used by {{w|archaeology|archaeologists}} and is invaluable in terms of estimating the point in time a piece of organic matter (such as a fossil) died. It uses the fact that carbon in Earth's biosphere maintains a known ratio between the isotopes &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C, &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C (irrelevant for carbon dating) and &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C. Its intake by living organisms (by photosynthesis, in the case of plants, or by consumption in the case of non-plants, accounting for known {{w|Fractionation of carbon isotopes in oxygenic photosynthesis|fractionation}} differences) is also relatively stable, until the organism dies and stops taking in carbon compounds. From that point on, the relative concentration of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C in the dead organism can only decrease through radioactive decay. By measuring the relative amount of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C left in the organism's remains, archaeologists can determine how long ago that organism last actively replenished its carbon, and thus how long ago it died.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</summary>
		<author><name>RG</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=407814&amp;oldid=prev</id>
		<title>Eelitee: not all</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=407814&amp;oldid=prev"/>
				<updated>2026-03-08T00:38:53Z</updated>
		
		<summary type="html">&lt;p&gt;not all&lt;/p&gt;
&lt;table class=&quot;diff diff-contentalign-left&quot; data-mw=&quot;interface&quot;&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
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				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;← Older revision&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;Revision as of 00:38, 8 March 2026&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l13&quot; &gt;Line 13:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 13:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{w|Carbon dating}} is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of {{w|carbon}}. This method is commonly used by {{w|archaeology|archaeologists}} and is invaluable in terms of estimating the point in time a piece of organic matter (such as a fossil) died. It uses the fact that carbon in Earth's biosphere maintains a known ratio between the isotopes &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C, &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C (irrelevant for carbon dating) and &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C. Its intake by living organisms (by photosynthesis, in the case of plants, or by consumption in the case of non-plants, accounting for known {{w|Fractionation of carbon isotopes in oxygenic photosynthesis|fractionation}} differences) is also relatively stable, until the organism dies and stops taking in carbon compounds. From that point on, the relative concentration of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C in the dead organism can only decrease through radioactive decay. By measuring the relative amount of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C left in the organism's remains, archaeologists can determine how long ago that organism last actively replenished its carbon, and thus how long ago it died.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{w|Carbon dating}} is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of {{w|carbon}}. This method is commonly used by {{w|archaeology|archaeologists}} and is invaluable in terms of estimating the point in time a piece of organic matter (such as a fossil) died. It uses the fact that carbon in Earth's biosphere maintains a known ratio between the isotopes &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C, &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C (irrelevant for carbon dating) and &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C. Its intake by living organisms (by photosynthesis, in the case of plants, or by consumption in the case of non-plants, accounting for known {{w|Fractionation of carbon isotopes in oxygenic photosynthesis|fractionation}} differences) is also relatively stable, until the organism dies and stops taking in carbon compounds. From that point on, the relative concentration of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C in the dead organism can only decrease through radioactive decay. By measuring the relative amount of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C left in the organism's remains, archaeologists can determine how long ago that organism last actively replenished its carbon, and thus how long ago it died.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;−&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Here, however, [[Ponytail]], in the role of a {{w|cosmology|cosmologist}}, takes a rather different perspective on using carbon for dating. She is interested only in the mere ''presence'' of carbon, which tells her that the skeleton being studied was formed after the first carbon in the universe was created in the first round of stars fusing elements, 13.6 billion years ago. This is not useful information for differentiating artifacts originating on {{w|Earth}}, which is itself less than ''5'' billion years old, since it would apply to &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;all &lt;/del&gt;of them.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Here, however, [[Ponytail]], in the role of a {{w|cosmology|cosmologist}}, takes a rather different perspective on using carbon for dating. She is interested only in the mere ''presence'' of carbon, which tells her that the skeleton being studied was formed after the first carbon in the universe was created in the first round of stars fusing elements, 13.6 billion years ago. This is not useful information for differentiating artifacts originating on {{w|Earth}}, which is itself less than ''5'' billion years old, since it would apply to &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;the vast majority &lt;/ins&gt;of them.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;The title text looks like the kind of statement that would provide corroborative dating evidence for an archaeological site. The type and composition of tools can help to place a site, relative to others, on a {{w|Tool#History|developmental timeline}}. Here, however, they claim that the presence of stone tools dates the site as later than a non-existent age of helium tools. Tools made out of stone, usually dating from the {{w|Stone Age}}, are often solid and durable, making them great choices for heavy duty tasks, and well-preserved in the archaeological record. {{w|Helium}} is a gas and is difficult to shape into a solid mass for use as a tool.{{Citation needed}} It would also be near impossible to identify such tools if they had existed, since they would tend to disperse easily. Helium was produced in great quantities after the {{w|Big Bang}}, accounting for about ~25% of the mass of atoms produced by the early universe, so would have been available before stone was, but there were no people around at the time to fashion tools from it.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;The title text looks like the kind of statement that would provide corroborative dating evidence for an archaeological site. The type and composition of tools can help to place a site, relative to others, on a {{w|Tool#History|developmental timeline}}. Here, however, they claim that the presence of stone tools dates the site as later than a non-existent age of helium tools. Tools made out of stone, usually dating from the {{w|Stone Age}}, are often solid and durable, making them great choices for heavy duty tasks, and well-preserved in the archaeological record. {{w|Helium}} is a gas and is difficult to shape into a solid mass for use as a tool.{{Citation needed}} It would also be near impossible to identify such tools if they had existed, since they would tend to disperse easily. Helium was produced in great quantities after the {{w|Big Bang}}, accounting for about ~25% of the mass of atoms produced by the early universe, so would have been available before stone was, but there were no people around at the time to fashion tools from it.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</summary>
		<author><name>Eelitee</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=406735&amp;oldid=prev</id>
		<title>27.96.196.236: /* Explanation */ clarify what decreases in the dead organism</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=406735&amp;oldid=prev"/>
				<updated>2026-02-20T22:33:21Z</updated>
		
		<summary type="html">&lt;p&gt;‎&lt;span dir=&quot;auto&quot;&gt;&lt;span class=&quot;autocomment&quot;&gt;Explanation: &lt;/span&gt; clarify what decreases in the dead organism&lt;/span&gt;&lt;/p&gt;
&lt;table class=&quot;diff diff-contentalign-left&quot; data-mw=&quot;interface&quot;&gt;
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				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;← Older revision&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;Revision as of 22:33, 20 February 2026&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l11&quot; &gt;Line 11:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 11:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;==Explanation==&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;==Explanation==&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{incomplete|This page was created recently by a SPEAR MADE OF FREE ELECTRONS. Don't remove this notice too soon.}}&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{incomplete|This page was created recently by a SPEAR MADE OF FREE ELECTRONS. Don't remove this notice too soon.}}&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;−&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{w|Carbon dating}} is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of {{w|carbon}}. This method is commonly used by {{w|archaeology|archaeologists}} and is invaluable in terms of estimating the point in time a piece of organic matter (such as a fossil) died. It uses the fact that carbon in Earth's biosphere maintains a known ratio between the isotopes &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C, &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C (irrelevant for carbon dating) and &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C. Its intake by living organisms (by photosynthesis, in the case of plants, or by consumption in the case of non-plants, accounting for known {{w|Fractionation of carbon isotopes in oxygenic photosynthesis|fractionation}} differences) is also relatively stable, until the organism dies and stops taking in carbon compounds. From that point on, &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;its &lt;/del&gt;relative concentration in the dead organism can only decrease through radioactive decay. By measuring the relative amount of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C left in the organism's remains, archaeologists can determine how long ago that organism last actively replenished its carbon, and thus how long ago it died.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{w|Carbon dating}} is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of {{w|carbon}}. This method is commonly used by {{w|archaeology|archaeologists}} and is invaluable in terms of estimating the point in time a piece of organic matter (such as a fossil) died. It uses the fact that carbon in Earth's biosphere maintains a known ratio between the isotopes &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C, &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C (irrelevant for carbon dating) and &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C. Its intake by living organisms (by photosynthesis, in the case of plants, or by consumption in the case of non-plants, accounting for known {{w|Fractionation of carbon isotopes in oxygenic photosynthesis|fractionation}} differences) is also relatively stable, until the organism dies and stops taking in carbon compounds. From that point on, &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;the &lt;/ins&gt;relative concentration &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C &lt;/ins&gt;in the dead organism can only decrease through radioactive decay. By measuring the relative amount of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C left in the organism's remains, archaeologists can determine how long ago that organism last actively replenished its carbon, and thus how long ago it died.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Here, however, [[Ponytail]], in the role of a {{w|cosmology|cosmologist}}, takes a rather different perspective on using carbon for dating. She is interested only in the mere ''presence'' of carbon, which tells her that the skeleton being studied was formed after the first carbon in the universe was created in the first round of stars fusing elements, 13.6 billion years ago. This is not useful information for differentiating artifacts originating on {{w|Earth}}, which is itself less than ''5'' billion years old, since it would apply to all of them.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Here, however, [[Ponytail]], in the role of a {{w|cosmology|cosmologist}}, takes a rather different perspective on using carbon for dating. She is interested only in the mere ''presence'' of carbon, which tells her that the skeleton being studied was formed after the first carbon in the universe was created in the first round of stars fusing elements, 13.6 billion years ago. This is not useful information for differentiating artifacts originating on {{w|Earth}}, which is itself less than ''5'' billion years old, since it would apply to all of them.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</summary>
		<author><name>27.96.196.236</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=406046&amp;oldid=prev</id>
		<title>82.132.238.7: /* Explanation */</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=406046&amp;oldid=prev"/>
				<updated>2026-02-12T10:58:17Z</updated>
		
		<summary type="html">&lt;p&gt;‎&lt;span dir=&quot;auto&quot;&gt;&lt;span class=&quot;autocomment&quot;&gt;Explanation&lt;/span&gt;&lt;/span&gt;&lt;/p&gt;
&lt;table class=&quot;diff diff-contentalign-left&quot; data-mw=&quot;interface&quot;&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
				&lt;tr style=&quot;vertical-align: top;&quot; lang=&quot;en&quot;&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;← Older revision&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;Revision as of 10:58, 12 February 2026&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l17&quot; &gt;Line 17:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 17:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;The title text looks like the kind of statement that would provide corroborative dating evidence for an archaeological site. The type and composition of tools can help to place a site, relative to others, on a {{w|Tool#History|developmental timeline}}. Here, however, they claim that the presence of stone tools dates the site as later than a non-existent age of helium tools. Tools made out of stone, usually dating from the {{w|Stone Age}}, are often solid and durable, making them great choices for heavy duty tasks, and well-preserved in the archaeological record. {{w|Helium}} is a gas and is difficult to shape into a solid mass for use as a tool.{{Citation needed}} It would also be near impossible to identify such tools if they had existed, since they would tend to disperse easily. Helium was produced in great quantities after the {{w|Big Bang}}, accounting for about ~25% of the mass of atoms produced by the early universe, so would have been available before stone was, but there were no people around at the time to fashion tools from it.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;The title text looks like the kind of statement that would provide corroborative dating evidence for an archaeological site. The type and composition of tools can help to place a site, relative to others, on a {{w|Tool#History|developmental timeline}}. Here, however, they claim that the presence of stone tools dates the site as later than a non-existent age of helium tools. Tools made out of stone, usually dating from the {{w|Stone Age}}, are often solid and durable, making them great choices for heavy duty tasks, and well-preserved in the archaeological record. {{w|Helium}} is a gas and is difficult to shape into a solid mass for use as a tool.{{Citation needed}} It would also be near impossible to identify such tools if they had existed, since they would tend to disperse easily. Helium was produced in great quantities after the {{w|Big Bang}}, accounting for about ~25% of the mass of atoms produced by the early universe, so would have been available before stone was, but there were no people around at the time to fashion tools from it.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;−&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is generated in the atmosphere by interactions between nitrogen and cosmic rays, and it is radioactive with a half-life of approximately 5,730 years. It decays over time even as it is replenished, leaving its relative concentration in the environment a matter of the balance between its creation (by cosmic rays, which vary slightly over time, but in a way that can be enumerated) and decay (a constant proportion). Carbon dating is a useful method only so long as the remaining concentration of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C can be measured accurately, which extends to approximately 9 &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;to &lt;/del&gt;10 half-lives (50,000 to 60,000 years) until the continued halving of the remaining isotope becomes statistically &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;(&lt;/del&gt;or physically&lt;del class=&quot;diffchange diffchange-inline&quot;&gt;) &lt;/del&gt;difficult to accurately determine, as well as for lengths of time that are significantly ''less'' than &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;the &lt;/del&gt;half-life. Other forms of {{w|radiometric dating}}, based on other elements and isotopes, are used for lengths of time, as well as situations where such carbon-chemistry is not a reliable component of a sample. Even the ratios between abundances of stable isotopes can vary, providing historical information about things such as temperatures and atmospheric mixing, via {{w|isotope geochemistry}}, as well as in a wider form {{w|radiometric dating}} for which the presence of stable decay products in a sample can be used to show the original concentrations &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;and therefore reveal the subsequent passage &lt;/del&gt;of &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;time&lt;/del&gt;.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is generated in the atmosphere by interactions between nitrogen and cosmic rays, and it is radioactive with a half-life of approximately 5,730 years. It decays over time even as it is replenished, leaving its relative concentration in the environment a matter of the balance between its creation (by cosmic rays, which vary slightly over time, but in a way that can be enumerated) and decay (a constant proportion). Carbon dating is a useful method only so long as the remaining concentration of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C can be measured accurately, which extends to approximately 9 &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;or &lt;/ins&gt;10 half-lives (50,000 to 60,000 years) until the continued halving of the remaining isotope becomes statistically or physically difficult to accurately determine, as well as for lengths of time that are significantly ''less'' than &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;this isotope's &lt;/ins&gt;half-life. Other forms of {{w|radiometric dating}}, based on other elements and isotopes, are used for &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;different &lt;/ins&gt;lengths of time, as well as situations where such carbon-chemistry is not a reliable component of a sample&lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;, or may further validate the result in situations where their respective useful scenarios overlap&lt;/ins&gt;. Even the ratios between abundances of stable isotopes can vary, providing historical information about things such as temperatures and atmospheric mixing, via {{w|isotope geochemistry}}, as well as in a wider form &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;of &lt;/ins&gt;{{w|radiometric dating}} for which the presence of stable decay products in a sample can be used to show the original concentrations of &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;subsequently decayed atoms for even better cross-comparison of how much samples such as this will have aged&lt;/ins&gt;.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;The themes of the comic are similar to [[2723]], which imagines a periodic table published just after the Big Bang, when most elements did not yet exist.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;The themes of the comic are similar to [[2723]], which imagines a periodic table published just after the Big Bang, when most elements did not yet exist.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</summary>
		<author><name>82.132.238.7</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=406032&amp;oldid=prev</id>
		<title>82.13.184.33: /* Explanation */ Rearranging to 'get to the explanation' quicker - first paragraph had become unwieldy with detailed explanation of radioactive generation and decay</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=406032&amp;oldid=prev"/>
				<updated>2026-02-12T09:27:04Z</updated>
		
		<summary type="html">&lt;p&gt;‎&lt;span dir=&quot;auto&quot;&gt;&lt;span class=&quot;autocomment&quot;&gt;Explanation: &lt;/span&gt; Rearranging to &amp;#039;get to the explanation&amp;#039; quicker - first paragraph had become unwieldy with detailed explanation of radioactive generation and decay&lt;/span&gt;&lt;/p&gt;
&lt;table class=&quot;diff diff-contentalign-left&quot; data-mw=&quot;interface&quot;&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
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				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;← Older revision&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;Revision as of 09:27, 12 February 2026&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l11&quot; &gt;Line 11:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 11:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;==Explanation==&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;==Explanation==&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{incomplete|This page was created recently by a SPEAR MADE OF FREE ELECTRONS. Don't remove this notice too soon.}}&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{incomplete|This page was created recently by a SPEAR MADE OF FREE ELECTRONS. Don't remove this notice too soon.}}&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;−&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{w|Carbon dating}} is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of {{w|carbon}}. This method is commonly used by {{w|archaeology|archaeologists}} and is invaluable in terms of estimating the point in time a piece of organic matter (such as a fossil) died. It uses the fact that carbon in Earth's biosphere maintains a known ratio between the isotopes &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C, &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C (irrelevant for carbon dating) and &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C&lt;del class=&quot;diffchange diffchange-inline&quot;&gt;. &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is generated in the atmosphere by interactions between nitrogen and cosmic rays, and it is radioactive with a half-life of approximately 5,730 years. It decays over time even as it is replenished, leaving its relative concentration in the environment a matter of the balance between its creation (by cosmic rays, which vary slightly over time, but in a way that can be enumerated) and decay (a constant proportion)&lt;/del&gt;. Its intake by living organisms (by photosynthesis, in the case of plants, or by consumption in the case of non-plants, accounting for known {{w|Fractionation of carbon isotopes in oxygenic photosynthesis|fractionation}} differences) is also relatively stable, until the organism dies and stops taking in carbon compounds. From that point on, its relative concentration in the dead organism can only decrease through &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;the &lt;/del&gt;radioactive decay. By measuring the relative amount of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C left in the organism's remains, archaeologists can determine how long ago that organism last actively replenished its carbon, and thus how long ago it died&lt;del class=&quot;diffchange diffchange-inline&quot;&gt;. This method is useful only so long as the remaining concentration of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C can be measured accurately, which extends to approximately 9 to 10 half-lives (50,000 to 60,000 years) until the continued halving of the remaining isotope becomes statistically (or physically) difficult to accurately determine, as well as for lengths of time that are significantly ''less'' than the half-life. Other forms of {{w|radiometric dating}}, based on other elements and isotopes, are used for lengths of time, as well as situations where such carbon-chemistry is not a reliable component of a sample. Even the ratios between abundances of stable isotopes can vary, providing historical information about things such as temperatures and atmospheric mixing, via {{w|isotope geochemistry}}, as well as in a wider form {{w|radiometric dating}} for which the presence of stable decay products in a sample can be used to show the original concentrations and therefore reveal the subsequent passage of time&lt;/del&gt;.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{w|Carbon dating}} is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of {{w|carbon}}. This method is commonly used by {{w|archaeology|archaeologists}} and is invaluable in terms of estimating the point in time a piece of organic matter (such as a fossil) died. It uses the fact that carbon in Earth's biosphere maintains a known ratio between the isotopes &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C, &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C (irrelevant for carbon dating) and &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C. Its intake by living organisms (by photosynthesis, in the case of plants, or by consumption in the case of non-plants, accounting for known {{w|Fractionation of carbon isotopes in oxygenic photosynthesis|fractionation}} differences) is also relatively stable, until the organism dies and stops taking in carbon compounds. From that point on, its relative concentration in the dead organism can only decrease through radioactive decay. By measuring the relative amount of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C left in the organism's remains, archaeologists can determine how long ago that organism last actively replenished its carbon, and thus how long ago it died.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Here, however, [[Ponytail]], in the role of a {{w|cosmology|cosmologist}}, takes a rather different perspective on using carbon for dating. She is interested only in the mere ''presence'' of carbon, which tells her that the skeleton being studied was formed after the first carbon in the universe was created in the first round of stars fusing elements, 13.6 billion years ago. This is not useful information for differentiating artifacts originating on {{w|Earth}}, which is itself less than ''5'' billion years old, since it would apply to all of them.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Here, however, [[Ponytail]], in the role of a {{w|cosmology|cosmologist}}, takes a rather different perspective on using carbon for dating. She is interested only in the mere ''presence'' of carbon, which tells her that the skeleton being studied was formed after the first carbon in the universe was created in the first round of stars fusing elements, 13.6 billion years ago. This is not useful information for differentiating artifacts originating on {{w|Earth}}, which is itself less than ''5'' billion years old, since it would apply to all of them.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;The title text looks like the kind of statement that would provide corroborative dating evidence for an archaeological site. The type and composition of tools can help to place a site, relative to others, on a {{w|Tool#History|developmental timeline}}. Here, however, they claim that the presence of stone tools dates the site as later than a non-existent age of helium tools. Tools made out of stone, usually dating from the {{w|Stone Age}}, are often solid and durable, making them great choices for heavy duty tasks, and well-preserved in the archaeological record. {{w|Helium}} is a gas and is difficult to shape into a solid mass for use as a tool.{{Citation needed}} It would also be near impossible to identify such tools if they had existed, since they would tend to disperse easily. Helium was produced in great quantities after the {{w|Big Bang}}, accounting for about ~25% of the mass of atoms produced by the early universe, so would have been available before stone was, but there were no people around at the time to fashion tools from it.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;The title text looks like the kind of statement that would provide corroborative dating evidence for an archaeological site. The type and composition of tools can help to place a site, relative to others, on a {{w|Tool#History|developmental timeline}}. Here, however, they claim that the presence of stone tools dates the site as later than a non-existent age of helium tools. Tools made out of stone, usually dating from the {{w|Stone Age}}, are often solid and durable, making them great choices for heavy duty tasks, and well-preserved in the archaeological record. {{w|Helium}} is a gas and is difficult to shape into a solid mass for use as a tool.{{Citation needed}} It would also be near impossible to identify such tools if they had existed, since they would tend to disperse easily. Helium was produced in great quantities after the {{w|Big Bang}}, accounting for about ~25% of the mass of atoms produced by the early universe, so would have been available before stone was, but there were no people around at the time to fashion tools from it.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot;&gt;&amp;#160;&lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;&lt;/ins&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot;&gt;&amp;#160;&lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;&amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is generated in the atmosphere by interactions between nitrogen and cosmic rays, and it is radioactive with a half-life of approximately 5,730 years. It decays over time even as it is replenished, leaving its relative concentration in the environment a matter of the balance between its creation (by cosmic rays, which vary slightly over time, but in a way that can be enumerated) and decay (a constant proportion). Carbon dating is a useful method only so long as the remaining concentration of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C can be measured accurately, which extends to approximately 9 to 10 half-lives (50,000 to 60,000 years) until the continued halving of the remaining isotope becomes statistically (or physically) difficult to accurately determine, as well as for lengths of time that are significantly ''less'' than the half-life. Other forms of {{w|radiometric dating}}, based on other elements and isotopes, are used for lengths of time, as well as situations where such carbon-chemistry is not a reliable component of a sample. Even the ratios between abundances of stable isotopes can vary, providing historical information about things such as temperatures and atmospheric mixing, via {{w|isotope geochemistry}}, as well as in a wider form {{w|radiometric dating}} for which the presence of stable decay products in a sample can be used to show the original concentrations and therefore reveal the subsequent passage of time.&lt;/ins&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;The themes of the comic are similar to [[2723]], which imagines a periodic table published just after the Big Bang, when most elements did not yet exist.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;The themes of the comic are similar to [[2723]], which imagines a periodic table published just after the Big Bang, when most elements did not yet exist.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</summary>
		<author><name>82.13.184.33</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=405994&amp;oldid=prev</id>
		<title>Elizium23: clarify</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=405994&amp;oldid=prev"/>
				<updated>2026-02-12T01:55:56Z</updated>
		
		<summary type="html">&lt;p&gt;clarify&lt;/p&gt;
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				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;← Older revision&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;Revision as of 01:55, 12 February 2026&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l11&quot; &gt;Line 11:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 11:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;==Explanation==&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;==Explanation==&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{incomplete|This page was created recently by a SPEAR MADE OF FREE ELECTRONS. Don't remove this notice too soon.}}&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{incomplete|This page was created recently by a SPEAR MADE OF FREE ELECTRONS. Don't remove this notice too soon.}}&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;−&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{w|Carbon dating}} is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of {{w|carbon}}. This method is commonly used by {{w|archaeology|archaeologists}} and is invaluable in terms of &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;determining &lt;/del&gt;the time a piece of organic matter (such as a fossil) &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;came from&lt;/del&gt;. It uses the fact that carbon in Earth's biosphere maintains a known ratio between the isotopes &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C, &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C (irrelevant for carbon dating) and &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C. &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is generated in the atmosphere by interactions between nitrogen and cosmic rays, and it is radioactive with a half-life of approximately 5,730 years. It decays over time even as it is replenished, leaving its relative concentration in the environment a matter of the balance between its creation (by cosmic rays, which vary slightly over time, but in a way that can be enumerated) and decay (a constant proportion). Its intake by living organisms (by photosynthesis, in the case of plants, or by consumption in the case of non-plants, accounting for known {{w|Fractionation of carbon isotopes in oxygenic photosynthesis|fractionation}} differences) is also relatively stable, until the organism dies and stops taking in carbon compounds. From that point on, its relative concentration in the dead organism can only decrease through the radioactive decay. By measuring the relative amount of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C left in the organism's remains, archaeologists can determine how long ago that organism last actively replenished its carbon, and thus how long ago it died. This method is useful only so long as the remaining concentration of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C can be measured accurately, which extends to approximately 9 to 10 half-lives (50,000 to 60,000 years) until the continued halving of the remaining isotope becomes statistically (or physically) difficult to accurately determine, as well as for lengths of time that are significantly ''less'' than the half-life. Other forms of {{w|radiometric dating}}, based on other elements and isotopes, are used for lengths of time, as well as situations where such carbon-chemistry is not a reliable component of a sample. Even the ratios between abundances of stable isotopes can vary, providing historical information about things such as temperatures and atmospheric mixing, via {{w|isotope geochemistry}}, as well as in a wider form {{w|radiometric dating}} for which the presence of stable decay products in a sample can be used to show the original concentrations and therefore reveal the subsequent passage of time.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{w|Carbon dating}} is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of {{w|carbon}}. This method is commonly used by {{w|archaeology|archaeologists}} and is invaluable in terms of &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;estimating &lt;/ins&gt;the &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;point in &lt;/ins&gt;time a piece of organic matter (such as a fossil) &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;died&lt;/ins&gt;. It uses the fact that carbon in Earth's biosphere maintains a known ratio between the isotopes &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C, &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C (irrelevant for carbon dating) and &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C. &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is generated in the atmosphere by interactions between nitrogen and cosmic rays, and it is radioactive with a half-life of approximately 5,730 years. It decays over time even as it is replenished, leaving its relative concentration in the environment a matter of the balance between its creation (by cosmic rays, which vary slightly over time, but in a way that can be enumerated) and decay (a constant proportion). Its intake by living organisms (by photosynthesis, in the case of plants, or by consumption in the case of non-plants, accounting for known {{w|Fractionation of carbon isotopes in oxygenic photosynthesis|fractionation}} differences) is also relatively stable, until the organism dies and stops taking in carbon compounds. From that point on, its relative concentration in the dead organism can only decrease through the radioactive decay. By measuring the relative amount of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C left in the organism's remains, archaeologists can determine how long ago that organism last actively replenished its carbon, and thus how long ago it died. This method is useful only so long as the remaining concentration of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C can be measured accurately, which extends to approximately 9 to 10 half-lives (50,000 to 60,000 years) until the continued halving of the remaining isotope becomes statistically (or physically) difficult to accurately determine, as well as for lengths of time that are significantly ''less'' than the half-life. Other forms of {{w|radiometric dating}}, based on other elements and isotopes, are used for lengths of time, as well as situations where such carbon-chemistry is not a reliable component of a sample. Even the ratios between abundances of stable isotopes can vary, providing historical information about things such as temperatures and atmospheric mixing, via {{w|isotope geochemistry}}, as well as in a wider form {{w|radiometric dating}} for which the presence of stable decay products in a sample can be used to show the original concentrations and therefore reveal the subsequent passage of time.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Here, however, [[Ponytail]], in the role of a {{w|cosmology|cosmologist}}, takes a rather different perspective on using carbon for dating. She is interested only in the mere ''presence'' of carbon, which tells her that the skeleton being studied was formed after the first carbon in the universe was created in the first round of stars fusing elements, 13.6 billion years ago. This is not useful information for differentiating artifacts originating on {{w|Earth}}, which is itself less than ''5'' billion years old, since it would apply to all of them.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Here, however, [[Ponytail]], in the role of a {{w|cosmology|cosmologist}}, takes a rather different perspective on using carbon for dating. She is interested only in the mere ''presence'' of carbon, which tells her that the skeleton being studied was formed after the first carbon in the universe was created in the first round of stars fusing elements, 13.6 billion years ago. This is not useful information for differentiating artifacts originating on {{w|Earth}}, which is itself less than ''5'' billion years old, since it would apply to all of them.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</summary>
		<author><name>Elizium23</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=405985&amp;oldid=prev</id>
		<title>81.179.199.253: /* Explanation */ Some additional info, and minor changes to some of what was already there. (Hmm, edit-conflict, tried to integrate the intent of that into this once more.)</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=405985&amp;oldid=prev"/>
				<updated>2026-02-12T00:20:58Z</updated>
		
		<summary type="html">&lt;p&gt;‎&lt;span dir=&quot;auto&quot;&gt;&lt;span class=&quot;autocomment&quot;&gt;Explanation: &lt;/span&gt; Some additional info, and minor changes to some of what was already there. (Hmm, edit-conflict, tried to integrate the intent of that into this once more.)&lt;/span&gt;&lt;/p&gt;
&lt;table class=&quot;diff diff-contentalign-left&quot; data-mw=&quot;interface&quot;&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
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				&lt;tr style=&quot;vertical-align: top;&quot; lang=&quot;en&quot;&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;← Older revision&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;Revision as of 00:20, 12 February 2026&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l11&quot; &gt;Line 11:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 11:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;==Explanation==&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;==Explanation==&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{incomplete|This page was created recently by a SPEAR MADE OF FREE ELECTRONS. Don't remove this notice too soon.}}&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{incomplete|This page was created recently by a SPEAR MADE OF FREE ELECTRONS. Don't remove this notice too soon.}}&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;−&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{w|Carbon dating}} is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of {{w|carbon}}. This method is commonly used by {{w|archaeology|archaeologists}} and is invaluable in terms of determining the time a piece of organic matter (such as a fossil) came from. It uses the fact that carbon in &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;earth&lt;/del&gt;'s biosphere &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;contains &lt;/del&gt;a known ratio between the isotopes &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C, &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C (irrelevant for carbon dating)&lt;del class=&quot;diffchange diffchange-inline&quot;&gt;, &lt;/del&gt;and &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C. &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is generated in the atmosphere by interactions between nitrogen and cosmic rays, and it is radioactive&lt;del class=&quot;diffchange diffchange-inline&quot;&gt;, &lt;/del&gt;with a half-life of approximately 5,730 years&lt;del class=&quot;diffchange diffchange-inline&quot;&gt;, decaying &lt;/del&gt;over time&lt;del class=&quot;diffchange diffchange-inline&quot;&gt;. Its &lt;/del&gt;relative concentration in the environment &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;is fairly stable — &lt;/del&gt;a balance between its creation &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;and decay, depending on the rate of bombardment &lt;/del&gt;by cosmic rays, which &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;varies &lt;/del&gt;slightly. Its intake by organisms (by photosynthesis, in the case of plants, or by consumption in the case of non-plants) is also relatively stable, until the organism dies and stops taking in carbon compounds. From that point on, its relative concentration in the dead organism &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;decreases by &lt;/del&gt;radioactive decay. By measuring &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;how much &lt;/del&gt;&amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;is &lt;/del&gt;left in the remains &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;of an organism&lt;/del&gt;, archaeologists can determine how long ago that organism &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;consumed &lt;/del&gt;carbon, and thus how long ago it &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;lived&lt;/del&gt;. This method is useful only so long as the remaining concentration of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C can be measured accurately, approximately 9 to 10 half-lives&lt;del class=&quot;diffchange diffchange-inline&quot;&gt;, or &lt;/del&gt;50,000 to 60,000 years. Other forms of {{w|radiometric dating}}, based on other elements and isotopes, are used for &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;other purposes&lt;/del&gt;. Even the ratios between abundances of stable isotopes can vary, providing historical information about things such as temperatures and atmospheric mixing, via {{w|isotope geochemistry}}.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{w|Carbon dating}} is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of {{w|carbon}}. This method is commonly used by {{w|archaeology|archaeologists}} and is invaluable in terms of determining the time a piece of organic matter (such as a fossil) came from. It uses the fact that carbon in &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;Earth&lt;/ins&gt;'s biosphere &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;maintains &lt;/ins&gt;a known ratio between the isotopes &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C, &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C (irrelevant for carbon dating) and &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C. &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is generated in the atmosphere by interactions between nitrogen and cosmic rays, and it is radioactive with a half-life of approximately 5,730 years&lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;. It decays &lt;/ins&gt;over time &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;even as it is replenished, leaving its &lt;/ins&gt;relative concentration in the environment a &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;matter of the &lt;/ins&gt;balance between its creation &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;(&lt;/ins&gt;by cosmic rays, which &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;vary &lt;/ins&gt;slightly &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;over time, but in a way that can be enumerated) and decay (a constant proportion)&lt;/ins&gt;. Its intake by &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;living &lt;/ins&gt;organisms (by photosynthesis, in the case of plants, or by consumption in the case of non-plants&lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;, accounting for known {{w|Fractionation of carbon isotopes in oxygenic photosynthesis|fractionation}} differences&lt;/ins&gt;) is also relatively stable, until the organism dies and stops taking in carbon compounds. From that point on, its relative concentration in the dead organism &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;can only decrease through the &lt;/ins&gt;radioactive decay. By measuring &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;the relative amount of &lt;/ins&gt;&amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C left in the &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;organism's &lt;/ins&gt;remains, archaeologists can determine how long ago that organism &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;last actively replenished its &lt;/ins&gt;carbon, and thus how long ago it &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;died&lt;/ins&gt;. This method is useful only so long as the remaining concentration of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C can be measured accurately, &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;which extends to &lt;/ins&gt;approximately 9 to 10 half-lives &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;(&lt;/ins&gt;50,000 to 60,000 years&lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;) until the continued halving of the remaining isotope becomes statistically (or physically) difficult to accurately determine, as well as for lengths of time that are significantly ''less'' than the half-life&lt;/ins&gt;. Other forms of {{w|radiometric dating}}, based on other elements and isotopes, are used for &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;lengths of time, as well as situations where such carbon-chemistry is not a reliable component of a sample&lt;/ins&gt;. Even the ratios between abundances of stable isotopes can vary, providing historical information about things such as temperatures and atmospheric mixing, via {{w|isotope geochemistry}}&lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;, as well as in a wider form {{w|radiometric dating}} for which the presence of stable decay products in a sample can be used to show the original concentrations and therefore reveal the subsequent passage of time&lt;/ins&gt;.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Here, however, [[Ponytail]], in the role of a {{w|cosmology|cosmologist}}, takes a rather different perspective on using carbon for dating. She is interested only in the mere ''presence'' of carbon, which tells her that the skeleton being studied was formed after the first carbon in the universe was created in the first round of stars fusing elements, 13.6 billion years ago. This is not useful information for differentiating artifacts originating on {{w|Earth}}, which is itself less than ''5'' billion years old, since it would apply to all of them.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Here, however, [[Ponytail]], in the role of a {{w|cosmology|cosmologist}}, takes a rather different perspective on using carbon for dating. She is interested only in the mere ''presence'' of carbon, which tells her that the skeleton being studied was formed after the first carbon in the universe was created in the first round of stars fusing elements, 13.6 billion years ago. This is not useful information for differentiating artifacts originating on {{w|Earth}}, which is itself less than ''5'' billion years old, since it would apply to all of them.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</summary>
		<author><name>81.179.199.253</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=405984&amp;oldid=prev</id>
		<title>BunsenH: there's slight variation, as noted later</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=405984&amp;oldid=prev"/>
				<updated>2026-02-12T00:07:56Z</updated>
		
		<summary type="html">&lt;p&gt;there&amp;#039;s slight variation, as noted later&lt;/p&gt;
&lt;table class=&quot;diff diff-contentalign-left&quot; data-mw=&quot;interface&quot;&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
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				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;← Older revision&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;Revision as of 00:07, 12 February 2026&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l11&quot; &gt;Line 11:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 11:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;==Explanation==&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;==Explanation==&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{incomplete|This page was created recently by a SPEAR MADE OF FREE ELECTRONS. Don't remove this notice too soon.}}&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{incomplete|This page was created recently by a SPEAR MADE OF FREE ELECTRONS. Don't remove this notice too soon.}}&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;−&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{w|Carbon dating}} is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of {{w|carbon}}. This method is commonly used by {{w|archaeology|archaeologists}} and is invaluable in terms of determining the time a piece of organic matter (such as a fossil) came from. It uses the fact that carbon in earth's biosphere contains a known ratio between the isotopes &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C, &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C (irrelevant for carbon dating), and &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C&lt;del class=&quot;diffchange diffchange-inline&quot;&gt;, which has been constant for a very long time&lt;/del&gt;. &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is generated in the atmosphere by interactions between nitrogen and cosmic rays, and it is radioactive, with a half-life of approximately 5,730 years, decaying over time. Its relative concentration in the environment is fairly stable — a balance between its creation and decay, depending on the rate of bombardment by cosmic rays. Its intake by organisms (by photosynthesis, in the case of plants, or by consumption in the case of non-plants) is also relatively stable, until the organism dies and stops taking in carbon compounds. From that point on, its relative concentration in the dead organism decreases by radioactive decay. By measuring how much &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is left in the remains of an organism, archaeologists can determine how long ago that organism consumed carbon, and thus how long ago it lived. This method is useful only so long as the remaining concentration of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C can be measured accurately, approximately 9 to 10 half-lives, or 50,000 to 60,000 years. Other forms of {{w|radiometric dating}}, based on other elements and isotopes, are used for other purposes. Even the ratios between abundances of stable isotopes can vary, providing historical information about things such as temperatures and atmospheric mixing, via {{w|isotope geochemistry}}.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{w|Carbon dating}} is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of {{w|carbon}}. This method is commonly used by {{w|archaeology|archaeologists}} and is invaluable in terms of determining the time a piece of organic matter (such as a fossil) came from. It uses the fact that carbon in earth's biosphere contains a known ratio between the isotopes &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C, &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C (irrelevant for carbon dating), and &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C. &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is generated in the atmosphere by interactions between nitrogen and cosmic rays, and it is radioactive, with a half-life of approximately 5,730 years, decaying over time. Its relative concentration in the environment is fairly stable — a balance between its creation and decay, depending on the rate of bombardment by cosmic rays&lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;, which varies slightly&lt;/ins&gt;. Its intake by organisms (by photosynthesis, in the case of plants, or by consumption in the case of non-plants) is also relatively stable, until the organism dies and stops taking in carbon compounds. From that point on, its relative concentration in the dead organism decreases by radioactive decay. By measuring how much &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is left in the remains of an organism, archaeologists can determine how long ago that organism consumed carbon, and thus how long ago it lived. This method is useful only so long as the remaining concentration of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C can be measured accurately, approximately 9 to 10 half-lives, or 50,000 to 60,000 years. Other forms of {{w|radiometric dating}}, based on other elements and isotopes, are used for other purposes. Even the ratios between abundances of stable isotopes can vary, providing historical information about things such as temperatures and atmospheric mixing, via {{w|isotope geochemistry}}.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Here, however, [[Ponytail]], in the role of a {{w|cosmology|cosmologist}}, takes a rather different perspective on using carbon for dating. She is interested only in the mere ''presence'' of carbon, which tells her that the skeleton being studied was formed after the first carbon in the universe was created in the first round of stars fusing elements, 13.6 billion years ago. This is not useful information for differentiating artifacts originating on {{w|Earth}}, which is itself less than ''5'' billion years old, since it would apply to all of them.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Here, however, [[Ponytail]], in the role of a {{w|cosmology|cosmologist}}, takes a rather different perspective on using carbon for dating. She is interested only in the mere ''presence'' of carbon, which tells her that the skeleton being studied was formed after the first carbon in the universe was created in the first round of stars fusing elements, 13.6 billion years ago. This is not useful information for differentiating artifacts originating on {{w|Earth}}, which is itself less than ''5'' billion years old, since it would apply to all of them.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</summary>
		<author><name>BunsenH</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=405963&amp;oldid=prev</id>
		<title>2001:16B8:CC03:8600:3A22:B176:FC7F:29FB: /* Explanation */ balderdash</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=405963&amp;oldid=prev"/>
				<updated>2026-02-11T22:20:49Z</updated>
		
		<summary type="html">&lt;p&gt;‎&lt;span dir=&quot;auto&quot;&gt;&lt;span class=&quot;autocomment&quot;&gt;Explanation: &lt;/span&gt; balderdash&lt;/span&gt;&lt;/p&gt;
&lt;table class=&quot;diff diff-contentalign-left&quot; data-mw=&quot;interface&quot;&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
				&lt;tr style=&quot;vertical-align: top;&quot; lang=&quot;en&quot;&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;← Older revision&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;Revision as of 22:20, 11 February 2026&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l11&quot; &gt;Line 11:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 11:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;==Explanation==&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;==Explanation==&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{incomplete|This page was created recently by a SPEAR MADE OF FREE ELECTRONS. Don't remove this notice too soon.}}&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{incomplete|This page was created recently by a SPEAR MADE OF FREE ELECTRONS. Don't remove this notice too soon.}}&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;−&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{w|Carbon dating}} is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of {{w|carbon}}. This method is commonly used by {{w|archaeology|archaeologists}} and is invaluable in terms of determining the time a piece of organic matter (such as a fossil) came from. It uses the fact that carbon &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;consumed by living organisms &lt;/del&gt;contains a ratio between the &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;carbon &lt;/del&gt;isotopes &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C, &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C, and &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C. &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is generated in the atmosphere by interactions between nitrogen and cosmic rays, and it is radioactive, with a half-life of approximately 5,730 years, decaying over time. Its relative concentration in the environment is fairly stable — a balance between its creation and decay, depending on the rate of bombardment by cosmic rays. Its intake by organisms (by photosynthesis, in the case of plants, or by consumption in the case of non-plants) is also relatively stable, until the organism dies and stops taking in carbon compounds. From that point on, its relative concentration in the dead organism decreases by radioactive decay. By measuring how much &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is left in the remains of an organism, archaeologists can determine how long ago that organism consumed carbon, and thus how long ago it lived. This method is useful only so long as the remaining concentration of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C can be measured accurately, approximately 9 to 10 half-lives, or 50,000 to 60,000 years. Other forms of {{w|radiometric dating}}, based on other elements and isotopes, are used for other purposes. Even the ratios between abundances of stable isotopes can vary, providing historical information about things such as temperatures and atmospheric mixing, via {{w|isotope geochemistry}}.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{w|Carbon dating}} is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of {{w|carbon}}. This method is commonly used by {{w|archaeology|archaeologists}} and is invaluable in terms of determining the time a piece of organic matter (such as a fossil) came from. It uses the fact that carbon &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;in earth's biosphere &lt;/ins&gt;contains a &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;known &lt;/ins&gt;ratio between the isotopes &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C, &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;(irrelevant for carbon dating)&lt;/ins&gt;, and &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C&lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;, which has been constant for a very long time&lt;/ins&gt;. &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is generated in the atmosphere by interactions between nitrogen and cosmic rays, and it is radioactive, with a half-life of approximately 5,730 years, decaying over time. Its relative concentration in the environment is fairly stable — a balance between its creation and decay, depending on the rate of bombardment by cosmic rays. Its intake by organisms (by photosynthesis, in the case of plants, or by consumption in the case of non-plants) is also relatively stable, until the organism dies and stops taking in carbon compounds. From that point on, its relative concentration in the dead organism decreases by radioactive decay. By measuring how much &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is left in the remains of an organism, archaeologists can determine how long ago that organism consumed carbon, and thus how long ago it lived. This method is useful only so long as the remaining concentration of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C can be measured accurately, approximately 9 to 10 half-lives, or 50,000 to 60,000 years. Other forms of {{w|radiometric dating}}, based on other elements and isotopes, are used for other purposes. Even the ratios between abundances of stable isotopes can vary, providing historical information about things such as temperatures and atmospheric mixing, via {{w|isotope geochemistry}}.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Here, however, [[Ponytail]], in the role of a {{w|cosmology|cosmologist}}, takes a rather different perspective on using carbon for dating. She is interested only in the mere ''presence'' of carbon, which tells her that the skeleton being studied was formed after the first carbon in the universe was created in the first round of stars fusing elements, 13.6 billion years ago. This is not useful information for differentiating artifacts originating on {{w|Earth}}, which is itself less than ''5'' billion years old, since it would apply to all of them.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Here, however, [[Ponytail]], in the role of a {{w|cosmology|cosmologist}}, takes a rather different perspective on using carbon for dating. She is interested only in the mere ''presence'' of carbon, which tells her that the skeleton being studied was formed after the first carbon in the universe was created in the first round of stars fusing elements, 13.6 billion years ago. This is not useful information for differentiating artifacts originating on {{w|Earth}}, which is itself less than ''5'' billion years old, since it would apply to all of them.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</summary>
		<author><name>2001:16B8:CC03:8600:3A22:B176:FC7F:29FB</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=405962&amp;oldid=prev</id>
		<title>2001:16B8:CC03:8600:3A22:B176:FC7F:29FB: /* Explanation */ predicting is something you do before you've got a material piece of evidence in your hand.</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=3205:_Carbon_Dating&amp;diff=405962&amp;oldid=prev"/>
				<updated>2026-02-11T22:15:27Z</updated>
		
		<summary type="html">&lt;p&gt;‎&lt;span dir=&quot;auto&quot;&gt;&lt;span class=&quot;autocomment&quot;&gt;Explanation: &lt;/span&gt; predicting is something you do before you&amp;#039;ve got a material piece of evidence in your hand.&lt;/span&gt;&lt;/p&gt;
&lt;table class=&quot;diff diff-contentalign-left&quot; data-mw=&quot;interface&quot;&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
				&lt;tr style=&quot;vertical-align: top;&quot; lang=&quot;en&quot;&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;← Older revision&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;Revision as of 22:15, 11 February 2026&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l11&quot; &gt;Line 11:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 11:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;==Explanation==&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;==Explanation==&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{incomplete|This page was created recently by a SPEAR MADE OF FREE ELECTRONS. Don't remove this notice too soon.}}&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{incomplete|This page was created recently by a SPEAR MADE OF FREE ELECTRONS. Don't remove this notice too soon.}}&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;−&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{w|Carbon dating}} is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of {{w|carbon}}. This method is commonly used by {{w|archaeology|archaeologists}} and is invaluable in terms of &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;predicting &lt;/del&gt;the time a piece of organic matter (such as a fossil) came from. It uses the fact that carbon consumed by living organisms contains a ratio between the carbon isotopes &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C, &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C, and &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C. &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is generated in the atmosphere by interactions between nitrogen and cosmic rays, and it is radioactive, with a half-life of approximately 5,730 years, decaying over time. Its relative concentration in the environment is fairly stable — a balance between its creation and decay, depending on the rate of bombardment by cosmic rays. Its intake by organisms (by photosynthesis, in the case of plants, or by consumption in the case of non-plants) is also relatively stable, until the organism dies and stops taking in carbon compounds. From that point on, its relative concentration in the dead organism decreases by radioactive decay. By measuring how much &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is left in the remains of an organism, archaeologists can determine how long ago that organism consumed carbon, and thus how long ago it lived. This method is useful only so long as the remaining concentration of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C can be measured accurately, approximately 9 to 10 half-lives, or 50,000 to 60,000 years. Other forms of {{w|radiometric dating}}, based on other elements and isotopes, are used for other purposes. Even the ratios between abundances of stable isotopes can vary, providing historical information about things such as temperatures and atmospheric mixing, via {{w|isotope geochemistry}}.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;{{w|Carbon dating}} is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of {{w|carbon}}. This method is commonly used by {{w|archaeology|archaeologists}} and is invaluable in terms of &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;determining &lt;/ins&gt;the time a piece of organic matter (such as a fossil) came from. It uses the fact that carbon consumed by living organisms contains a ratio between the carbon isotopes &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C, &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C, and &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C. &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is generated in the atmosphere by interactions between nitrogen and cosmic rays, and it is radioactive, with a half-life of approximately 5,730 years, decaying over time. Its relative concentration in the environment is fairly stable — a balance between its creation and decay, depending on the rate of bombardment by cosmic rays. Its intake by organisms (by photosynthesis, in the case of plants, or by consumption in the case of non-plants) is also relatively stable, until the organism dies and stops taking in carbon compounds. From that point on, its relative concentration in the dead organism decreases by radioactive decay. By measuring how much &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C is left in the remains of an organism, archaeologists can determine how long ago that organism consumed carbon, and thus how long ago it lived. This method is useful only so long as the remaining concentration of &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C can be measured accurately, approximately 9 to 10 half-lives, or 50,000 to 60,000 years. Other forms of {{w|radiometric dating}}, based on other elements and isotopes, are used for other purposes. Even the ratios between abundances of stable isotopes can vary, providing historical information about things such as temperatures and atmospheric mixing, via {{w|isotope geochemistry}}.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Here, however, [[Ponytail]], in the role of a {{w|cosmology|cosmologist}}, takes a rather different perspective on using carbon for dating. She is interested only in the mere ''presence'' of carbon, which tells her that the skeleton being studied was formed after the first carbon in the universe was created in the first round of stars fusing elements, 13.6 billion years ago. This is not useful information for differentiating artifacts originating on {{w|Earth}}, which is itself less than ''5'' billion years old, since it would apply to all of them.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td style=&quot;background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Here, however, [[Ponytail]], in the role of a {{w|cosmology|cosmologist}}, takes a rather different perspective on using carbon for dating. She is interested only in the mere ''presence'' of carbon, which tells her that the skeleton being studied was formed after the first carbon in the universe was created in the first round of stars fusing elements, 13.6 billion years ago. This is not useful information for differentiating artifacts originating on {{w|Earth}}, which is itself less than ''5'' billion years old, since it would apply to all of them.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</summary>
		<author><name>2001:16B8:CC03:8600:3A22:B176:FC7F:29FB</name></author>	</entry>

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