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Carbon 14 dating 2 | Life on earth and in the universe | Cosmology & Astronomy | Khan Academy

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Carbon 14 Dating 2. Created by Sal Khan. Watch the next lesson: https://www.khanacademy.org/science/cosmology-and-astronomy/life-earth-universe/measuring-age-tutorial/v/potassium-argon-k-ar-dating?utm_source=YT&utm_medium=Desc&utm_campaign=cosmologystronomy Missed the previous lesson? https://www.khanacademy.org/science/cosmology-and-astronomy/life-earth-universe/measuring-age-tutorial/v/carbon-14-dating-1?utm_source=YT&utm_medium=Desc&utm_campaign=cosmologystronomy Cosmology & Astronomy on Khan Academy: The Earth is huge, but it is tiny compared to the Sun (which is super huge). But the Sun is tiny compared to the solar system which is tiny compared to the distance to the next star. Oh, did we mention that there are over 100 billion stars in our galaxy (which is about 100,000 light years in diameter) which is one of hundreds of billions of galaxies in just the observable universe (which might be infinite for all we know). Don't feel small. We find it liberating. Your everyday human stresses are nothing compared to this enormity that we are a part of. Enjoy the fact that we get to be part of this vastness! About Khan Academy: Khan Academy offers practice exercises, instructional videos, and a personalized learning dashboard that empower learners to study at their own pace in and outside of the classroom. We tackle math, science, computer programming, history, art history, economics, and more. Our math missions guide learners from kindergarten to calculus using state-of-the-art, adaptive technology that identifies strengths and learning gaps. We've also partnered with institutions like NASA, The Museum of Modern Art, The California Academy of Sciences, and MIT to offer specialized content. For free. For everyone. Forever. #YouCanLearnAnything Subscribe to Khan Academy’s Cosmology & Astronomy channel: https://www.youtube.com/channel/UChNPnEkW8LYZ5Rwi8_A2-DA?sub_confirmation=1 Subscribe to Khan Academy: https://www.youtube.com/subscription_center?add_user=khanacademy
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Text Comments (40)
Laura Gordon (5 months ago)
Finally, the missing component has been found. The base is the comparable organism today. That is we compare the amount of carbon 14 in the dead thing to the amount of carbon 14 in that same type of living thing. Great teacher!
Lite Wave (1 year ago)
Thank you Sal for your efforts. I admire the way you spend time to teach those in need. But, even when we check a layer in a tree's trunk for the ratio of carbon-14 to carbon-12 , wouldn't it be so, that the ratio of carbon-14 atoms to carbon-12 atoms in a specific layer when it was formed would also change as the decay happens inside the layer as well, as time passes by ? So, doesn't this mean that the ratio we would get now from a layer will not be the ratio that was, when the layer was formed ?
umar khayam (8 months ago)
1:49 check it out , i think it has what you need...
No mention of the atmospheric nuclear tests as a primary agent in the generation of carbon-14 from the late 1940s to the 1960s? The atmospheric concentration of carbon-14 in the Northern Hemisphere doubled at its peak, in October 1963.
Jereme leBourgeois (3 years ago)
That does not look like a bone, haha
Aaron Reynolds (5 years ago)
Did you watch the video at all? Plus what proof do you have of the supposed big flood? Faith can't be used in logical conversations.
Aaron Reynolds (5 years ago)
Gspotter keep in mind that radiocarbon dating is just one form of resting the dates of fossils and needs to be applied in the correct situation. Even with variations in C14 levels it's still able to disprove the young earth theory. What evidence do you have to back up your viewpoints? Your argument is running on circular logic where you’re making assumptions, but unlike science you're not providing evidence for your view.
Jeanluc Thomson (5 years ago)
Good on ye Spotter. Carbon dating is completely useless, as the Flood (proved by upside down fossilised forests and fossilised shell fish at top of mountains) would mess everything up. Also, we have no idea how much radiation there was a century ago, let alone millennia.
GSpotter63 (5 years ago)
read this.. h t tp : / / bryce710 (dot) tripod (dot) com/id10 (dot) html
GSpotter63 (5 years ago)
Sorry, but it has already been proven that Speleothems, even as long as 10 feet can, and have formed in under 200 years making them useless for dating anything.
GSpotter63 (5 years ago)
Sorry, but the oldest living tree whose age can and has been verified ( not estimated ) is "Methuselah" in California 4,844 YO not 10,000 YO.
GSpotter63 (5 years ago)
The fact that in the past, insects grew to as much as 8 times their present size indicates that there were times that o2 levels and atmosphere pressure (14 N) was indeed much higher. If the amount of N14 in the atmosphere was higher that would increase the number cosmic ray collations resulting in more CO14 formation. So, tell me again how you can be so sure that this dating method is so reliable?
GSpotter63 (5 years ago)
If either the content of the atmosphere ( N14 O2 ) or the amount of cosmic radiation were to have changed in the past then the amount of Co14 in the atmosphere and consequently in the plants and animals will have been very different at their death making the Co14 dating method highly inaccurate. Can you guarantee and verify that the cosmic radiation or the levels of N14/O2 has remained the same for the past 100,000 years?
w00timan (5 years ago)
they work it out by measuring the amount of beta radiation being emitted from the sample, every time a particle decays it will release a beta particle, when a sample has been recorded for enough time you can work out a rough rate of decay, which can be used to work out how long it will take for half the sample to decay. however random a decay may initially look it will always have a measurable rate of decay if looked at for long enough. I think...id give it a search online
w00timan (5 years ago)
I don't have a source to forward to you, I'm just saying what i remember from physics. This guy who created this video does a whole video on half life however. In answer to your first question it isn't a constant as such, 14C can decay at any time, after 5730 years there will almost never be exactly half of the 14C left. But there will be around half left. I suggest watching the other video, it will be explained much better than I could ever explain it.
ChronologyQuest (5 years ago)
Thanks for the clarification. I must admit that the concept of Half-life has caused me to reflect. Is there a good resource you would suggest that would help me understand how this methodology was developed? What aspects of Science depend on the accuracy of this method? Also, my original question still seems to be left unanswered (concerning the constant rate of decay).
w00timan (5 years ago)
Each 5730 years roughly half will decay, not half of the original amount but half what was left (as carbon 14 has a 50/50 chance it will decay in 5730), like dividing the amount by 2 every 5730 years rather than subtracting half the original amount each time. It will take around 50-60,000 years for all the carbon 14 to have decayed as said in the video. The 50/50 chance that carbon 14 will decay remains the same every 5730 year stage.
ChronologyQuest (5 years ago)
May be a silly question but how can we be sure that the rate of radioactive decay is constant? Also, if carbon 14 decays completely (according the the calculation presented) after 11,460 years (i.e. 2 half-lifes @ 5730 yrs), how can it be that we would be able to calculate anything to be older than this. Thanks for your help.
Takeo Kimura (2 years ago)
It is not one half then the next half--it is half, then half of half, then half of half of half and so on to immeasurable
amaizenblue (5 years ago)
carbon dating typically isn't used on anything less than about 200 years. We rely on archaeological and documented history methods for that.
nekojx (6 years ago)
en.wikipedia.*rg/wiki/List_of_oldest_trees (*=o) Prometheus 4,862 years (verified) probably have older trees, but as you have said carbon is to determine the date for relatively closer ages, like 0-10 000, for older fossils there is other methods, an example for method to find the date of million years old bone is the method of proportion of fluorine and phosphate or other elements isotopes ;)
PaleHearse (6 years ago)
Just so you know.. the way they get the 10K data for tree rings is by overlapping the rings in living trees to the rings in dead ones. Because the trees exhibit growth rings that are specific to the variability in growing seasons, you can use this variability to find, say, the pattern in the last hundred years of a tree's life and match it to the first 100 years of a younger tree's life.
Roger Cathey (6 years ago)
sonic dot net slash bristlecone slash dendro dot html Link to the pine story.
Roger Cathey (6 years ago)
Bristle-cone pines have been dated at 9,000 years or more using living and dead cores. I guess the oldest living supposedly is only 4,000 plus years. Yet I recall that some yahoo cut down a living specimen and realized he'd cut down a tree that was older than that. I seem to recall near to 9000. Now the area is, according to the documentary I saw, supposedly protected from such idiots. There could be a 10,000 year old tree out there.
hamoan66boi (6 years ago)
@TheFrugalGamer He was just using that number as an example.
GreenSlugg (6 years ago)
@MonsterSlayer14 The idea is that you can check the assumption that the Carbon-14 levels have been constant in the atmosphere. In a nutshell, it is known that the levels of Carbon 14 have had major fluctuations. You cannot use C14 dating on anything after the Industrial Revolution, because of the increase in normal carbon in the atmosphere (which would make things that died after the industrial revolution look older). I am actually putting together a lot of Carbon Dating info on my web site.
MonsterSlayer14 (6 years ago)
so you take a sample off the tree ring specified for that year and from that sample you can measure what the c14 lvl was??
Maracachucho (6 years ago)
@TheFrugalGamer You're right man, you completely missed it. You use tree rings. Though he didn't address this particular point in too much detail. Just look it up.
paulceltics (7 years ago)
stonetop (7 years ago)
@99pinkrose It represents the amount of growing that a tree does in a given year. During the spring and summer it grows quickly, while during the late autumn the tree grows slowly.
99pinkrose (7 years ago)
What is reason behind distinct line in tree barks suggestive of 1 year??
noxure (7 years ago)
@Hooya2 I see. So basically you need an isotope that decays into a different element that can only be contained by the rock if it's solid.
Pudersepp (7 years ago)
/.../ The visible portion of the 13-foot-tall (4-meter-tall) "Christmas tree" isn't ancient, but its root system has been growing for 9,550 years, according to a team led by Leif Kullman, professor at Umeå University's department of ecology and environmental science in Sweden. /.../ From National Geographic. 10k years is possible for a tree.
cokey (7 years ago)
@sangboi lol you're banned.
Sang Bui (7 years ago)
everybody type "gift" before youtube.com!
cyberprodigy (7 years ago)
I love your videos. You are a great teacher. Keep up the good work. :)
elbillaf Fiend (7 years ago)
Excellent video, Sal. Here's a video that explains what some of the fellas below are talking about: v=aLFKM886l4Q Another point regarding other radiometric dating: v=iGDrq8rikJc You may also want to google "reservoir effect."
AcanLord (7 years ago)
@noxure Carbon dating is not really used on true fossils as they lack carbon, so yeah different materials are used.
noxure (7 years ago)
Do they have a calibration method for really old stuff, or do they use different techniques? Comparing fossils from different continents and then use observations from tectonic movement or something? Also, just realized that when you're talking about 200 million years an error margin of 1 million years is equally accurate as an error margin of 100 years on 20.000. That's pretty weird. :)
wizwazzle29 (7 years ago)
yayyy first comment! :)

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