Carbon 14 dating 1 (video) | Khan Academy
Getting Graded: An expert on radiocarbon dating, long-time assistant professor at . Consider then, the fossil remains of organisms that had lived near the surface to carbon date their biological dinosaur tissue (YouTube video below), which. Topics A primer on radioactive decay Carbon dating Radioisotope dating. Topics Carbon dating Radioisotope dating The Biblical age of the earth.
Now, when I did that, I made a pretty big assumption, and some you all have touched on this in the comments on YouTube on the last video, is how do I know that this estimate I made is based on the assumption that the amount of carbon in the atmosphere would have been roughly constant from when this bone was living to now?
And so the question is, is the amount of carbon in the atmosphere and in the water, and in living plants and animals, is it constant? And if it isn't constant, how do you calibrate your measurement so you can actually figure out how much carbon there is relative to living plants and animals at that time?
And the way that you can make that calibration, because it turns out it isn't perfectly constant, the way that you can make that calibration, there's two ways, and I have pictures here of both of them, one is to look at tree things.
And I'm told this will work up to about 10, years. Up to 10, years old. I don't know of any 10, year old trees, I don't think anyone does, but maybe there's some remains of old trees.
How Does Radiocarbon Dating Work?- Instant Egghead
And you can look at their tree rings, and I think most of us are familiar with this idea that every year that a tree grows, it forms another layer of bark. Unlike common carbon 12C14C is unstable and slowly decays, changing it back to nitrogen and releasing energy. This instability makes it radioactive.
So a bone, or a leaf or a tree, or even a piece of wooden furniture, contains carbon. When the 14C has been formed, like ordinary carbon 12Cit combines with oxygen to give carbon dioxide 14CO2and so it also gets cycled through the cells of plants and animals. Because 14C is so well mixed up with 12C, we expect to find that this ratio is the same if we sample a leaf from a tree, or a part of your body. However, as soon as a plant or animal dies, the 14C atoms which decay are no longer replaced, so the amount of 14C in that once-living thing decreases as time goes on.
Obviously, this works only for things which were once living. It cannot be used to date volcanic rocks, for example. Anything over about 50, years old, should theoretically have no detectable 14C left. That is why radiocarbon dating cannot give millions of years. In fact, if a sample contains 14C, it is good evidence that it is not millions of years old.
First, plants discriminate against carbon dioxide containing 14C. That is, they take up less than would be expected and so they test older than they really are.
Furthermore, different types of plants discriminate differently.
This also has to be corrected for. This would make things which died at that time appear older in terms of carbon dating. Then there was a rise in 14CO2 with the advent of atmospheric testing of atomic bombs in the s. This would make things carbon-dated from that time appear younger than their true age.
Accordingly, carbon dating carefully applied to items from historical times can be useful.
They rely more on dating methods that link into historical records. Outside the range of recorded history, calibration of the 14C clock is not possible. We need to know two things How fast C decays measured in half-lives - this is known: Are their attacks on the opposition valid — are they distorting data to make other views look non-credible?
Dating Fossils and Rocks.
When we read statements in textbooks and journals we should ask ourselves some questions 38 Textbooks Biology: Visualizing Life, Holt, Rinehart, Winston,p. The stability partly depends on the relative number of protons and neutrons. In alpha decay one element parent decays into a daughter by emitting an alpha particle.
An alpha particle is a helium nucleus He-4 - atomic mass-4 and atomic number 2 Example: Hour Glass Example Can you calculate how long you were outside? Were the assumptions taken into account? AD Lava flows at Mt. Ngaurhoe, New Zealand Potassium-argon: Etna basalt, Sicily Potassium-argon: The rocks were dated using 4 different methods. The range between the oldest and youngest date was almost 4-billion years.
Apollo 16 brought back some moon rocks that were dated at billion years. To fix the problem they subjected the rocks to acid to melt out the lead and then re-dated and got 4.
Carbon 14 dating 2 (video) | Khan Academy
Science magazine Jan 30, Sunset Crater in n. Arizona is known to be a recent volcano. Indian artefacts and relics are found within the rocks formed by the eruption. The volcano last erupted some years ago.