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Carbon-14 Radioactive Dating Worked Example | Doc Physics

114 ratings | 18701 views
I'm thinking about getting back into dating. I'm only going to be seeing bits of cloth and broken plates, so there's no need to tell my wife. Besides - they're not what they used to be in terms of activity... Maybe I shouldn't put this on the internet. What, use restraint while posting to the web? Naah. It'll be fine. In other news, I hope this shows you how you can solve any radioactive dating problem from a very tiny amount of info. It's all related via some simple equations, so get familiar with them.
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Text Comments (35)
John Ledbury (4 months ago)
Why do all Americans when explaining stuff talk like cartoon animals? Is there something wrong with them?
shubhahara manohar (6 months ago)
Sir, why do you not use the equation of activity to calculate decay constant? Why use only equation of half life to calculate decay constant?
maffak321 (9 months ago)
Thank you professor deadpool <3
Emily Behnke (10 months ago)
I love the enthusiasm!!
Levi Wyant (1 year ago)
Animaniacs
Theolyn Warrender (1 year ago)
Where did 6.02x10^23 come from?
Hoor Angel (6 months ago)
1 g contain 6.022*10^23 of particles..
Milan Parmar (1 year ago)
That's Avogadro's constant: https://www.britannica.com/science/Avogadros-number
Ali Abdullah (1 year ago)
damn i am going to miss your videos
mAdcaNdy (1 year ago)
XD dot dot dot dot dot
robrob (1 year ago)
Can someone tell me how they work out the initial amount of the isotope in a sample fossil in practice? I understand these quite recent items like pottery have been in the assumed conditions the most recently so they can almost be sure it will have absorbed the assumed amount of carbon in its lifetime..but if they find a fossil...how do they know how much it contained when it lived and how much the atmosphere was letting through at the time? It seems the whole answer hangs on the assumptions which are made there...since the only data gathered in the now, where we can observe it, is the remaining isotopes in the sample. And if you look at the scale on which they get the ages..A little difference would make a huge difference in the answer. Is this whole theory built on the assumption that small amounts of isotope mean old age? Couldn't the start of the influx have been at a more recent time with some event that changed the atmospheric conditions of the earth? Like after a meteor strike? It makes more sense that all the dinosaurs lived at the same time so if they all lived at the extinction event they would have gotten practically no exposure compared to the organism since then. Surely just the date ranges prove that we are dealing with distinct starting conditions?
robrob (1 year ago)
Theo - I was asking the poster. And really...you saw my last comment was 4 months ago...and you still decided to post THAT garbage?! Maybe this is the wrong topic for you! Especially if you have problems with reading...
Theolyn Warrender (1 year ago)
Sir, this is YouTube, not your English essay.
robrob (1 year ago)
Sorry, I'm really trying to work out the math equation here. If you can use the current rates of absorption, decay and influx as constants. And you have the differences in quantities between the first saved and last saved amounts as a product not of time to decay but time to absorb and decay to present rates. And you can work out when the isotopes were first introduced by taking the highest saved amount today (oldest tree?) vs the smallest saved amount as the starting point( you would only need to assume a short amount of time here do develop a scale which you can calibrate with different quantities in fossils. Then you can make predictions of the amounts of isotopes to find in different layers/fossils. Cant you then solve for a more accurate age of the earth somewhere?
robrob (1 year ago)
So the sample in your experiment. Which is not a fossil but a piece of grass that was cut and put into pottery. It absorbed carbon according to the rates we experience today on the correct scale. So there when you assume the carbon absorbed during lifetime(starting amount) in your sample, you are actually correct! If the dinosaurs had absorbed isotopes and died just after the 0 event, they would have absorbed little carbon and lost most of it before we could measure it. Other isotopes absorbed at the same time with longer half lives would still be detectable. And the first ones to die after 0 event would have the least detectable isotopes in order of its time from 0 event and burial.
robrob (1 year ago)
The only real question you can answer about fossils, ice and rock(mud/magma then) for that matter, with the modern rates of influx, is how long time the had to absorb before they were, fossilized or solidified/frozen. And you can measure the rate of influx with the ice because each layer just has a certain amount of time to absorb at today's rates from the top down and from the bottom up to and from the 0 event.This is reading the data according to what we can see.
Stephen Lantapon (2 years ago)
dot dot dot dot dot
David Jiménez Linares (2 years ago)
Bravísimo!Thanks a lot!
MR (2 years ago)
Good job, I think you have proven that CD has many flaws and is inaccurate
Jim Joyce (9 months ago)
You watch one YouTube video and think you've disproven Carbon Dating? Go sit on the toilet for a while and think about it a bit harder than that. I figure you're a creationist. . .
MR (2 years ago)
Good job, I think you have proven that CD has many flaws and is inaccurate
MR (2 years ago)
I think you've just proven CD doesn't work
Wester Visser (2 years ago)
Why do you say the activity drops with a factor of 10 ?
Sonil (3 years ago)
ahahaha "Dating" dead things made me laugh :D
mAdcaNdy (1 year ago)
same!
Doc Schuster (5 years ago)
I'm no expert on that, but I bet wikipedia could help. 14 is made consistently in the upper atmosphere, and we know its concentration in the atmosphere as a function of time well. I presume the concentration to be uniform in the atmosphere throughout Earth, probably from isotropic radiation sources that produce it. As plants build themselves with CO_2, they sample the ratio present at that time. That's all I know!
James Chen (5 years ago)
Hello! If you have time, I have some questions: How do we determine the carbon-14/carbon-12 ratio? and is it universal to the composition of all life currently living and in the past? I'm guessing that since there are so many C atoms.. on the order of at least 23 to 26/7(?), that some how the concentration of carbon-14 in carbon is stabilized or universal? But isn't that sample a reaally tiny part of the atmosphere/biosphere?

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