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Radioactive Dating

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Have you ever wondered how paleontologists and geologists determine the age of fossils or geologic events which occurred in the past? Explore the processes of radioactive decay and radioactive dating.
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Text Comments (81)
apop- his (22 days ago)
What is between 0-5700 year... i understant that if we have 100 carbon atoms then after 5700 years we only have 50. But is there a time between like we have only 75 atoms in 2800 years. Another question is there same amount of carbon in all things (plants, bone). How do you know what number you starting with?
Rick and Rygel (27 days ago)
Eventually wouldn't you have 10 atoms left? Then five, then... Two or three? Can't have half an atom. Then one or two? Then zero or one? Then one forever?
Stephen Fletcher (1 month ago)
Great video. But how do you tell how long a bone found has been decaying? And how do we know that Potassium has a half-life is 1,3 billion years?
LemonGameshark (1 month ago)
Cant believe they call this garbage “science”
Samira Baikelova (1 month ago)
i like bananas
Fortnite Clips (1 month ago)
Saved me for my quiz tmr thx
OC Run (1 month ago)
Why should dating a nonorganic element in a totally mineralized fossil give the age of the fossil?
rent a shill (8 days ago)
I’m beginning to think that there are very few people on this planet who understand radiometric dating. That’s ok, that means you’re no worse than anyone else. Let’s work on fixing this. I’ll teach you how to date like a geologist! Fossils are almost never radiometrically dated. Almost never. Maybe never, but I’m including the probability of dating methods I’m not familiar with. Almost every method of radiometric dating, excluding radiocarbon, is applicable to only igneous and occasionally metamorphic rocks. That naturally excludes fossils. But of course, we know the age range for fossils. How do we know them? We can date igneous (volcanic) units near our fossil. Say you’ve got a fossil and have no clue how old it is. It came from a geologic unit you can’t date either, which is unfortunate- if you could date the rocks you found it in, you’d know the exact age more-or-less because bones need to be buried immediately in order to fossilize. Bummer you can’t get an exact date. But all is not lost! There is a thin layer of volcanic ash stratigraphically 2 meters above your fossil outcropping just a couple kilometers from where you found it; you’ve had it dated and the lab says it’s 65 million years old. There’s also a basalt lava flow 3 meters below it that outcrops in a nearby valley, which the university lab dated to be 82 million years old. Fantastic. How old is your fossil? It’s 65–82 million years old. It’s in between layers of that age and so that is your age range. Want to get more precise than that? Sorry, you can’t… not with the data you have. But find more fossils in other locations and build yourself a database of dates to get a more accurate range of possibilities. Now, fossils are sometimes used to date rocks. Actually, very often. There are some types of fossils, called index fossils, which only occur during very specific periods in Earth’s history (one day, human fossils may become fantastic index fossils). Once you’ve used hundreds of samples to confirm that your fossil only falls within a certain range of dates, you can get lazy and stop spending thousands of dollars on radiometric dating. Your rock unit has a Paradoxides genus trilobite fossil sticking out of it? Great, it’s 514–497 million years old. If that’s as precise an age range as you need, you’re done! Easy peezy. So in short, we don’t date fossils. If we could date fossil minerals, we would know the age of the bones to within a few thousand years since fossilization has to happen fast, but since we can’t generally date those, that’s a non-issue. We date igneous rocks above and below fossils to get a range of possible dates. Once we’ve got a ton of data, we can save ourselves some time and use well-constrained fossils to date the rocks they’re in.
Nabeel ahmed (2 months ago)
Thank yew sir u have cleared my all concept about this. Its really helped me .. I am ur new subscribers.
Afnan Abood (3 months ago)
Thank you soo much this was so helpful for me to understand this concept
Mehboob Ali (4 months ago)
very nicely explained. thanks. it was very useful for me.
Swapnil Dongare (4 months ago)
You explain very wel. But how we know the exact amount of C14 present in the parent molecule.
Grace Giles (4 months ago)
I would like for creationists/ believers of Noah’s Ark to see this
Dan Strayer (4 months ago)
Why? You actually think you can reason with those fanatics? You cannot counter, convince, or alter the opinion of fanatics with reason, facts, or scientific method.
Anthony Butterley (4 months ago)
So many stupid creationist comments here. I love the claim that you have to assume the conditions at the beginning, bahahahaha. Claiming other people have a problem with assumptions coming from creatards is hilarious. Let me ask you, how do you know the bible is factual, were you there?
Jo (5 months ago)
This was super helpful!
Mark & Angela Girard (5 months ago)
I wonder if 1/2 lives are constant throughout the entire universe or are modified due to planetary constraints.
Starman94 (5 months ago)
I have a bunch of arrowheads found from a field I wonder what the half-life will be in them
eclipse (5 months ago)
I wanna know about this Rubidium 87 with half life of 50 billion freaking years, thats decays into Stronium 87 which is also naturally occurring. First off RB 87 was found 157 years ago. Have they been studying the same specimen since then to get such precise mathematical calculations? Even 157 years if so compared to 50 billion years is literally nothing!!!, are they telling me that we are so precise we can make such observations with precise measurements like that? Has someone been studying the same specimen for 157 years to collaborate this? That time period would at least be more feasible. I read that both substances are naturally occurring in a meteorite. How do they know what the levels of RB 87 and SR 87 are natural in a rock from outer space lol? If compared to earth then its just hopeful ignorant guessing right? The calculation made to age such a rock relies on time elapsed on the rock, unknown natural levels of SR 87 and natural decay of RB 87 resulting in more SR 87, which seems/is impossible since its an object from space with unknown origin! and unknown time elapsed! and also unknown history!. I can probably believe this about dating things on earth, but not objects from space with literally zero history until it crash landed. To my understanding the crash and/or travel through the atmosphere can alter the meteorite. From reading it seems they can measure the exact amounts of "stuff" in the meteorites/objects by vaporizing and measuring with a mass spectrometer.
IRC03 (5 months ago)
toxic relationships
Poseidon63 (6 months ago)
We have multiple absolute dating methods. Radiocarbon dating, dendrochronology (tree/wood dating), thermoluminescence dating, archaeomagnetic dating (looking at the orientation of rocks during pole shifts), amino acid dating, obsidian hydration dating Do you know that for the time frames in which these methods are valid, they all give consistent results with each other.
ThermaL1102 (6 months ago)
do people know already now that this is a totally wrong way of dating things ? or not ? just curious you can not accurately date any 2 different bones from different species with the same dating method , it's just plain wrong you can not accurately date any 2 different rocks period different bones have different densities , so decay different , bang , there goes the theory a 4 year old can figure this out even the word ''decay'' is a wrong term for it , things don't decay , they transform their state of being , never ''decay'' you can't date a fossillesed tree like that , yet another material dated with the same method you HAVE to account for these changes in the calculations , or their plain wrong which all dates are because of this the universe is more then 4-5 quadriliion years old , yes QUAD , that's another zero on top of a trillion , times 4 or 5 4-5 quadriliion years , and the beings that created the first one are even older , they made them , simple fact still think the universe we live in is only 14 billion years ? think again people have NO concept of time , a watch isn't gonna help with these calculations nor is a dating method that's constructed by humans , we're just to dumb we're putting houses together for a couple thousand years now with bricks , what do we do in OUR time ? still the same , basically putting 2 bricks on top of each other ... what have we actually learned from our god , gods , goddesses , churches , mosques , jesuses , guru's , you name it ? it's all a smoke screen with pretty lights and shiny golden streets and mansions as big as you want , haha the biggest joke is on us , cause we all just gobble it up like a big fat juicy buttery steak , don't we some bright light in your face and some fake love in your veins , basically ( like a junkie ) , and of we go , with our heads in the clouds again , where they want us as long as your head is in the clouds , it's not focused on yourself , is it ? so you can't discover who you are they make you THINK GOD is out there watching YOU and you will be judged , while as a matter of fact , YOU ARE GOD when you know this , you can brake free of religion , there's no need for it religion IS the evil there's NO evil WITHOUT religion religion is the key that locks the door to ones SELF free yourself of religion and you will know what being free REALLY is a GOD doesn't need religion , does it ? WAKE UP ... dammit ! wake the fuck up damn this went an whole other way then intended , sorry for that , but i'm gonna leave it anyway , maybe it shakes someone AWAKE in the process , cause ... mmh mmh
Frostboy4 (1 month ago)
What did you smoke?
Saleh Wahem (6 months ago)
The best video about radioactive dating ever! Now I got it thx
Morewecanthink (7 months ago)
Thats very nice explained. But the conclusion that this measures age is due to presuppositions without any valid foundation, the assumptions of amount of elements in the beginning, that there weren't a more rapid loss or an addition of elements in the past. The dating of rocks or layers with known ages produces as well thousands and millions of 'years'. So far to the reliability of the timescale in which evolutionary scientists trust. They conclude what they presuppose.
Rubik Cube (7 months ago)
Good explanation.. easy to understand 👍👍👍👍👍
williamstdog9 (7 months ago)
WRONG!! You DONT know the initial conditions in the long ago past! And not only is this method DEEPLY Flawed due to the assumptions in the equation, if anything it PROVES a young earth, NOT an old one, due to carbon found in diamonds!! Oops, how’d that happen? Lol! Flaw in your lil method there!
Oscar Napieralski (3 months ago)
@Joseph Snoe oooooo nice burn.
Joseph Snoe (7 months ago)
It's cute how you think you know what you're talking about
williamstdog9 (7 months ago)
Are you for real?!?!? You CANNOT GET ACCURATE AGES USING THIS DATING METHOD!!! Get serious man!! Why don’t you tell your “students” the TRUTH?!!: you date the rocks by the fossils in them, and the fossils by the rocks!! It’s totally circular reasoning!!
killertim101 (2 months ago)
+Dan Strayer What education are you referring to? You're trying to downplay that guy but you're downplaying yourself...Any "education" on the matter of dating fossils is assuming/estimating based off of calculation. No matter how hard or complex the calculation, in the end, the math for dating fossils relies on guessing.
Dan Strayer (4 months ago)
yes. no education. at all.
Soujiro Seta (6 months ago)
Are you some kind of idiot?
Tropax K (7 months ago)
What an excellent teacher, I could listen to you all day sir. Thanks.
Nenad Marinkovic (7 months ago)
Awesome.I always wonder how... Ty
Destiny Lab (7 months ago)
I have a question I am trying to figure out. How old is molten lava?
Destiny Lab (7 months ago)
Hmmm...looks like I have gotten multiple different answers to this question....how are you arriving at that 4 billion year old date?
Joseph Snoe (7 months ago)
About 4 billion years
PABITRA BADHUK (8 months ago)
Hii Seth, excellent video! Can you tell about what are the techniques available for absolute dating of fossils older than 70k years? Thanks!
Space Cadet (8 months ago)
Excellent and logically explained basics of Radioactive dating. If the rest of your videos are equally lucid, you get another supporter.
MOHAMED ANWAR (9 months ago)
Perfect thanks
Mohammadsadegh Salehi (9 months ago)
Great Video! However, you are making a huge assumption that the parent contained 100% of the radioactive element. This method is not accurate at all because you never can find a fossil with 100% of the radioactive element.
John-Henry Aylward (6 months ago)
Mohammadsadegh Salehi exactly my thought ;)
Mohammadsadegh Salehi (9 months ago)
Rima Guha Mallick (10 months ago)
Thank you very much..........This lecture contains the most lucid explanation of radioactive dating.....
Ron Davis (10 months ago)
Very interesting subject  - Thanking you for your input  -
X00MER (10 months ago)
the best thing is that we have a new biology teacher and he thinks he knows everything and that he is a professional in everything so by his calculations he thinks the earth is 50,000 yo because he used carbon dating.
YapYap The Destroyer (10 months ago)
X00MER lol smart guy
rafael pacheco (11 months ago)
You're really an excellent teacher!!! Thanks!
Jeremy Potton (1 year ago)
very well explained, thank you. Love the examples
Great explanation Seth and very understandable video. Thank you a lot.
Extra-Ordinary (1 year ago)
Margaret Mcaurthur (1 year ago)
Hi there. Nice video. I have a couple questions. If carbon 14 is created in the upper atmosphere by cosmic rays penetrating through the magnetic field, and knowing that the magnetic field is deteriorating at  a rate of 5% per century, wouldn't that tell us there was a far less concentration of C14 hundreds of years ago leaving the current understanding of carbon dating inaccurate? Oh, well I guess that's only one question. haha thanks
Ted Pepper (1 year ago)
Sooo much wrong information. Nuclear power plants produce energy via Fission. That is not even close to what you are taking about. Half lives are not always the same they may be consistent but there are elements that show changes over time. That is only an assumption. Higher atomic number nuclei don't have the same number of proton to neutrons in their stable elements. The three assumptions used for Radioactive dating are 1. there is no daughter in the original sample (unlikely assumption except for Ar-Kr dating which has proven to be highly questionable for accuracy) 2. There has been no addition or removal of the material from the sample (not sure how you verify that unless you are sampling material that is known to have no process that can prevent the transport of the radioactive materials in or out) 3. That there has been no change in the half-life. ( this has been shown to be questionable)
Randy Young (3 months ago)
+Space Cadet Your common sense is 100% wrong though. The core assumption of K-AR testing is that it can tell you exactly when the liquid magma turned to solid rock, which is what Ted Pepper was mentioning. In a nutshell, the argon (a noble gas) is supposed to off-gas through the liquid magma. The K40 (radioactive potassium that decays to the argon) theoretically cannot leave the rock in either state however. This is supposed to result in a condition where there is no AR at the moment that the rock freezes to a solid. The age of the magma is irrelevant because they are looking only for the argon created since solidification. K-AR testing thus measures the amount of Argon in the rock and concludes that 100% of it must be the result of K-40 decay SINCE the magma became solid. Ted Pepper is right. Unfortunately, when tested on magma from known eruptions (like Mt. St. Helens) the dates have come back millions to billions of years old. This MUST mean that the underlying assumptions that AR will offgas is wrong.
Space Cadet (8 months ago)
Ted Pepper Common sense alone tells me that the rock formed from a lava flow is NOT a few years old. The date of lava eruption and formation of a rocky surface is not the date of the rock. The now solidified rock was previously liquid rock of the same material created within the Earth millions of years ago, swirling inside the earth in lava pockets, channels or areas closer to the Earths core. Its the same material, just liquidfied, so the dating reveals a general creation date of the liquid material (now hardened) within the Earth, not the date of when it was ejected from the caldera.
Ted Pepper (1 year ago)
Well as for Pd transportation, that makes since that it would not transport in because it is a very large non-inert atom and would have trouble migrating into the crystal lattice of the zircon. No argument with that. But Radon which is inert and a gas would be very likely to transport into the crystalline structure and within just a few days will decays to Pd. So the transport atom just has to be in the Uranium decay chain and transportable, which I'm uh thinkin' and inert gas would be. Also in zercon crystals the decay of U238 produces 8 alpha decays on the way to Pd. If the rocks were millions of years old helium produces from these alpha decays should be long gone. But they find the amount of helium in the rock consistent with about 6000 thousand year old rock. think they did various types of radiometric dating (including isochronic dating) on rocks from very recent lava flows and found the rock millions of years old and not a few years old as expected based on the actual known time of the rock formation. As far as consent decay rates there are isotopes which have decay rates that very depending on the suns distance from earth. Radioisotope decay rates of radium (226Ra) and silicon (32Si) varies periodically. This may not seem strange at first, but when measured, this fluctuation in decay rate has a period of approximately a year. You have to know and trust assumption, which most of historical (forensic) science is based on. Don't believe every thing they tell you.
Ted Pepper (1 year ago)
Well as for Pd transportation, that makes since that it would not transport in because it is a very large non-inert atom and would have trouble migrating into the crystal lattice of the zircon. No argument with that. But Radon which is inert and a gas would be very likely to transport into the crystalline structure and within just a few days will decays to Pd. So the transport atom just has to be in the Uranium decay chain and transportable, which I'm uh thinkin' and inert gas would be. I think they did various types of radiometric dating (including isochronic dating) on rocks from very recent lava flows and found the rock millions of years old and not a few years old as expected based on the actual known time of the rock formation. As far as consent decay rates there are isotopes which have decay rates that very depending on the suns distance from earth. Radioisotope decay rates of radium (226Ra) and silicon (32Si) varies periodically. This may not seem strange at first, but when measured, this fluctuation in decay rate has a period of approximately a year. You have to know and trust assumption, which most of historical (forensic) science is based on. Don't believe every thing they tell you.
BezoomnyBratchny (1 year ago)
Ted Pepper These are not assumptions. Uranium-lead dating is done on zircon. Zircon crystals have been repeatedly shown to reject lead whilst forming. And for potassium-argon dating, argon is an inert gas which is enough in and of itself. But just to be doubly sure, argon has been looked for in minerals that are low in potassium and no excess argon has been found. And to top it all, isochron dating rules out contamination even further. For uranium-lead dating for example, it takes several rock samples and measures not one but two different sets of uranium isotopes and their corresponding daughter elements. Then it places the ratio of the first parent isotope to daughter element (207Pb/235U) on the x axis of a graph and the second parent isotope to daughter element (206Pb/238U) on the y axis of the graph and draw a line between each of the several data points (each of the rock samples). Any contamination would cause the line not to be straight. It would stick out like a sore thumb and even allow them to identify when the system became open and for how long it lasted. To say that a straight line is not enough is to make two huge assumptions of your own: 1. That two different isotopes and/or daughter elements will both contaminate in exact alignment to one another and 2. That several samples get contaminated the same way and to the exact same extent As for half lives changing, there is no reason to think that they do. Uranium isotopes and potassium isotopes both decay by emitting electrons so being exposed to extreme pressure is the only way that it would even be concievable that their rate of decay might change. Beryllium (which also decays via beta decay) has been tested under such conditions and there was no significant change. Additionally, we know that the decay rates were the same at various points in the past. Supernovae produce lots of radioactive isotopes which in turn produce gamma rays. Measurements of the frequency and fading rates of these gamma rays have been taken and those measurements allow for the decay rates of the isotopes produced by those supernovae to be known. Measurements have been done on a number of supernovae, one that is 169,000 light years away, one that is 60,000,000 light years away and even supernovae from billions of light years away. So 169,000 years ago, 60,000,000 years ago and billions of years ago, the rates of decay were the same as they are today. So we come again to some assumptions of your own. To claim that this isn't enough would be to make one of these huge assumptions: 1. Decay rates change and it's just a coincidence that every single time we checked them at a different time in history, it happened to be at a time when they were the same as they are today or 2. Decay rates change and they were in fact different at the times of the various supernovae explosions than they are today and it's just a massive coincidence that each of the (faulty) gamma ray measurements working independently (and on completely different principles to) the corresponding radiometric dating methods for each of the isotopes measured with said gamma rays all happen to give the same results to those radiometric dating measurements.
R90624 (1 year ago)
Wait, atom is not radioactive because of 'not equal number of protons and neutrons'. Just look at table of nuclides. Z to n ratio is not constant. Look at Cr (z=24, n=28), Fe (z=26, n=31) etc.
Jordan Parton (7 months ago)
blue (1 year ago)
Some of the yt videos about carbon dating says scientists compare left of C14 to C12 (cause the ratio of those two is aproximately the same in the living organismas and in the atmosphere). And some of the videos (like yours) says scientists compare C14 to N14. So do they use both methods? How can they tell for sure that ratio of C12 and C14 was the same 50 000 years ago and today? And what scientific method did they use to find out that the time of decay is always the same? Also if we can find N14 in living organisms (I pressume it stays when organism dies), how can we know which ones are from C14 decay and which one's are not? sorry for all the questions, but I'm new to the subject and curious..
Samoan Brown (1 year ago)
I go to ucla and I’m taking my an anthro class where this was so confusing in the textbook but you broke it down perfectly!!
A.H. Aziz (1 year ago)
That was very informative and easy to understand. I’m a literature graduate and yet I understood your lesson completely. Greetings from Iraq 🌹
best explanation about this on youtube
nope nopenope (1 year ago)
Interesting. But how do they know how much of the isotope the object had to start with. As in your question 5 (11:28) "What is the approximate age of an igneous rock that contains only 1/4th of its original potassium-40". How do they know how much potassium-40 that rock originally had?
Justin McCartney (6 months ago)
And what happens if the parent material is water soluble, but the daughter material is not? Exposure to water at any point would remove some of the parent material and throw off the ratio, making it look significantly older. This has been show with rocks formed very recently being dated as millions of years old.
viggy (6 months ago)
but the daughter material is not potassium-40 though, so adding it to the remaining parent material would not give the original amount of K-40.
Zulu (6 months ago)
yea its literally just a ratio thing; daughter material + radioactive = 1
john kissler (7 months ago)
Only thing that makes sense is taking the amount of daughter material and adding it to the remaining amount of parent material. This would tell you how much parent material the specimen started out with.
Gage Slaughter (8 months ago)
They don’t. Unless the find another rock of the same “type” with a maximum content of potassium’. But that doesn’t even fly. Because you are correct. They are missing a factor in the equation.
Christopher Perez (1 year ago)
this helped me so much
Randy Robles (1 year ago)
no it didn't
Waffle' nt (1 year ago)
Oh my God please replace my earth systems teacher. You're making this way easier to understand
Very informative. Thank you
s. shahtes (1 year ago)
thanks, man that's a very intellectual, could you tell me all radio active element? how many are they?
mehfoos (1 year ago)
Small nitpicked correction/additional info: Half lives can undergo time dilation in accordance with relativity. In fact, particle accelerators use this to calculate precise half-lives.
kennyw (1 year ago)
True, but he's not referring to protons in accelerators or radioactive atoms traveling at very near the speed of light or near a strong magnetic field (black hole). He's referring to radioactive atoms in a resting state (embedded in geologic formations, etc.).
MyGamerTV (2 years ago)
BearKire (2 years ago)
Your voice reminds me about Steve Jobs. Thanks for a great video!
MMA Kingdom (3 years ago)
Great video!

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