How Does Radiocarbon Dating Work? - Instant Egghead #28

How do scientists determine the age of fossils that have been under the surface of the earth for thousands of years? Scientific American Editor Michael Moyer explains the process of radiocarbon dating.

[woodfamily]

Thank you!! My son, right as I tuck him in: "Dada, how do scientists know how old something is?" Me, cleverly and not showing my panic: "It's bedtime. Ask me first thing in the morning. I'll tell you all about it" as I run to the internet for answers! haha.

[xPeterthepallyx]

You've just explained this better than 3 of my Geology professors. Thank you.

[JackSolomonTV]

i have a carbon dating asignment and ihad no idea what i was doing. after i watched this i still have no idea what im doing

[TimCrinion]

Let's assume that C12 and C14 have 'reliable' half lives. How do we calculate how old something is unless we know the original C12:C14 ratio in an organism? Also, how do we know that radiation has collided with N14 at a constant rate throughout history? Wouldn't creatures near the poles be less exposed to it than creatures at the equator?

[Nickoflouse]

This video is a great introduction to radiometric dating. It provides a great baseline understanding of carbon-14 dating in a simple, easy to understand manner. It explains how the carbon gets into organic material and how the ratios work in calculating the half-life of a sample. However, this is too short to provide any in depth explanation of how carbon-14 is formed and some of the flaws of carbon-14 dating. For example, the description states “How do scientists determine the age of fossils” while radiocarbon dating is helpful in some cases, most fossils are too old to be radiocarbon dated. Overall, this video is a quick and basic introduction to radiocarbon dating.

[yangsi]

Only one word- Best Video ever on Carbon dating

[ElegantMovement]

Finally a straight forward video on the subject!
Just a few questions:

How did scientists determine the half-life of C14 ("5730 years on average") and other elements?
Also, to measure the ratio of C12 to C14, don't you need to know where they both started to calculate? For example, if two different organisms lived and died around the same time, do they have the same ratio of C12 to C14 throughout their lives and at the very moment they die?
I don't know if this chart was accurate, but it showed that an organism starts with more C14 than C12, but earlier he said that most Carbon molecules are C12. Am I missing something?

Thanks!

[notwendy]

This helped my class a lot in what were learning! They send you the thanks of all thanks! Ill keep showing my class these types of videos because your awesome!

[gnhman]

I have a few questions:

How do scientists know that the half life of C-14 is 5730 years?
How do scientists know the initial amount of C-14 inside of the organism when the organism died?

[kalv.]

Simple and to the point. Thanks Michael!

[changeark]

I just wanted to know something brief about carbon dating and this short video clips helps me a great deal. Thanks!!!

[moumitahalder]

you have explain it better than my teacher and 3 other books of Anthropology in 2minutes.. Thank You..

[geradod]

"For humans, you would ask to see their birth certificate." in what woRLD WOULD YOU NOT ASK THE PERSON, AND INSTEAD ASK TO SEE THEIR BIRTH CERTIFICATE LMAO

[jcruz]

"Animal and plant remains can undergo a variety of physical and chemical changes during fossilisation. This results in fossils showing varying styles and degrees of organic preservation:

minimal decay with only some loss of soft tissue
preservation of a skeleton with minimal change
removal of all organic material except carbon, which remains as a film in the rock"

Youtube does not allow me to post the reference link :(

[CherryCakeLane]

Perfect! This video was the most helpful video I found on Carbon Dating! I've been trying to understand how scientists date the Earth as oppose to fossils, this video explained things in such a way that I could apply the wisdom to understand dating the planet better, thank you!

[chemeng]

Great questions below, and video, used it to explain this to my kids. For the questions, the ratio of C14 to C12 is relatively constant across geography and across time. For Geography this is due to the cosmic ray creation of C14 far up in our atmosphere, this is where light rays that are also relatively constant over the centuries create C14 with cosmic bombardment, similar to the norther lights phenomenon. Since it's so high in the atmosphere by the time it reaches ground level it's virtually homogeneous globally. Over time we know it's constant as we have carbon dated events from thousands of years ago, events who's dates we know from written tests, everything from Egyptian mummies to medieval artifacts, to trees that are still alive and over 4000 years old. We have proof that carbon dating is very effective. To go further back in time you can use other radioactive elements with much longer half lives, and unlike C14 turning into C12 + nitrogen gas, these other longer half life elements often break down into 2 other elements that are not gases such as nitrogen, as such with those you have further help determining the age as you have 2 remnants of the original radioactive isotope. These other longer range radioactive products come from the molten core of the earth, and they too are equally mixed in the molten core, but with longer half lives you also get less precision and you'll usually see comments of plus or minus hundreds of thousands or millions of years, versus C14 that can date on a level of plus or minus a few decades. Lots of work and proof went into this marvelous insight into how to date something over thousands and millions of years.

[prashantvicky]

Great explanation. It had always confused me, now I can understand the history books better.

[UWBadgers]

Thank you for your reply. Does it mean that the ratio of C14 to C12 in the atmosphere remain constant unless disturbed by "any occasional spikes of C14 levels"? If so, any living organisms that breath in the air should have a constant C14:C12 ratio until they die when the C14 level start to decrease because no new C14 is taken in. Please correct me if I'm wrong.

[moeman]

One thing I don't get about half life, say every 5700 years half of it decays, and it keeps going on that pattern, when does it decay completely?

[fugitive]

Welp after hearing people say over and over, "carbon dating isnt that reliable" And hearing this, it seems like a very legitimate way to date things. I mean its not like you can get a accurate date but close enough is still pretty good.