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how do we date things that are millions of years old?


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#1 blackhole123

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Posted 9 June 2006 - 12:17 AM

I recently got away from my dads religeon ( http://en.wikipedia....ian_conventions , dont even get me started on that cult) . He believes in a very literal translation of the bible. This means he believes that the earth is only around 10,000 years old.

Whenever i try to tell him how he is wrong and how we can tell how old things are he just denies that it is possible to figure that out. I know that it has to do with looking at how much of a substance is left and then dating it with its half life (or something like that). He just doubts that we can know what the half life for a substance is.

So my question is, how do we know how fast these rocks break down when it takes so long?

Its very frustrating when he expects me to be able to prove every little thing, which i usually can, then he still denies it and wants me to believe something that he cant prove. O well i guess you cant fight ignorence...


wow that turned into a long post for that simple question...
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#2 Cap'n Refsmmat

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Posted 9 June 2006 - 12:44 AM

http://en.wikipedia....iometric_dating
http://en.wikipedia....iocarbon_dating

We know the half-lives because we can put the materials in the lab and determine how much of the material decays over a given period of time, and then we simply extrapolate that out to thousands of years. There are certain materials that have half-lives of days, so we know how radioactive materials behave and what they do.

Mind you, radiometric/radiocarbon dating is only accurate out to a point, when we start to use fossil layers and other materials found near the dated material for dating purposes.
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#3 tomgwyther

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Posted 9 June 2006 - 12:44 AM

hhmm. interesting. there are may different ways of dating things, liveing matter for example can be dating according to the amount of C14 (Carbon 14) left in it's dead tissue.. i.e. all living tissue has a set amount of C14, when it dies, this substance decays at a known rate. that's how we can 'carbon date bones, plants etc.
I could go on for hours about how other parts of our world/Universe are dated, but it can get rather complicated... If you realy look into it, it all makes perfect sense, even a child can understand it.
I once walked a mile or so into the grand canyon, Arizona and pulled a seashell from a 300 million year old rock-face to show it to the Creationist christian I was with... he ran like a scared child!

I simpathise with you completely, I've given up trying to explaine the amazing complexities of our world to fundamentalist christians, because they always have a lame excuse for every thing! (i.e. It's God's will; God put fossils there to test our faith... etc etc...

Religion is a very easy way for some people to explain the world, not one I subscribe to myself, but it's best to let them be happy in their own belife, than to try to prove to them otherwise.

Our planet's history is staring us in the face every day; we can see how old it is with a little research, It is actually more amazing than the bible would have us belive.


Tom
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#4 akcapr

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Posted 9 June 2006 - 12:48 AM

btw carbon dating only works for organic things that are like up to 40,000 yrs old or something, after that it becomes innacurate. so you cant use it to measure million old things.
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#5 tomgwyther

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Posted 9 June 2006 - 12:52 AM

Twas only an example of how to date a substance... anyway. 40,000 years is longer than the Bible would have us belive the world has existaed for!

Thank you for pointing that out though!!!
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#6 blackhole123

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Posted 9 June 2006 - 01:17 AM

so how long does it take for a sedimentary rock layer to form? When i point out that humans and dinosaurs could not have lived during the same period because of the dinos being in such a lower layer he just says that it doesnt take long for rock layers to form.

Also when i talk about Pangea and ask how that could have all happened in 10,000 years he says it happened during "abrahams flood". What a load of crap.

My father isnt what you would call "scientifically literate".
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#7 Cap'n Refsmmat

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Posted 9 June 2006 - 01:21 AM

http://en.wikipedia....ki/Stratigraphy
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#8 blackhole123

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Posted 9 June 2006 - 01:26 AM

btw carbon dating only works for organic things that are like up to 40,000 yrs old or something, after that it becomes innacurate. so you cant use it to measure million old things.


why? correct me if im wrong but i thought uranium had a half life of hundreds of thousands of years.
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#9 Cap'n Refsmmat

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Posted 9 June 2006 - 01:30 AM

Carbon dating uses carbon-14, not uranium. Uranium simply doesn't permeate like carbon-14 does (animals inhale carbon all the time).
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#10 blackhole123

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Posted 9 June 2006 - 01:32 AM

ok thanks for clearing that up. this will all probably be good to know for my stupid earth science exam.
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#11 tomgwyther

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Posted 9 June 2006 - 01:39 AM

Rock layers can form very quickly in the case of a volcanic eruption, or slowly in the case of sediment being layed down by a river or ocean, I'm not a geologist so I don't have to the exact figures to hand right now, rock layers vary considerably from place to place.

As for Pangea, that's easy, we can see where the continants are now; we can see where they were 100 years ago, we can see them moving.

Europe and America were about an inch closer to each other last year then they are now, so 100 years ago they would have been 100 inches closer, 500 million years ago, they would have been 500 million inches closer (Joined up!)


Alot of what is writen in the bible was writen around 1000 years after the birth of Christ, by people with political bias, and/or people involed in spreading the 'Christian word' to so called 'Pagans' many facts were distorted in this process, for public relations reasons and for the good of the church.
Unfortunatly, these writings have been taken as fact by maby fundamentalist Christians, thus distoring the origional message the bible tries to put across.

p.s. I am a complete athiest; I've studied science since I was a child, my wife is a born and raised Christain, albiet a sensible one!
So I've been able to see both side of the argumnet on your original question.
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#12 silkworm

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Posted 9 June 2006 - 02:11 AM

I recently got away from my dads religeon ( http://en.wikipedia....ian_conventions , dont even get me started on that cult) . He believes in a very literal translation of the bible. This means he believes that the earth is only around 10,000 years old.

Whenever i try to tell him how he is wrong and how we can tell how old things are he just denies that it is possible to figure that out. I know that it has to do with looking at how much of a substance is left and then dating it with its half life (or something like that). He just doubts that we can know what the half life for a substance is.

So my question is, how do we know how fast these rocks break down when it takes so long?

Its very frustrating when he expects me to be able to prove every little thing, which i usually can, then he still denies it and wants me to believe something that he cant prove. O well i guess you cant fight ignorence...


wow that turned into a long post for that simple question...


Actually, YEC's believe that the Earth is 6010 years old via biblical scholarship by James Ussher.

And it is not a simple question. Radiometric dating/radioactive decay are fairly complex to understand what is going on and appropriate uses and methods, and it will probably be a little tough to grasp if you haven't had any chemisty. I'm sure you'll have more specific questions.

Also, I'd let your father have his religion. It's as inappropriate to use science to disprove his religion as it is for him to use his religion to disprove science. They exist in very different places and have very different methods and limitations.
"It's silly to debate the truth, but it's dangerous not to tell it."

#13 ecoli

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Posted 9 June 2006 - 04:10 AM

silkworm - but he shouldn't let his father misrepresent the science... you of all people should know that.
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#14 silkworm

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Posted 9 June 2006 - 04:28 AM

Right ecoli. I certainly agree. My father, whom is an absolute saint and I love to death, used to battle me on this but then I explained to him that that science has nothing to do with his faith and showed him a few things he's been more than cool. Don't debate him though, you can't.

You either have to meet him in theology or you each have to meet in science to argue. If blackhole123 uses science to disprove his father's religion, that God does or does not exist, that's a misrepresentation as well.

Also, I don't think his father is a misrepresenter of science, though he's probably had it misrepresented to him. Don't fuel that by claiming that science could test for God.

If I were you I'd find out what science is. How it's done, what it's limits are, etc. etc. etc.. and then if he wants to attack it make him meet you there.
"It's silly to debate the truth, but it's dangerous not to tell it."

#15 SkepticLance

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Posted 9 June 2006 - 05:17 AM

A nice dating system is the decay of Potassium 40 to Argon 40. This is nice since Potassium is solid and Argon is a gas. This means that when rock turns liquid, all the Argon bubbles out. It is like resetting a clock.

Thus, if we want to date a rock stratum, we look for rock that was once liquid - volcanic - magma or lava. At the time it was hot and liquid, all the Argon disappeared. This means that when we analyse the rock today, the Argon 40 in it is all from the decay of Potassium 40. By measuring the ratio between remaining Potassium 40 and Argon 40 we get a date, to when the rock was liquid. This method is good for many hundreds of millions of years.
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#16 woelen

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Posted 9 June 2006 - 06:43 AM

I recently got away from my dads religeon ( http://en.wikipedia....ian_conventions , dont even get me started on that cult) . He believes in a very literal translation of the bible. This means he believes that the earth is only around 10,000 years old.

Whenever i try to tell him how he is wrong and how we can tell how old things are he just denies that it is possible to figure that out. I know that it has to do with looking at how much of a substance is left and then dating it with its half life (or something like that). He just doubts that we can know what the half life for a substance is.

So my question is, how do we know how fast these rocks break down when it takes so long?

Its very frustrating when he expects me to be able to prove every little thing, which i usually can, then he still denies it and wants me to believe something that he cant prove. O well i guess you cant fight ignorence...


wow that turned into a long post for that simple question...

Estimating ages of rocks can be done on the basis of uranium radioactive decay. Uranium has two naturally occurring isotopes (U235 and U238) with different half-life times. IIRC the age of rocks is estimated, based on the ratio of U235 and U238 in samples of those rocks. With the U-method, estimates can be made, going back hundreds of millions of years back in time.

On the other hand, I would not try to attack the religion of your father. I myself am a christian, who believes that earth has an age of billions of years and I tell other christians that for me, it is not important at all how old earth is. Of course, I have certain questions about theories of evolution and origin of life and I stand somewhere in the middle, not accepting the literial 6000-year old theory, nor fully accepting the current theories of evolution. I have LOTS of questions and hardly any answers on these things, but not having answers to this does not cripple my belief, it makes me humble. So, I can perfectly believe in a billion years old earth and an even older universe, and at the same time be a christian. You could try to explain that to your father, telling him that he does not have to throw away his belief, when he accepts that earth is very old.
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#17 blackhole123

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Posted 9 June 2006 - 08:32 PM

i could tell him that but he just says that any science that doesnt follow the bible literally, is wrong.

and also, way off topic, could someone explain how people say that intelligent design is science?
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#18 reor

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Posted 9 June 2006 - 10:04 PM

What i don't understand is why people glorify scriptures when believing in god. Written word is always biased and i doubt any "God" would hand out flyers! I have no issues with God, i only have problems with people who follow other peoples preaching/teaching and justifying it with "God".

Edit: Science doesn't contradict God, it can only contradict the Bible, which is biased!
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#19 akcapr

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Posted 9 June 2006 - 11:04 PM

seems to me that science has alot more proof to it than the bible tho
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#20 ecoli

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Posted 10 June 2006 - 12:34 AM

seems to me that science has alot more proof to it than the bible tho


The bible isn't about proof, tho.
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