I don't understand carbon dating.?

Question

I get that it uses the half-life of the substance to determine how long it's been around, but wasn't all matter created at the same time (Big Bang)? Or does it only concern the molecular level (i.e. how long two atoms in the substance have been bonded together as a molecule)? Can anyone give me a relatively simple answer for these questions? This may be a dumb question, haha, but I'm just curious. Thanks a bunch!

Answer 1

Carbon dating is a type of radiometric dating based on the known decay rate of radioactive isotopes.  The radioisotope of carbon is C-14, which is useful to measure the age of a carbon-bearing object to a maximum of around 50,000 years.  Geologists very rarely use the C-14 radioisotope as the half life is too short.  We use things like Sr, Rb, K, U, and Pb which have half lives of millions or hundreds of millions of years. For example, the half life of U-235 is just over 700 million years, so that particular isotope is much more useful to date geological materials than carbon, as the earth is 4.55 billion years old.

Another example is U-238 which has a half life of 4.5 billion years, which happens to be the age of the earth. That is one of the ways we have shown beyond any reasonable doubt how old the earth is, and also the time since the Big Bang.

Look up radiometric dating on Wikipedia and you will get an excellent explanation.

Answer 2

Check the info in the source link provided. You will find it helpful and easy to understand.

Don't worry about the big bang, it doesn't enter the picture when you talk about Carbon-14 dating. Carbon dating is for more 'contemporary' items.

Answer 3

Here is a pretty good link that simplifys it pretty good.

Answer 4

It only works on once-living things (organic matter).

Carbon dating can be used on material which was living in the last few tens of thousands of years, and which got its carbon from the air. The method has become more accurate in the last few decades.

The Theory

Carbon 14 is a radioactive isotope of carbon. It is produced in the upper atmosphere by radiation from the sun. (Specifically, neutrons hit nitrogen-14 atoms and transmute them to carbon.)

Land plants, such as trees, get their carbon from carbon dioxide in the air. So, some fraction of their carbon is C14. The same is true of any creature that gets its carbon by eating such plants. We can measure this in living things today.

Suppose such a creature dies, and the body is preserved. The C14 will undergo radioactive decay, and after 5730 years, half of it will be gone. Eventually, all of it will be gone. So, if we find such a body, the amount of C14 in it will tell us how long ago it was alive.