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1. Title:
Benefits and risks of Carbon-14
Topic:
Radiation
Question:
What are the benefits and risks of carbon-14 for carbon-dating?
Answer:
Carbon-14 (C-14) dating is a way of determining the age of certain
archeological artifacts of a biological origin up to about 50,000 years
old. It is used in dating things such as bone, cloth, wood and plant
fibers that were created in the relatively recent past by human
activities.
C-14 dating becomes less accurate over about 50,000 years and it
should not be used to date items over about 100,000 years old.
C-14 is created in the atmosphere. It decays to C-12, the most stable
form of Carbon, with a half-life of 5730 years – this means that after
5730 years, half of the C-14 in an object will have turned to C-12.
After another 5730 years, half of the remainder will have turned to C-
12 and so on.
When an organism dies, it stops absorbing C-14 and the C-14 already
in its body starts to turn to C-12. The ratio of C-14 to C-12 in the
remains of an organism indicates how long it has been dead. The
method assumes that the C-14 / C-12 ratio in the atmosphere over the
last 50,000 or so years is the same as it is today – a potential source
of error.
Naturally occurring C-14 is in the food we eat and the air that we
breathe and represents no threat to our health. There is radiation all
around us from Carbon-14 and other sources. The harm it causes in
our cells is low; our bodies are used to it and are able to repair the
damage.
Nobel Prize winner Georges Charpak has calculated that a 70 Kg
human body contains potassium-40, C-14 and other radioactive
minerals, producing an activity of 10,000 disintegrations per second
(Beckerels), most of them absorbed by body tissues leaving only a
small amount to be detectable. He also considers the effect of a single
fast electron emitted by a radioactive atom. Such an electron would

2. disturb less than 105 atoms. Each cell in the human body contains
about 1014 atoms and a body has about 1014 cells – a total of about
1028 atoms..
These numbers provide some perspective to the cellular harm caused
by natural radioactivity. The body is constantly repairing the small
damage it causes.

3. USES OF CARBON DATING IN ARCHAEOLOGY
Prior to the development of radiocarbon dating, it was difficult to tell when
an archaeological artifact came from. Unless something was obviously
attributable to a specific year -- say a dated coin or known piece of artwork
-- then whoever discovered it had to do quite a bit of guesstimating to get a
proper age for the item. The excavator might employ relative dating, using
objects located stratigraphically (read: buried at the same depth) close to
each other, or he or she might compare historical styles to see if there were
similarities to a previous find. But by using these imprecise
methods,archeologists were often way off.
Fortunately, Willard Libby, a scientist who would later win the 1960 Nobel
Prize in Chemistry, developed the process known as radiocarbon dating in
the late 1940s. It's still the most commonly used method today. In a
nutshell, it works like this: After an organism dies, it stops absorbingcarbon-
14, so the radioactive isotope starts to decay and is not replenished.
Archaeologists can then measure the amount of carbon-14 compared to
the stable isotope carbon-12 and determine how old an item is.
For the most part, radiocarbon dating has made a huge difference for
archaeologists everywhere, but the process does have a few flaws. For
example, if an object touches some organic material (like, say, your hand),
it can test younger than it really is. Also, the larger the sample the better,
although new techniques mean smaller samples can sometimes be tested
more effectively. The data can be a little off particularly in younger artifacts,
and anything older than about 50,000 years is pretty much too old to be
tested because at that point the majority of the C-14 has decayed to
practically undetectable levels. There's also still usually a wide window of

4. time that an object can fall into. And lastly, the ratio of C-14 to C-12 in the
atmosphere (and hence the ratio in organic remains) has fluctuated to a
certain extent over the millennia, something that can lead to misleading
discrepancies that need to be corrected for.
Despite these limitations, radiocarbon dating will often get you a decent
ballpark figure. While other methods of dating objects exist, radiocarbon
dating has remained vital for most archaeologists. For example, it makes it
possible to compare the ages of objects on a worldwide scale, allowing for
indispensible comparisons across the globe. Before this, it was anyone's
guess how different digs' timelines compared to one another over great
distances. But now archaeologists studying, say, the development of
agriculture across the continents are able to determine how different
societies stacked up against one another throughout the millennia.
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