Radiocarbon dating facts for kids

Radiocarbon dating helped verify the authenticity of the Dead Sea scrolls.

Radiocarbon dating, also called carbon dating or carbon-14 dating, is a cool way to figure out how old things are. It works for objects that used to be alive, like wood, bones, or plants. This method uses a special type of carbon called radiocarbon, which is slightly radioactive.

How Radiocarbon Dating Works

This amazing method was created in the late 1940s by Willard Libby at the University of Chicago. He even won a Nobel Prize in Chemistry for it in 1960!

Carbon-14 in Nature

Here's how it works:

• A special type of carbon, called ¹⁴C, is always being made in the Earth's air.
• This happens when cosmic rays from space hit nitrogen in the air.
• This new ¹⁴C then mixes with oxygen to form radioactive carbon dioxide.
• Plants take in this carbon dioxide through photosynthesis.
• Animals then get ¹⁴C by eating these plants. So, all living things have a tiny bit of ¹⁴C inside them.

Dating Dead Things

When a plant or animal dies, it stops taking in new carbon. From that moment on, the ¹⁴C inside it starts to slowly disappear. This happens because ¹⁴C is radioactive and breaks down over time.

• Scientists measure how much ¹⁴C is left in a sample, like a piece of old wood or a bone.
• The less ¹⁴C there is, the older the sample is.
• ¹⁴C has a "half-life" of about 5,730 years. This means that after 5,730 years, half of the ¹⁴C in a sample will have broken down.
• This method can reliably date objects up to about 50,000 years old. Sometimes, with special care, even older items can be dated.

Making Dating More Accurate

Since the 1960s, scientists have been working to make radiocarbon dating even more precise.

Calibration Curves

The amount of ¹⁴C in the air hasn't always been exactly the same. To fix this, scientists use a special tool called a calibration curve.

• This curve helps convert the measured ¹⁴C amount into a more exact calendar age.
• Think of it like a conversion chart that adjusts for past changes in the atmosphere.

Other Adjustments

Scientists also make other small corrections:

• Different types of living things can take in ¹⁴C slightly differently. This is called "fractionation."
• The amount of ¹⁴C can also vary in different parts of the world, or in different environments like the ocean. These are called "reservoir effects."

Human Impact on Carbon-14

Humans have also changed the amount of ¹⁴C in the air:

• Burning fossil fuels: When we burn coal and oil, we release old carbon that has almost no ¹⁴C left. This makes the amount of ¹⁴C in the air go down.
• Nuclear tests: In the 1950s and 1960s, above-ground nuclear tests released a lot of new ¹⁴C into the air. By 1965, the amount of ¹⁴C in the atmosphere had almost doubled!

How Scientists Measure Carbon-14

Originally, scientists used machines that counted the tiny bursts of energy (called beta radiation) given off by decaying ¹⁴C atoms.

• Today, a method called accelerator mass spectrometry (AMS) is used most often.
• AMS is much better because it counts every single ¹⁴C atom in a sample.
• This means scientists can use much smaller samples, like a single plant seed.
• It also gives results much faster.

Impact on Archaeology

Radiocarbon dating has changed archaeology in a huge way. It's often called the "radiocarbon revolution."

• It helps archaeologists date ancient sites more accurately than ever before.
• It also lets them compare the ages of events across different parts of the world.
• Thanks to radiocarbon dating, we now have a much clearer timeline for important moments in history. This includes the end of the last ice age and the start of the Neolithic (New Stone Age) and Bronze Age in different regions.

Images for kids

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  Atmospheric ¹⁴C for the northern and southern hemispheres, showing percentage excess above pre-bomb levels. The Partial Test Ban Treaty went into effect on 10 October 1963.

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  North Ronaldsay sheep on the beach in North Ronaldsay. In the winter, these sheep eat seaweed, which has a higher δ¹³C content than grass; samples from these sheep have a δ¹³C value of about −13‰, which is much higher than for sheep that feed on grasses.

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  Measuring ¹⁴C is now most commonly done with an accelerator mass spectrometer

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  The Northern hemisphere curve from IntCal20. As of 2020, this is the most recent version of the standard calibration curve. The diagonal line shows where the curve would lie if radiocarbon ages and calendar ages were the same.

See also

In Spanish: Datación por radiocarbono para niños