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Radiometric Dating Methods
When trying to determine the age of different rocks, artefacts, or other ancient objects, scientists use an approach called Radiometric Dating. You might have heard of carbon dating, which is a type of radiometric dating, but there are lots of other types.
Radiometric Dating works because some chemicals (radioactive ones) break down, or decay, over time, at a speed that is always the same. We use different chemicals for different situations:
Radiocarbon dating - used for dating objects less than 50,000 years old.
Potassium-argon dating - used for dating objects from 0.1-4 billion years old.
Uranium-lead dating - used for dating objects up to 4.5 billion years old.
These radioactive chemicals don't break down piece by piece however. Instead, half of them break down every set number of years, and the time this takes to occur is known as a half-life.
Imagine a pizza π. When it arrives you decide to eat half of what's left every day. So the first day you eat half. Then the second day you eat half of the half that's left, which is a quarter. Swipe through the images to the right to see your pizza get eaten.
When there is 1/16 left, your friend arrives and asked how old the pizza is. You explain your system and they can figure out that it's 4 days old. This is the basis of radiometric dating, but with much longer timescales and less pizza.
Project - Use dice to model half-life decay
While half-lives of radioactive elements are predictable, they aren't always perfect, and there is sometimes some error or variation. To demonstrate this and model half-lives, we can use a game of chance to gather some data.
The first thing you will need is a lot of dice!!! (or a dice simulator like this one here).
π²π²π²π²π²π²π²π²π²π²π²π²
You'll need at least 20 dice, and they can be any type as long as they have numbers on them. You can also flip coins as well, as they are like 2 sided dice. The more you use the better.
Once you have collected your dice, make note of exactly how many you have. You can use the document provided to keep track, or just write it down.
Next roll (or flip) all of the dice, trying not to lose any. Then remove all of the odd numbers (and tails), and count the remaining dice. Make a note of how many are left over, it should be around half of what you started with.
Use the remaining dice to repeat this process until you reach 1-0 left:
Roll what's left
Remove all of the odd numbers (and tails)
Count what's left and make a note
Present the data that you've gathered in a table.
Use dice to model half-life decay.pdfImagine that your pile of dice are the radioactive elements breaking down.
Once there is 1 dice left, how many half-life cycles have you done?
If every cycle is 150 years, how old would your pile of dice be?
How many dice would be in the pile when it was half as old?
Try to graph your data using paper or data software like excel. It should look similar to the image on the right.
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