What is radioactive dating?

I totally thought it was something that replaced speed dating.

Radiometric dating (often called radioactive dating) is a technique used to date materials, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates.

Eating out where you’ve melted by the end of the night.

More seriously, certain elements emit radioactive particles at a particular, known rate; this rate decreases with time. You measure the rate of emission (or the rate of the rate of emission, not sure which) to figure out how long it’s been emitting particles, i.e., how old it is.

Radiometric dating is a method of figuring out how old something is by the ratio of a certain isotope to the radioactive isotope that decayed into it. Since the half-life of the radioactive isotope is known we can determine how long it has been since the material we are checking has formed.

Take Carbon-14 dating for example. Carbon-14 is a radioactive element that is common in all types of living things. Carbon-14 is radioactive and decays into Nitrogen-14. Carbon-14 has a half-life of 5700 years. By measuring the ratio of Carbon-14 to Nitrogen-14 in a sample we can use the half-life to determine how long the sample has been dead.

There are other radiometric dating techniques as well. Uranium-238 and Potassium-40 can also be used for dating.

Continuing @Shuttle128 ‘s explanation. The half-life means the strength of the radiation decreases by half every 5700 years. So, if it reads 500 rads right now, in 5700 years it will read 250 rads, and 5700 years after that it will read 125 rads. Mathmatically, you can then measure what it is now, and know how old it is by how low the rads are.
Hope this helped.

@filmfann Rads are a unit of radiation exposure and is not in any way used in radiometric dating.

Mass spectrometers are used to determine the content of the sample. The numbers of atoms are related to the age by this equation:

D = Do + N[e^(λt) − 1]

Where t is age
D is number daughter atoms in sample
Do is number daughter atoms in original composition
N is number parent atoms in sample
λ is the inverse of the half-life

So I think the missing piece is just how that translates to the actual dating. And this isn’t my thing, so I’m just confirming here…

In the Carbon-14 example. The assumption is that there would be 100% Carbon-14 and no Nitrogen-14 when the sample is formed.

If you find equal Carbon-14 and Nitrogen-14 (a 50%-50% mix) in a sample then you’d be one “half-life” away from creation, so 5700 years.

Three times the Nitrogen-14 (25%-75% mix) would mean two half lives had passed or 11400 years, and so forth. Correct?

@Shuttle128 You’re probably right. It’s been years since I did this. But the concept is correct.

@funkdaddy Actually no, well sort of. As I edited in above (a bit too late I’m afraid) we don’t assume that the daughter atoms are zero at t=0. I believe what we normally do is determine from a large sample of data, what most newly formed samples contain. Since radioactive decay is an exponential function we use the equation above to determine the date. However, it can sort of be done the way you suggest.

From a non-scientific point-of-view: I think it makes an excellent catch-phrase for habitually going out with people who are a really bad match.