This article http://news.yahoo.com/space-explosion-b ... 16367.html points out that possibly a gamma ray burst created carbon 14 and beryllium 10. So my question is, if a radiological event in the past can create carbon 14 how is it that it can be considered a reliable dating source? I understand half life and decay rates being constant, but if an event creates more of what we are using to date an object, wouldn't that skew the data a bit?

I would think that if a gamma ray burst had hit the Earth anytime when life existed on the planet, it would likely have sterilized the entire planet and destroyed the Ozone Layer. Not to mention the fact that gamma ray burst aren't spherical explosions, but actually small, thin streams of incredibly high-energy particles shooting off into space from the poles of a dying star. And since space is, well, really freaking big, it's unlikely that one of them would ever hit the Earth. It's an interesting problem, the mystery of the tree rings, but I don't think a gamma ray burst caused it, unless it was a glancing blow from one.

In answer to your original question, yes it would skew the results, and I'm not sure how they work around it. Maybe some sort of statistics system or something.

First, even if we were hit with a gamma-ray burst, would the C14 make it as far as Earth? Massive stuff experiences drag and would not make it on average nearly as far as the gamma rays.

Second, if this did create a glut of the stuff, then everything from that age would appear to be younger than it was. Within a few decay times the level would be back to normal.

I think the implication was that the gamma radiation would irradiate the carbon already here on Earth and turn it into Carbon-14, not that the GRB would bring the C-14 with it.

It would create a geological layer rich in C14, similar to the KT boundary. By looking at the layers before and after it, one could determine just what had happened, and what the true age of the C14 layer is.

K... Y...?

KT?

OK. Read the mechanism. That's... interesting. I hadn't realized that was the mechanism.

Derp. Fixed now.

I'd heard the Ordovician Extinction was due to a gamma ray burst, but Carbon 14 is only useful for the last fifty thousand years anyways. Earlier dates are found by other methods.

why do you need different dating methods for different time periods?

As i understand it, it skews the dating of parts of organisms that stopped it's metabolism in a certain time period (I don't know if it is just one tree ring that has more carbon 14 or if it is more, with less excess every year.)

So with wooden objects you want to date, given the knowledge of the tree ring mystery, you now need to check how many yearrings that wooden object contains, and check multiple year rings to see if there is an unusual decline in carbon 14 to know if it comes from a tree ring mystery year. Datings that have been made before that was known and factored in, would propably be wrong. They would date things too young.

If there was a time where there was considerably less radiation hitting earth, it would lead to dating stuff from then as older. Though given we know, that year rings are checked for carbon 14, it either had not happened in times, where we have a year ring chain to, or it is already known and i assume factored in by carbon daters.

I don't know what the effect on bones would be. Propably you have a year ring equivalent but i am not sure.

As to why it is considered a reliable method. With every measuring method there are pitfalls that have to be avoided. Like putting an ordinary thermometer into direct sunlight can give you the wrong readings. Just looking at one single gauge is seldom giving you reliable readings. But once you know about certain interference factors, you can factor them in.

Why would you need different dating methods for different periods? Some like tree ring dating only work as long back, as we have an uninterrupted chain. with radiometric dating, if the object is too young or too old, measuring mistakes due to inexactess of your sensors alone gives error margins that just allow you dating like "very young" or "incredibly old" but nothing more usefull.

This http://irregularwebcomic.net/3262.html is a quite readable explaination of how radiometric dating works, and my ideas here are largely based on that, because i have read this recently.

In short, because you run out of C14 if it's too old. So you need to use something else that decays slower. Something that decays slowly enough that on the shorter time scales you wouldn't see a difference.

so why not use those methods for dating younger items as well?

Because it decays slowly enough that on the shorter time scales, you wouldn't notice the difference.

Perspective: Short term time scales for age dating could range anywhere between decades to a few hundred years. Long term age dating can be anywhere from a hundred thousand to a few million years. Possibly more.

Plus you don't always have all neccessary elements in one item.

If it has not uranium in it, you can't date it based on uranium decay.