Start Carbon dating how stuff works

Carbon dating how stuff works

However, radioisotope dating may not work so well in the future.

Other useful radioisotopes for radioactive dating include Uranium -235 (half-life = 704 million years), Uranium -238 (half-life = 4.5 billion years), Thorium-232 (half-life = 14 billion years) and Rubidium-87 (half-life = 49 billion years).

The use of various radioisotopes allows the dating of biological and geological samples with a high degree of accuracy.

At that time there would have been zero lead in it. So it was, after years of attempting to measure the age of the Earth (or, more specifically, the time since it was last molten) in a regular lab, that Clair Patterson bravely announced “Dudes and dudettes of science… ” Turns out that burning gasoline, among its other little known deleterious effects, throws lead into the air.

Since carbon-14 has a half-life on the order of thousands of years, it’s useful for figuring out the age of organic materials that have been independent of the atmosphere for thousands of years. That’s not great: once everything on Earth is peppered with lead, it’s difficult for scientists to do their science.

The carbon-14 decays with its half-life of 5,700 years, while the amount of carbon-12 remains constant in the sample.

By looking at the ratio of carbon-12 to carbon-14 in the sample and comparing it to the ratio in a living organism, it is possible to determine the age of a formerly living thing fairly precisely. So, if you had a fossil that had 10 percent carbon-14 compared to a living sample, then that fossil would be: t = [ ln (0.10) / (-0.693) ] x 5,700 years t = [ (-2.303) / (-0.693) ] x 5,700 years t = [ 3.323 ] x 5,700 years Because the half-life of carbon-14 is 5,700 years, it is only reliable for dating objects up to about 60,000 years old.

As water freezes and each molecule falls into place, atoms that don’t fit in the forming ice crystal are excluded. For example, zircon (a crystal) is perfectly happy to incorporate uranium, but excludes lead.

Impurities, such as dissolved air, are either forced out or concentrated in the last region to freeze. It so happens that uranium decays into lead with a half-life of 4.5 billion years.

There are many different kinds of radiometric dating that are used to date things that are non-organic (which is part of how we determine the age of the Earth).

They each rely on a couple of different (thoroughly verified) principles.

Carbon dating is the most famous form of “radiometric dating”.