How is absolute dating used to evaluate geologic time

Now it is time to put those math skills to good use.

At one half-life, you would have approximately 50% Carbon-14 and 50% Nitrogen-14.

The best radioactive element to use to date human fossils is Carbon-14.

There are several reasons why, but the main reasons is that Carbon-14 is a naturally occurring isotope in all forms of life and its half-life is about 5730 years, so we are able to use it to date more "recent" forms of life relative to the Geologic Time Scale.

If we measure the rate at which various salts are added to the oceans by weathering, we could calculate the time it took to reach modern day salinity.

We are reasonably adept at manipulating the physical world in terms of spatial relationships and physical parameters (temperature, pressure), but Time is comprehensible to us as long as we can track it in terms of seconds, minutes, hours, days, and years, but once we go beyond the realm of our own time experience, our perception tends to get fairly vague.

In other words, half (50%) of the Carbon-14 you started with has decayed into the daughter isotope Nitrogen-14.

However, your readout from your radioactivity measuring instrument says you have only 25% Carbon-14 and 75% Nitrogen-14, so your fossil must have been through more than one half-life.

This is what your readout said, so your fossil has undergone two half-lives.

Now that you know how many half-lives have passed for your fossil, you need to multiply your number of half-lives by how many years are in one half-life. Your fossil is of an organism (maybe human) that died 11,460 years ago.

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