How Do Scientists Determine the Age of Dinosaur Bones? | HowStuffWorks
Fossils are generally older than about 10, years, or longer ago than the end of the last Pleistocene glacial event. A dinosaur footprint According to radiometric dating, this era was roughly to million years ago. Dating the Fossils and Artifacts that Mark the Great Human Migration. The latter are called radioactive isotopes, and over time they will decay, giving off. There are two main methods determining a fossils age, relative dating and absolute dating. Relative dating is used to determine a fossils approximate age by.
Think of the nucleus as a pyramid of building blocks. If you try to add extra blocks to the sides pyramid, they may stay put for a while, but they'll eventually fall away. The same is true if you take a block away from one of the pyramid's sides, making the rest unstable.
Eventually, some of the blocks can fall away, leaving a smaller, more stable structure. The result is like a radioactive clock that ticks away as unstable isotopes decay into stable ones.
You can't predict when a specific unstable atom, or parent, will decay into a stable atom, or daughter. But you can predict how long it will take a large group of atoms to decay.
The element's half-life is the amount of time it takes for half the parent atoms in a sample to become daughters.
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The atoms in some chemical elements have different forms, called isotopes. These isotopes break down at a constant rate over time through radioactive decay.
Showing Their Age | History | Smithsonian
By measuring the ratio of the amount of the original parent isotope to the amount of the daughter isotopes that it breaks down into an age can be determined. We define the rate of this radioactive decay in half-lives.
If a radioactive isotope is said to have a half-life of 5, years that means after 5, years exactly half of it will have decayed from the parent isotope into the daughter isotopes. Then after another 5, years half of the remaining parent isotope will have decayed.
While people are most familiar with carbon dating, carbon dating is rarely applicable to fossils. Carbon, the radioactive isotope of carbon used in carbon dating has a half-life of years, so it decays too fast. It can only be used to date fossils younger than about 75, years. Potassium on the other hand has a half like of 1. This makes it ideal for dating much older rocks and fossils.
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They ignore evidence that does not fit their preconceived notion. What would happen if a dinosaur bone were carbon dated? The age they came back with was only a few thousand years old.
This date did not fit the preconceived notion that dinosaurs lived millions of years ago. So what did they do? They threw the results out.
This is common practice. They then use potassium argon, or other methods, and date the fossils again.
How Do Scientists Determine the Age of Dinosaur Bones?
They do this many times, using a different dating method each time. The results can be as much as million years different from each other!
They then pick the date they like best, based upon their preconceived notion of how old their theory says the fossil should be based upon the Geologic column. So they start with the assumption that dinosaurs lived millions of years ago, then manipulate the results until they agree with their conclusion. Their assumptions dictate their conclusions.