How does anthropologist know if the fossils or other things are stayed on earth for a very long time?

Question

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Answer 1

You're asking how anthropologists and archeologists and geologists and paleontologists date things? (Your question is unclear, and you don't explain it at ALL.)

There are a bunch of methods, depending on the type of thing, and how old it is.

If it's a human artifact, it might be dated by what it is and how it was made, or by dating the fossils near it.

It's a big topic; there are websites and books on the subject, if you want to read up.

But since you put no time or thought into your question, I'm not strongly motivated to waste any more time trying to answer.

Explaining what you know and what you want to learn would help.

Answer 2

Radio Carbon dating techniques or even isotopic dating techniques.

Answer 3

Well, for anthropologists, who study the origin, behavior, and the physical, social, and cultural development of humans, there are a lot of artifacts and remains that need to be dated so that we can have an accurate picture of the human time line. Like archaeologists, they have a number of different methods for finding the approximate age of such items.

A common method for items buried in the earth over time is the item's depth in the soil and what kind of layers make up the earth covering the item. Scientists can estimate how long earth has been accruing over the object. In general, the deeper it is buried over naturally occurring layers of earth, the older the item is.

Another, more accurate method is radiocarbon dating. This method measures the amount of radioactive decay of Carbon-14, an unstable isotope of carbon that exists in trace amounts on earth. We know the half-life of Carbon-14 (5730 years), so by observing how much the isotope has decayed in an item, we can determine its approximate age using fairly simple math. See the wikipedia link in my source for a fascinating look into how radiocarbon dating works.

Answer 4

Carbon dating tells scientists how old something is.

Answer 5

Quickly:

Stratigraphy: This rule says the newest items are on top and the deeper you dig, the older they are. The deepest artifacts, just about the sterile layer should be the oldest.

Artifact dating: You find a coin dated 1950, you can be certain the site is younger then that. You find artifacts of a certain design (Clovis points) you know from other sites and dating about how old they are

Carbon 14: All living things have carbon 14 in them. When they die the carbon 14 decays (leaves) at a known rate. By measuring what's left you can get a good date stamp on an item. Generally it's limited to the last 40,000 years.

Dendrochronology : This is tree ring dating. Tree rings show the pattern of weather over a number of years. You match that pattern in another tree and then can extend it. This gives you a tree ring record going back many years. To date things, you find (say) a roof beam, record the pattern in it and match it to the know record.

Potassium-argon: This dates items that are millions of years using the same concept as carbon 14. An advantage is you aren't limited to once living matter.

Thermoluminescence: This can date items such as pottery. You can measure the last time an item was heated.

Paleomagnetic Dating: The north magnetic pole moves now at about 25 miles a year. When things are heated to high temperature (lava, large campfires, pottery kilns) the magnetic particale in them become alinged towards the pole. By measuring the direction, once can see where the magnetic pole was and get a date.

Hydration: Obsidian is a volcanic rock that makes good tools. When a surface is exposed during manufacture of the tool, it starts absorbing water. This can be measured and dated.

Isotopic dating: Argon, uranium and lead (as in paint) can be dated in artifacts. Again it's measuring what is left

All these methods require clean samples, good measurement and patience. In the case of Carbon 14 it's know the amount of carbon 14 in the air has changed over time. Also different things (shellfish) absorb carbon at different rates.Finally, contamination (car exhaust on living trees, smoking around an artifact) can change the results.