How do they date bones into the Millions of years?

[icantlogoff]

I am guessing this is the right forum to ask this.

http://www.cnn.com/2006/TECH/science/09/20/human.ancestor.ap/index.html

I understood that carbon dating is only accurate for about 70,000 years , and that radiometric(?) dating is only good on rocks etc. I know there is very simple answer to this , but i could not find it on a Google search yet?

many thanks in advance

regards

Steve

[blutoski]

I am guessing this is the right forum to ask this.

http://www.cnn.com/2006/TECH/science/09/20/human.ancestor.ap/index.html

I understood that carbon dating is only accurate for about 70,000 years , and that radiometric(?) dating is only good on rocks etc. I know there is very simple answer to this , but i could not find it on a Google search yet?

many thanks in advance

regards

Steve

I haven't read the paper in question, but there are a few possibilities... usually the fossils are found in a strata of known date, and dated in that way. The strata are dated using radiometrics, usually unrelated to the fossil project.

This is why you sometimes find a wide range of dates like "4.5 to 4.9 million years old" - it was found between two layers of known dates, but who knows how old the actual fossil is, specifically.

[DangerousBeliefs]

I don't see any simple answers...

http://www.talkorigins.org/faqs/dating.html

If I'm understanding this correctly, the age of the strata in the earth is pretty well defined. Scientists date the rock in the strata. So if fossils of a particular animal are found consistently in that strata, it's from that time.

[blutoski]

I haven't read the paper in question, but there are a few possibilities... usually the fossils are found in a strata of known date, and dated in that way. The strata are dated using radiometrics, usually unrelated to the fossil project.

This is why you sometimes find a wide range of dates like "4.5 to 4.9 million years old" - it was found between two layers of known dates, but who knows how old the actual fossil is, specifically.

Oh: and sometimes you get lucky. A fossil may be buried in lava. This means it's physically stuck in rock that can be dated with radiometrics directly. The Laetoli footprints in volcanic ash uncovered by Meave Leaky are a perfect example, although not technically fossils.

Also: there are other types of geological dating that can go back further than c14 - thermoluminescence and optically stimulated luminescent dating, for example.

[Smart_Cookie]

Oooh Oooh ... let me, let me!!!

I'm interested in anthrolopology and I found this very interesting set of Anthropology tutorials a few months ago. They're here (http://anthro.palomar.edu/tutorials/). (Palomar University)

The specific tutorials on dating methods are here:

Topic Overview (http://anthro.palomar.edu/tutorials/)
Relative Techniques (http://anthro.palomar.edu/time/time_3.htm)
Chronometic Techniques - Part One (http://anthro.palomar.edu/time/time_4.htm) and Part Two (http://anthro.palomar.edu/time/time_5.htm)


The short answer is that carbon dating is not the only method available.

Hope they help! They're not too long. They're divided into manageable, bite-sized sections. And there's even practice quizes.

[icantlogoff]

thank you all for such a quick responce.

now some more reading


regards

steve

[SusanB-M1]

I'm interested in anthrolopology and I found this very interesting set of Anthropology tutorials a few months ago. They're here. (Palomar University)

I have found this subject more and more interesting over the past few years, so I have made a note of the link. Although I didn't ask the question, thank you.

[Beerina]

What I want to know is they find a rock on top of the ice deep in the Antarctic. Ok, it must be a meteorite. But then they say "It's from Mars."

How do they know? How do they know it wasn't from the Moon, or some other planet, or wasn't an asteroid?

[Mashuna]

What I want to know is they find a rock on top of the ice deep in the Antarctic. Ok, it must be a meteorite. But then they say "It's from Mars."

How do they know? How do they know it wasn't from the Moon, or some other planet, or wasn't an asteroid?

They know that rocks are from Mars, gravel is from Venus :p

[KingMerv00]

What I want to know is they find a rock on top of the ice deep in the Antarctic. Ok, it must be a meteorite. But then they say "It's from Mars."

How do they know? How do they know it wasn't from the Moon, or some other planet, or wasn't an asteroid?

Just a guess:

Isotope ratios? Perhaps there are some compounds that are more/less common on Mars?

Is it red? :D

Edit:

Aha...here you go:
http://www.lpi.usra.edu/lpi/meteorites/Technicalities.html#MARSORIGIN

[Meadmaker]

What I want to know is they find a rock on top of the ice deep in the Antarctic. Ok, it must be a meteorite. But then they say "It's from Mars."

How do they know? How do they know it wasn't from the Moon, or some other planet, or wasn't an asteroid?

Layman's response here: Comes from reading Science News articles, or similar stuff. Take it for what it's worth until someone more knowledgable comes along.

The crust of Mars is different from the crust of Earth. Different chemical composition, due to its smaller size and lack of water. Also, the martian atmosphere is so much thinner that different gases get absorbed into the surface rock.

Different sized bodies have different crust compositions because, over time, heavier stuff sinks. There's more iron in the middle of the Earth than at the surface because iron is heavier than silicon and aluminum, which end up at the surface. The bigger the heavenly body, the more pronounced the difference, because gravity is more likely to pull the heavy stuff in. Asteroids are pretty uniform, with lots of heavy metals near the surface. On Earth, most of the heavy stuff got pulled down over the eons. On Mars, it's somewhere in the middle.

When they find a rock that matches the crust of Mars much better than that of Earth, they conclude it is Martian.

[RandFan]

thank you all for such a quick responce.:) That's what I always get also. And there is never a charge. If they only knew I charge other people for the same answers.

[Molinaro]

The meteors that are known to come from Mars (there are 11 of them) actualy have tiny pockets of the martian atmosphere trapped inside them. The composition of the gas pockets in those rocks is identical to the makeup of the Martian atmosphere as measured by the Viking landers.