The Naked Scientists

The Naked Scientists Forum

Author Topic: How do we date the Earth?  (Read 15914 times)

Offline chris

  • Neilep Level Member
  • ******
  • Posts: 5337
  • Thanked: 65 times
  • The Naked Scientist
    • View Profile
    • The Naked Scientists
How do we date the Earth?
« on: 10/04/2009 11:02:09 »
The accepted age of the Earth is about 4500 million years. How do scientists know this?

Chris


 

Offline RD

  • Neilep Level Member
  • ******
  • Posts: 8128
  • Thanked: 53 times
    • View Profile
How do we date the Earth?
« Reply #1 on: 10/04/2009 21:09:35 »
By the abundance of certain radio isotopes on Earth ...

Quote
The ages of Earth and Moon rocks and of meteorites are measured by the decay of long-lived radioactive isotopes of elements that occur naturally in rocks and minerals and that decay with half lives of 700 million to more than 100 billion years to stable isotopes of other elements. These dating techniques, which are firmly grounded in physics and are known collectively as radiometric dating, are used to measure the last time that the rock being dated was either melted or disturbed sufficiently to rehomogenize its radioactive elements.
http://pubs.usgs.gov/gip/geotime/age.html

 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
How do we date the Earth?
« Reply #2 on: 11/04/2009 04:26:48 »
How do they know where to start finding rocks?
 

Offline RD

  • Neilep Level Member
  • ******
  • Posts: 8128
  • Thanked: 53 times
    • View Profile
How do we date the Earth?
« Reply #3 on: 11/04/2009 04:35:46 »
How do they know where to start finding rocks?

A Geiger counter would be useful to find Uranium ... http://scifun.chem.wisc.edu/CHEMWEEK/PDF/Uranium_Clock.pdf
 

Offline Madidus_Scientia

  • Neilep Level Member
  • ******
  • Posts: 1451
    • View Profile
How do we date the Earth?
« Reply #4 on: 11/04/2009 10:17:04 »
How do we date the Earth?

That's a good question, where do you take a nice planet out for dinner these days?

Maybe you could get her a ring :P
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
How do we date the Earth?
« Reply #5 on: 11/04/2009 12:18:49 »
I think it's a he.
 

Offline Karen W.

  • Moderator
  • Naked Science Forum GOD!
  • *****
  • Posts: 31653
  • Thanked: 5 times
  • "come fly with me"
    • View Profile
How do we date the Earth?
« Reply #6 on: 11/04/2009 12:50:37 »
How do we date the Earth?

That's a good question, where do you take a nice planet out for dinner these days?

Maybe you could get her a ring :P

Great minds think alike! Lol...

 Take her for a nice spin....Show her the stars... and buy her a silver platter so she can see every cloud has a silver lining or you could just introduce her to the man in the moon!

  Seriously I honestly don't know....but could examining the core of the earth...shed any light on its age.. or perhaps the solar system?

ialways thought it was from rock and mineral samples so I assumed going deeper towards or into the center or core could answer how old the earth could be!
 

Offline chris

  • Neilep Level Member
  • ******
  • Posts: 5337
  • Thanked: 65 times
  • The Naked Scientist
    • View Profile
    • The Naked Scientists
How do we date the Earth?
« Reply #7 on: 11/04/2009 13:01:27 »
Take her out for a coffee at...Starbucks...!
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
How do we date the Earth?
« Reply #8 on: 11/04/2009 14:36:46 »
It's a very good question Chris and one that deserves a lot of attention.

Have we dated radioactive isotopes and rocks rather than the age of the earth?
 

Offline Karen W.

  • Moderator
  • Naked Science Forum GOD!
  • *****
  • Posts: 31653
  • Thanked: 5 times
  • "come fly with me"
    • View Profile
How do we date the Earth?
« Reply #9 on: 11/04/2009 15:02:51 »
Take her out for a coffee at...Starbucks...!

ummmmmmmm that would send her into orbit!

What about the samples of the core etc....
 

Offline RD

  • Neilep Level Member
  • ******
  • Posts: 8128
  • Thanked: 53 times
    • View Profile
How do we date the Earth?
« Reply #10 on: 11/04/2009 15:30:07 »
Have we dated radioactive isotopes and rocks rather than the age of the earth?

The isotope ratios tell when the rock solidified, so tell the age the surface of the Earth became solid.

Quote
These dating techniques, which are firmly grounded in physics and are known collectively as radiometric dating, are used to measure the last time that the rock being dated was either melted or disturbed sufficiently to rehomogenize its radioactive elements.
http://pubs.usgs.gov/gip/geotime/age.html


Quote
The oldest minerals dated so far by the U/Pb technique are zircons from Jack Hills in the Narryer Gneiss Terrane, Yilgarn Craton, Western Australia, with an age of 4.404 billion years, interpreted to be the age of crystallization.
http://en.wikipedia.org/wiki/Zircon
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
How do we date the Earth?
« Reply #11 on: 12/04/2009 04:23:08 »
Quote
The oldest minerals dated so far by the U/Pb technique are zircons from Jack Hills in the Narryer Gneiss Terrane, Yilgarn Craton, Western Australia, with an age of 4.404 billion years, interpreted to be the age of crystallization.
http://en.wikipedia.org/wiki/Zircon
So it could be possible that the Earth could have even older rocks right?
 

Offline RD

  • Neilep Level Member
  • ******
  • Posts: 8128
  • Thanked: 53 times
    • View Profile
How do we date the Earth?
« Reply #12 on: 12/04/2009 06:17:08 »
So it could be possible that the Earth could have even older rocks right?

Probably all of Earth's first (oldest) crust has been recycled by plate tectonics.

[Meteorites which have fallen to Earth since Earth's surface solidified would be older than any native Earth rocks].
« Last Edit: 12/04/2009 14:51:17 by RD »
 

Offline Yomi

  • Hero Member
  • *****
  • Posts: 548
  • HERE IN AM TO TAKE AWAY THE NOBEL PRIZE
    • View Profile
How do we date the Earth?
« Reply #13 on: 12/04/2009 14:03:15 »
BY Carbon dating process just as done for rocks .... Try carbon dating in the oldest rock.... ;D ;D
 

Offline _Stefan_

  • Hero Member
  • *****
  • Posts: 814
    • View Profile
    • My Photobucket Album
How do we date the Earth?
« Reply #14 on: 12/04/2009 14:41:30 »
Carbon dating is not used for materials over a certain age. The isotope ratios of other elements are used instead.
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
How do we date the Earth?
« Reply #15 on: 12/04/2009 15:20:01 »
Another question was asked on the forum: How long would it take with plate tectonics and erosion to completely eradicate all evidence of human existence.

A reply in the region of 3 million years. This timescale is a minute proportion of the highest estimation of the Earth’s age.

Along with humans, went rocks, concrete, iron, steel, stainless steel, glass, all vanished in an estimated 3 million years. (metaphorically speaking)

What, if any chance do we have of truly guestimating the age of the earth with any degree of accuracy ?

At best we have a minimum age for the Earth!

Andrew
« Last Edit: 12/04/2009 17:57:29 by Andrew K Fletcher »
 

Offline _Stefan_

  • Hero Member
  • *****
  • Posts: 814
    • View Profile
    • My Photobucket Album
How do we date the Earth?
« Reply #16 on: 12/04/2009 16:22:17 »
Would you care to cite evidence for what you have asserted? The geological record practically falsifies that claim.

The ability of radiometric dating to provide the approximate ages of materials is beyond reasonable doubt.
 

Offline Madidus_Scientia

  • Neilep Level Member
  • ******
  • Posts: 1451
    • View Profile
How do we date the Earth?
« Reply #17 on: 12/04/2009 16:42:06 »
lol @ Starbucks
 

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 6564
  • Thanked: 7 times
  • Moderator
    • View Profile
How do we date the Earth?
« Reply #18 on: 12/04/2009 18:16:13 »
Another question was asked on the forum: How long would it take with plate tectonics and erosion to completely eradicate all evidence of human existence.

A reply in the region of 3 million years. This timescale is a minute proportion of the highest estimation of the Earth’s age.

Along with humans, went rocks, concrete, iron, steel, stainless steel, glass, all vanished in an estimated 3 million years. (metaphorically speaking)

What, if any chance do we have of truly guestimating the age of the earth with any degree of accuracy ?

At best we have a minimum age for the Earth!

Andrew

Yes, we have a minimum age - about 4.5 billion years BUT this a very accurate age - (zircon crystals) and the other derivations of the Sun solar System as derived from energy expenditure budgets and the backward extrapolation of when the Sun could have originally been formed are very close to the zircon crystal date. The crystals leave no room for any "guestimating."

 

Offline Madidus_Scientia

  • Neilep Level Member
  • ******
  • Posts: 1451
    • View Profile
How do we date the Earth?
« Reply #19 on: 13/04/2009 18:22:26 »
BY Carbon dating process just as done for rocks .... Try carbon dating in the oldest rock.... ;D ;D

Carbon dating is used on things that were once living, it won't work on rocks.
 

Offline RD

  • Neilep Level Member
  • ******
  • Posts: 8128
  • Thanked: 53 times
    • View Profile
How do we date the Earth?
« Reply #20 on: 13/04/2009 21:39:18 »
Carbon dating is used on things that were once living, it won't work on rocks.

Minerals do contain organic ("once living") carbon, e.g. coal, limestone. The reason carbon dating cannot be used on them is the half life of Carbon14 (@ 5700 years) is too short compared with the age of the rock (e.g. coal @ 300 million years): there is no longer a measurable level of Carbon 14 in them.
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
How do we date the Earth?
« Reply #21 on: 14/05/2009 19:37:22 »
So how do we jump from a minimum age to a maximum age based only on the samples examined?

 

The Naked Scientists Forum

How do we date the Earth?
« Reply #21 on: 14/05/2009 19:37:22 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums