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Age of Earth, evidence

  1. Dec 30, 2005 #1
    What are the methods currently being used to date the earth and/or universe?

    I was talking to a buddy and he was on a role about 10,000 and the age of the earth and the unreliability of carbon dating.

    What are some of the methods now being used?

  2. jcsd
  3. Dec 30, 2005 #2


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  4. Dec 30, 2005 #3
    Carbon dating is no good, for sure. Its half life is only a few thousand years, so it is not accurate after many half lives are gone. Plus its only for bio material.

    Other things can be used:

  5. Jan 3, 2006 #4
    It appears that most everything is based on radioactive decay or other types of decay. Is there any other approaches that would come from a totally different direction?

  6. Jan 3, 2006 #5
    Most methods of dating the Earth come from radiometric dating or something that has to do with half-lives, radioactive decay and isotopes. Radiometric dating is reliable, accurate and about the only methods that can go back far enough.

    There are shorter-span dating methods that focus on thousands of years rather than millions. Ice core dating looks at seasonal variations in ice layers. They drill up core samples from glaciers, Antarctica and Greenland.

    There is varve sediment dating, which involves examining seasonal variations in sediment deposited underwater. Sediment from summer and sediment from winter look different you see. For example, seeds and organic materials from spring can be taken away by rivers to be deposited on a lake bed. When the summer or winter comes, pollination does not occur. Meaning we have an absence of seeds. With variation within seasons, we can date the varves (that's what we call the sediments).

    And dendrochronology. Examining tree rings. Or examining coral growth. In fact, there are many dating methods. We mostly use these shorter-span methods for verifying and double-checking radiometric dates.
    Last edited: Jan 3, 2006
  7. Jan 4, 2006 #6
  8. Jan 4, 2006 #7
    I'm not an expert at physics, but couldn't we rougly approximate the age of the Earth by the age of the sun? Is there anyway a special telescope built especially for this could catch some type of background/reflection of the sun's light? Wouldn't this be a good starting point? Then as technology advances we could detect the reflection of the reflection of Earths reflected light? Anyone follow me?
  9. Jan 8, 2006 #8
    What about dating in terms of the overall universe, using Einstein's theory of Relativty and other methods similar to this

  10. Jan 31, 2006 #9
    Hi Nautica,

    Thought this looked interesting so I thought I would add mythoughts...

    - Radiometric dating is not inaccurate. Individual readings maybe be false for various reasons but the vast majority of readings are consistent with each other and with the idea that the earth is about 4.5 billion years old. The links above should give all you need on that.

    - The age of the universe is relatively simple to determine. Edwin Hubble observed that everything in the universe seems to be moving away from us and that the speed with which they are moving away is directly proportional to the distance that they are. This means that at some point in the past, all objects were in the same place. Dividing the distances by the speed tells you the time it has taken to reach the present situation. This seems to be about 13/14 billion years which is more or less consistent with the age of the oldest things in the universe.

    In practise, the age of universe calculations are rather difficult due to the precision of the observations that need to be made, nonetheless it is likely that the Universe age is approximately right.

    - When someone suggests the Universe is less than 10,000 years old, I find it useful to invite them to look into the sky at night. They will see stars. Many stars are tens of thousands of light years away. With a telescope you can see objects that are millions of light years away. That means it has taken millions of years for the light to reach us. Thats it - Young Universe theory dead - as far as i know there is no sensible come back from this.
  11. Jan 31, 2006 #10
    The guys out in the oil patch can date the age of a patch of oil using geological data. There are layers to the lithosphere, (earth's crust) that indicate geological events and other events that can provide benchmarks for dating the age of a feature.

    There are many ways to date things. Imagine the physical length of time it takes to form a crystal... then calculate the period of time during which it was formed and what layer of the lithosphere it is found to reside.

    Let's examine another method. How deep is the layer that indicates the entire earth was on fire because of an impact by a large meteor or asteroid? It has been determined by dating the layers of the earth that the last cataclysmic event like that took place 65 million years ago... according to the positioning of the layer of specific ejecta and crispy, burnt sediments.

    We could also count the rings on petrified wood. How long does wood take to be petrified and how long was the wood alive before beginning the petrification?

    These are just some of the considerations that lead to the answers concerning the age of certain things. There are no birth certificates or videos of birthdays for this sort of examination. But mother nature does keep a record.
  12. Feb 1, 2006 #11
    The other day I was looking into dynamo theory, and I realized that as the Earth cools, the magnitude of the magnetic field should decrease. I know that as lava cools, the little bits of iron align themselves in the direction of the Earth's magnetic field. If the magnitude of the magnetic field is also recorded in the rocks, we could use the paleomagnetic record as another approximate method of dating given the following assumptions:
    • We can obtain the magnitude of the Earth's magnetic field from ancient rocks
    • The strength of the magnetic field is proportional to the Earth's temperature
    • We know the rate at which the Earth is cooling

    Does anything like this exist?
  13. Feb 1, 2006 #12
    Top google result for "paleomagnetic record":

  14. Feb 1, 2006 #13
    Is being done as we speak, continuously all over the world.

    Life isn't that easy. There is a very hot planet with no magnetic field and a cool one with a weak but distinct magnetic field. The magnetic field is thought to be generated by convection currents in the fluid outer core. The several convection cells are assumed to counter rotate generating opposite magnetic fields that mostly cancel each other. The Earth magnetic field being the resultant vector. But a little change (chaos) in the convection cells and the direction of the magnetic field may go astray and even reverse.

    Yes but it's irrelevant. There is also heat being generated in the Earth inner core.
    Last edited: Feb 1, 2006
  15. Feb 17, 2006 #14


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    Good summary on determining the age of the universe...

    getting down toward the bottom line...
  16. Mar 14, 2006 #15
    There are several methods of dating fossils; differing methods sometimes don't agree with each other, and we have to use a little common sense. That's where it gets a little tricky. Let's say an artifact is from a layer indicating an age of 3 million years, and carbon and other isotopic dating methods agree that it is 3 million years old, other fossils in the same dig support the idea that it is 3 million years old, and other empirical data indicate that it is 3 million years old, but the molecular clock, which assumes that pigs evolved at a constant rate for the last 10 million years, says it is 1.9 million years old, and the theory you're trying to prove says it should be 1.9 million years old, go with the molecular clock.
    That's how several items in the archaeological record got their dates. Unfortunately, once an artifact has been dated, no matter how inaccurately, those of us with a different theory have a devil of a time arguing that the date which is more consistent with the majority of the evidence should be used.
  17. Mar 14, 2006 #16
    Magnetic Dating (no, not going to the movies with a magnet)


    Magnetic dating! Who woulda thought!? This article explains the technique well with diagrams etc...... its based on the fact that the magnetic poles reverse periodically... read the article!
    Last edited: Mar 14, 2006
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