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How do you prove the earth is old in the easiest way possible? If you decide to go with atom decomposition, you have to also be able to show the decomposition rate and the exponential law which describes it. I don't want to calculate its exact age, but prove it is at least as old as 10000 years. A few million years would be nice.

I don't want the historical way of proving it, I want the easiest, just as the Foucault pendulum is the easiest way to prove the earth rotates on itself, even though it was shown centuries earlier by heliocentricism, which was derived from planet trajectories. I don't think the various atom dating techniques are the best way to do it.

I don't mind people editing my question but please keep its original meaning.

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closed as too broad by Kyle Kanos, heather, John Rennie, JamalS, Jon Custer Jan 1 '17 at 5:22

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ Problem is that these arguments aren't going to work with the people who think the Earth is < 10Kya old $\endgroup$ – Martin Beckett Dec 30 '16 at 20:25
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    $\begingroup$ en.wikipedia.org/wiki/… $\endgroup$ – Count Iblis Dec 30 '16 at 20:30
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    $\begingroup$ Probably related: physics.stackexchange.com/q/154588. but, IMO, this is not really a physics question. On top of that, any method of showing earth's age is valid & hence is too broad on top of being primarily opinion based $\endgroup$ – Kyle Kanos Dec 30 '16 at 20:34
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    $\begingroup$ You could do a back-of-the-envelope calculation to show just how improbable it is that human life could have evolved from inorganic matter in less than 10000 years. $\endgroup$ – WillO Dec 30 '16 at 21:50
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    $\begingroup$ @WillO The people I want to prove it to are not really into evolution. $\endgroup$ – user5751924 Dec 30 '16 at 22:00
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I doubt if this is a physics question, at least directly, but the physics response might be:

Look at the moon and the worn, smoothed surface craters on it, with the very slow rate of erosion of the lunar surface, these craters must have been formed a long time ago.

The moon has been in orbit around the Earth a long time, as the tidal effects have created the small grains of sand that make up the beaches. That took a while.....

We don't see very many obvious craters on Earth because of weathering processes and ocean coverage, except for comparatively rare examples, such as the well known Barringer crater in Arizona.

There are lots of other examples, but I have a feeling from your post that you may have issues with the accepted age of the Earth, so please tell me if you have any objections to the above.

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    $\begingroup$ Those are good points. I don't have any issues with the age of the earth, but I would like to convince my grand mother. And atom isotopes didn't work, especially since I can't really put a single radon atom in her hands and say "look, it has a half life of a few billion years and the concentration of this isotope is constant in the center of the earth " . This is why I need a kind of Foucault pendulum $\endgroup$ – user5751924 Dec 30 '16 at 20:20
  • $\begingroup$ Your granny won't accept anything you say on this subject. If she's got to this stage of her life without believing science over religion, she won't change now. And maybe if you convinced her you'd be doing more harm than good, as it might erode what comfort her beliefs give her at a time of her life when they're rather important. I'd say let it slide for the greater good. $\endgroup$ – StephenG Dec 30 '16 at 22:42
  • $\begingroup$ "We don't see very many obvious craters on Earth ... except for the well known Barringer crater". That's because the Earth was created 6020 years ago. The Moon was created the day before, complete with eroded craters. Seriously, @user5751924 , where do you or your granny live? I'm in a Rocky Mountain valley where you can find pieces of coral reef in a landslide on top of glacial debris. Is there evidence like that where you live? $\endgroup$ – Keith McClary Dec 31 '16 at 6:13
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Grandma is likely to be familiar with a map of the World, so you can explain that the continents used to be part of a single super-continent and that you can still see that from the shapes of the current continents, e.g. South America fits well into Africa. The typical rate of a few centimeters per year at which continents drift away from each other is well known but you must then build your argument around this rate. The goal is then to make plausible that it is of the order of a few centimeters per year and not many hundreds of meters per year.

We can read here:

The rate of plate movement along the San Andreas fault, 33 millimeters (1.3 inches) each year, is about how fast your fingernails grow. As a result, Los Angeles City Hall is now 2.7 meters (9 feet) closer to San Francisco than when it was built in 1924.

Now if instead of 33 millimeters per year, the movement were of the order of hundreds of meters per year, then Los Angeles would have moved tens of kilometers closer to San Fransisco and roads would buckle and would be in need of repair constantly.

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