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"Everybody knows" that Newton and Kepler calculated the age of the earth. My problem is that, whilst "everybody knows" this, no-one gives a reference that I can read for myself.

If, for example, I want to read what Thomas Burnett believed, I download a copy of Telluris Theoria Sacra and I can read for myself that he accepted the reality of Noah's flood. The same is true of St Augustine's beliefs as there are several online translations of City of God Against the Pagans.

But Newton and Kepler?

Zilch. Sweet F.A. Absolutely nothing.

Even when a website references a text, either I can't find the text, or there is no age-of-the-earth calculation in the text that I can find.

So, did either Newton or Kepler calculate the age of the earth, or is this just an urban myth? If it's true, does anyone have references that I can look at for myself. These will have to be secondary references (English translations) as I expect the actual primary reference to be in Latin, and sadly, I only read English.

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    $\begingroup$ This question would probably be a better fit for either SE History or SE History of Science & Mathematics. $\endgroup$ – Fred Oct 24 '19 at 15:34
  • $\begingroup$ I'm happy for you to move it to either of those sites if you think it would get more appropriate attention. $\endgroup$ – Barry Stone Oct 24 '19 at 16:06
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Your question may be better suited to either SE History or SE History of Science and Mathematics. The date of the so called creation of the Earth has nothing to do with Earth Science.

For Kepler I found he wrote the book KANONES PUERILES, in it he calculates the creation date to be 27 April 4997 BC.

The published works of Newton reveal little. Some authors on Newton mention an unpublished document he wrote in either 1704 or 1705. Any calculations he may have done regarding the so called date of creation may be in his unpublished writings.

You may need to review the bibliographies of authors who wrote biographies on Newton, such the 1855 book by Sir David Brewster, Memoirs of the Life, Writings, and discoveries of Sir Isaac Newton, volume 2.

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  • $\begingroup$ Fred, thanks for taking the time to reply. Unfortunately, it tells me that this is not going to be a simple quest. Before I posted the question I had already seen and dismissed the first web page you reference because I can't find any usable link to Kanones. I have now downloaded a pdf of Memoirs from Internet Archive and I need to trawl through that, but I'm not hopeful given that the webpage itself didn't reference any calculation. If the calculation is in unpublished writings, I will need to go down the traditional route of library access to original works, which is a major task. $\endgroup$ – Barry Stone Oct 24 '19 at 16:24
  • $\begingroup$ @BarryStone: I don't envy you, good luck! ;-) $\endgroup$ – Fred Oct 24 '19 at 16:32
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I have never heard that Newton or Kepler calculated the age of the Earth, so I think it is most probably an urban myth. What I can tell you is that if they did any such calculation it must have been hopelessly inaccurate. In the 17th century, Archbishop Usher calculated the age of the Earth from Biblical sources and decided it was about 6,000 years old. In the mid-nineteenth century, Lord Kelvin, an eminent physicist, made a calculation based on how long it would take to cool down to its present temperature from an incandescent state, and came to the conclusion that it was about 100,000,000 years old.

Although he did better than Archbishop Usher, the reason for Lord Kelvin's inaccuracy was that in his day the atom and radioactivity were a closed book, so he couldn't take radioactive decay into account when doing his calculations. Radioactive decay not only keeps the Earth's interior hot, but enables us to measure the age of the Earth with reasonable accuracy. The decay of uranium to lead in zircons from very ancient rocks tells us that the Earth is about 4.5 billion years old.

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    $\begingroup$ Today on Google Books, I found "How old is the universe" by David Wientraub, Page 14 states that . Isaac Newton's "Chronology of Ancient Kingdoms: Amended" contains Newton's calculation of creation to 3998 BC, I have now ordered the book by Wientraub and found "Chronology" on Internet Archive. (If Newton's date of creation is in Chronology, it's well hidden). But assuming I can find the actual calculation, that still leaves Kepler. Even Wientraub doesn't give a reference for Kepler's calculation. He just states that Kepler's date for creation was 3993 BC. Any suggestions? $\endgroup$ – Barry Stone Oct 25 '19 at 15:39
  • $\begingroup$ I told you it would be hopelessly inaccurate. Kepler's was probably Biblical. $\endgroup$ – Michael Walsby Oct 25 '19 at 17:49
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    $\begingroup$ According to Wientraub, Kepler's calculation was a mixture of astrophysical calculation (unsurprising given how much time he had spent working out his eponymous laws) and some groundless assumptions about where the earth would have been when God created it (apparently, at solar apogee and in the constellation of Aires. Don't ask!). I have emailed Weintraub to ask him about both Kepler's and Newton's calculations. (Newton's Chronology is 400 pages of numerical gibberish). I have no idea if Wientraub will respond, but if you don't ask... $\endgroup$ – Barry Stone Oct 25 '19 at 19:15

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