It reminds me of the same question asked in this book, "The Birth of Time: How Astronomers Measured the Age of the Universe" by John Gribbin. The bottom line wa

It reminds me of the same question asked in this book, "The Birth of Time: How Astronomers Measured the Age of the Universe" by John Gribbin. The bottom line was that the calculations always have some approximations, which can throws off a number by a large factor.