It's because of this urban legend that has gone around forever.
Based upon this rule, the only time that a man can date a woman his own age is when he's 14 years old (because half of 14 is seven, and seven plus seven is 14).
Groundwater recharge is often difficult to quantify because of its spatial and temporal variability and because of the challenges of measuring it directly.
However, recharge estimates are an important component of water budgets developed to accurately assess groundwater availability.
Radioactivity was discovered in 1896 by French physicist Henri Becquerel.
By 1907 study of the decay products of uranium (lead and intermediate radioactive elements that decay to lead) demonstrated to B. Boltwood that the lead/uranium ratio in uranium minerals increased with geologic age and might provide a geological dating tool.
As radioactive Parent atoms decay to stable daughter atoms (as uranium decays to lead) each disintegration results in one more atom of the daughter than was initially present and one less atom of the parent.
The probability of a parent atom decaying in a fixed period of time is always the same for all atoms of that type regardless of temperature, pressure, or chemical conditions. The time required for one-half of any original number of parent atoms to decay is the half-life, which is related to the decay constant by a simple mathematical formula.So the ripe old age of 14 -- the age when you still have pimples, are as insecure as can be and are unlikely to get anything more than a kiss from a woman your own age -- is the only time when you can enjoy dating a woman your own age? Add seven to that, so you can date a 12-year-old -- an older woman"?What about if your 10-year-old looks at you and says, "I'm ready to date, Dad"? There is so much a 12-year-old can teach a 10-year-old -- advanced coloring, advanced texting, and so many other important life skills. You're 20 years old and, under this rule, you can date a 17-year-old. There you are in college, and you get to go back to high school again to find a girlfriend.The number of parent atoms originally present is simply the number present now plus the number of daughter atoms formed by the decay, both of which are quantities that can be measured.Samples for dating are selected carefully to avoid those that are altered, contaminated, or disturbed by later heating or chemical events.Nevertheless, there is substantial evidence that the Earth and the other bodies of the Solar System are 4.5-4.6 billion years old, and that the Milky Way Galaxy and the Universe are older still.