Yes, many of our friends are now multi-millionaires from stock options during the dot com boom in their 20s, and we wasted that time in graduate school when we could have been getting ridiculously wealthy. Butв I have a good life now. I have mad skillz. Being a professor is a lot like being productively retired in that you work all the time on stuff you love doing that makes the world a better place.
And I certainly would not want to be having babies during graduate school in my 30s when I could be done with graduate school in my 20s. It is also extremely unlikely that I would have had the earnings potential with my liberal arts degree that I have with my technical PhD, even taking into account compounding lets keep in touch dating what I could have made while in grad school from what I actually madeв. As for working full-time while getting a PhD, you are not going to get out of a top 5 graduate school in 5 years while working full-time.
And many scholarships preclude working more than part-time for the program itself.
Carbon is distributed throughout the atmosphere, the biosphere, and the oceans; these are referred to collectively as the carbon exchange reservoir,  and lets keep in touch dating component is also referred to individually as a carbon exchange reservoir.
The different elements of the carbon exchange reservoir vary in how much carbon they store, and in how long it takes for the 14 C generated by cosmic rays to fully mix with them. This affects the ratio of 14 C to 12 C in the different reservoirs, and hence the radiocarbon ages of samples that originated in each reservoir. There are several other possible sources of error that need to be considered. The errors are of four general types:. To verify the accuracy of the method, several artefacts that were datable by other techniques were tested; the results of the testing were in reasonable agreement with the true ages of the objects.
Over time, however, discrepancies began to appear between the known chronology for the oldest Egyptian dynasties and the radiocarbon dates of Egyptian artefacts. The question was resolved by the study of tree rings: Coal and oil began to be burned in large quantities during the 19th century.