The third, which by the end was the most acute, presented a problem that outlasted the controversy itself. He did not need to wait long. In Sir Arthur Eddington came up with the answer: the fusion of hydrogen into helium. One referred to the depth of the sediments and the time they would have taken to accumulate; the other referred to the salinity of the oceans, compared with the rate at which rivers are supplying them with sodium salts.
In hindsight, both theories were deeply misguided, for similar reasons. They assumed that current rates—of sediment deposition and of salt transport by rivers—were the same as historical rates, despite the evidence they had that our own age is one of atypically high geologic activity. Worse, they measured inputs but ignored outputs. The rock cycle, as we now know, is driven by plate tectonics, with sedimentary material vanishing into subduction zones.
And the oceans have long since approached something close to a steady state, with chemical sediments removing dissolved minerals as fast as they arrive. Nevertheless, by the late 19th century the geologists included here had reached a consensus for the age of the earth of around million years.
Having come that far, they were initially quite reluctant to accept a further expansion of the geologic timescale by a factor of 10 or more. And we should resist the temptation to blame them for their resistance. Radioactivity was poorly understood. Different methods of measurement such as the decay of uranium to helium versus its decay to lead sometimes gave discordant values, and almost a decade passed between the first use of radiometric dating and the discovery of isotopes, let alone the working out of the three separate major decay chains in nature.
The constancy of radioactive decay rates was regarded as an independent and questionable assumption because it was not known—and could not be known until the development of modern quantum mechanics—that these rates were fixed by the fundamental constants of physics.
It was not until , when under the influence of Arthur Holmes, whose name recurs throughout this story the National Academy of Sciences adopted the radiometric timescale, that we can regard the controversy as finally resolved. Mobile Newsletter chat subscribe.
The Solar System. How old is planet Earth? People have been trying to figure that out since, well, since the beginning of time. Now That's Interesting. According to NASA , the sun is a yellow dwarf star. It's a hot ball of glowing gases and its gravity is responsible for holding the solar system together. How many more years will Earth survive?
Scientists suggest that in about 7. Therefore, the AIG argument that we do not know that decay rates are constant demonstrates a profound misunderstanding of empirical data and mathematical relations that describe the natural world around us. In fact, they completely disregard the many different types of dating techniques scientists use that each confirm one another.
For instance, other forms of absolute dating exist such as tree ring counting, thermoluminescence, electron spin resonance, and many other different types of radiometric techniques. I encourage you to explore these techniques here and understand this for yourself. Each technique demonstrates the earth is much older than 6, years old and when combined with the various different techniques of relative dating using rock strata and formations, it becomes apparent that we have solid scientific evidence that the earth is much older than what AIG thinks.
To further demonstrate how flawed their argument is, I will introduce one other aspect of their argument against using scientific methods to determine the age of the earth. Scientists also must battle an issue called the Great Unconformity, which is where sedimentary layers of rock appear to be missing at the Grand Canyon, for example, there's 1. There are multiple explanations for this uncomformity; in early , one study suggested that a global ice age caused glaciers to grind into the rock , causing it to disintegrate.
Plate tectonics then threw the crushed rock back into the interior of the Earth, removing the old evidence and turning it into new rock.
In the early 20th century, scientists refined the process of radiometric dating. Earlier research had shown that isotopes of some radioactive elements decay into other elements at a predictable rate. By examining the existing elements, scientists can calculate the initial quantity of a radioactive element, and thus how long it took for the elements to decay, allowing them to determine the age of the rock.
But rocks older than 3. Greenland boasts the Isua supracrustal rocks 3. Samples in Western Australia run 3. Research groups in Australia found the oldest mineral grains on Earth. These tiny zirconium silicate crystals have ages that reach 4. Their source rocks have not yet been found. Meanwhile, scientists have also found 7-billion-year-old stardust on Earth. The rocks and zircons set a lower limit on the age of Earth of 4.
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