Question:
Was not the uranium 238 here on Earth with a half-life supposedly of 4.47 billion years created during the supernovae of a previous first generation star? That would seem to mean that it first started decaying right after the explosion and all during the reassemblage of the nebulae material that formed the Sun and planets(no matter if it were from slow self amalgamation or helped along with nearby blast waves of other early supernovae). This "accretion time" has to be taken into account. This yet unknown accretion time is vital in trying to find the age of the Earth itself in my opinion. If the Uranium 238 was decaying for a billion years or more in the pre-solar nebulae for example, would we not have to alter the age minus a billion years. Lord Kelvin may have not considered radioactivity in his famous thermodynamical approximation of earth but I think we are ignoring the importance of accretion time of the pre-solar system nebulae. What sayeth the radiomectrically dated zircons?
Answer:
The problem is that we're not 100% sure when uranium was created nor it's relationship to when the universe was created. But you can use elements as an example of how long they have been around. Plus it's also possible that uranium is being created by the nuclear decay of Polonium. The theory is sound, but has many holes in it.
In 4.47 billion years, half of the original U 238 would be Pb 206. Radiometric dating relies on comparing the total of the Uranium to the total of the Lead in a sample that has not lost any of either element to anything other than the U-Pb decay. Both of these elements are reasonably easily disturbed and accretion would undoubtedly be less than ideal for maintaining a parent/daughter ratio that would allow for accurate radiometric dating. So any radiometric dating could only show an age younger than the last disturbance (such as Earth's accretion) that could cause loss of uranium or lead from the sample.
At least that's how I understand it.
More Questions & Answers...
I want to make a solar panel. How?
Was the "STEREO" Solar satellite successfully launched by NASA recently? When will it send back data?
3x Solar V10i alarms?
Will we humans ever travel out of our solar system??is it possible r just for movies?
Landscape lighting - hard-wired electrical vs solar-powered?
How does the use of solar power alleviate our dependence on fossil fuels?
Where can i get the number and names of the moons for our solar system?
Solar energy?