Confused1
From Wikipedia:-

Naturally occurring uranium is composed of three major isotopes, uranium-238 (99.28% natural abundance), uranium-235 (0.71%), and uranium-234 (0.0054%). All three isotopes are radioactive, creating radioisotopes, with the most abundant and stable being uranium-238 with a half-life of 4.4683×109 years (close to the age of the Earth), uranium-235 with a half-life of 7.038×108 years, and uranium-234 with a half-life of 2.48×105 years.

1/ Can we assume there was no preference to form any particular isotope? - leading to the conclusion that the isotopes were originally present in equal proportion?

Can we remember how to use the half-life to get the date of formation based on the assumption made in 1/ ?

The second isotope should give a check on the validity of the assumption made in 1/ .. so all we need is some maths.

Time passes.

-C2.

Confused1
No players so far .. OK

Where T is the time elapsed and t is the half-life
N is the starting number of atoms and n the finishing

n=N(1/2)^(T/t)

log(n)=log(N) + log[(1/2)^(T/t]
log(n)=log(N) + (T/t)log(1/2)
log(n) - log(N) = (T/t)log(1/2)
T=t[log(n) - log(N)]/log(1/2)

There is usually a mistake .. we shall see ..
All we need now is a calculator.

-C2.

Lasand
Confused1
Thanks for that.

QUOTE

This 'single stage' is, however, an oversimplification. In fact, multiple supernovae from over 6 billion to about 200 million years ago were involved. Additionally, studies of the isotopic abundances of elements, such as silicon and carbon in meteorites, have shown that more than ten separate stellar sources were involved in the genesis of solar system material. Thus the relative abundance of U-235 and U-238 at the time of formation of the solar system:

Interesting to see what can be inferred from relatively simple observations.

-C2.
demon00seven
I've read somewhere that Uranium is very precious metal and can be used in exploding materials, is it true, then the use of this metal or whatever should be under proper check. What you think Scientific people.
zhikim528
The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 75 percent hydrogen．
Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well． Helium has been found in old stars， in relatively young ones， in interstellar gas， and in the distant objects known as quasars． Helium nuclei have also been found to be constituents of cosmic rays that fall on the earth （cosmic “rays” are not really a form of radiation； they consist of rapidly moving particles of numerous different kinds）． It doesn’t seem to make very much difference where the helium is found． Its relative abundance never seems to vary much． In some places， there may be slightly more of it； in others， slightly less， but the ratio of helium to hydrogen nuclei always remains about the same．
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