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A simple question about radioactive decay

by dmehling
Tags: decay, radioactive, simple
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basheer uddin
#19
Apr30-14, 11:44 AM
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this may be helpful
http://www.britannica.com/EBchecked/...t-of-half-life
https://hps.org/publicinformation/ate/q8270.html
jtbell
#20
Apr30-14, 11:05 PM
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I'd like to remind everybody about Zz's comment:

Quote Quote by ZapperZ View Post
And before this thread gets into trouble, I will warn that the topic MUST be on physics and not divert to opinion about your own beliefs.
I see this as including both pro- and anti- "young earth creationism" comments. We don't get into those sorts of discussions here, nor discussion of religious beliefs in general.

I've deleted some posts accordingly.
sophiecentaur
#21
May1-14, 04:36 AM
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Quote Quote by jtbell View Post
I'd like to remind everybody about Zz's comment:



I see this as including both pro- and anti- "young earth creationism" comments. We don't get into those sorts of discussions here, nor discussion of religious beliefs in general.

I've deleted some posts accordingly.
It has to be OK, as long as the word "Creationism" is not used, surely, or we could not discuss anything involving periods of time greater than a few thousand years. It is a difficult path to steer. I have to admit, if PF is to avoid becoming like a thousand other sites.
abitslow
#22
May1-14, 09:54 AM
P: 140
{Edit: abitslow: I have edited the formatting of your post to add blank lines and quotes to make it easier to read. Please consider using these in future posts. Otherwise, your post looks like one big lump of a continuous paragraph. - Zz.}

If it takes 4.4 billion years for uranium-238 to decay into thorium-234...
This is wrong. As already said, but perhaps in a way that is not clear and plain enough.

This is equivalent to saying that since the average life expectancy is 80 years, then it will take Bob 80 years to die. A particular atom of U-238 may decay now, may decay in 10 years, or 1000 or 1,000,000 or 100,000,000,000,000,000,000. All half-life can talk about is the average for a (large) group of atoms.

If you do the math for a mole of U-238, that is 6E23 atoms, from the calculation it is apparent that measuring a sample for a couple of minutes will give you a very good statistical average. ( Assuming that the probability of decay is constant, it is a simple matter to determine what half life is for atoms with half-lives well into the billions of years (given enough of a sample).).

I don't understand why many of the posts haven't been removed for being off topic and not Physics, but I want to point out that you are unlikely to have a better shot at undermining the science about deep (pre)history as the top scientific minds that the Vatican has thrown at the same question. It is good that you are questioning it, as you will see that there are several assumptions about the constancy of the Laws of Physics over time, and their independence from other influences. It is virtually certain that you will discover nothing new here by analysis of the known facts, too many great minds have already tried that. It is possible that by going out and gathering NEW facts (or recognizing the applicability of 'unrelated' facts) you will advance the science. Go get 'em, tiger!


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