Some Theory...

[Guest Yoshmaista]

I remember my Chemistry teacher telling us about a theory the other day (I'm in Chem I, just started, and we were doing radioactive decay). Started with a Z, and basically said nothing can ever totally reach another destination, or in the case of radioactive materials fully decay, because you're always halving distance, or the appropriate factor, and nothing halved=0. Had to do with half-lifes...anyways...help?

[jadote]

I don't know of any theory, but a graphing amount of material as a function of time would yield an exponential (decay) function. As time increases, the amount would get closer and closer to zero but never reach it.

 

 

http://library.tedankara.k12.tr/chemistry/vol1/nucchem/trans91.htm

[greg1917]

I dont quite see how that applies to the real world though.

 

In a mathematical sense it will continue for ever, but when dealing with a radioactive sample, the sample will eventually all decay. It might take a long time, but surely when there were only 4 atoms left to decay, after a half life there would then be 2, then 1, then eventually that atom would randomly decay. ie not go on forever.

 

Granted when it gets down to such small numbers of atoms then it may not strictly follow the actual half life value because any instance of decay is random, but the sample cant go down to 0.5 atoms, then 0.25 atoms, then 0.125 atoms.

[jadote]

I've seen that there are two answers for that. I heard that engineers would answer the amount would get so small we couldn't measure it anymore, and physicists would answer the amount would continue to halve until only a few atoms remained which would randomly disperse.

 

In other words, yeah, you're right.

[Ms. DNA]

The theory Yoshmaista is talking about is one of Zeno's paradoxes. Zeno was a Greek philosopher. You can learn more abut him and this paradox here:

 

http://www-gap.dcs.st-and.ac.uk/~history/Mathematicians/Zeno_of_Elea.html

[Guest Yoshmaista]

Thanks! Exactly what I was lookin for DNA .

[Radical Edward]

as has been pointed out, that idea is called Zeno's paradox. However I think it needs to be pointed out, that with regards to radioactive decay, it is only an approximation (albeit a fairly good one) for a couple of reasons. Firstly for detection purposes, once the levels of a material drop far enough, they will be drowned out by the background radiation. This is why things like carbon dating only work back to a few tens of thousands of years. Secondly, atoms only exist in integer quantities. You can't have a fraction of a uranium atom. once a uranium atom decays, it is not uranium anymore.

[fafalone]

If you have a single atom in an isolated system where decayed particles are not allowed to react; eventually you will indeed have nothing but pure energy. p+/e-/n all will decay eventually... even photons are believed to decay.

[Crash]

what? including all anti-particles?muons,pions and all those groups