PART I (continuation) Let me refresh your memory on one of the most popular joke in the 90’s re boy/girl dating. GIRL: Laro tayo ng ‘hide and seek’. Pag nakita mo ako, magpapahalik ako sa iyo. BOY: Eh, papano kung hindi kita makita? GIRL: Nasa likod lang ako ng piano. :) There are many methods of absolute dating (not an iota of the kind above ha) but to serve the purpose of the topic I am discussing presently, I’ll explain (briefly Marcela, peksman!) the process of radiometric dating. Radiometric dating is a powerful tool in reconstructing our planet’s history. The invention of mass spectrometer led to the discovery of isotopes and the calculation of accurate decay rates. We learned in 6th grade that atoms are composed of nucleus of a nucleus orbited by negatively charged electrons. The nucleus is made up of protons with a positive charge, and neutrons, particles with no charge and we all looked up the ceiling and wondered what the #*%^ our teacher was talking about?! In high school, we learned that every atom of a given element has the same number of protons in the nucleus and we again looked up and sighed, “What now?”. In college, we learned that each element may have one or more isotopes. Different isotopes of a given element have the same number of protons but a different number of neutrons and we all said, “Ah...Aha!”, and still don’t get it. And so, to understand those things, I entered the seminary, studied English Literature, went out, and ended up to become a lawyer. The end. Joke, joke, dyowwwwk!! Radioactive elements are unstable atoms that give off particles. Emitting these particles transforms the unstable atoms into different, more stable elements. It is called radioactive decay, and it occurs AT A CONSTANT RATE specific to each isotope of each element. The original radioactive material is called the parent; the stable product is called the daughter. The rate of decay is described by the hal-life of the isotope - the average time an atom of a radioactive element remains in the parent state. When the half-life has elapsed, half the parent element will have decayed into the daughter element. For example, Potassium-40 decays into Argon-40 with a half-life of 1.25 billion years, so that after 1.25 billion years half of the K-40 in a rock will have become Ar-40. That means that if a rock sample contained equal amounts of K-40 for every one atom of Ar-40, it would be 1.25 billion years old. If the sample contained three atoms of K-40 for every one atom of Ar-40, it would be 625 million years old and if it contained one atom of K-40 for every three atoms of Ar-40 it would be...c’mon my friends!...help me here!...1.875 billion years old. Whew!! (to be continued)
Posted on: Sun, 18 Aug 2013 19:58:05 +0000
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