isotope
You want to keep your brain healthy and not slip into dementia in your old age? Read stuff that fascinates and challenges you. That’s my strategy. This is from ‘Life’s Engines How Microbes Made Earth Habitable’ by Paul G. Falkowski.
“A chemical element is defined by the number of positively charged particles, protons, in the nucleus of its atom.”
Ok, I got that I think. I’m ready to go on.
“An isotope contains more or fewer neutrons relative to the number of protons. Neutrons have no charge, but they function as the ‘glue’ in the nuclei of atoms, keeping the protons from repelling each other.”
Wow, I did not know that although I had head the word ‘isotope’ before. This is an isotope of that and such what . . .
“Every element has several isotopes. For example, carbon contains six protons. The most abundant isotope of carbon contains six protons and six neutrons and therefore is denoted carbon-12. But there is also an isotope of carbon that contains six protons and seven neutrons (carbon-13), and one that contains six protons and eight neutrons (carbon-14). The former is stable—that is, it exists indefinitely; the latter is radioactive, that is, one of the neutrons decays to become a proton, thereby forming nitrogen-14, which is stable and exists indefinitely. When a neutron in carbon-14 decays to become a proton, the atom simultaneously emits a negatively charged particle, an electron, which is often called a beta particle. The emission of beta particles can be detected very accurately and so can be used for determining the abundance of carbon-14 in the original material. The half-life of carbon-14 is approximately 5700 years; that is, after about 5700 years one-half of the carbon-14 atoms in a population will have become nitrogen-14.”
I had to read that twice. Ok make that 3 times. It seems that nitrogen 14 is derived from carbon 14 when it loses a neutron due to radioactive decay.
“The radioactive decay of carbon-14 potentially allows dating of materials that contain carbon, for example in bones, teeth, wood, and so on. But after tens of thousands of years, virtually all the carbon-14 will have decayed, and the signal will be too weak to be useful for dating materials. Coal and petroleum, which were formed many millions of years ago, no longer have any detectable carbon-14; they are much older than several half-lives of the radioactive isotope. Fortunately, however, there are other naturally occurring radioactive isotopes with half-lives of hundreds of millions, even billions, of years. Two of these are isotopes of uranium: uranium-238 and uranium-235.
These two natural isotopes of uranium were formed in a very hot, very short-lived star that exploded, called a supernova, that gave rise to our solar system long before our star, the Sun, began to shine. The uranium isotopes were incorporated into meteorites as our solar system was formed. Uranium-238 has a half-life of 4.46 billion years, while that of uranium-235 is 704 million years. Ultimately these two isotopes decay to two different, stable (nonradioactive) isotopes of lead.”
Now I get it.
“The study of uranium isotopes was strongly supported in U.S. national laboratories during the Second World War for the obvious reason that one of the isotopes could be used to make an atomic bomb. However the discovery of uranium isotopes led to many practical applications aside from the production of weapons. Indeed, radioactivity in naturally occurring elements in rocks allows us to date events in Earth’s early history, including the earliest evidence of microbial life.”
Which is the point of his tirade - how they dated the formation of the earth by studying a meteorite that landed in northern Arizona 50,000 years ago. It was formed around the same time as the earth but it hadn’t undergone any of the changes that earth rocks do. When they measured it’s uranium clocks it turned out to be 4.55 billion years old which is generally accepted to be the age of our planet as well. So if that is true, how long has life existed on earth?
By measuring biochemical traces found in really old rocks and other clever tricks, scientists have determined that life first appeared about 3.5 billion years ago. But wait a minute, we know from the fossil record, that the first multi-cellular recognizable life forms popped up some 600 million years ago. That means . . . let’s see . . . hmmm . . . for almost 3 billion years there were just tiny microbial single celled life forms floating around in the primordial seas?
Yes that’s what it means, microscopic single celled life forms adapting and mutating and communicating and exploring away in the primordial seas. And what did they discover? Photosynthesis for one thing - how to make food out of sunlight, symbiosis for another thing - how working together as a team increased your chances for survival. Messenger molecules were invented so they could talk to each other. Predation was also developed as they discovered they could eat each other and they set up defenses and decoys; microbial cultures - you are my friend and we speak the same language, you are my enemy and I wish you would just go away.
These earliest life forms established patterns of behavior that would result in the colonization of a heretofore barren world by living organisms. Today we have a network of millions of different species all related and connected, a biosphere, and living in every imaginable habitat not just the oceans. We still use messenger molecules called words, we still do symbiosis, it’s called teamwork, and we still predate each other and set up militaries and politics. Oh yeah, and we learned how to farm, domesticate the plants.
It’s fascinating to me. I’ll probably live to be 110.