I hope your Thanksgiving Day has been wonderful thus far. If it has, come back to this later if it is still Thanksgiving and enjoy family, friends, and relaxation. Otherwise I hope this is an entertaining way to unwind. In the spirit of recycling, here is an image that seems to capture the gist of some of our favorite holidays.
A while back I posted about the meaning of canary in a coal mine. Why do people dwell on the gloom and doom from climate change, nuclear war, or frankly almost any scenario that people can stumble upon that might end badly. So why us and why now? Is it more media, more spare time to ponder, projections based upon knowledge rather than mysticism? It seems that humans, at least for a longish time seek meaning and significance to the things they see around them rather than viewing them as natural events of some probability that just happen. Imagine what it might have been like when all we had managed was sharpening a stick to see a shooting star, the aurora borealis, a volcano, or a tidal wave for example. Absent any understanding about how the world works, each of these events would have been difficult to come to terms with. An eclipse or even a harvest moon might be a mind-bender.
What is different about the world for the first time in its history is that we now have a process to figure out how things work methodically. Slowly we have even begun to predict things about the natural world with some success. We all have heard some version of the shopworn observation that meteorologists have it great, they are right less than half the time. The ability to forecast the weather has proven very hard but we are finally improving quickly. My favorite validation of that is my tennis “commissioner” who forecasts the best days to play with the best chance of great conditions. Looking out 8-10 days ahead only 50 years ago would have been unheard of. Wow.
We read a book about storms and shipwrecks on the Great Lakes perhaps one to two years ago in my book club. It was pretty interesting as I did not understand the scale of shipbuilding for the lakes nor the impact of storms on very large lakes. Lake Superior, a dominant feature that governs the shape of my home state of Minnesota is an interesting example. Lake Superior has a scale all its own, with spots people surf, remarkable waves in certain conditions, and dynamics for ships that make it much more an inland sea than a lake. Did you know that Lake Superior is larger than ALL OF THE OTHER Great Lakes combined (measured by volume)? Why this tangent? The National Weather Service was only established in 1849! Before that time, we were all simply at the mercy of folks remarking “my bones hurt”, I think it will rain tomorrow. I think we have all heard the expression “Red sky at night, sailors delight. Red sky in morning, sailor’s warning.” While there is nothing wrong with a rule of thumb, it is a wonderful thing when you start methodically studying natural phenomena.
What I am interested in discussing this evening is mass extinctions and how we finally KNOW when they occurred. However, it is equally likely that I might not get that far. First of all, I am far from knowledgeable about the topic. I enjoy it when I read an article that seems authoritative about a topic that it seems hard to understand where the evidence comes from. While it was not my favorite subject in school, Earth Science, coupled with archeology and paleontology seem to have presented remarkable clear stories about things that occurred a long time ago. The scale of time is always important as a context. We think the earth is about 4.6 billion years old. Humans seem to emerge around 2 million years ago. We haven’t had any mass extinctions since we got here but scientists seem confident that there have been five such events in the last half a billion years. The last one took out the dinosaurs around 58M years ago. I remember laughing heartily when an issue of the Economist reported the opening of a museum in Kentucky with dioramas of children holding hands with dinosaurs. As the saying goes, don’t let the facts get in the way of a good story!
The previous five mass extinctions have been given names for the ages they spanned. The names are long and hard to remember so I am skipping them here. While there is some disagreement, a consensus of scientists is moving toward a belief that we may be living in another mass extinction. Manmade climate change is controversial enough so we will not wade into that morass this evening.
At this point, we do begin counting on the fossil record. Technology is neutral and so is science. When you couple the fossil record with nuclear decay, science offers us a way to TRULY UNRAVEL the story of our planet’s history. I can remember when chemistry class introduced me to nuclear decay. When it comes to how the world works, I am happy that Willard Libby, a chemist from the University of Chicago uncovered an amazing secret of how the world works. I believe that Willard Libby managed to create an amazing line in the sand and it was PRETTY RECENT. Stories, theories, and beliefs before 1946 and after 1946 would now be exposed to a challenging new standard provided by the scientific method. Willard Libby unlocked the wonder of carbon-14 dating. Whenever I read something about the history of the planet, if it was published before 1946, I am suspect because such an explanation lacked a fully scientific basis and required some conjecture.
While people like to dwell on the hair-trigger difference between fact and theory, everything on this planet that is alive that we have studied so far (and we’ve been very busy) is carbon-based. I think that some marvelous Star Trek episodes might have explored the options, but I digress. While it is theoretically possible that life might be based upon something besides carbon, the world informs us that is extremely unlikely. So now, the next time someone talks about theory vs. fact, be reminded why theoretically appears in the last sentence.
This is when things get pretty cool. As long as you are alive, a certain, very small fraction of all the carbon in your body is an unusual isotope C-14 rather than good old generic C-12 which almost everything is made of. Once a living thing dies, that bit of radioactive carbon (C-14) just starts to decay. Once Dr. Libby explained the mechanics of the clock, we were on our way. The amazing part is when you come upon something dead for a while (even like a fossil) the amount of C-14 that is leftover will describe pretty accurately what the date of the funeral was. That, in a nutshell, is what C-14 dating is all about. The wonders of mathematics and a half-life (how long it takes for 50% to disappear) of 5700 years make this a great way to figure out how old stuff is.
In an earlier post, I commented on how I did not enjoy Earth Science in high school. In context, I realize that the textbook was IRRELEVANT to our modern understanding and we would have been better off with a different subject. Throughout the 1960s and 1970s, based upon the new ability to date fossils, a new science of plate tectonics would emerge. Now that I understand that we had no reliable method to date things until 1946, the speed that the new theory emerged and solidified is impressive! Until then we were in the dark and could only make “educated” guesses. If we lacked scales and could only depend upon the carnival “guess your weight booth”, it only seems reasonable that we would ABANDON such approaches once we had a scale (unless we wanted a large stuffed animal). In the same way, theories of the age of the earth or the ages when certain beasts lived on the earth established before C-14 dating immediately become anti-reason to me. The next time someone tells you the earth is 6000 years old, you need not challenge them as that might be corrosive. You can, however, safely ignore any conclusions based upon the 6000-year hypothesis. C-14 dating is considered quite reliable for about ten half-lives or approximately 50,000 years. That is how science works.
By the way, for the skeptics out there, C-14 dating inspired all sorts of other techniques to date things even further back in time. Once we came to UNDERSTAND the half-life of the C-14 isotope and then many other atomic isotopes, the ratios of one isotope to another can yield a great way to date things further back. The mathematics is a little trickier but builds on the same principles of measuring how much of certain isotopes prevail. While it is not directly related to this post, I have a background from my early career in nuclear power generation. The controversy related to the storage of nuclear waste centers on the half-lives of some of the more dangerous isotopes. The half-life of plutonium-239, one of the waste products of nuclear fission is 24,100 years. It is hard to build a barrel that will last that long. The plutonium released at the Fukushima accident presents a danger to the environment for about twenty half-lives so about 500,000 years.
Here is a song that covers all of recorded history and it focuses on the ideas that vex us all. Hope you return for a future post. Sometimes I struggle to present challenging topics. I would love to hear back from people whether this post did a good job explaining things. Constructive criticism is GREATLY appreciated.
Explained Carbon dating for me
That was fun. A good review of carbon dating. Learned something already this morning.