Posting the lazy sunday video at 4pm: That means it’s an exceptionally lazy day!
But it’s also an exceptional video — one of my favorites that I’ve seen on the whole of the internet. (Gasp!) Piecing together clips from dozens of science documentaries and specials overlaid with stunning music, the youtube user UppruniTegundanna starts out tracing the history of humans, integrating technological and artistic development. Then it takes a turn to beautifully visualize the most severe mass extinctions on this planet before starting from the beginning — from the big bang, formation of the solar system and earth, the first molecules and the evolution of life as we know it.
It’s a lot of ground to cover and it’s so well done. Get ready for 12 straight minutes of butterflies and chills. I haven’t failed to get them each time I watch it, an unquantifiable number of times at this point.
In this video and his others, the artist seems to truly grasp the magnificence of the universe. At its heart, this video is about natural disasters, embracing extinction and death as key to how we got here. In a lovely blog post this week, Patrick Clarkin wrote:
Eugenie Scott, Director of the National Center for Science Education, has written that for many laypeople the notion that evolution is an unguided, mechanistic process implies that “life has no meaning.” However, contrast that view with how many scientists write about nature. The sense of awe and reverence that is exuded is palpable.
And this video exemplifies this — true awe at the fact that we exist at all.
I am thankful for many things in my life and one of those is that, still in high school, I discovered not only one but two intellectual passions. One, as you know, is biology and the other is Latin and classical history. I struggled a bit in college because I felt like I was split in two, spending half of my time in classes for each, and never able to wholly invest myself in the study of either. I simply couldn’t choose and the two fields felt mutually exclusive — after all, what could be more different than analyzing ancient texts that many argue are dead in our time and working to understand concepts at the fringe of modern discovery?
But that all changed when I read Lucretius for the first time. In De Rerum Natura he explained and beautifully illustrated with words the Epicurean doctrine, bringing me to tears at times. And at the heart of that philosophy is the atom — and when I read that word (he uses “primordium,” the origin or beginning, or “seminarerum,” literally the seeds of things) my world changed. I had found an overlap — the study of classical science! While I wasn’t able to take any other classes on the topic, the idea didn’t stray far.
While Aristotle gets a lot of attention, his work is typically slated as philosophy rather than science. Not only does he have many works on natural history, but there are many other classical scientists that we only have a few scraps of, or are referenced by later authors with no source material to look back on. But many of the works of these early scientists and philosophers are gems in which we can see the reflection of the early days of modern scientific inquiry — both in the things they got right and, more frequently, the things they got wrong.
Now I’m finding that, if I decide to go back to school, this is what I want to study. I have these books — so why not start exploring the idea further on my blog? So, yes, I will. Welcome to Classical Science on Culturing Science.
I’m going to start off with a lovely quote from Erasistratus of Ceos (or Erasistratos of Keos) who wrote around 280 BCE about the nature of scientific inquiry — and it sounds more than a bit familiar. None of his writings are extant, but he was quoted by the medical researcher and philosopher Galen, who lived in the 100s CE.
Those who are completely unused to inquiry are, in their first attempts, blinded and dazed in their understanding and straightway leave off the inquiry from mental fatigue, and are no less incapable than those who enter races without being used to them. But the man who is used to inquiry tries every opening and he conducts his search and turns in every direction and so far from giving up the inquiry in the space of a day, does not cease his search throughout his life. Directing his attention to one idea after another that is germane to what is being investigated, he presses on until he arrives at his goal.
I don’t think that requires any commentary.
For this project, I will be ever indebted to the work of Georgia Irby-Massie and Paul Keyser who put together a sourcebook of Greek science. The above translation is quoted in their book from G.E.R. Lloyd’s Greek Science after Aristotle. At some point I do plan on throwing my own translations into the mix (only Latin, obviously) — get pumped!
Balancing the needs of endangered species that can damage human property and the people that own the property is quite the trick — one that hasn’t exactly been figured out yet. Ranchers call the conservationists arrogant hippies, conservationists call the ranchers heartless and selfish.
And as with so many of the battles in our species, it all comes down to property — who has right to the land? I think it’s a particularly interesting facet of the right-to-property debate because it really is so easy to understand where each side is coming from, especially as an outsider, while such squabbles (or wars) within our own species get complicated very quickly.
This short video by Jeffrey Mittelstadt, a UNC master’s student in documentary journalism, does a great job articulating the argument between the two “sides” by interviewing a rancher and a government worker working to protect the Florida Panther. You can read an interview with him as well.
Hat tip to Jason Goldman
Every thirteen years they come. After over a decade underground, they build burrows to the earth’s surface and emerge in synchrony, clawing and crawling up through the soil, rip their skins down the back and are reborn as adults. And after a month, they will be dead, whether consumed by the animals awaiting their arrival or as a part of their lifecycle, with the females having laid eggs in the soil to develop for another thirteen years.
Some cicadas emerge every single year — annual or “dog days” cicadas — but two broods are on much lengthier cycles. This year, 2011, Brood XIX cicadas have already begun emerging throughout the southern United States. In 2004, I was lucky enough to experience the emergence of Brood X and won’t have the honor again for yet another decade, after a total of 17 years in 2021.
Their peak in 2004 coincided with Princeton University’s alumni weekend — which I attended as a bored high schooler — and what poor timing for that event! The endless drone of the insects forced us to yell just to make conversation; the air was so dense with their swarms that they would fly into unsuspecting Princeton grads with a size and velocity that was actually painful; sidewalks and windshields were splotched with the pale green stains of the squished deceased.
Besides providing a weekend of entertainment for high school hooligans witnessing the torture of exasperated ivy-league graduates, the emergence of millions upon millions of cicadas for just a single month provides an ephemeral pulse of resources. Once dead, their decaying bodies add nutrients to the soil (1) and streams (2), increasing soil microbes (3) and detritivorous insects (4), while their predation on roots as nymphs and plants, young ones in particular, as adults can decrease tree (5, 6) and plant (7) growth in the cicadas’ emergence year.
This deluge of huge, nutritious bugs should be a boon for their predators as an undepletable food source. While one study (8) found no change in a population of white-footed mice after Brood X emerged, the same study saw the number of short-tailed shrews increase four-fold — now that’s a lot of shrews!
So you’d probably expect a similar reaction from insect-eating birds — that some would have no change, but some would benefit greatly from the cicada surge, especially since their migratory nature would allow them to gather by the cicadas during emergence years. But when ornithologist Walter Koenig and entomologist Andrew Liebhold compared populations of 24 bird populations over the course of 37 years from the Breeding Bird Survey data set with periodic cicada pulses (9), they found only two species that showed up just for the cicadas — both North American cuckoo species. Out of the other 22 species, only 6 populations increased; the remaining 16 declined, and 5 of them with statistical significance.
They had three hypotheses to explain why so many bird populations were decreasing, according to a large observation-based bird survey, even when the birds were practically drowning in ample food resources. The overwhelmingly loud noise of cicada calling could drown out bird calls for the birdwatchers, creating an observer bias artificially lowering the reported number of birds in the area — the detectability hypothesis. Alternatively, all the racket could keep the birds from hearing one another, disrupting their communication and driving them to quieter areas with fewer cicadas — the repel hypothesis. Or the birds populations could be declining for another reason, affecting them beyond the ranges of the cicadas — the true decline hypothesis.
Koenig and Liebhold just published a reanalysis (10) in March 2011 in Ecology to test their ideas about why these bird populations are dropping. Again, they used the Breeding Bird Survey data for the 12 species showing the greatest decline from their previous paper, but also compared populations to the counts from the previous winter (Christmas Bird Counts) and incorporated notes about cicada prevalence from the counts where they could.
Their results supported the true decline hypothesis — that the birds’ population declines are not related to the emergences at all. They suggest that the drop in population numbers could be an indirect effect of the cicada emergences, however. The voracious plant consumption of the cicadas could be negatively affecting other insect prey sources or otherwise adversely impacting the immediate habitat. Additionally, while North American cuckoos are not typically nest parasites, this behavior — laying their eggs in the nests of other birds — has been observed when cuckoos are under intense competition with one another, as in this situation.
Some scientists (11) suggest that cicadas emerge on such odd timescales — 13 and 17 years, I mean, c’mon! — specifically to mess with their predators. If they emerged too frequently, their tactic of completely overwhelming the area with their presence, basically guaranteeing that many of them will successfully reproduce no matter how many housecats and cuckoos are fed — predator satiation — wouldn’t work. If they emerged more frequently, the gains of their predators from the cicadas’ previous emergence may still be lingering, effectively increasing their predators’ numbers each year until the cicadas themselves were overrun. (A hard scenario to imagine, I know — that would take even more shrews!)
But could the cicadas have evolved to take advantage of such a long-term concept? That they would have to effectively “wait” for their predators to be on the decline before they emerge again? Some biologists have even hypothesized that the latency periods of 13 and 17 years are significant because they are prime numbers! Take it away, Dr. Nicolas Lehmann-Ziebart:
[A]ssume that cicada predators consist of species having cyclic or ‘‘quasi-cyclic’’ dynamics with either two- or three-year periods. This leads to high predator abundances, and high predation rates, in years divisible by either two or three. Because primes are the only numbers between 10 and 18 that are not divisible by 2 or 3, broods of prime-period cicadas frequently escape high predation levels and hence tend to dominate hypothetical cicadas with nonprime periods. This mechanism for generating prime numbers relies on either externally driven two- and three-year cycles of predators, or predators that have strict fecundity schedules creating dynamics that tend to show two- or three-year oscillations.
Lehmann-Ziebart and his undergrads suspect that the cicadas emerge in these odd patterns as a balance between predator satiation and competition within the cicadas themselves. They, unfortunately, couldn’t find an obvious explanation for the prime numbers, though suggest it could have to do with a genetic counting mechanism.
Another explanation for this odd pattern of bird decreases coinciding with great cicada food sources is shoddy data. The Bird Breeding Survey is performed by mere citizens after all — can’t trust them! JUST KIDDING! There have been criticisms of the survey, including new observer bias (a n00b bird counter gets better each year, so the early years are unreliable and this bias is not accounted for), its road-based sites and transects for the counter’s ease could cause bias due to car traffic, and variation in the number of counters year-to-year. Nonetheless, the survey covers an incredible amount of ground — with each route covering nearly 25 miles — and over 400 bird species and has been ongoing since 1966. Pretty good for any large-scale data set which will always have caveats.
It looks like the jury’s still out on why bird populations decline during cicada emergences, though I suspect it’s a combination of many factors — bird communication problems, detectability bias, ecosystem changes induced by the cicadas and the overall variability in bird populations and routes.
(1) Wheeler, G., Williams, K., & Smith, K. (1992). Role of periodical cicadas (Homoptera: Cicadidae: Magicicada) in forest nutrient cycles Forest Ecology and Management, 51 (4), 339-346 DOI: 10.1016/0378-1127(92)90333-5
(2) Pray, C., Nowlin, W., & Vanni, M. (2009). Deposition and decomposition of periodical cicadas (Homoptera: Cicadidae: Magicicada) in woodland aquatic ecosystems Journal of the North American Benthological Society, 28 (1), 181-195 DOI: 10.1899/08-038.1
(3) Yang, L. (2004). Periodical Cicadas as Resource Pulses in North American Forests Science, 306 (5701), 1565-1567 DOI: 10.1126/science.1103114
(4) Yang, L. (2005). Interactions between a detrital resource pulse and a detritivore community Oecologia, 147 (3), 522-532 DOI: 10.1007/s00442-005-0276-0
(5) Speer, J., Clay, K., Bishop, G., & Creech, M. (2010). The Effect of Periodical Cicadas on Growth of Five Tree Species in Midwestern Deciduous Forests The American Midland Naturalist, 164 (2), 173-186 DOI: 10.1674/0003-0031-164.2.173
(6) Koenig, W., & Liebhold, A. (2003). Regional impacts of periodical cicadas on oak radial increment Canadian Journal of Forest Research, 33 (6), 1084-1089 DOI: 10.1139/X03-037
(7) Yang, L. (2008). PULSES OF DEAD PERIODICAL CICADAS INCREASE HERBIVORY OF AMERICAN BELLFLOWERS Ecology, 89 (6), 1497-1502 DOI: 10.1890/07-1853.1
(8) Krohne, D., Couillard, T., & Riddle, J. (1991). Population Responses of Peromyscus leucopus and Blarina brevicauda to Emergence of Periodical Cicadas American Midland Naturalist, 126 (2) DOI: 10.2307/2426107
(9) Koenig, W., & Liebhold, A. (2005). EFFECTS OF PERIODICAL CICADA EMERGENCES ON ABUNDANCE AND SYNCHRONY OF AVIAN POPULATIONS Ecology, 86 (7), 1873-1882 DOI: 10.1890/04-1175
(10) Koenig, W., Ries, L., Olsen, V., & Liebhold, A. (2011). Avian predators are less abundant during periodical cicada emergences, but why? Ecology, 92 (3), 784-790 DOI: 10.1890/10-1583.1
(11) Lehmann-Ziebarth, N., Heideman, P., Shapiro, R., Stoddart, S., Hsiao, C., Stephenson, G., Milewski, P., & Ives, A. (2005). EVOLUTION OF PERIODICITY IN PERIODICAL CICADAS Ecology, 86 (12), 3200-3211 DOI: 10.1890/04-1615
“Now that I think about it, many universal constants are more certain than death and taxes..”
Funny video, starring a cute boy, about how NASA helps to increase the awesome of the USA! Why is NASA worth .45 cents of each of your tax dollars?
NASA: Decreasing the suck. Increasing the awesome.
I’m not a physicist and, as such, would appreciate comments/emails alerting me to any errors! And yes, I did feel like I had to write this whole thing up before approaching radiation ecology. Welcome to my brain.
White Sands, New Mexico, 1954. An FBI agent, a police sergeant, and two scientists venture into a sandstorm, goggles pressed to their eyes, with one goal in mind: to find an odd footprint that they suspect is connected to recent area deaths. The scientists exchange knowing glances when they find it. “Something incredible has happened in this desert,” Dr. Graham says.
A minute later, the air swells with alien screams and the blinding sand clears to reveal their source: a giant ant, nearly 8 feet long. The agent and sergeant shoot frantically — “get the antennae! get the other antenna!” Graham yells. With its senses disabled, the ant collapses into machine gun fire. The team looks on in wonder: what is this thing and where did it come from? “It appears to be from the family Formicidae: an ant,” says Graham. “A fantastic mutation probably caused by lingering radiation from the first atomic bomb.”
This is a scene from the 1954 film Them!, one of many horror movies inspired by the first atomic bomb tests in the southwest United States. (And a great one, at that!) This idea seems preposterous now: radiation causing mutations that cause ants to grow to enormous sizes and feast on humans. Or atomic waste dumped into the ocean landing upon a human skull, creating a murderous zombie. Or a woman’s irradiated brain causing her grow to 50-feet — “incredibly huge, with incredible desires for love and vengeance!”
But is it really so preposterous? Radiation has taken on its own character, not only because of the immediate fears represented in film and books to the present day, but also because it is so hard to describe. It’s simultaneously envisioned as vats of poisonous waste, particles streaming from the sky — fallout — that can burn human skin, and atoms suspended in the air or water that can be incorporated into living tissue, festering there for decades and causing miniscule damage to DNA.
When I spoke to Tim Jannik of the Savannah River National Laboratory for The Scientist, he had to remind me what radiation really is. “What people often forget is that radiation is simply just energy,” he said. “When you get exposed to radiation, your body is absorbing energy.”
Ward Whicker, a radioecologist at Colorado State University whom I also interviewed for The Scientist, pushed it further: not only is radiation a simpler idea than that held in the public mindset, but it is also omnipresent in our lives. “People in general have a hard time understanding that we live in a very radioactive environment naturally,” he said. “Life has evolved in a radiation environment.”
Of course, we mostly think about radiation during times of crisis, whether it’s concern about nuclear weapons or, more recently, the flooding and subsequent breakdown of the Fukushima nuclear power plant. After discussing radiation for several days in terms of its hazard and then having these conversations of its basic nature in our environment, I realized that I really couldn’t remember very much about what radiation actually is! One thing led to another — or, rather, one wikipedia page led to another — and, after a few days of research, I felt I actually understood, on a basic level, how radiation works.
It felt wonderful to have radiation demystified! So, in case some of you are also struggling to think back to high school physics, I thought I’d write up what I learned.
The split nucleus
Radiation is a broad term that has taken on a very specific meaning for those of us who aren’t physicists. Radiation, from the same root as “ray,” describes something that travels in waves — and if you can think back to high school physics, remember that if something is a wave, it is also a particle. So sunlight — a form of radiation — is a wave, but is also composed of particles, photons. The same goes for UV and radio waves: Also particles. What we call “energy,” some amorphous force, is actually matter. Henceforth, when I mention “radiation” I will be referring to nuclear radiation: the waves/energy/particles that radiate from a nucleus.
As long as we’re on the subject of words that have taken on their own mythology, I may as well add another to the mix: nuclear. For some reason, I have two compartments for the word “nuclear” in my brain. One describes those tightly packed balls in the center of atoms, the nucleus, around which race electrons in various configurations. The other is more conceptual: a word that describes a great power, much like the One Ring, that can be used for good hypothetically, but is also dangerous.
But, of course, the actual meanings of nuclear in each case is one and the same, as nuclear power and all its gifts and danger are the product of activity at the nucleus of atoms — in particular, its breaking apart.
It takes a great deal of energy to compact neutrons and protons together into a tight ball and hold them there. So you can probably imagine that, if the nucleus does manage to break, energy is released. And this energy release, my friends, is nuclear radiation. (Its actual movement is also called radiation, but I’m referring to radiation as the actual energy.) There are different kinds of nuclear radiation — alpha particles, beta particles, gamma particles, neutrons, and others — that differ in what materials they are able to penetrate and the strength of the energy they carry. There are two ways a nucleus can break:
- It is unstable enough to disintegrate on its own.
- If it collides with another particle or nucleus with enough force.
A nucleus that is unstable enough to break apart on its own is an isotope, meaning it’s picked up a neutron or two that fly through the air constantly. This heavier nucleus cannot be held together by the same amount of energy, and thus it typically splits into smaller elements, a neutron or few, and energy. There are around 340 naturally-occurring isotopes that we know of that are radioactive in this way, but that’s leaving out some that (a) split so quickly that we can’t recognize their existence in the first place or (b) haven’t split yet since the formation of the earth, but they may still.
The second way for a nucleus to split is to be struck with another particle, a neutron for example, with enough force that the energy holding the nucleus together is disrupted and it breaks into smaller parts. This is the reaction that scientists organize in particle colliders to try and identify all the little particles released at the breaking point.
There really isn’t a huge distinction between these two methods: In both cases, a neutron strikes a nucleus, disrupting the energy holding it together, and causing it to break. It’s just a matter of time — either it happens immediately, or the neutron joins the nucleus for a little and, eventually, causes its demise.
This is the reaction that occurs in nuclear power plants. Many of these plants use Uranium-235, the only naturally occurring isotope that can sustain a nuclear chain reaction. A nuclear chain reaction is when one nuclear reaction leads to one or more — like knocking the first domino in a row. When Uranium-235 is struck with a neutron, it can release 3 more neutrons during its breakdown. If just one of these three manages to strike another atom of Uranium-235, another reaction occurs, ad infinitum.
And the main point: When any of these reactions or related ones occur, a bit of radiation (energy/waves/particles) is released with it, the extra energy that once was part of the nucleus and held it together. This energy is collected in nuclear power plants to generate electricity by heating water, for example. And it’s this energy that can do damage to our cells.
The danger of radiation
Most forms of radiation in our day-to-day lives are relatively benign — visible light, microwaves and radio waves, for example — and can’t do much harm, with their energy simply causing heat, if that.
But some radiation, such as alpha particles or UV rays, are tough little buggers that can interact and change other molecules that they run into by pulling off electrons. And it’s these resulting molecules — the oft advertised free radicals — that can damage DNA, causing mutations. With enough DNA damage, the cells commit suicide (apoptosis), and large amounts of cells dying quickly is what makes people exposed to large amounts of radiation to become sick.
If you’re in the vicinity of a large amount of radiation — such as when nuclear power plant cooling is disrupted, nuclear fuel is ignited, as at Chernobyl, or a nuclear bomb explodes — a lot of energy is reaching your body, both in the form of heat, which can cause burns, and nuclear radiation.
Cells in your body that divide very rapidly are the first to cause illness, as losing a group of these can quickly effect the total number due to their exponential growth. These are blood-forming bone marrow cells, and their damage can cause anemia due to a drop in red blood cells and a weakened immune system from a drop in white blood cells. Intestinal cells divide quickly, but not as rapidly as bone marrow cells, so they’re the next to be affected, causing symptoms such as nausea and vomiting, dehydration, and digestion trouble. At very high radiation doses, the cells that don’t divide are affected, in particular nerve cells, causing neurological problems from headache to coma. And these problems combined can kill.
If the radiation manages to damage DNA without killing the cells, this damage could still cause problems that could potentially lead to cancer later in life. Another concern for cancer-causing radiation is when radioactive isotopes accumulate in tissue, decaying and releasing energy within the body. (Read on! I dare you.)
Bioaccumulation of radioactive isotopes
Much of the concern in the aftermath of the Fukushima reactor accident has been about various radioactive isotopes: Iodine-131, Cesium-137, and Strontium-90, to name a few. These are isotopes that are taken up by the body when eaten and are incorporated into tissues because their biochemistry is similar to iodine, potassium, and calcium, respectively.
Non-radioactive iodine is necessary for proper thyroid function, but when Iodine-131 is taken up by the thyroid instead, the isotope is stored in the thyroid, slowly able to release its radioactive energy and particles over time. This long-term exposure in a very small area can lead to thyroid cancer. However, Iodine-131 decays relatively quickly: In just 8 days, a sample of Iodine-131 will be half the size it began. In other words: on average, half of the nuclei in the sample will have decayed after 8 days, proportional to but not an exact measure of the decay rate of a single nucleus (Thanks, Liz!). However, it releases alpha radiation, a stronger form of radiation that creates free radicals more easily and quickly, so it’s best to avoid it despite its short lifespan.
Cesium-137 and Strontium-90, however, take around 30 years each to halve in size, slowly releasing radiation over that period of time. Cesium-137 imitates potassium and is taken up into muscle tissue where it can remain for half a year before it is recycled out by proper potassium, giving it a fair bit of time to release radiation. Strontium-90 takes the place of calcium, building up in bone and bone marrow. Unfortunately, this isotope gets stuck there and isn’t cycled out like Cesium-137, and can cause bone cancers and leukemia.
These latter two — with 30 year half-lives — can accumulate in plants or animals and, when humans ingest them, become incorporated into our bodies. That is the fear behind much of the environmental impact talk: Will Strontium-90 enter the food chain? How far from the reactor will it spread? And how long do we have to wait before the food is safe again?
The answers to these questions are mostly unknown because we simply don’t have enough experience with them. As I will elaborate on in my next post, very little work has been done studying the ecosystems at Chernobyl, giving us little insight into how these isotopes remain in the environment.
Congratulations! You made it through. I hope I was able to successfully explain radiation and its basic effects to you. Please leave any questions, comments and corrections in the comments or send me an email.
Post edited 4/10/11 to clarify explanation of a radionuclide half-life
Right now there are over 150,000 people watching a Bald Eagle nest in Decorah, IO with me over webcam.
Isn’t the internet wonderful?
Join the cool club and look at some cute/ugly baby birds (or just the momma eagle nesting) with us on ustream
UPDATE: According to Wired, there is still another chick that hasn’t hatched yet! And it will probably hatch within the next 48 hours! You know what that means: NO SLEEPING. NO GOING OUTSIDE. I hope it doesn’t hatch during my commute…