Science In Real Life

So, some of the other grad students and I were discussing something or other about neutrinos. I don’t remember exactly what prompted it, but I proposed the question: How likely is it for a human body to register the presence of a neutrino during an average 70 year lifespan? Before I get into telling you guys about the answer, I should explain why the question is of any interest whatsoever.

Ever since the idea of neutrinos, tiny weakly-interacting electrically neutral particles, was proposed by a guy named Wolfgang Pauli on Dec 4, 1930, neutrino detection has been a matter of volume. The largest detector in the biz, Super-Kamiokande, contains 50000 tons of pure water, and registers about 5000 neutrino detections per year. That should stagger you. Consider that uncounted millions of neutrinos pass through every gallon of empty space every single second of every single day. And yet it takes the biggest structures mankind can muster to record just a few of the interactions. This is because interactions, on the level of fundamental particles, between neutrinos and ordinary atoms are exceedingly rare. Thus the question of human bodies as neutrino detectors acquires at least the status of a curiosity worth spending a few hundred words analyzing.

Now, down to business. According to Wolfram Alpha, 50000 tons of pure water has a volume of about 750,000 human bodies. Human bodies are, let’s be honest here, mostly water. So it’s not a stretch to say that it takes 750,000 of us to interact with 5000 neutrinos per year. A quick division gets us 150 humans interacting with one neutrino per year. Each and every one of us has a 1/150 chance of physically interacting with one of the 2×10^20 neutrinos that pass through our bodies every year. Postulating a 70 year lifespan, we all of us have slightly less than even odds on becoming a living neutrino detector for just one neutrino sometime within our lives.

So what happens if you’re one of the lucky ones? Not a whole lot. At this point, things start to depend on how much energy the neutrino has. But we can still draw some general conclusions. Without getting into the details of the various possible reactions, one thing you would absolutely get is an energetic electron or five. Depending on what the neutrino hits, you might also get a sudden episode of alchemy – a carbon atom changing to a nitrogen isotope, for example. More electrons would result when it decays back to carbon. And all of these things would be throwing out light rays. What does this mean for you, the consumer? Very little. Depending on where this happens, you might end up with a single broken molecule. Such detritus is routinely cleaned out by cellular processes. But, if you’re really unlucky, that broken molecule could cause a mutation in the DNA of one of your cells. If you’re really really unlucky, the mutation could be in an activated gene, which might cause that cell to die. Maybe you should look into some cellular insurance. I’m sure they have a neutrino clause in the policy.

Written June 21, 2010.

Today is Monday, and today I have to go to a funeral. To a scientist, in some ways, death is both more and less permanent. There is no empirical justification as yet for any kind of afterlife, and so we lose the comforting notion that the mind, soul, or other consciousness of a loved one continues to be a part of our world or of any other. Ashes to ashes, dust to dust, in the truest and most literal sense of the expression. A human being, according to my own amalgamation of the ideas of several scientific disciplines, is a highly energetic mass of complex molecules undergoing a continual and continually changing set of intricate regulatory processes enabling it to absorb oxygen, nutrients, and information and interact with other human beings to survive, reproduce, and thrive. To those of who object “Is that all?” I suggest that they underestimate the complexity of those molecules and their regulatory processes.

So what happens when a human being dies? These days death is defined by Western medicine as irreversible loss of electrical activity in the brain. Aside from a few difficulties with taking the relevant measurements, this is a perfectly serviceable definition. But it’s only the beginning of the process. What really gets us happens on the cellular level. Without the larger-scale processes like breathing, individual cells (those marvelous factories for proteins and energy) simply shut down. The bakery cannot make any cakes if it does not get any flour. The bakers lose their jobs, the building falls into disrepair and eventually falls apart. Thus it is with the cell. Of course, there the analogy fails, because bakeries are not continually fending off an invading army of decomposer bacteria. Without the active defense of the immune system (in all its multifarious glory), everything can eat us. This is why corpses stink. It’s not all your pent-up farts finally escaping, it’s the farts of the bacteria as they chow down on your femurs. Death is a disgusting business. Dying with dignity, or glory, is just not possible. You break down, you decay, you rot. You are eaten, digested, and absorbed. Nothing of what you were remains.

Or does it?

Those brutally hungry bacteria may efficiently disassemble your large scale structures, but your molecules mostly remain intact. Your atoms almost certainly so. Are you destroyed, or are you merely disseminated? There is some weight, and some lingering comfort, in this viewpoint. In a deep sense of the word, what you were remains. Now no longer part of a single human body, what you were disperses, joining other molecules from other lost loved ones to feed a bird, or roll along in an ocean wave. This is the conservation of matter and energy at its most personal, at its most touching. Nothing ever really dies, nothing is ever truly lost. Everything is reduced, recycled, reused, and reincarnated. Even those of us who are still alive are made of the remains of those past. The same molecules that made Caesar, Cleopatra, Aristotle, and Joan of Arc are us today. And it goes further than that – before that, the atoms that make those molecules were part of incomprehensibly massive stars that exploded with astronomical force to produce the substances that formed Earth and the rest of our solar system. When our system ends, out of the remaining gas clouds may form new stars, and the cycle will begin once more.

Ashes to ashes, dust to dust.

So, some of you loyal readers may have been wondering where Science In Real Life has been lately. To you I offer my apologies – the formats in which I have attempted to write this blog, while fun and educational, have ultimately proven unsustainable for reasons peculiar to my own foibles. However, all hope is not lost. I have a new idea for a more natural way to communicate the scientific thinking that goes on in my head, one that is in some ways truer to the original stated mission of this blog. Over the next few weeks I will be testing this idea, and if all goes well you will start seeing new entries, in a looser and more fluid format. Until then, happy sciencing.