Urban Street Dogs

Homeless dog navigating a Moscow subway

During my first year of college a stray dog, living across the street in what we called a hobo camp next to the railroad tracks, adopted me. We were told he hopped morning trains into town returning each evening to camp. He avoided humans but hung around the hobo camp and outside our back door waiting for our nightly scraps of food. Then he discovered beer and hard cider leftover from one of our many parties. He spent more and more time in the house searching for beer. He eventually decided he owned our apartment and any food or beverage of his choosing. He stopped hopping trains. Of course, we gave him a name, Khan (fittingly rhymes with Con). 

During a college party night, Kahn introduced himself to one of our guests by grasping the guest's arm with a soft bite but just enough to hold him hostage until Kahn got his share of beer. Kahn occasionally would awaken with a hangover, chewing tin cans to shreds. 

At the end of the school year, Kahn moved to a farm (happily ever after) and I moved to a dorm that didn't allow pets. What stayed with me through the years was how adept Kahn was at surviving and manipulating his environment. One strategy worked at the camp and another at our house.

To this day, I can't pass up an interesting article about the adaptability of street dogs (aka free-ranging urban dogs). For example, much has been written about street dogs in Moscow. Unlike wild dogs, a pack leader often is not the strongest dog in the pack but is the most intelligent. The leader establishes memes that increase survival rates in the urban environment.

 Examples are: the mugger, a dog that sneaks up behind a person about to take a bite of food and sharply barks to startle the person into dropping the food; the pimp, a pack leader will accompany an especially cute dog that attracts attention (and food) from people, the leader, of course, takes his or her cut; and the psychic, a dog that is exceptionally good at reading people and displaying behavior that best manipulates that person. Dogs have been proven to be the only non-primate species that can "read" human faces focusing on the right side of the face which is said to reveal more emotion than the left side.

Another meme is associated with the famous metro dogs. These dogs live in the subways and have learned to catch particular trains or combinations of trains to particular locations of interest (a park, a dog-loving chef, etc.). They return to their sleeping quarters at the end of their urban adventure. To get to a particular destination, it appears that the metro dogs have learned to use some combination of scents at stations, human announcements of station names, habits of regular commuters, and estimates of how long the train has been in motion.

Then there are the dogs of Bucharest. Their survival depends on avoiding automobiles in streets congested with cars and people. Street dogs gather at street intersections waiting with pedestrians until cross-traffic stops before proceeding with the crowd. Even when people are not present some Bucharest dogs have learned to obey traffic lights. Since dogs don't discriminate between red and green well, it is assumed they have learned the position of the brighter light as a cue to cross safely.

So the next time you see a street dog, take time to observe some surprisingly complex adaptive behavior. That's why they're still on the street.

Just Passing Through

The Nobel Prize was given to Takaaki Kajita and Arthur B. McDonald this year (2015) for their discovery that neutrinos have mass; nearly infinitesimal mass, but some mass, and it matters. Neutrinos are the smallest known particles in the universe.  It's hard to conceptualize how small they are though I will try to explain.

The discovery explains some of what we call dark matter. The majority of mass in the universe is "dark" because it cannot be detected like photons; dark matter is detected only by its gravitational influence on objects we can directly detect. Dark matter itself is invisible, hence dark. How much dark matter can be accounted for by neutrinos is unknown.

Neutrinos are important because they probe deeper into matter than any other known particle. We, unlike x-rays, are invisible to any possible neutrino detector. We think we are made of "solid" matter. But we are made of atoms which are 99.999999999999% empty space. What isn't empty space in an atom (outside of its nucleus) is made up of electrons so electrons are much, much smaller than atoms. Neutrinos are less than 1/100,000th the size of electrons; they are so much smaller than atoms that they fly right through them as if they weren't there. For example, by some estimates between 50 trillion and 100 trillion neutrinos originating from the sun's nuclear reactions pass through your body every second (note that the number in the cartoon is way off; more than 65 billion neutrinos pass through your thumbnail each second). They pass through you as if you didn't exist. In fact, most neutrinos from the sun pass through the entire earth as if it weren't there. 

However, more than 50 years ago, 100,000 gallons of cleaning fluid buried very deep in a mine in South Dakota produced an average of one argon molecule per day indicating that a single neutron interacted with a chlorine molecule. Raymond Davis, Jr. figured out how to detect the rare argon molecule in the cleaning fluid. Forty years later, in 2002, he was awarded the Nobel Prize for his discovery. 

Unlike quarks and other subatomic particles, neutrinos are not constituents of matter. They just fly through the universe so fast that their speed cannot be distinguished from the speed of light. But neutrinos are now known to have mass and therefore cannot, in theory, actually reach the speed of light (there are erroneous reports, likely due to measurement errors, that neutrinos travel faster than the speed of light).

So are neutrinos of any practical use to us? Neutrinos are invisible to us and we are invisible to neutrinos, they don't coalesce into solid matter, and they don't seem to take much notice of matter as they fly through everything in their path. But neutrinos are potentially practical for two important reasons. Neutrinos, unlike anything else we know, can be used to communicate through any amount of matter on earth. One neutrino detector was able to receive an intelligible message through solid rock thicker than a football field. In theory, using neutrino transmitters and detectors, we could transmit messages from Western Australia to Maine through the center of the earth.

A second practical use of neutrinos is that understanding them gets us significantly closer to understanding the universe and the laws of physics that govern it. For example, because neutrinos aren't much obstructed by matter, we can detect neutrinos emerging from an exploding star over 100,000 light-years away. Because neutrinos provide a window into the universe at a far smaller scale than even the Large Hadron Collider in Geneva, the prospects for major breakthroughs in physics are greatly enhanced. The more we understand the universe, the more we can harness natural phenomena to our benefit. This is why the Nobel Prize in physics singled out the scientists who first detected neutrinos for the award this year.