Three Physicists...

Bernoulli, Schrodinger, and Newton. Three famous physicists. What in the world do they have to do with a drive through East Africa? Well, we'll get to that...

After leaving the Zinjanthropus memorial, we drove up the gorge to the main road and turned north, leaving Oldupai behind. Climbing to the level of the plains, we soon found a road, or perhaps I should say track, leading west toward the Serengeti. The main road runs along the south margin of the gorge, but is known for being a rough, difficult drive. The north road is easier on the vehicles and passengers, and would allow us to stop at an interesting landmark.

The land out here is flat in the way Kansas is flat. If you look in the far distance you will spot the top an occasional isolated hill (remnant of a volcanic past) but little obscures your view of the horizon except dust and heat shimmer. Vegetation is sparse, shade is nonexistent, and water is nowhere to be found. If you are standing outside of the car it is a little over 3 miles to the horizon, so you are at the center of a circle covering more than 28 square miles, 18,000 acres, where you are the tallest thing in sight, and nothing moves.

Ok, that is a little dramatic, though not far from the truth. I think over the time we travelled directly west we saw one gazelle, one jackal, one giraffe, and a couple of vehicles, but that was about it. Oh, except for the Maasai family, but we're coming to that.

One of the reasons we took the northern road was that we wanted to stop at a place called Shifting Sands (Lat 2 deg 56.703 min S, Long 35 deg 18.859 min E). If you get out Google Earth and zoom in on this location you will see a small, black, isolated, crescent sand dune. You should also be able to spot the track it has made over many years leading off to the east. Known technically as a barchan (pronounced bar-kan), this dune is made of fine, uniform volcanic sand, and moves downwind at a rate of about 50 feet per year. It is not a large dune, perhaps 10 feet high and 150 feet between the points of the crescent, but it has a wonderful symmetry and a constant hiss fills the air as the windblown grains move across the packed surface of the windward face.

The most interesting aspect of a barchan is the coherency that it exhibits. It is often supposed that the sand is magnetic, which causes it to stick together. The real reason, however, is the unique crescent shape. The wind generates a vortex in the lee of the dune which drives sand swept off the crest back toward the base, keeping the dune intact. From a scientific and engineering perspective, it is a beautiful example of a phenomenon called flow separation (thus the reference to Bernoulli, if you were wondering). Barchans generally start when sand piles against the upwind side of a rock because of strong winds that always blow from the same direction. The pile grows until a critical size is achieved that allows the nascent dune to detach from its host rock and start its slow downwind trek.

Barchans are not uncommon where conditions are right, and can grow to enormous size, merging into dune crests extending many miles. Such giant dunes can be found in Namibia along the Skeleton Coast, but there are even barchans on Mars! If you look at some of the pictures from the Mars Exploration Rovers you will find also wind ripples in the sand very similar to these covering the windward face of the barchan...

When we arrived at Shifting Sands there were no other vehicles or people (or animals, for that matter) in sight. It felt very, very remote. We spent about 10 minutes circumambulating the dune and talking about its uniqueness. As I rounded the northern tip, though, I looked up and, to my complete surprise, saw an entire family of Maasai just a few yards away. Apparently, the Maasai have perfected quantum teleportation as a means of getting around (thus, Schrodinger). I had no idea where they had come from. Once we got home I used Google Earth to spot their small boma several hundred yards off to the west, almost lost in a small, sparse patch of scrub.

The Maasai were intent on trade. They had spotted us, gathered the family (man, two women, three children, and dog) and their wares (beaded bracelets and necklaces) and had set out to cover the distance to us before we left. They did all this and covered the half mile to us in 90F heat in just 10 minutes. Not an easy feat (for us, at least). These people, hardened to the land, probably do it several times a day.

Catherine bought several bracelets - the price was good and we could be pretty sure that they hadn't been mass produced in a factory in Arusha. Fortunately, David and Julius were there to translate for us. The family spoke Swahili, but no English. They also were unwilling to take payment in US dollars, which is very unusual in Tanzania. They were so remote that it was unlikely that they could easily use dollars. Fortunately we had shillings, so we were able to complete the transaction.

We almost ran afoul of our Maasai friends. Catherine had taken a few pictures (five to be exact) of the family when the father became somewhat agitated. Through our interpreters it became clear that he wished to be compensated for the pictures. After some back-and-forth, it was determined that we would give them one of our two liter bottles of water for the privilege of the pictures - cost: about US$0.80. A give-away for us, but clean, safe water has considerable value when scarce. This was another situation where I came away with a deeper understanding of both poverty and our relative place of privilege in the world.

Our business successfully concluded, we moved on, our destination Ndutu lodge by sunset. We travelled for another hour or so before we met up with the rough southern road again, and continued on west for an additional 30 minutes. Clouds were starting to build up by this time, and rain was threatening. Suddenly, with no warning, Julius slowed, left the road, and struck out to the southwest across the plain. Now, to my thinking Julius had clearly gone insane, although I held my tongue. My paranoid streak had visions of being stranded in the middle of nowhere, with night falling and lions prowling around the truck while we huddled inside...

Then we hit a particularly large bump, and I was jolted back into reality. David did take this opportunity, however, to relate a tale of getting stuck in similar circumstances when he was working in the Serengeti. Did I mention that he has excellent timing?

As we bounced across the countryside following a couple of faint tracks my back and kidneys began painfully rebelling at the length and roughness of the day's ride. I was wishing I had a kidney belt and hoping I wouldn't find blood in my urine at the end of the day. Soon, though, we had a little bit of diversion - it started raining! This was our introduction to the infamous Serengeti slip-n-slide. Rain tends to sit on the flat surface of the well-baked ground and form a thin layer of mud. Very, very slippery mud. Driving becomes more an exercise in momentum than friction (say, Newton's First Law of Motion, rather than the Third). This had particularly interesting implications since the obstacles were were facing now included the occasional bit of wildlife in addition to ruts and potholes.

After an hour driving southwest, David pointed out a treeline several miles distant (the horizon for a six foot person is only three miles away, but you can see tall objects at much greater range). The distance was deceptive, however, and it took another 20 minutes to reach the trees. By this time it was about 4 pm and the clouds were clearing quickly. Another 20 minutes of weaving through the Acacia forest and we found ourselves approaching Ndutu lodge at the south end of Lake Ndutu. The long day of travel that had started at dawn on the rim of Ngorongoro and reached back in time 1.8 million years at Oldupai was at an end, and my kidneys rejoiced.

Bernoulli, Schrodinger, and Newton, however, made no comment.