Yesterday I drove north to the Bay of Fundy, the triangle of water that separates the western half of Nova Scotia from the mainland. As the sign proudly informs you when you get within fifty miles of the coast, this is the home of the highest tides on earth.

Tides turn out to be one of those things that grow more complicated the more you learn about them. Luckily, the reason for the extreme tides in the Bay of Fundy is pretty simple. The Wikipedia explains it:

The time it takes for a large wave to travel from the mouth of the bay to the opposite end, then reflect and travel back to the mouth of the bay, coincidentally matches the time from one high tide to the next. The result of this coincidence of timing is that that repeating wave is reinforced by the tidal rhythm, and consequently the world's highest tides are found in that bay.

Resonance, baby! Think Ella Fitzgerald breaking the wineglass, except that Ella is the Moon and the wineglass is a gorgeous triangular bay some fifty miles long.

A couple of sources also mention a 40:1 resonance between the Bay of Fundy and the larger Gulf of Maine system (bounded by the coast and the continental shelf), but I'm not sure what they're talking about.

The upshot is that fourteen cubic kilometers of water commute back and forth between the ocean and the inner bay, twice a day. This is so much water that its weight actually lifts and drops a part of Nova Scotia with it, by an infinitesimal amount.

I wanted to see a place called Cape Split, a west-facing spike of land at the mouth of the Minas Basin, where all of the moving tidal water has to squeeze through on its way in or out. In the hours between high and low tide, there is more water flowing here than through all of the rivers on the planet put together.

The drive up from Halifax is probably beautiful (I saw distant hints of mountains and sea through the sheets of rain), and the number of 'Scenic Overlook' road signs near Wolfville made me envious of people who have seen the bay under clearer skies. To me, it was a diffuse grey mist, with occasional bursts of autumn color peeking through. The hurricane had spent itself before getting this far north - the trees hadn't been stripped bare, and it was still full autumn.

Cape Split itself is a promontory of undeveloped land - there is road access, but the last bit requires a hike along an unmaintained forest footpath. An ominous sign at the trailhead reads:

Hikers are advised to wear hunter's orange between Sept. 15 and May 15.

Instead of safety orange, I was wearing a dark sweater and jeans, and the persistent rain meant that half of me was going to be covered in earth-tone mud. I might as well have been wearing artificial antlers. But there was no gunfire to be heard - always an encouraging sign - and I was feeling lucky.

The sign warned on:

Be advised the hike is four hours long - two there, two back.

Sure, I thought, four hours for an out-of-shape weekend hiker. But without a backpack weighing me down, how long could it take? After all, I'm at the absolute peak of my marathon training. Every muscle in my body is tuned for endurance and speed - I could probably run most of the trail, and slow down only to ford the really muddy parts. Who were these Canadian trail maintaners, to think they could intimidate me?

Four hours later, I emerged from the forest, drenched and exhausted and covered in mud. My hands were so cold that it took me ten minutes to work my car key out of my back pocket, and another five to get in the car and start the the heater working. Shades of Jack London. But I made it.

And the last part of the sign hadn't been an exaggeration:

Prepare to see one of the wonders of nature.

Cape Split is covered in pine forest until its very end, where the trail spits you out onto a giant turf-covered cliff. There are two smaller, inaccessible cliffs further on, and everywhere to the right is an expanse of roaring water, where the tide collides with itself, trying to make its twice-daily appointment with the moon. It is very, very beautiful there, even when your sweater has absorbed your body weight in water, and you know you have to spend the next two hours dodging buckshot in the mud.

Now that the IEEE conference has ended, I have a chance to explore the beautiful city of Halifax.

Right, so maybe the IEEE conference was never a huge obstacle to begin with. But at least now I don't have to feel guilty about wandering the city. And thanks to fluke of airline pricing that made it cost less to stay two extra nights, I get to play the tourist.

Halifax is a small and very pretty city on the edge of a big natural harbor. It's built on a piece of land shaped something like the Suez penninsula - downtown is halfway up the Red Sea coast. In normal times, the most prominent thing about the city is the large citadel overlooking the city, as well as a pair of beautiful suspension bridges. Right now (not such a normal time) the most prominent thing about Halifax is the terrific number of downed trees.

Hurricane Juan roared through Nova Scotia just a few weeks ago, and now every major park in the city is closed, the paths blocked by fallen trees. My own ninth-floor window overlooks the block-sized Public Gardens, and out of forty trees there are five that are lying on their sides, torn out by the roots. Practically every tree in the city bears a bright scar of exposed wood from where it lost some branches. I even saw some uprooted parking meters - three feet of steel and concrete pulled clear out of the ground. There's a neat pile of cut branches and storm rubbish by the street in front of every house, waiting to be carted off.

You can see impressive pictures of the storm aftermath for yourself on the local photography site.

Yesterday I visited the Halifax citadel, which sits on a hill overlooking the central city and has magnificent views of the bay. Sadly, Halifax was hit hard by the darkest chapter in Canadian history - the epidemic of horrible sixties architecture - and no one in the fort had the presence of mind to open fire on the builders. So the Haligonian skyline is now a mix of nice old Victorian-style buildings, tall sea cranes, and a bunch of cardboard-colored squat boxes with chocolate brown windows.

The citadel itself is an old-style fort that is currently at version 4.0, the last upgrade taking place in 1856. Unlike the defensive batteries out in the bay, which guarded against Leviathans and pirates, the citadel was designed to protect Halifax from invasion by land. The potential invaders kept changing - first the local Indians, then the French, finally the United States - but the locals found it was always good to have a fort handy.

Now that the American threat has ebbed, the citadel is a museum of sorts, manned by soldiers in dorky kilts who get to shoot a cannon every day at noon. The innards of the museum are interesting and innocuous, except for the weirdly fetishistic Army museum, which has a 'gun nuts on eBay' vibe. There is a massive number of guns, medals, muskets, swords, and other hardware arrayed in glass cases, with many of the uniforms displayed on creepy pink-lipped plastic mannequins, all of whom are smiling. The walls have some terribly inept watercolors of Canadian gallantry in battle.

It looks funny for the first few rooms (muskets and sabers), but becomes macabre once the exhibit crosses into the Boer war and the early twentieth century. Canada has a long history of sending its young men off to die pointlessly for the British empire, and that history reaches its apotheosis in World War One. Canada joined the fighting in 1914 and suffered horrific losses - the Newfoundland regiment alone had an 80% casualty rate.

You would think the exhibit would allude to this, but instead it's an obsessive display of medals, regimental decorations, flags, guns, recruitment posters, and lovingly restored spiky German helmets. The tone even gets a little jocular - look at those funny-looking uniforms, and silly mustaches! More smiling milk-white mannequins.

Halifax was a boom town during both world wars - every Canadian soldier passed through here on his way to Europe. But it was also nearly obliterated towards the end of World War I, in 1917, when an ammunition ship carrying 2,500 tons of explosives collided with a Norwegian freighter in Halifax harbor. The ammunition ship caught fire immediately, but did not detonate for twenty minutes, giving it time to drift all the way to the downtown piers and attract a sizable crowd of onlookers.

When it finally went off, the blast levelled much of the town and killed or injured eleven thousand people. It was the biggest man-made explosion before the nuclear age. Five years earlier, Halifax had had to scramble to handle the hundreds of bodies brought in after the sinking of the Titanic. Now, in a terrible irony, the city was able to apply its expertise to counting and burying its own dead, and caring for the hundreds who had been blinded by flying glass when they went to watch the burning ship from their windows.

Most historical events in Canada seem to have a really good website associated with them - the Halifax Explosion is no exception, with several good links: There's a nice one-page summary site, a more comprehensive site from the CBC (try to ignore the part about the mini-series) and a good Wikipedia entry:

...Relief still came in from around North America and the world, but most speedy, and most generous was the help from Boston and from the state of Massachusetts to the south. To this day the citizens of Halifax still donate a large Christmas tree to Boston each year. The friendship also explains why even today many Nova Scotians are Boston Bruins and Boston Red Sox fans.

Which, with the hurricane, means it's been an especially rough month for the Haligonians.

I'm going to leave the hurricane damage and all the history behind me today, and drive north to see the highest tides on earth. Like the old proverb says, don't wait for Sunday to visit Fundy!

I flew in to Charlottesville last Thursday night in astonishingly bright moonlight. I didn't realize it, but the harvest hunter's full moon was on duty, and it had lit up the cloud tops right out to the horizon. You could count the rivets on the wing. There was a thick layer of stratus cloud just below us, with only an occasional gap giving away our true altitude, revealing a spider web of roads and subdivisions down on the ground.

As we neared Charlottesville, the plane made a long left turn to start its approach, and suddenly out popped the giant yellow moon. It was floating just above the horizon and wearing a long cloud on his head that looked exactly like a sombrero hat. All that was missing was the ball fringe.

"Buenos Noches", I thought.

I've been flying a lot this week - my itinerary makes a nice ASCII necklace:

BTV -> BOS -> ATL -> CHO -> CIN -> BTV -> MHT -> EWR -> YHZ

By some great luck, I have been seeing wonderful things from the plane all week. On the flight into Atlanta, there was thick overcast covering the city, and the plane descended into a sickly yellow world. The air was clear, but saturated with water. When the pilot extended the flaps for final approach, the entire wing burst into fog, from root to tip. Though the air around us was clear, the rear half of the wing was enveloped in a private, roiling cloud. It looked like someone had glued a hundred tons of cotton balls to the wing.

Many frequent fliers have seen the little wake vortices that sometimes spin off of a wing tip or a spar, but this was the first time I'd seen a whole wing swallowed up. A web search shows that condensation above lifting surfaces is very common, especially on military aircraft. That link points to the wonderful Gallery of Fluid Mechanics, which has photographs of all kinds of condensation and vortex action. In addition to garden-variedy wing fogs, there are more esoteric phenomena like the Prandtl-Glauert singularity, which is a condensation cloud that resembles a shock front. In this astounding movie clip, you can see a singularity form behind an F-16, disappear, and then re-form. Notice how severely the cloud buffets the plane - when the cloud re-forms, you can actually see the nose of the plane get shoved down. There's more info on the associated web page.

I flew from Charlottesville to Cincinnati at the black hour of six o'clock, the time when baggage handlers toss a football and the rest of the world sleeps. The airplane arrived over Ohio just as the pre-dawn twilight was brightening enough to show the ground, and I saw a giant snake of cloud eating its way across the landscape. It was the Ohio river, covered with thick morning fog. The scale of it was enormous - long tendrils of fog reached out into hollows, surrounding helpless towns. The Midwest was under attack by a giant angora python, and I was the only one who knew.

I've found that people who are not afraid of flying have little patience for people who are. We are the secret fraternity of armrest grippers; those who sit through takeoffs with eyes closed even though they aren't trying to sleep, others (my brothers!) who are compelled to stare out the window at the first tremor of turbulence, making sure the outside world doesn't flip over, and that the wings remain securely fastened to the sides of the plane.

Whenever I am particularly anxious about a flight, I buy an issue of Flying magazine to take on board with me. It is a balm for the scared traveller. Flying is aimed at the general-aviation pilot, weekend flyers who buzz around in small planes, and each issue is like a reassuring sermon. Hidden among all the GPS reviews, air show reports, and ads for airline training school is a morality tale, where the angels are Prudence, Sound Planning, Thoroughness, and Preparation, and the devils are Fatigue, Bad Luck, and Trying To Fly Under Visual Flight Rules In Marginal Weather Conditions. Pilots are exhorted to be Thorough, Prudent, and Practice Sound Planning, and are given vivid examples of what will happen if they do not. Each issue has a special section of FAA reports on recent crashes, a terse description of the incident followed by the body count, and where blame should properly be assigned. "March 30, 2002, On Approach to Talahassee. Injuries: 2 Fatal". There's also a regular column called "I Learned About Flying From That", which might as well be called "How I Almost Bought It In My Airplane", and my favorite colum, "Aftermath", where the author takes us through a single spectacular crash, detailing each fatal misstep leading to the gruesome accident.

The reason I find all this reassuring is because of the unspoken subtext that commercial air travel is really, really safe. General aviation pilots have a bit of a complex, because their fatality rate is uncomfortably high compared to road travel, let alone the utter safety of commercial aviation. This is exactly what I want to be reminded of when I am in a little Embraer jet at 37,000 feet, shaking like a Jello mold. In Flying magazine, you never see a report that says "Embraer pilot lost control of jet after wings snapped off in clear air turbulence. Injuries: 43 fatal". Instead, it's always "Piper cub pilot without instrument rating flew into thunderstorm", or "pilot became disoriented after flying into clouds at night", or "pilot allowed plane to enter graveyard spiral, overcorrected at 500 feet, plane broke up in flight".

Of course, there's a limit to the comfort you can get from a magazine in the stratosphere. But you take what you can get. I was heartened recently to discover that, after all this time, I had been wrong about what makes a plane fly in the first place. Instead of some dubious business about low pressure above the wing, there's the comforting thought of the plane pushing tons and tons of air down as it flies. I like the idea of the plane working hard to keep me in the air, not just relying on some kind of suction. So instead of Bernoulli, these days I fly with Isaac Newton. It's nice to look out over the wing and think I'm being kept aloft by sound English science, rather than some dodgy Continental quack.