Today I made hydrogen. I followed it up with some helium and a little carbon and oxygen. Tomorrow, if I have a little time on my hands, maybe I'll try for einsteinium.

No, I'm not doing tabletop fusion here at NOVA. I'm using NOVA's new iPad app, "NOVA Elements," which lets you create your own atoms and combine them to make the molecules in everything from a cup of coffee to a wristwatch. It's our first app for iPad and--though I may be a bit biased--I think it's very cool. Angry Birds cool. Complete double rainbow cool. Making your own atoms cool.

The app also includes an interactive periodic table loaded up with facts about each element--when it was discovered, what it looks like, where you'll find it in everyday (and not so everyday) objects--and video clips from "Hunting the Elements," our two-hour special about the periodic table. You can also watch the entire show through the app.

Just remember to turn on the sound: You will definitely want to hear those little Pew! Pew! Pew! sounds that the electrons, neutrons, and protons make as you fire them into your brand new atom. And you'll hear David Pogue, the host of the show and the face and voice of the app, guiding you through the menus and offering encouragement, kudos, and some tough-love commentary as you create your own atoms and molecules.

The app is totally free, and you can download it from the iTunes app store.

Have fun, and let us know what you think!

Muster drill: The drill is at 4:30 p.m. on day one, before we leave port. Crewmembers are outfitted in bright yellow vests and hold signs that point passengers in the right direction. The room key (which also serves as an onboard credit card and ID) has each passenger's muster station assignment clearly printed on it. Each passenger (including our infant niece) gets one; we are instructed to carry them everywhere.

Digital roll call at muster station: Arriving at our muster station, our room keys are scanned, checking us in. We're told to sit down in a particular location (a certain section of the small theater) and wait for further instruction. This is how it would happen in a real emergency. The staff are all knowledgeable and professional. A movie then plays (in English, but with instructions on how to obtain it in Spanish, French, Portuguese, German, and a few other languages) showing us how we will be alerted to an emergency, and how we should proceed. Also, a TV channel constantly showed the safety movie--in case there was nothing good on TV?

Safety instructions are posted in every room: The boat is so large that it's easy to get lost, so the instructions are helpful. During the muster drill, crewmembers are all over the ship holding up signs and pointing passengers in the correct direction. Because there are so many passengers, our muster station isn't actually at our lifeboat, but rather a designated meeting place where we would await further instruction, and be guided to our lifeboat if necessary. We also don't have lifejackets in our stateroom--if needed, we would receive them at our muster station. Our stateroom was on Deck 10--pretty far above the surface of the water--so it would make sense not to have lifejackets in our rooms. Unless they came equipped with parachutes...

Lifeboats: The lifeboats seat 370 people, and there are 18 of them on the ship. They even have bathrooms! If you do the math: 18 lifeboats x 370 passengers = 6,660 seats. Well, the ship holds more than 6000 passengers and 2500-plus crew, so the numbers don't quite add up.

Good things come in small packages: The difference is made up by the expandable life rafts held inside these plastic cylinders. But getting into them is not for the faint of heart. Here's why.

Just slide down the esophagus: Officially it's called the VIKING Evacuation Dual Chute, but we call it "the esophagus." We think you'll see why when you look at the diagram below, which is posted near the expandable rafts. The entrance point is on Deck 4. The exit point is water level (Deck 1). We're quite relieved that we don't practice using these devices at any point, although I guess that some people would find it fun. Probably the same people who think that the zip-line across the back of the ship is fun. Unfortunately, they don't ask you if you are afraid of heights before assigning muster stations and life rafts.

The Esophagus: Here are diagrams showing the "esophagus" in action. It's important not to wear high heels in the esophagus. Could make the trip a bit shorter. (We're relieved to learn that our muster station has us assigned to a "real" lifeboat.)

Crew drill: On the second day of our trip, there is a drill for the crew. Over the ship's PA system, we hear "Bravo Bravo Bravo" and a location. This is code for a fire drill. Crewmembers in full fire-fighting gear head off toward the location announced. The ship's many water-tight doors seal. When the drill is over, the crewmembers let us take their photo. Bravo (fire) team members have red tags on their IDs; EMS-type team members have blue tags. (Our waiter had a blue tag.) The full muster drill we went through is done prior to each sail. There is an all-hands drill once every 2 weeks. On the intervening weeks, the crew is split into half, with the halves alternating drill weeks. The Bravo team practices weekly.

We went to the New Mexico desert to blow up a car. It was an ugly car--a white 1970s Cadillac, rescued from the junkyard. In the trunk, 300 pounds of ammonium nitrate and fuel oil, the same lethal ingredients that the Oklahoma City Bomber used to destroy the Federal Building in 1995. Our car bomb, we were told, would vaporize sections of the Cadillac and level the modular building standing next to it. And our explosives were just one 15th the size of the bomb in Oklahoma City.

This was one of our most anticipated shoots for our two-hour NOVA special, "Hunting the Elements"--and also one of the most horrifying. We had stepped into a virtual terrorist's playground--the Energetic Materials Research and Testing Center at New Mexico Tech--and our morbid curiosity grew with each demonstration. Here, bomb experts and scientists spent their days teaching emergency personnel how to respond to nightmare scenarios, and the daily menu of demos was extensive. For an appetizer, a briefcase bomb that blew the torso off a wooden dummy and a pipe bomb that obliterated a watermelon and the table it was sitting on. For the main course, a letter bomb that amputated and wedged a mannequin's foot in the ceiling and a wooden dummy suicide bomber whose improvised explosive device shot bolts through metal signs like bullets.

We filmed all four explosions with a special high-speed camera that played back the action in eerie slow-motion detail. But it was the dessert course--the grand finale car bomb--that most horrified...and fascinated...our crew. As we watched the playback of the slow-mo footage, a dome of super-heated gas--invisible in real time--appeared above the initial fiery blast, and with each frame, moved up and outwards, warping our view of the desert behind it into a wavy, trippy landscape. "That's the shock wave," one of the bomb technicians said, pointing to the gaseous dome. It's not just the heat and debris from the bomb that'll kill you, he told us. It's the shock wave that'll knock you dead.

Suddenly everyone on the crew wanted to rewind the video. It's not that we'd never heard of a shock wave--most people can tell you it's a wave of energy released when you set off a bomb, literal or otherwise (as in...your dad's reaction to the sentence, "I just totaled the car..."). But few of us realized this was the primary source of destruction. When most of us non-scientists think of bombs, we think of the fiery blast and the lethal projectiles it sends shooting into the air. We were riveted as the ordinance technician described this dome of energy that expanded too quickly to see with the naked eye. "Often, we find victims on the scene who've died without a scratch on them," he explained. They might escape the fire, but a shock wave can literally liquefy their insides.

Now the room was alive with questions: What exactly was a shock wave? How did it work? And why did some chemical reactions create them, while others just caused a fire?

Turns out the answers lie not just in chemistry, but in physics.

Chemistry tells us how fire works. When you strike a match or introduce energy from any heat source (like friction or lightning) to a fuel (like wood or gasoline), carbon atoms in the fuel combine with the oxygen in the atmosphere. In other words, they "oxidize," or burn.

This is how explosives work too. The only difference is the speed of the reaction. Fire needs oxygen to burn, but it has to forage for it in the atmosphere. But a substance like gunpowder, for instance, packs its own oxygen. When ignited, the fuel molecules recombine with oxygen, just as they do with fire--only much more quickly since the oxygen is right there, more available. Instead of the sizzle of a flame, when a gun fires, you hear a bang. That bang is the calling card of an explosion...and it's caused...by a shock wave.

Speed up the reaction even further, however, and the shock wave becomes incredibly destructive. Gunpowder is a relatively slow explosive and its destruction is fairly limited. That's why you can shoot a bullet out of a gun without destroying the barrel. But a high explosive like the ammonium nitrate fuel oil bomb in the car trunk can deliver mass calamity in an instant. Made of unstable molecules with incredible amounts of stored-up energy, these compounds react instantaneously, liberating all that energy in the form of a high-pressure wave traveling at supersonic speeds. According to scientists at New Mexico Tech, in just billionths of a second, a shock wave can produce pressure up to 500,000 times the earth's atmosphere, can travel as fast as six miles per second, and can heat the air to more than 9,000 degrees Fahrenheit.

With power like that, the shock wave pushes away everything in its path, from buildings to bodies--often without even breaking skin. This is where we can really see the role of physics. Think of how crushing a soda can displaces the liquid or air inside it. Our bodies are filled with air-containing organs (lungs, intestines, eardrums) that crush, distort, and tear under the sudden pressure of a blast. There may be no penetrating injury from debris or shrapnel, but victims may hemorrhage with massive internal bleeding.

A shock wave even displaces the air particles in the atmosphere. And this fact, the technician told us, generates the bomb's second lethal force. When the shock wave pushes away the air surrounding the detonation site, it creates a vacuum that sucks air particles and debris back towards the bomb site. When you see glass inside a structure after a bomb attack, the technician said, people tend to think the bomb detonated from outside. It's a common error. Often, the glass was just sucked back in by the vacuum created by the shock wave.

When we inspected the briefcase bomb site after detonation--the charred wooden half-torso sitting in front of the remnants of a desk in a modular building--sure enough, there was glass inside the structure from the windows shattered in the blast. An hour later, after detonating the car packed with explosives parked in front of the structure, the entire building lay in pieces on the ground. Standing miles away in a bunker, we felt a grand rush of adrenaline, followed by a mix of horror both at the destruction and our own fascination with it. These were some of the most devastating--and exciting--reactions chemistry had to offer, and as horrified as we were, we wanted to slow them down and watch them again. Not just to see the wreckage wrought by explosives, but to marvel at the invisible force that wrecked it all in the first place.

"Hunting the Elements" premieres Wednesday, April 4 at 9 p.m. ET on most PBS stations. Please check your local listings to confirm when it will air near you.

Theodore Gray's mad scientist lair sits hidden amidst miles of cornfields outside the small college town of Champaign, Illinois. If you drive by too quickly, you'll miss the entrance, an unmarked gravel driveway off an unnamed country road. Turn in, and where you'd expect to see a quaint farmhouse at the end of the driveway, you'll find an industrial-size hangar filled with a 10-year-old-boy's fantasy toys: model rocket kits, mechanical gizmos, rusting antique farm machinery, and jars marked with skulls and crossbones.

The perfect spot for a mad scientist's lair.

The Lair, as Theo calls it, was one of the last stops on our three-month NOVA film shoot for "Hunting the Elements," a two-hour special about chemistry's famous periodic table. Our crew had been crisscrossing the country and had even traveled to Russia, and we'd dropped our host, New York Times technology columnist David Pogue, into some of the most dramatic scenarios we could find: a tank of sharks that would (hopefully) be repelled by rare earth metals; a firework testing range, where explosions colored by strontium, copper, and barium were launched amidst a pelting Nor'easter; a desolate stretch of the New Mexico desert, where we blew up a Cadillac Deville with 300 pounds of ammonium nitrate and fuel oil.

Each of these places revealed details about specific elements, but few of them told us much about the periodic table itself, and this is why we headed to the Illinois flatlands to see Theo Gray. Co-founder of Wolfram Research and author of the gorgeous photographic book The Elements, Theo is quite simply a world-class connoisseur of the elements, and he has the collection--2,379 elemental samples--to prove it.

Until I met Theo, the periodic table was pretty much a mystery--a series of letters and numbers that I recognized, but didn't much understand. My last encounter with the chart, like most people's, was in high school chemistry. But, as it turns out, the chart itself isn't actually that complicated--it was just that I was approaching it wrong. The trick, Theo explained, was to stop thinking like a chemist, and to start thinking...like a matchmaker. On the far right of the chart were the noble gasses, confirmed bachelors that don't mix with the riff-raff. On the far left, the alkali metals, desperate lonely hearts that react with nearly every element that comes along. In between were the metals, elements that sometimes react, and sometimes don't. And this genius chart that has persisted without challenge for more than a century is the predictive key, pinpointing which pairs will last, and which will go bust.

Is it a love connection? Image via Wikipedia .

It's not easy to make a television show about a list of elements, especially one that most people recognize but don't know how to read. Even more daunting, the periodic table doesn't just catalog the elements. It describes their atoms, and the squares around their names are arranged from left to right by the increasing number of protons inside their atoms' nuclei. That alone is more chemistry than most non-chemists want to think about.

But this is where Theo Gray comes in. To understand the chart, he explained, you don't have to know a thing about atoms. A case in point: Dmitri Mendeleev, the 19th-century Russian scientist who created the periodic table, invented it before the structure of atoms was even discovered. He knew the elements' physical characteristics and how they behaved chemically when they came into contact with each other, but he knew nothing about protons, neutrons, and electrons. This, Theo explained, is the key to decoding the periodic table--and Mendeleev's stroke of genius. Without knowing any of the physics to explain the phenomenon, Mendeleev realized it was the elements' behavior--and their reactivity to each other--that should determine the chart's organization. And there has never been a experiment in the century since he designed the chart that has proven him wrong.

To see what he was talking about, Theo told us, we'd have to step into his Lair where he'd set up a makeshift lab bench. Above it, he had hung a net of popcorn and when we tasted it (which we did), it was clear it was in need of a certain seasoning. To improve the taste, however, we'd all have to suit up in protective eyewear, and David Pogue, Theo's designated on-camera assistant, would have to be encased in a flame-retardant shirt and gloves. The experiment, Theo explained, involved two of the most reactive elements on the periodic table: chlorine gas, which can liquefy your insides, and sodium metal, which explodes on contact with water.

Making salt.

What we had were two "desperate Lonely Hearts," Theo explained--two unstable elements that would readily react with each other. Lonely Heart Number One, sodium, came from the table's far left-hand column of the alkali metals, while Lonely Heart Number Two, chlorine, lived on the other side of the table in the halogen column, just left of the noble gasses. Alone, these elements were poisons, but when Theo allowed heated chlorine gas to come into contact with a chunk of sodium metal, a cloud of sodium chloride--salt--wafted up into the bag of popcorn.

Delicious!

Where can I find butter on the periodic table?

So how does salting up popcorn explain the structure of the periodic table? The simple answer: elements with similar chemical properties live in columns, or families, on the table, and each element in the family reacts in a similar fashion. Some families are full of giving elements, others contain desperate ones looking for handouts, and some are aloof and disconnected from their neighbors, content to fly solo.

Today we have a deeper understanding of how the particles that make up atoms conspire to produce these reactions, but Mendeleev himself didn't know any of this when he designed the table.

After visiting Theo's lair, the periodic table suddenly made sense. The chart I'd thought was just a list of individual elements is actually about their reactivity--the chemistry among elements. There is a reason we use that word to describe our human attractions--some relationships make it, and others combust. If only we humans had a table of our own to tell us which ones were which.

"Hunting the Elements" premieres Wednesday, April 4 at 9 p.m. ET on most PBS stations. Please check your local listings to confirm when it will air near you.