1941: German engineer Konrad Zuse unveils the Z3, now generally recognized as the first fully functional, programmable computer.

Because Zuse designed and built his computer inside Nazi Germany, which was already at war, his achievement went unnoticed outside Germany until after the Third Reich's collapse. In the meantime, the Harvard Mark 1, a computer produced by an American team, appeared in 1944 and is still occasionally cited as the first of its kind.

Complicating Zuse's claim of priority, an air raid destroyed his computer, as well as all accompanying photographs and documentation. Zuse rebuilt the Z3 15 years after the war ended, to demonstrate its capabilities and to establish his claim to the patents associated with the machine.

The Z3, Zuse's third computer in a series of four, used the simple binary system for performing complicated mathematical computations -- its outstanding feature.

Zuse is also remembered for devising Plankalkül (calculation plan), an early programming language designed, although never implemented, for engineering purposes. Additionally, he's credited with founding the world's first computer startup company, Zuse-Ingenieurbüro Hopferau, or Zuse Engineering Office of Hopferau (Bavaria), in 1946.

Zuse's achievement, according to his son, was even more remarkable considering he worked independently, even in isolation, and remained unaware of contemporary developments in computer science. And unlike computer pioneers in the Allied countries, Zuse received precious little support from his government. The Nazis saw little military value in his computers and provided only very minimal funding.

Years later, Zuse was generously funded by Siemens and some other German companies when he rebuilt his Z1 computer as part of a retro computing project.

A replica of the Z3 (and the Z4) is on display at the Deutsches Museum in Munich.

(Source: Various)

President Bush, Gov. Arnold Schwarzenegger and the big automakers agree on this much: They love hydrogen-powered fuel cell technology and its promise of a zero-emission, petroleum-free future.

Unfortunately, experts say it will be 40 years or more before hydrogen has any meaningful impact on gasoline consumption or global warming, and we can't afford to wait that long. In the meantime, fuel cells are diverting resources from more immediate solutions.

"As a climate strategy, it's not very good," said Dr. Joseph Romm, executive director of the Center for Energy and Climate Solutions and author of The Hype About Hydrogen: Fact and Fiction in the Race to Save the Climate. "We don't have the time."

Climate experts and alternative-fuel researchers, including some hydrogen proponents, agree that hydrogen is at best a long-term solution. In the short and medium term, however, other technologies offer far greater benefit at far less cost: Cleaner internal combustion engines, hybrids and plug-in hybrids.

Some worry that these near-term solutions are being short-changed. But hydrogen advocates counter that the answer isn't cutting hydrogen funding, but increasing funding for research into a wide variety of alternatives to oil.

"The few million we're spending to change our energy policy is like sending one platoon to Normandy," said Paul Williamson, director of the Hydrogen and Alternative Energy Research and Development program at the University of Montana. "It's just not going to happen."

To some extent, politicians and policymakers recognize that hydrogen remains a long way off, which is one reason the California Air Resources Board has told automakers to build 58,000 plug-in hybrids by 2014. And automakers are building cleaner gasoline and diesel engines while developing hybrids.

But the emphasis remains squarely on hydrogen.

Congress appropriated $283.5 million for the Hydrogen Fuel Initiative this year, bringing its investment to $1.16 billion since 2004. California's "Hydrogen Highway" may be floundering, but the Air Resources Board is handing out $7.7 million to build hydrogen stations even though the last three agencies to receive state funding gave it back.

Many hurdles remain to be cleared before hydrogen is a viable source of energy -- not the least of which are making, storing and distributing it on a large scale. Meeting these challenges will require, in the words of several hydrogen proponents, a "Manhattan Project"-level of research and funding. And we're a long way from the hydrogen economy President Bush envisioned in his 2003 State of the Union.

The transition has begun though, and California is leading the way even as it keeps relaxing the rule dictating how many electric and hydrogen vehicles automakers must build. There are 175 fuel cell vehicles in California and more coming. Honda will begin leasing its hydrogen-powered Clarity FCX this summer and General Motors will put its Equinox fuel cell vehicles in 100 driveways this year. Hyundai plans to begin mass-producing fuel cells cars in 2012, and GM -- which has invested more than $1 billion in hydrogen -- says it will have 1,000 vehicles on the road in California by 2014.

But few people expect to see fuel cell vehicles in showrooms before 2020, and we won't see any large-scale benefit from them until 30 years after that.

"2050 is when hydrogen might -- might -- have a significant impact," said John Heywood, director of the Sloan Automotive Laboratory at the Massachusetts Institute of Technology.

The timeline has more to do with economics than science. There are roughly 240 million vehicles in America and about 16 million new vehicles sold each year. That means it takes about 15 years to turn over the fleet. But it takes even longer for new technologies to penetrate the market.

Heywood cites hybrids as an example. They may seem ubiquitous, but after 10 years, hybrids accounted for just 2.2 percent of domestic auto sales last year. Run the numbers and Heywood estimates fuel cell vehicles will need 25 years to make up 35 percent of new vehicle sales and 20 years beyond that to get to 35 percent of the U.S. fleet.

We can't wait that long. Scientists increasingly agree that industrialized nations must cut greenhouse gas emissions as much as 80 percent by 2050 if we are to curb global warming. The Environmental Protection Agency says fuel economy may have to rise to 75 mpg within 30 years to hit that target. California law requires easing emissions even further than that by 2050. Hitting these targets will require putting 379,000 zero-emission vehicles on the road by 2020 and 7.6 million by 2050, according to the Union of Concerned Scientists.

Hydrogen critics argue that plug-in hybrids and electric vehicles are the answer. But electricity brings its own challenges. Plug-in technology can cut fuel consumption by up to 62 percent, but it adds $8,000 to $11,000 to the cost of the car, according to the National Renewable Energy Laboratory (.pdf). EVs like the Subaru R1e and Mitsubishi's MiEV have a range of no more than 100 miles. The Tesla Roadster gets 220 miles and charges in about 3½ hours, but it costs $98,000 and its lithium-ion battery pack which weighs 1,000 pounds.

"The reality is, as much as everyone in the industry has hoped for affordable, high energy batteries, they don't exist yet," said Ron Cogan, editor of GreenCar.com and Green Car Journal. "We're not there yet with battery electric vehicles or hydrogen. We're on a path to both."

And we'll need both if we're to address global warming and our dependence on oil, climate experts say. Even critics like Romm aren't suggesting we scrap hydrogen entirely. For all its challenges, hydrogen still presents the opportunity, however distant, for a sustainable source of energy that can displace petroleum.

For now, the issue isn't electrics or hydrogen but electrics and hydrogen.

"Given that timeline and the number of vehicles we're talking about, we have to keep working on battery electric vehicle and fuel cell vehicles at the same time," said Spencer Quong of the Union of Concerned Scientists. "Both of them have huge challenges, and if we don't work on both of them, we won't meet our objectives."

Kevin Sites in the Hot Zone - Chapter 15: Coming HomeIn this final chapter of "A World of Conflict," Kevin Sites returns home to the U.S., only to confirm what he suspected -- that in the year that he was gone little had changed.

Kevin Sites in the Hot Zone - Chapter 14: Israel-Hezbollah WarThe war between Israel and Hezbollah shook the landscape in the Middle East.

Kevin Sites in the Hot Zone - Chapter 13: Sri LankaKevin Sites covered Sri Lanka as violence erupted between the government and Tamil Tiger rebels, pushing a nation with so much to lose back to the brink of all-out war. In rebel-held territory Sites interviewed Tiger fighters about their tactics and reported on the many effects of war still seen in the region.

Kevin Sites in the Hot Zone - Chapter 12: Nepal and KashmirKevin Sites covered Nepal during a time of sweeping political change that followed mass nationwide protests, forcing the autocratic King to cede power.

Kevin Sites in the Hot Zone - Chapter 11: Child BrideIn Afghanistan, Kevin Sites met a 12-year-old girl named Gulsoma, whose incredible story of resilience resonated with millions of people worldwide. She was only six years old when she was sold to a neighbor family in Kandahar as a child bride.

Kevin Sites in the Hot Zone - Chapter 10: AfghanistanReporting from Afghanistan in spring 2006, more than four years after the U.S.-led coalition ousted the Taliban, Kevin Sites found that war is not over in the country.

Kevin Sites in the Hot Zone - Chapter Nine: ChechnyaIn Chechnya during the winter of 2005-2006, Kevin Sites reported on a region still reeling from lingering conflict between Russia and Islamic separatists. The conflict engulfed Chechnya in the 1990s, and even now, half of the population is yet to return. Those that have eke out a living amid the rubble.

Kevin Sites in the Hot Zone - Chapter Eight: Iran

Kevin Sites in the Hot Zone - Chapter Seven: IsraelIn Israel, Kevin Sites interviewed Kinneret Boosany, a victim of a suicide bombing at a Tel Aviv cafe in 2002.