No-one spirited direct from 1899 to the present would find advances in surface transportation unbelievable, but aerospace would amaze them.
While ships, cars and trains have seen massive gains in efficiency, they are still fundamentally the same machines. Within the past 100 years, however, powered flight has not only been invented but mastered.
Air transport, with telecommunications as its crucial partner, has shrunk the world. It is the ability to travel anywhere on the planet within 24h that makes news from 10,000km away relevant to us all. No-one, any longer, can feel insulated from world events because of distance.
A visitor from 1899 would see that Concorde has made supersonic flight unsurprising, if still glamourous. And, as the new century starts, Airbus Industrie is preparing to launch its A3XX, and Boeing its 747-X, presaging an era in which 1,000-passenger airliners will take to the air, offering levels of safety and reliability undreamed of at the dawn of the jet age.
When there will be a successor to Concorde depends as much on future attitudes towards aviation and the environment as it does on advances in technology. In fact, just as the developed world is having to decide what to do about road transport congestion and the pollution caused by its "success", air transport is facing air traffic control and airport congestion, and serious questions about aviation's contribution to global warming.
Our time traveller would also recognise that aerospace technology has, at least until recently, been driven by military demands. In the First World War, aviation may have had a negligible effect on the course of the conflict, but the war massively accelerated the rate of aircraft development. In 1914, aeroplanes struggled to get airborne. Four years later they could dogfight and drop bombs.
In the Second World War, military aviation's greatest influence was to extend the battle well beyond "the front line", adding to its military complexity and escalating the impact on the civilian population. Once the first atomic bombs had been dropped on Nagasaki and Hiroshima, the world had changed forever.
The subsequent development of the intercontinental ballistic missile ensured that no nation could believe itself immune from nuclear strike. Arguably, this fearsome capability also prevented Word War Three.
While our visitor from the past would have to acknowledge that nuclear war remains a possibility, it is clear that a revolution in conventional weaponry has given the military the ability to strike with surgical precision, promising to limit casualties among soldiers and civilians.
It remains to be seen whether today's precision munitions, coupled with emerging information warfare capabilities, can have the same deterrent effect that saw us safely through the Cold War.
Perhaps man's ability to break free from Earth's bonds is what would most surprise our visitor from 1899. Neil Armstrong's "one small step" on to the moon's surface is probably the most inspiring event in the history of exploration - and not only for those who watched it as it happened on their black and white television sets.
As the 20th century closes and the 21st opens, space remains the "final frontier" for our industry. With the past year's spate of launch vehicle failures, the continuing controversy over the cost, schedule and rationale for the International Space Station and now NASA's missing Mars probes, it might seem that much of the excitement of space has worn off.
But for an industry that has advanced from the Wright Flyer to the Voyager planetary probe exploring beyond the furthest reaches of our galaxy in less than 100 years, the exploration and exploitation of space still provides one of the greatest opportunity for technological and commercial advancement, and the potential to continue transforming our everyday lives.
The end of the 20th century may have been hijacked by the computer and communications industries, but many of the crowning technological achievements of the past 100 years have been in aerospace.
Source: Flight International
