In the cockpit of a multi-million dollar jet fighter, a pilot makes a split second mistake that ends in disaster. After talking to his instructor, he takes off for a second "flight" in his simulator. SIMULATORS have made training for many professions far safer, more effective and less expensive than it would be if the students were in command of the real thing. MODERN MARVELS traces the history of these "synthetic reality" devices back to the 1929 Link Pilot Trainer, an open cockpit mounted to a universal joint and activated by pipe organ bellows. From this inauspicious beginning, simulators have developed into extraordinarily sophisticated devices that can emulate entire tank battles, the passage of supertankers through narrow, storm-tossed straits, and landing jet airliners in dangerous conditions. Climb inside some of the multi-million dollar devices that offer an invaluable substitute for on-the-job training.