A mechanical watch has no batteries, it has no electricity or computers either. Only springs and gears!
On April 13, 1970 two days after the launch of the Appolo 13 lunar exploratoin mission, the crew heard a very loud BANG. Astrounaut John Swigert radioed ground control and uttered the famous words: "Huston, we have a problem". In fact an oxygen tank had exploded. The command module's normal supply of electricity, light and water was lost, and they were about 200,000 miles from Earth.
The Speedmaster was the only watch in the world that managed to pass NASAs rigorous test.
Astronauts lives were at stake.
The main source of oxygen and electricity was no longer operational. The craft was crippled and landing on the Moon was no longer an option. One of the big questions was, "How to get back safely to Earth?" The crafts navigation system wasn't designed to help in this situation.
The onboard computers were not programmed to handle this kind of situation.
The computers on board were of no use, the craft had to be operated manualy,but luckily, Swigert had his trusty Omega Speedmaster on his wrist! With help of ground control he used it to time a very delicate 14-second manoeuvre to put the craft on a safe trajectory back to Earth.
"The flight was a failure in its initial mission. However, it was a tremendous success in the ability of people to get together, like the mission control team working with what they had and working with the flight crew to turn what was almost a certain catastrophe into a successful recovery."
It worked!
The Apollo crew landed safely in the South Pacific Ocean on April 17. The watch helped save the crew when no computer could!