Seismograph - History of Seismograph
When the Earth shook in the ancient world, the Maimas from Peru believed that their god had come for a visit. Footsteps, then, was their explanation for the cause of an earthquake. Today, it is common knowledge that earthquakes are due to the movement of the large tectonic plates that compose the core of the Earth. However, creative technologies to measure these quakes have emerged throughout the centuries and currently form what we know today as a seismograph.
A Chinese man named Change Heng built the first seismograph in 132 AD. It was built as a large tin pot with eight vertical dragons each facing downwards. All of the dragons contained a single metal ball in their mouths. When an earthquake caused the tin to vibrate, this seismograph was designed to release the ball from the dragon's mouth nearest to source of the quake. It was extremely effective, and even once alerted the local people of an earthquake occurrence that wasn't even felt.
In the modern world, John Milne invented the first seismograph in 1880. This seismograph detected earthquakes through a long pendulum that was attached to a stylus. When the earth shook, the stylus then wrote on a carbon-coated paper. This produced a pattern that detected the direction and intensity of the quake. A limitation of this design, however, was that the pendulum was left un-dampened, which resulted in calculations that were affected by random vibrations in the room. Thus, the development of a dampened pendulum was created in 1898.
Today's seismographs, known as electromagnetic seismographs, use a coil that is moved through a magnetic field when the Earth trembles. This movement creates an electrical current that is fed to a machine, which measures the current and provides details about the source and direction of the quake. Multiple scientists around the world pioneered this idea in the early 1900s.
With the development of the electromagnetic seismograph, the monitoring of earthquakes greatly expanded in the 20th century. The World-Wide Standardized Seismography Network was establishing 1960s to monitor earthquakes in over 60 countries. Additionally, in 1984, the United States formed a national system within the National Science Foundation to continually monitor and research earthquakes. Today, even though it's known that footsteps aren't the cause of the Earth's tremors, much is yet to be discovered about their large influence on the planet. Therefore, seismographs continue to be an important tool used to study these earth-rattling quakes.