The World's first Seismograph

Actually seismograph is a word devoted to the measurement of earthquakes precisely. As far as earthquake is concerned, it is one of the most disastrous hazards faced by humans in their history, and still we are experiencing it.

As we all know that it is scientifically proved fact that the mountains are actually designed by ALLAH to control the earthquakes on earth. But there is a question here. Why earthquakes hit mostly the regions populated with mountains? The answer to that question is simple. Because most of the patients are found to be in a doctor’s clinic!!!

The history of china tells us that it experienced many earthquakes in ancient times due to presence of mountainous region. So to deal with that they strongly feel that they must have something to deal with earthquakes. Unfortunately in the modern era, we are still unable to control the earthquake but at that time a wonderful thing happened. A Chinese guy, Zhang Heng invented the world’s first ever seismograph for the prediction of earthquake. Let us see how it works. Actually this seismograph is based on very simple but intelligent principles of vibration. Ok let us discuss it:

The material chosen for this seismograph is fine cast bronze. This seismograph had a diameter of eight ‘chi’, and was shaped like a wine jar. Keep in mind that ‘chi’ is the unit of length used by Chinese for the measurement of length in ancient times. Calculations show that one chi is almost equal to 0.237 meters. As in this case the diameter of wine jar is eight chi, it implies that its diameter is almost 1.896 meters. So now it is easy to imagine the size of that seismograph. Inside this wine jar, Zhang Heng made it possible to hang a mass with some string (you can say it a pendulum). He clamped the string at the one end with a hole in the top lid of the wine jar. And at the second end he attached a mass. After adjusting the pendulum within the jar he surrounded the pendulum within the jar by eight levers pointing in eight directions. These levers are aligned in such a way that the angle between them is 45 degrees. So that the eight levers are covering the 360 degrees. He projected the some length of levers outside the wine jar and here he attached the crafted dragon mouths. So there are 8 dragons total on the outside of jar. Below each dragon he precisely aligned the crafted toads. Zhang Heng then place the balls within the mouth of each dragon. Now let us see how this arrangement works. A strong earthquake in any direction would tilt the pendulum inside the jar in that direction. The mass of pendulum strikes the lever in that direction. Due to which this lever transforms the momentum from the mass of the pendulum to corresponding ball within the mouth of the dragon. This ball fell in the mouth of the toad with clanging sound. So two purposes are achieved simultaneously with this invention. It enabled the personnel to determine the time of earthquake by hearing the clanging sound of ball. And it enabled the personnel to determine the direction of occurrence of earthquake by determining that which ball among the eight fell into the mouth of toad. It is quite amazing to know that how intelligently people are thinking at that time.

Conceived and Complied by: Engr. Ammar Aziz