People in Jabodetabek, even to South Tangerang on Saturday morning were shocked by the sound of a loud bang or eruption, whose source is still a mystery. The pounding was so real, some people reported, a tremor was felt in the doors and windows of the house.
What and where do you think the sound is coming from? After the statement appeared that at that time there was no eruptive activity from the volcano, especially from Anak Krakatau, it is interesting to examine the source of the explosion.
As an electrical engineer and teaches electrical physics, I was intrigued to find the answer. It could be true, it could be wrong – but at least there is a basis and a logical explanation so that it avoids us from excessive anxiety and worry, especially in situations like this, which make our immunity decrease.
In my opinion, it is possible that the boom came from the sound of thunder or thunder that was produced by striking lightning. There are 2 types of lightning, namely negative lightning and positive lightning.
I am not going to go into how this thunderbolt occurs as it will be lengthy in theory. But what is interesting is that positive lightning rarely occurs according to data, only 5% of all lightning strikes occur.
Positive lightning power can be 10 times that of ordinary lightning (negative lightning). The connection can reach a distance of 40 km (similar to the distance from Jakarta Bogor) and the voltage generated reaches 1 billion volts. The sound of shaking will be terrifying, like a bomb exploding.
This positive lightning strike in the world of electricity is called positive cloud to ground lightning, which means that the positive charge in the upper cloud meets the positive charge on the earth’s surface.
Generally what happens is a negative charge located in the lower cloud, meeting a positive charge on the earth’s surface (ground).
As we know, air is a bad conductor, so the occurrence of lightning will definitely release a huge amount of energy. Even the resulting temperature reaches 25,000 degrees Celsius or 5 times the temperature on the surface of the sun.
Now, why does it sound far enough?
One of the natural phenomena that makes the sound of lightning louder is that the air layer at the top of the cloud is warmer than the air layer on the earth’s surface.
This event is called temperature inversion or the suppression of a layer of cold air by a layer of warm air. these conditions aren’t normal, they’re generally not – the temperature gets colder as the altitude rises.
This condition makes the sound produced from the lightning can not spread up and in all directions but like moving along the surface of the earth, so that it sounds stronger and farther away. So the thunder sound waves like following an audio channel or what is called tropospheric ducting.
We can say that when we pop a balloon indoors, with a balloon being popped outside the room. Which sounds clearer? Or if you have ever watched a big music concert, you need to make a roof on stage. One of the goals of the roof is to strengthen the acoustics of the stage so that the sound of the music can spread to the audience. The roof functions much like hot air trapping cold air underneath.
Moreover, the atmosphere of Bogor, Depok, and Jakarta is in a condition of Large-Scale Social Restrictions (PSBB), almost quiet, so that the sound is clearer, similar to a boom.
What I don’t know is where the source of the lightning is – is it when it rains in Jakarta, Bogor or Depok? Wallahua’lam. Hopefully it is useful to broaden our insight.
–##–
By:
Dr. Ing. Eko Adhi Setiawan
from Hijauku