Do you Remember when you were a kid, and whenever you found a sea shell you held it near your ear to hear the sound of the sea? Most of us does it till today. The clear sound kept within the shell is marvelous and so beautiful.... But how exactly is the sound captured or heard inside the shell?? What makes the shell sing the song of the ocean?
It is predictable most likely that the sound inside the shell as we all can hear is actually an ambient noise from around you. The seashell that you are holding just slightly above your ear captures this noise, which resonates inside the shell. The size and the shape of the shell therefore has some effect on the sound you hear. Different shells sound different because different shells accentuate different frequencies. You don't even need the seashell to hear the noise. You can produce the same "ocean" sound using an empty cup or even by cupping your hand over your ear. Incredible! I only wish we knew this when we were naive little kids back then...
Lightning Strikes Again
It is common knowledge that lightning is generated in electrically charged storm systems, and that many of them are mostly deadly, dangerous and even unpredictable.
During thunderstorm conditions the turbulence in the cloud causes the charges to separate in such a way that the negative charges concentrate in the base of the cloud. Since like charges repel, some of the negative charges on the ground are pushed down away from the surface, leaving a net positive charge on the surface.
Opposite charges attract, so the positive and negative charges are pulled toward each other. since the negative charges (electrons) are many thousands of times smaller than the positive charges (ions--charged atoms) they move much more easily and cover most of the distance. This first, invisible stroke is called a stepped leader.