Most people know that lightning is a massive discharge of electrical energy from the heavens to earth. It's power is so intense that it momentarily heats the air in the path of the surge hotter that the surface of the sun! This causes the brilliant flash we see as lightning and the shock-wave through the air we hear as thunder. In actual fact they are one and the same event but because light travels so much faster we see it essentially instantaneously, whereas the sound takes a while to catch up. Roughly four and a half seconds for each mile travelled.
But not many people know that a lightning discharge also, almost always, involves a small discharge upwards from the earth before the main strike occurs. These upward sparks are known as "positive streamers".
What happens in a lightning storm is that the base of the thundercloud accumulates a massive negative charge as electrons are knocked off the rapidly ascending ice particles in its core. The earth underneath the cloud is thus positively charged with respect to the cloud-base. The earth and the cloud-base become like the two terminals of a giant battery, super-charged with energy.
As the energy in the cloud seeks to find a way down to the ground, the energy in the ground is also seeking to find a way up to the cloud. Think of them like the jump-leads attached to the two ends of the battery. When the leads touch, that's when the sparks fly!
The interesting thing is, that whilst it is the heavens that holds all the energy, it is released in response to an "upwards spark" from the earth.
I was thinking of this yesterday in connection with prayer. These "upward sparks" are a wonderful illustration of how God uses our prayers. All the power is his, but he chooses to release the awesome power of heaven in response to these little "upward sparks" of prayer send up from the earth!
Our prayers may not seem like much, but all the power of heaven is waiting to be discharged in response in a way that will connect heaven to earth, and make an impact that will be felt for miles.
[If you would like to see a picture of one of these upward sparks, have a look at this picture, and look carefully at the telegraph-pole on the left-hand side of the main lightning strike]