Answers

2016-02-10T16:53:05+08:00
When a heat cold weather mixed together to the cloud it makes lightning

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2016-02-10T16:54:41+08:00
Lightning is an electric current. 
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Lightning comes from the sky down, but the part you see comes from the ground up. A typical cloud to ground flash lowers a path of negative electricity  (that we cannot see) towards the ground in a series of spurts...