Because opposites attract, the negative charge at the bottom of the storm cloud wants to link up with the ground’s positive charge. Once the negative charge at the bottom of the cloud gets large enough, a flow of negative charge called a stepped leader rushes toward the Earth. The positive charges at the ground are attracted to the stepped leader, so positive charge flows upward from the ground. When the stepped leader and the positive charge meet, a strong electric current carries positive charge up into the cloud. This electric current is known as the return stroke. We see it as the bright flash of a lightning bolt.
Thunder and lightning occur at roughly the same time although you see the flash of lightning before you hear the thunder. This is because light travels much faster than sound
Emmett Till's murder was such a spark in the civil rights movement because there was proof that Emmett was not guilty of what the people accused him of, he was only 14 years old at the time of his death and because the people that killed him admitted in a national newspaper that they killed him and were still found not guilty.
