lightning

Hi, Bob. Most of the time, earth is more positive. However, "positive lightning" (less than 5% of all lightning strikes) are the reverse.

Lightning goes both upwards and downwards.

Trees have hollow, water-filled cells, and as such can be a better conductive path than the surrounding air.

There's quite a bit of good basic information in the Wikipedia article on lightning:

Good luck Chris

You can calculate the voltage produced across a given width of ground (say, the distance between your feet when standing!) when a lightning bolt strikes. A couple ten thousand amperes can develop a lot of voltage, especially with a fast event like a lightning bolt.

Tim

When the lightning current goes through the tree, the water inside the wood instantly boils, causing the tree to explode like a bomb.