Fog!                                                            3/27

     1.  In "Twister" the eye or center of the tornado is calm.  Is that true?

              Since the direction of the wind on one side of a funnel is opposite to the direction on the opposite side of the
                 funnel, the wind velocity must be zero in the funnel's center.  A tougher question to deal with is that of the size of
                 the central area wherein the wind speed is negligible.  (The laws of physics imply that the wind velocity and
                 direction can only change gradually with position so there can be no entirely abrupt reversal of wind direction and
                 speed with position, the speed must be exactly zero somewhere.)  Two eyewitness observers of the centers of
                 tornados have reported that the inside of the funnel is calm and quiet (not for long!).  Both have reported a bluish
                 light apparently caused by lightning zigzagging between the funnel walls above them, and both reported smaller
                 funnels within the main funnel, probably suction vortices.

     2.  Are humans positively or negatively charged? Is there anything other than the fact that we are "tall" attract
         lightning?  Does carrying an umbrella further endanger us?   I have also heard that wearing rubber helps.
         Should we lug around big rubber boots during a lightning storm for protection?

                 Humans are normally electrically neutral i.e., neither positively nor negatively charged.  However when a charged
                 cloud base passes over us, it induces a charge in us just as it does in the ground surrounding us, creating a charge
                 imbalance which is opposite that in the cloud base above, since the charge on the cloud repels like charges in us and
                 the ground.  Hence a negative cloud base above us drives away some of the electrons within us and the nearby
                 ground, leaving us and the neighboring ground with a net positive charge.  On the other hand, a positive cloud base
                 above us attracts extra electrons from the region surrounding us, giving us and the ground in our immediate vicinity
                 a net negative charge.

                 There is nothing about a human body that attracts lightning other than the fact that it is a reasonably good conductor
                 which normally stands higher than the surrounding ground level.  Anything that conducts electricity and effectively
                 increases our height such as holding a conducting object, like an umbrella, or standing next to a lone or tall tree,
                 increases the likelihood of our being struck by lightning.  On the other hand, holding erect a long piece of PVC pipe or
                 some other insulating object does not increase our likelihood of being struck unless that object is wet and therefore
                 conductive.

                 Rubber boots, because of their insulating properties, will prevent us from acquiring an induced charge in the vicinity
                 of a charged cloud, and therefore decrease the probability of our being struck by lightning.  However, unless
                 circumstances would prevent seeking out a sheltered, protected location in a lightning storm, it would probably not,
                 for most people, be worth the inconvenience of keeping a pair of rubber boots in their possession.  Caution:  In a
                 rainstorm or in other circumstances which would result in wet rubber boots, their protective qualities would be greatly
                 reduced.

                 Curiously, even though it is usually wise to avoid metallic objects in a lightning storm, being surrounded by a metallic
                 shell is different.  It is quite safe, because, if struck by lightning, the charge flowing through that metallic shell will flow
                 along its outer surface.  Thus the interior of an automobile, or a location inside a metal building is quite safe as long as
                 we don't become part of that surface, e.g.,  by sticking our head out of a car window or standing in an external
                 doorway of such a building.