The Earth has an electric field. On average, this field points vertically downwards and it has a magnitude of about 100 N C-1 (Newtons per Coulomb). It exists because the Earth’s surface carries a negative charge of – 5 x 105 C, while the upper atmosphere carries a compensating positive charge. An average of 400,000 thunderstorms a day sustain a relatively constant electric field.
Light. Most of us take it for granted during the day. And at night, we have learned to domesticate it. Light, the natural agent that stimulates our sense of sight and makes things around us visible.
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