Why don’t birds get electrocuted while perching on power lines?
It’s not voltages per se that kill, but voltage differences, which are needed for electricity to flow. If a bird lands on a single power line at, say 35,000 volts, the lack of a voltage difference keeps it safe. If it extends its wings and touches another power line at a different voltage, though, it will be electrocuted. That’s why electricity companies put plenty of space between cables. Why does sunshine make me happy? There’s a fine balancing act in the brain and circulatory system that regulates our moods, boosting the feel-good factor or sometimes causing Seasonal Affective Disorder (SAD) in winter. The hormone melatonin, produced by the pineal gland in the brain, regulates our sleep/wake cycle, but excessive levels can cause depression. The action of light on our face suppresses melatonin synthesis, therefore boosting your overall mood. Evolutionary principles could apply too. There are plenty of nocturnal primates and presumably they aren’t always depressed. It seems likely tha
