A certain fraction of the world’s population (especially red headed, cricketing Australians) are paranoid about skin damage caused by over exposure to the sun. The public health message is that a little sun is good for you (we all need that vitamin D) but that too much is a very bad thing. How much is too much?
You can use a watch to calculate when to put your shirt back on, but that neglects how strong the sunlight actually is on any given day.
Today’s invention is a cheap tool to help protect people from sunburn. Take one of those ultra cheap credit card-sized, solar powered calculators and discharge it completely. Place a few layers of cellophane across the solar cell, calibrated so that the amount of sunlight required to first display “000000.00” is just less than the amount which causes skin damage. Attach the card to one’s clothing, where the display can be easily seen.
Once the safe limit has been reached, it’s time to head indoors. The card can be discharged and reused or simply jettisoned (given the fact that these are often freebies anyway). No more ‘boiled lobsters’ on the beach.