True darkness, it turns out, can be experienced but does not exist. If you have been down a deep mine where the guide tells you to turn off your lamp you will have seen – in not seeing – something close to it: an utter nothingness in which your body and mind seem to shrink
<strong>Letters: </strong>It is not just the quantity of light that has changed in recent decades, writes <strong>Anna Levin</strong>,<strong> </strong>but the quality of that light