I've been a mum for a relatively short time; I'm not exactly an expert when it comes to this whole parenting thing. Still, there is one piece of advice I can confidently dole out: don't instruct your child to run in front of a moving vehicle so that you can win an argument with strangers on the internet. This month, a software CEO called Dan O'Dowd, who is hellbent on trying to ban Tesla's "full self-driving" programme, launched an ad campaign claiming that if you put a Tesla in this mode it will mow down children. He based this assertion on a test he ran using a child-sized mannequin dressed in a safety vest, which came to a sticky end in the middle of a road in California. Musk's fans, who will not tolerate any criticism of the billionaire, immediately took issue with O'Dowd's assertions and decided to conduct their own tests – using a real child.

Inside a Schnucks grocery store in St. Louis, Missouri, the toilet paper and baking ingredients are mostly cleared out. A rolling robot turns a corner and heads down an aisle stocked with salsa and taco shells. It comes up against a masked customer wearing shorts and sneakers; he's pushing a shopping cart carrying bread. The robot looks something like a tower speaker on top of an autonomous home vacuum cleaner--tall and thin, with orb-like screen eyes halfway up that shift left and right. A red sign on its long head makes the introductions. Tally freezes, sensing the human, and the customer pauses, seeming unsure of what to do next. Should he maneuver around the robot? Or wait for it to move along on its own?