In Broken Hill, Australia’s oldest mining city, James Capper’s massive hydraulic sculptures—imagine a forklift has mated with a robot—actually crawl around and dig up red sand. Nearly 900 miles away, videos of the sculptures in action, their movements insect-like and inspired by the evolution of walking vertebrates, play in MONA’s gallery, where the outback terrain is evoked with red dirt on the floor. The English sculptor describes his creations as “speculative engineering”—they test the limits of engineering, play outside the lines. He says the sculptures are “solutions” to the question: How can engineering solve the changing planet’s urgent problems? —J.D.