Stephen Hawking must be a genius, because in his new PBS docuseries, “Genius by Stephen Hawking,” he manages to get ordinary people to understand some of the most complicated and seemingly unanswerable questions of the universe. The six-part series, which launches with two episodes Wednesday, May 18, and continues with two episodes a night for the next two Wednesdays, not only makes science accessible, but it’s also fun to watch, even if you’re an empty-headed TV critic who took earth science in high school because looking at rocks was preferable to other disciplines involving either a lot of math or eviscerated amphibians. Wednesday’s first episode asks: “Can We Time Travel?” And before you leap to the obvious conclusion that time travel is just the stuff of science fiction, three ordinary people walk several blocks in New York City to prove you wrong. [...] although the other guests are gone, the inquisitive trio members realize they can plot their course from Times Square to the West Side through a series of stacked, transparent maps, which, with tiny figurines, they use to essentially “time stamp” their walk. The first episode takes the ordinary trio to Arizona where they drive back and forth in DeLoreans to learn more about the possibilities and cold realities of time travel. There are, as Carl Sagan said, billions and billions of stars, and the odds are some of them have just the right combination of factors to support life. In general, for many years, only planets within a specified distance from their host stars were deemed as possible life supporters. [...] “Genius” shows us that there are mechanical ways that a planet or a planet’s satellite, such as Jupiter’s moon Europa, might be able to generate enough heat to keep water from freezing all the time. David Wiegand is an assistant managing editor and the TV critic of The San Francisco Chronicle.