SERIES FINALE: This show has featured 900 explosions and nearly 3,000 experiments, so it’s fitting – and completely unavoidable – that this 13-year-old Discovery Channel series goes out with a bang. In this case, it involves 5,000 pounds of industrial explosives, packed inside a cement truck. Just more of the big bang theories this group has explored for quite a while, under the auspices of several different hosts. And as a special treat, at 9 p.m. ET, as soon as the final Mythbusters episode concludes, the show returns with a reunion episode, bringing back all the original hosts. What took it so long?