A fly that died years ago is flying around a harbor that doesn't exist. Here's what's going on. Scientists took one female fruit fly and sliced its brain into about 7,000 pieces, each roughly 2,000 times thinner than a human hair. They photographed those slices 21 million times under an electron microscope. Then hundreds of people spent years tracing every connection by hand until they had the whole thing, all 139,255 neurons and 54.5 million synapses. That map is called FlyWire. Odyssey…