Lightning feels like settled science. We have the charge separation, the plasma channel, the 30,000-degree heat, the thunder shockwave — it's in every textbook, photographed a billion times, studied for centuries since Franklin's kite. Surely so common and so well-documented a phenomenon holds no real mysteries. And yet at its very origin sits a genuine, unsolved problem.
We do not actually know, in full, how lightning gets started inside a cloud. Here is the difficulty: decades of measurements have found that the electric fields inside thunderclouds, even at their strongest, are consistently too weak — often by a factor of ten — to rip air into a conducting channel the way the textbook story requires. By the known physics of air breakdown, the bolt shouldn't be able to initiate at all. Something else is triggering it, and the leading hypotheses are still being tested and argued. One major idea involves cosmic rays — high-energy particles from deep space striking the atmosphere and seeding avalanches of fast electrons (so-called "runaway breakdown") that could lower the bar enough to start a strike. Another points to the way electric fields concentrate around countless tiny ice crystals and water droplets. As it stands, the initiation of lightning — the first instant of the most familiar electrical event on Earth — remains an open research question. We can describe the bolt in exquisite detail — its temperature, its current, the branching geometry of its channel — and still not say what lights the match.
Jesus reaches for lightning to describe His own return: "as the lightning flashes in the east and shines to the west, so it will be when the Son of Man comes." It is a deliberate image. He is contrasting His coming with the false messiahs people will claim to have located in some inner room or remote desert — here he is, there he is. No, He says: when it is real, it will be like lightning — sudden, unmistakable, seen from horizon to horizon, impossible to stage-manage or miss. And there is a fittingness, given what we now know, that He chose the one familiar power whose origin we still cannot pin down. Lightning is at once utterly visible and not fully explicable — exactly the register of a God who reveals Himself unmistakably and remains, in His depths, beyond our accounting.
Much of mature faith is learning to live with that pairing: a God who is unmistakably revealed and yet beyond comprehension, at the same time. The temptation runs in two directions — to decide that because we can't fully explain Him, He must not be real; or to flatten Him into something fully explained, a tame doctrine we've mastered and no longer fear. The lightning refuses both. It is the most ordinary spectacle in the sky and we still can't say what starts it, and no one watching a bolt split the heavens mistakes their inability to explain it for an absence of power. Let your unanswered questions about God sit where your unanswered questions about lightning sit: not as evidence against the power, but as the measure of how far it exceeds you. He will come like the lightning — and He is, even now, more than you can account for.