In 1954, Jim Lovell, who would later lead the Apollo 13 space mission, was flying his Banshee night fighter when his plane experienced a total electrical failure.
There he was, the middle of the ocean in the middle of the night, with no instrumentation and no way to find his ship. But as he looked out into the darkness, he noticed a glimmer of photo luminescent algae that had been stirred up in the wake of his aircraft carrier. He followed the trail back to his ship and landed safely.
If the lights hadn’t gone out, he never would have found his way home.
It’s fascinating to consider how our eyes are designed.