Judah wrote:
But I don't even think there's all that much
difference between flying through soup at 3000' when the top of the
white stuff outside your window is light by the sun or the moon.

The difference (in my mind, and with my 40-something eyes) is that it's
harder to see stuff in the cockpit at night. Every task from instrument
scan, to reading a chart, to tuning a radio, to copying an in-flight
reroute becomes more difficult.

Task overload is insidious. It's taking you a little longer than usual to
find the right approach plate and get the radios set up, but you're still
keeping up so it's not a big deal. Then the controller tells you they just
switched runways, fly direct to some waypoint you've never heard of, expect
some different approach, contact the next controller on 123.45, etc, etc,
and suddenly you realize you're way behind. Maybe during the day you would
have been able to keep up, but at night the added workload of having to do
everything by flashlight sent you down the tubes.

There's also a lot more in the way of visual illusions at night. I've
broken out plenty of times and spotted what I thought was the approach
lights, only to realize it was a nearby highway.