You’re extremely intelligent,brainy,well read, you soak up knowledge like a sponge.
But there’s STILL some things you simply cannot understand.
It WON"T sink in, and it is just totally beyond you.
*** The MAN/WOMAN thing doesnt count…***
I know the technical/mechanical side of photography. You can explain it to me all day, but I will NEVER REALLY understand how THAT IMAGE got on THAT PICTURE.
and we won’t even talk about airplanes and the flight thereof.
Very small demons.
This explains quite a bit about the world, actually.
I thought it was elves.
I don’t understand how the tinfoil keeps the alien rays out of my brain. I don’t need to understand as long as it keeps working though.
I would have to agree with you on this one. The shutter opens for a fraction of a second…how does it get that image on the piece of paper for me to see?
Also, the telephone. Just the basic principle. And why it still works when the electricity goes out.
And TV. I just know if I opened it up, there would be a bunch of little tiny people in there performing, right? 
The Infield Fly Rule
The arrangement of cells in the primary visual cortex in lower layer iv.
I still don’t understand how instant-messaging programs work. How the heck does something I say make it to someone else’s computer?
For me it’s the concept of colors “clashing” I’ll just never get. If They’re pretty close to the same color doesn’t that mean they almost match?
I have alot of trouble getting my head around the theory of relativity - I’ve had it explaned quite a few times, and its still pretty far out there, as far as I’m concerned.
That and Squeeze-A-Snack. How do they make fake cheese so darn tasty?
Al.
Partial differential equations. That’s where I hit the wall in college.
The same way it makes it to the SDMB computer. 
I don’t understand file compression. How can a honking 50 MB WAV be converted into a 5 MB MP3 and not lose 90% of it’s content?
Donald Duck never wears shorts, but when he gets out of the shower, why is he wearing a towel?
And Goofy…what is he? cow or dog?
Cells. How does nucleus, membrane, cytoplasm and organelles make a living, breathing being. What’s so magic about transfereing oxygen, iron and electic pulses that makes things actually alive?
Little demons?
I don’t understand how the phone works, either. Or the TV. Or the internet. As far as I’m concerned, it’s all PFM (Pure F*ckin’ Magic).
I still don’t get how sometimes I can have a case of beer and feel buzzed, but other nights, I’ll have two (beers, not cases) and have the same feeling. It’s not an “empty stomach” thing, I always eat.
Why the switch for my truck’s exterior lights have two positions.
Position one turns on all of the exterior (parking) lights except the headlights.
Position two turns the headlights.
Why would one need to turn on the exterior lights w/out the headlights?
Please don’t bother explaining it. I’ve heard a BUNCH of reasons, and none really make sense to me.
Yeah. Telephone. Thing that rings when some guy five hundred miles away wants my attention. Kind of like a magical guided echo.
The earth being a sphere. “Any fool can see that it’s flat,” as the flat-earth guy said.
The concept of there being no up or down in space. Terry Pratchett called it “So far up there is no down”. Something tells me that if we send probes far enough in all directions, we’ll find a vast carpeted floor. And an ageing plastered ceiling.
How something as domestic and crockery-associated as ceramics can possibly be involved in something as cool as space travel.
Why they couldn’t have built machines like today’s PCs twenty years ago.
And now a small subsection: Things I Still Don’t Believe
Aeroplanes. I’m sorry, I know I get on in one country and off in another, I know I can SEE the ground fall away and then return… but I do NOT believe I’m flying. I am clearly sitting in a long living room, watching television. I am NOT flying, okay? I can get up and walk to the toilet if I want to.
Evolution. Stalagmites. In fact any process that takes unimaginable lengths of time. I just don’t buy it. I have no religious problem with it - it just takes too long for my attention-span to handle. In fact, I don’t believe much existed before I was born at all. I don’t understand it=I don’t believe it.
I second photography.
And how the moon affects tides. God as my witness, ths phenomenon makes no sense to me. I stopped being madly in love with my geography professor when he couldn’t explain it to me. I realized he was just human.
I never understood Star Trek. Well, just one particular aspect. Ok, stars are suns right? So how come when they were flying through space they didn’t see more suns? Those stars were always far away, and always small.
The appeal of golf.
I tried golf at university and found it to be perhaps the most aggravating and anger-inducing pastime ever But every day I go past the driving range on the way to work and I see the golfers out there prectising… not even actual golf, just preparation for a part of the game!
And how did golf come to be so wound up in the executive and corporate culture anyways?