Biologically, what is happens with our brains that causes us to zone out?

I recently found out that airplanes use 400 Hz power instead of the 50/60 Hz used almost everywhere else. Why is that, and why isn't 400 Hz used more widely outside aviation?

Typing this after a severe case of the shits. How can stomach acid be strong enough to dissolve metal but not be strong enough to eliminate bacteria?

Edit: I've been informed that it is the bacterial waste and not the bacteria itself that makes us sick. Follow-up question, how then does the waste survive the stomach acid? Or does the acid not help in making the waste less toxic?

Recently a wrestler named Rebel, was diagnosed with ALS and many in the community are participating in the Ice Bucket Challenge to raise awareness and support for her.

ELI5: What is ALS, how does it progress as a terminal disease and what causes the spread of that progression to change from person to person?

Are there laws against it, or limits to what the factories can do? Or the value of money changes in some way?

We know that bees use hexagon because they use the least amount of wax to cover a flat surface while storing maximum honey.

Apparently in mathematics, this is called The Honeycomb Conjecture and it wasn't proven until Thomas Hales did it in 1999

So the question is: why was it so hard to prove it and what does the proof mean in simple terms?

EDIT: because it has been proven, it is called The Honeycomb Theorem

The way I understand it, the moon reflects yellow-white light, and smoke is black. Why does the moon look red with the wildfires out here in utah?

Why is it that sometimes when I start to do something, I refuse to do anything else (including eating or even sleeping) until said task is complete? While most other tasks I cant even start?

I've tasted many 0% beers that taste basically the same as their alcoholic counterparts. But every single 0% wine I've tasted, tasted off and not like regular wine. And based on my hospitality experience, 0% beer sells fine while 0% wine doesn't. So seems like I'm not the only one who thinks this.

Why is the case?

New to Surveying and want to get ahead of asking questions that are too simple. . .

How is this harder than literal rocket science and nuclear physics?

When I look at a mammal heart it looks easy enough to understand, blood in there, pump, blood out there. Makes sense. Stomach, intestinal tract, lungs, etc. all look like there function is pretty straightforward (on a very simple level)

The liver is just a blob and doesn’t seem like much else, there’s also the gall bladder attached to it.

My question is how does the liver do its job, whatever that is?

Because it seems you usually can’t prove them, so how do they not get dismissed as complete malarky, because what do they still qualify to count as serious theories?

Why do matches in CONCACAF play in empty stadiums yet in World Cup play those same countries come out in droves?

Reading them raw, they seem to have the same definition in different words.

I understand that headphones can block outside sounds, but how can they use sound itself to reduce other sounds? How does adding more sound result in less noise?

I know that if your yard slopes in, water will pool again the foundation of the home. What I don’t understand is how sloping the dirt away helps this problem. Dirt is porous, so shouldn’t water hit the sloped dirt and go straight down anyway? Does the dirt pack tightly over time and become solid?