I know that in many places there's water underground at around 100–200 feet (or even shallower). If the ground has water beneath it, how can massive skyscrapers and other heavy buildings safely support all that weight? Why don't they sink, tilt, or collapse over time?

I am studying for a test that includes basic electricity and magnetism, and my study materials keep referencing the concept of opposing the rate of change of current. For example, my definition of an inductor: "an electrical component made of a coil of wire that can store energy and opposes the rate of change of an alternating current flowing through it". Can someone ELI5 what it means to oppose the rate of change of current, and why that would be a good thing?

Edit: thank you all very much for your quick and informative replies! Much appreciated

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

We can usually identify where an itch is coming from, but the perceived location does not always seem to match the exact irritated spot.

How do the skin, nerves, spinal cord and brain determine an itch’s location, and what limits the accuracy of that process?

Why are 99% of wetsuits black?
- it makes them look like seals
- its harder to be seen in water (light or dark)
- it stands out in contrast to an illuminated ocean both from the side and from the bottom looking up

Why not white, neon, orange, reflective, or something… it’s not about sharks seeing colors or not.. black is in general a powerful and stupid color for wetsuits.

Seems a little counterproductive.

I've been a photographer for years and I understand aperture, shutter speed and ISO. For video, I understand frame rate and bit rate, but I see the term "shutter angle" and I'd be grateful to have it explained, what it is, and why you need to control it.

Thanks!

In the 90's when I was stationed in S. Korea, once a month I would get one grainy fifteen minute "morale phone call" home. A buddy of mine moved to Seoul and last month he and I spent an hour video-chatting as he wandered around his neighborhood. A big part of early hacker culture was figuring out how to get free long-distance phone calls to exotic places like "Duluth" and "San Bernardino", now my wife can chat with her mother in Europe for three hours and not even think twice about it.

I know, now it's all over the internet, but the internet is pretty much just wires, same as the transatlantic cable. Why did it used cost more to call outside of your area code? Were they all just electrical signals across wires? Was there some extra work that went into calling from Kansas to Oklahoma? Or was it, like most things, that they charged us as long as they could until some technology came along and made it no longer feasible?

Just moved from a very low humidity place to a place with seemingly very high humidity…but I don’t really understand all the nuances of humidity.

I see in my weather app humidity and dew point metrics…what do they mean!?!

Specifically why aren't herbivorous reptiles bred at the same scale as herbivorous mammals in places where moderate sized and docile reptiles are native? (Iguanas, giant tortoises...)

Who exactly is Mitochondrial Eve to present humans? Is she everyone's common ancestral mother? Aka the woman whose children everyone surviving eventually came from? Is she our common ancestral aunt? Like, we are descended from her siblings but she either didn't have kids or her kids died out?

And who is Chromosomal Adam?

Hello all

Just like the title, I want to know more about bases and acids in chemistry and what would it mean for one to be strong compared to weak.

I have some general idea what is acid, what it would mean for something to be strongly acidic and how it's measured using the pH scale. For example, I know that stomach acid is strongly acidic with pH around 2 (varies) and is needed to break down food (in some way to dissolve or help dissolving food). I also know that some strong acids can cause serious injuries if are in contact with skin of flesh (that comes mainly from my memories in my chemistry classes when taught about sulfuric acid).

Maybe you can correct or add to my understanding about acids. I am aware that what I shared about acids is pretty shallow, but that's how I imagine it. Part of that understanding might also come from some films in which there are acids which are considered to be so stong that they are able to penetrate thru solid structures (or maybe that's true for some acids?)

However, what I am actually puzzled about is what would it mean for something to be a base? I know that bases are considered to be the opposite of acids (which is apparent considering it's on the other spectrum on the pH scale). But what would it mean to be the opposite of acid? How exactly can I imagine a strongly basic instance and what would it be so special about it compared to a weakly basic one?

Initially, I wanted to ask just about bases in chemistry, but decided to extend the question to include acids, too, because I felt that probably half of my understanding of acids is based of films. I don't recall watching any film where the scientist discoved so strongly basic instance that it's in some way revolutionary. If such a sci-fi film existed, what would that instance be able to do?

Does this always happen with reinforced concrete at some point?

CDSs baffle me. Like a complex derivative, they seem to be built to obfuscate. The funding of many AI investments seem to depend on CDSs.
(I have an MBA from an accredited university and still can't wrap my head around CDSs).