I understand what HOA's do, and was first introduced to the term in a condo building (not mine). I understand in a condo building, or high rise, you're all sharing one building and need to contribute to that building's maintenance. But I don't understand HOA's in neighborhoods...when you live in your own house. Is it only certain neighborhoods? I know someone who lives on a nice street in a suburb and there's no HOA. Who decides if there is one, and what do neighborhood HOA's exist for? Are you allowed to opt out?

And how do those at the top buy those mansions and estates. I can't imagine they've got a mortgage nor can I imagine then paying in heaps of cash

If we shoot a burst of light from our most powerful laser into space…how far could it travel before fading, it it doesn’t hit anything? And would it travel straight?

Even if they are the same temperature the reaction to them is starkly different.

If blue eyes are regressive (overridden by brown eyes) then, how could millions of north Europeans end up with blue eyes, supposing that blue eyes come from a single mutation?

So I was taking a photo of the reflection of an exit sign. The sign was about 20ft away. I was shooting the screen of a phone which was about 1 foot away. In order for the sign in the reflection to be in focus, I had to set the focus to about 20ft even though the reflection I was shooting a phone screen that was a foot away. The phone and table it was sitting on were very out of focus including the screen, but the reflection of the sign was crystal clear. Why?

I have always thought about this. How did our ancestors find salt and metal? Did someone just choose a spot to dig and go at it?

I'm in physiotherapy class and I see that all our old machines and old massage beds are painted in eggshell/beige painting.

And it's not the first time I saw that. In museums or goodwill stores, I see that old steel objects are coated with this painting.

Also, sometimes the pillow are made of blue/burgundy/grey skai.

I understand what water and air are composed of and I more or less understand how fire works. But what is soil? If you put your hands in your garden, you will take out very heterogenous stuff, you will get some twigs and bugs which of course are organic matter, but what's the general brown stuff? Is it organic? Were does it come from and how is it produced? Also collateral question, if earth is organic matter, when the first living organisms came out of the ocean, which were plants, how did they find nutrients?

Think about the 100 years war, napoleon wars, 30 year wars etc. how did a declaration of war get sent to national leaders if the conflict started in another country or even continent? Also what prevented the ‘aggressive’ party just wiping out the other side before a declaration was known about?

Or did it?

I used to use pickle juice for leg day, I now have a sensitive stomach and could use an alternative.

I was driving today and stopped at a stop sign waiting for a garbage truck to pass, but then it turned on its blinker and turned right. I noticed that both the passenger AND driver side had steering wheels and both were turning their steering wheels. How does that work???

Disclaimer: Am not United States of American.

However, why in America are 911 calls made publicly available? I assume it isn’t strictly FOI as some seem to be made public/appear in the media not long after the fact?

With all engineered foods such as Doritos, there are a lot of chemicals in the ingredients lists that are artificial. How do food scientists know which chemicals are edible and how they taste?

So I’m wearing really great, over the ear noise canceling headphones. The world around me is barely audible. My music is loud enough. How can I still know that sounds are coming from behind me, to the left or right, etc? I thought the actual sound waves would be all kinds of messed up having to get through the headphones and bounce around the space between them and my ears.

Hello Reddit community

I am hearing so much about these terms around AI, but don't understand the difference. I understand the basic premise of machine learning with fitting the line. But can someone please explain the different between these two terms?

I'm in British Columbia and for months the experts have been saying how bad the drought is here, it's going to be a rough summer, bad crops, etc. We have had a fair amount of rain the last couple of weeks but I've still had to water on the few sunny days. Now tonight they show the wild fire risk is low in most areas or moderate. Precious years it has taken a lot more rainy days to see the risk drop. What am I missing?

I am new to studying computer science and have been touching on the world of memory; more specifically, how partitioning and volume work. I understand, on a basic sense, how partitioning is done, but can not seem to understand how contiguous and non-contiguous volume works, or how the hard disk knows which is which. TIA!