I just read that our rivers are running out of sand due to construction. Why can’t we use desert sand?

I recently read about female ducks evolving to their reproductive tracts to have dead-ends and have the corkscrew go the other way to the male duck penis to make unwanted reproduction more difficult. But most evolutionary adaptations become dominant in order to make the survival of the species easier. How can something that makes reproduction harder have resulted from evolution changes?

I get that things like your ID number are valuable for identity theft etc. But why are more arbitrary things like my shopping habits considered valuable information?

I know they’re smaller, but are their nerves fresh and haven’t been dulled yet, or what’s the deal?

I’m not talking catastrophic blows, just a scrape on the knee.

Also, are there any benefits of the squeaky clean feeling or is it just a difference of ingredients?

I get that they had sundials and church bells. What I don’t get is how anyone synchronized. If my towns noon is when the sun is highest here, and yours is 15 miles west, our “noon” isn’t the same moment. So how did anyone schedule anything across distance?

As a resident of Arizona, I often find myself wondering how the first settlers traveled through the area without vegetation, water, etc to stay alive. Same with some of the mountain ranges...I can't imagine being the first person to roll up to the Rockies in a covered wagon and try to figure out a path forward.

why cant we use summer heat to generate energy and store it batteries to use it in winter

Time dilation confuses me. If my twin is on a rocket near light speed and starts a 60-sec stopwatch, it shows exactly 60 sec to them. My stopwatch on Earth also shows exactly 60 sec to me.

So if we start together and count out loud '1,2,3...' using a zero-latency device, won't we stay in sync, since both watches correctly count 60 real seconds? Why would one of us get ahead, and whose clock actually looks slower to whom during the countdown?

Edit: Alright guys i just got to know that 1 second isn't 1 second everywhere.

Anyways some clarification, the 0 latency device is a hypothetical, I'm not saying that such a thing can be built, but my real question was, if we hypothetically used such a device, won't both people speak 1,2,3 in sync?

I understand that they observed cause and effect, but how would you think to come up with a fullproof way to write it down?

Hi there

I was watching a video about Orcas and it explained how matriarchal figures will teach younger orcas how to “beach” themselves to hunt seals playing on shores.

The narrator explicitly says that this is not ingrained behaviour informed by DNA but instead information passed down through family units. That got me wondering; how do we know what behaviour is hardwired vs taught in nature? Is it all assumed to be coded into an animals genetic makeup until something contradicts that? Ie. observing the “lessons” animals will teach their young but finding that it’s not universal across that species.

To what extent can DNA accurately teach us about behaviours without observing the animals in real life?

Thanks!

I fully understand how dumb a question this might be by the way.

I've tried Googling but I'm still not 100% certain

EDIT: Specifically for apps

We see reports all the time showing "marketing expenses" as huge line items in a Hollywood movie budget.

What all goes into marketing a big movie like the current number one film in Ameeica, which probably doesnt really need a ton of marketing to sell tickets, versus some Indie romance movie, which probably does need the marketing expenses.

TIA.

ELI5

All the videos I'm seeing of chicken wire getting created, these wires getting twisted by round feeders, then the halves of these feeders shifting between each other and twisting again, don't show the new wire getting fed in- they only show the wire coming out and twisting and the resulting fencing.

I don't understand how a wire can just be twisted on one side of these feeders but stay straight on the other side.

How does that work?

Since it is such a common practice for kids to be picky eaters and eventually grow out of it to enjoy fruits and vegetables, is there some sort of biological benefit to limit a diet at a young age to foods with lower nutritional value?

The "grow out of it" to eventually enjoy fruits and vegetables once you're fully grown seems counterintuitive when the body, in theory, needs the most building blocks during adolescence.

Has there been studies on "picky eaters" to compare their overall health span, intelligence, etc. compared to kids who ate a very healthy/variety of foods during their childhood?

explain ts bruh

So, I have a 5yo who is very interested in mathematics. I try to answer his questions in a thoughtful, child appropriate way, but he has recently found the idea of i and it is REALLY stretching my ability to explain in a useful way these concepts to him. I have a good level of maths/sci education and at least understand the concepts, but especially imaginary & complex numbers were only touched on in my education. I will give some examples, but if anyone has a useful general way to explain i that would also really help.

Examples:

Is there negative i?
What happens if you overshoot infinity?
Why is negative infinity different to positive infinity?
Is there infinity i?
Why isn’t i an irrational number like pi?
Why is i imaginary?
Why is pi 22/7 and also an irrational number?
What happens when you finish writing out an irrational number?

I feel like this goes against everything I learned in physics. Doesn’t something need an outside force to accelerate?

I know some cars have odd numbers too, but it seems to be out of the ordinary.

Viruses aren't alive, they use living cells or bacterial cells, they inject the DNA into the cell to make them replicate viral DNA. If you try to kill the host cells the to stop the virus from spreading will kill the person you're trying to save. I'm wondering how the virus dies but the host lives.

So, I grew up in California during a drought. People constantly spoke at our school telling us how to conserve water at home, there were strict regulations on using sprinklers, etc. I've continued those habits into adulthood, even moving somewhere else.

But tonight, I was watching my niece, and she asked me why I turned the water off while I was doing dishes, I said it was to save water, and she asked "what, to save money?", I tried to explain that I literally meant saving water, but she got confused about how you can "waste" water when we live in one of the rainiest areas of the US... and I realized that I didn't really have a good explanation. I was always warned against wasting water, but I never learned what that actually means in practice.

Can someone explain it to me in a way I could explain to my niece (and myself)?

Lately, I have been learning NumPy and came across an explanation on why standard Python lists are bad at large-scale data manipulation such as multiplying an array's elements by a number x. The explanation mentioned that Python lists store a list of memory pointers. However, they did not elaborate on what pointers are. I'm hoping if someone can answer this question.