Recent comments in /f/explainlikeimfive

ninetentacles t1_j6g0xnh wrote

Wouldn't your heart need to beat more forcefully to move the same volume of blood completely around your body at 60bpm than at 100bpm, though?

And are these your own actual numbers, or are people more likely to see a more modest decrease in resting heart rate, like from 70bpm to 60? 100 seems awful high for "resting"!

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NemyMongus t1_j6g0q4t wrote

It is truly because the IRS wants the tax income. The IRS actually cannot legally disclose any taxpayers return information to a law enforcement agency unless the law enforcement agency gets a court order granting them access. The important thing there is that the IRS can't tip off law enforcement, law enforcement has to be the one to initiate the request. The only exception to this is if terrorism is involved. It still requires a court order but the IRS can be the one to request the court order.

This only applies to your actual tax filings though. If you get audited, any information they gather through interviews etc can be turned over to law enforcement if there is evidence of a crime being committed. That is probably a functional workaround. If you report illegal income on your taxes, you'll get audited and the witness testimony from the audit is turned over.

https://money.cnn.com/2013/02/28/news/economy/illegal-income-tax/index.html

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saywherefore t1_j6g0edx wrote

Imagine four rods joined together with hinges to form a square. This structure is underconstrained; it can flip about into a rhombus. Now imagine you add an extra rod across the diagonal; the structure is precisely constrained and becomes rigid. It doesn’t matter what length the diagonal rod is (within limits), there will still be a single shape that the structure adopts. Now imagine you add another rod across the other diagonal. This structure is overconstrained; if the extra rod is slightly the wrong length then you will have to force it into position, distorting the structure.

The setup with one diagonal is statically determinate; it has the correct number of links and so cannot have any internal stress without an externally applied load. Importantly, if you apply an external load (for example pulling two opposite corners apart) then you can work out how that load is shared between the links and how much tension or compression each link experiences.

The example with two diagonal links is statically indeterminate, it may have internal stresses, and when an external load is applied you cannot trivially determine how that load is shared by the various links. This was very important when structures were designed by hand; it is much easier to work out how strong each member of a bridge truss needs to be if that truss is statically determinate.

There are mathematical ways of working out if a structure is statically determinate; basically the number of constraints must equal the number of degrees of freedom. But I find it much easier just to consider the intuitive examples.

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Warp-n-weft t1_j6g00hs wrote

It is worth noting that underground water isn’t necessarily a renewable resource.

Large amounts of water can be found underground in aquifers but that water can be old. Potentially hundreds of thousands of years old, deposited during the Pleistocene and it’s impressive ice age.

We can, and do, pump ancient water out to use today. But that water may not be able to recharge. Worse is if we experience subsidence of the aquifer. By withdrawing water we shrink the size of the container (the aquifer) and it potential volume cannot be increased. In some places in California the ground has subsided due to water extraction at a rate of a foot annually.

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ayerik t1_j6fyt22 wrote

And I think this is part of the answer. In today's pop culture, the US is king. The Barbary Slave Trade (BST) didn't impact US culture. Sure, it impacted European and likely African and even Western Asian society, with effects still felt today, but the Trans Atlantic Slave Trade (TAST) affected North America, South America, and Africa. Combined with the TAST captive numbering 10 times what the BST trafficked, it makes it a larger impact. Add in also that many textbooks are written in North America by North American publishers, and the topics are going to focus on New World events, particularly US History.

I also checked, and Greece's population is estimated to be about 10 million. The US is approximately 333 million. New York City alone is approximately 8.8 million. Canada has approximately 39 million, Mexico 129 million, and Brazil 217 million. And local impact is always larger than something from further away. Plus, over 13 years of schooling for students in the US and Canada, there's approximately 15,000 hours of school (180 days per year, 13 years, from about 5 (Kindergarten) through 18 (12th grade). That time has to be divided between reading, writing, math, science, social studies, and other curriculum requirements.

Let's say approximately 750 of those hours are spent learning about world history, which is what the BST falls under for anyone in North or South America. Those 750 hours needs to cover all of history, from the stirrings of Egypt, Mesopotamia, and the other early civilisations, through to at least post World War II, though that still leaves about 50 years of history untouched. That's approximately 6,000+ years of events covering 7 continents, because we do need to understand how North and South America fit into these, and we reall6only cover our own country in the rest of our history classes, not even really our neighbors. So there are many, many, many events that are left out that still have a major impact on society daily, even centuries later.we don't spend much time talking about Australia's colonization, about the changing political landscape of Europe beyond the Roman Empire, the Holy Roman Empire, the Crusades, and the World Wars. We barely touch on the Moors and Islamic spread through Europe, much less Africa and Asia. There is so much of history that gets culled out of what's taught because it's impossible to include everything. Greek history essentially covers Ancient Greece, through about Alexander, until the Romans dominated the Mediterranean.

I am someone who enjoys learning, including on my own. I've spent a lot of time watching history documentaries, and what I can find generally covers about the same content as the basic school curriculum covers. Ancient Rome, Ancient Egypt, Ancient Greece, snippets of China, snippets of other cultures, but mostly small and not well made. Lots of World War II, lots of the aggressive parts of history. But to understand anything else, there's just not much content for teachers to use to teach about things like BST, and tough choices about what not to teach to include BST, if their local curriculum mandates even allow the flexibility.

It's been said that history is written by the winners, and at this point in time, culturally, that's the US. Hopefully, it becomes more balanced in years to come, but the choices of what to cull to make room become even harder.

(And for reference, I grew up in New England, moved to Indianapolis for about 16 years, and have since moved to Canada.)

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a_bear_there_was t1_j6fyfz3 wrote

It demonstrably doesn't work.

Well, it "works" in the same way that a Ouija board works. There's a person in control of when the rods cross, just like there are human(s) in control of the planchette on a Ouija board. It's very easy for a person to influence the movements of both, without necessarily being conscious that they are doing so.

Inevitably, the person who is holding the rods has some idea of where to find water. Like others have pointed out, there are hints on the surface, like trees and plants, even the shape of the terrain. Once they have an idea of where to look, it's very easy to make the rods cross at that point.

And if there's not water there, then there's always an excuse. "The energy was not good that day." "There's an underground stream, but it's dried up now." "There is water, but you didn't dig deep enough." etc.

And of course, they almost always find *some* water because there's water nearly everywhere if you dig deep enough. And confirmation bias being what it is, they will always point to their successes as evidence that dowsing works, and their failures are just times where they did it wrong.

Again, they may not even realize that they're doing this. They may really believe it's magic.

Some don't of course. Some people are just charlatans. But there are plenty of true believers too.

Whichever they are, they don't have a real ability. Every time we run a properly controlled experiment, they do no better than random chance.

The James Randi Foundation used to do these tests, offering a million dollars to anyone who could demonstrate any one of a number of abilities (dowsing included). No one has ever successfully passed even the preliminary tests.

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cammer_habibi t1_j6fy4i9 wrote

Maybe one million Europeans were kidnapped and sold into slavery . Many European states waged war or paid tribute to free those slaves.

Contrast that with 15 million African slaves who were moved across the ocean and had almost no chance of being freed. Add onto that, the transition from the trans-oceanic slave trade to the system of slaves being born into slavery generation after generation.

They're completely different.

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cammer_habibi t1_j6fxv4m wrote

Some pirates kidnapping Europeans and selling them into slavery is very, very different from Europeans kidnapping and transporting African slaves thousands of miles away to work on colonial plantations.

No one is downplaying the Barbary slave trade. But it's incomporable to the trans-Atlantic trade.

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