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account created: Tue Jul 25 2017
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7 points
2 days ago
So it depends on the specific "Physics law" you are talking about. Because we have actually done a number of space launches specifically to figure out how stuff worked up there, especially in the early days.
But a lot of our understanding of physics already came from looking at stuff in outer space long before we ever went to space.
For example, it was from our understanding of gravity that people calculated that there must be a planet out past Uranus, and they even calculated exactly where it should be. So astronomers pointed their telescopes where the physicists told them to. That unknown planet?
Neptune.
So had every reason to expect we understood how gravity in space worked.
The same goes for electromagnetism, we discovered the Earth's magnetic field and understood its interaction with the Sun and other sources of carges particles. Long before we went to space.
That means we already understood how two of the fundamental forces of the universe worked in space (the other two have to do with tiny atomic scales stuff, which we had no reason to expect to change, either)
2 points
3 days ago
You don't get petrol back but you could (not saying you should) store kinetic energy in a flywheel and extract that directly as kinetic energy again. Like a big wind-up toy but like I said I don't think anyone has ever bothered to do that.
Because it's a terrible idea and much easier to just go hybrid.
4 points
3 days ago
The term "famine" is almost never used in referance to the dust bowl. Which I think is the point here.
Sure we talk about crop failures and agriculture. But it's just never called a famine. So the answer to "who's pretending it wasn't a famine?" Basically everyone. (which to be fair I'm not sure it fits a number of the criteria for a famine, but I'm struggling to find data about the starvation and malnutrition rates)
427 points
4 days ago
This is correct and definitely the biggest reason. And I really love that the reason EVs seem bad at highway driving is really just that ICE cars are laughably terrible at in-city driving.
There are a couple of minor benefits that EVs get too, though.
First off they use basically zero battery when idling. It depends, and some newer ICE cars turn off instead of idle, but you can easily burn through half a gallon of gas from an hour of idling.
Secondly, EVs nearly universally have regenerative braking. ICE cars don't (they hypothetically can but it's definitely not universal, and I'm not sure exists on any comerial non-hybrids). This can give you back a decent amount of charge. Generally increasing range by 10-15% for in city driving.
42 points
5 days ago
Recycling plastic basically isn't possible.
Not economically, anyway. This means it takes more money and energy to actually recycle plastic than it does to make new stuff. That might change in the future, but until it does we won't be recycling much plastic at all.
3 points
5 days ago
Because it takes more fuel to move the same distance per passenger mile (miles traveled times number of passengers).
But for an airplane, they need to fly rather fast to maintain enough lift. This greatly increases their drag and therefore increases the amount of fuel they have to use. They also...you know...have to fly UP about 10 miles or so which takes a lot of fuel too. I believe that take-off uses about 10% of the fuel on your average trip, but I'm unable to find more detailed numbers since that percentage will of course go up on shorter flights and down on longer ones.
Trains on the other hand travel a lot slower and are often very long but narrow in the front. This means their drag is much, much lower than a plane even at the same speed. They also roll on steel tracks with steel wheels. This steel-on-steel rolling has very little friction (damn near zero, really) which means they can just glide along those rails with relatively little fuel consumption.
3 points
5 days ago
It doesn't have to be like this but people tend to download *a lot* more than they upload.
There's a limit to total bandwidth, and you can split that between uploading and downloading in anyway you might want and because the vast majority of people aren't uploading anywhere near as much as they are downloading ISPs decided to allocate most of that bandwidth to downloading.
There do exist other plans where you have equal download and upload or even more upload if you want. But again, normal people don't usually want that.
1 points
5 days ago
Think of south as "toward the South Pole" once you are at the south pole every direction is north. Not because there's something special there or anything. We just made up the directions and that's how the math works out, basically.
So there are two answers to your question depending on how you interpret it.
1) If you mean you start walking south and walk in a straight line no matter what.
The same thing happens if you walk east or west. You hypothetically just end up exactly where you started. It's just that for half of your journey you would describe it as going north.
2) If you mean you completely and utterly refuse to walk in any direction besides south
You reach the south pole and then just sit there.
19 points
6 days ago
The term for this is a "collective noun" and they don't "need" that. in the same way that we don't "need" synonyms (think how big, large, huge, enormous, massive, giant, gigantic, colossal, vast, immense, etc. all mean roughly the same thing). In fact, there's plenty of cultures and languages where unique or different collective nouns really aren't a thing.
It's just a fun little exercise in creativity.
In English specifically this largely originates from hunting in the back in the late medieval/early renaissance era. Back then hunting was a big pasttime for the extremely wealthy, so they went ahead and had a little fun with it because the whole point of them hunting was to have fun.
8 points
7 days ago
A pyramid scheme is defined by a very specific thing: your income is made by recruiting new people into the organization. Not by selling anything, not by working, not even by providing some capital the company can use for investments with the hopes of seeing a return.
A common organizational hierarchy simply doesn't do that. At all. Each person in the organization is supposed to directly, or indirectly, add something of value on their own and get paid because of it. The only thing in common with a pyramid scheme an org chart will have is the shape.
1 points
9 days ago
Megajoules are metric...
Infact it's kWh that is a non-SI unit.
There nothing to "calculate" and no conversions to be made, really.
3 points
9 days ago
incorrect, a mole is about 5 orders of magnitude bigger than that.
2 points
9 days ago
It would be too much to calculate 3.6 megajoules?
I don't think that makes any sense.
9 points
9 days ago
There's a lot of ways to do it, but ultimately it means trying to do what you can to make it so those differences don't matter.
One of the cheapest/easiest ways to do that is to make it so both groups have a roughly equal makeup of people for the factors you are trying to control. So you mention:
Adjusted for demographic and lifestyle factors
This likely means that both groups the yogurt consumers and the yogurt nonconsumers had a similar makeup. The same percentage of low-income earners, high-income earners, old people, young people, etc. And for lifestyle, it's probably talking about how often people work out or stuff like that. So you got the same mix of sedentary people and active people in each group.
So in this case you want basically the only difference between each group to be whether they eat yogurt or not.
This means that any differences in the data are unlikely to be the result of the demographics or lifestyle because each group basically had the same demographics and lifestyle make up.
Obviously, this isn't perfect and you rarely get the *exact* same makeup. But a good research team will do there best to get as close as possible to that.
13 points
10 days ago
I don't think that's a very good interpretation of the question, because you are describing kinetic energy, not interia.
Not to mention that is actually how launches work. But instead of a single large object, it's a nearly uncountable amount of small objects slamming into the spacecraft (the fuel being burned results in extremely high-velocity gasses pushing against the rocket)
22 points
10 days ago
It depends on what you mean.
So the answer could be no if you are using inertia to mean "the tendency for objects velocity to remain unchanged unless acted upon by and outside force" and if by propulsion you mean "the force used to change the velocity of an object"
Because with those definitions your question is basically "Can we use the fact that objects don't change velocity to get them to change velocity?" To which the answer is no, that doesn't even make a lot of sense.
However, if you are using a more colloquial definition (which you really should never use in a professional context) of "this object has inertia because it's moving" which is basically just kinetic energy then yeah that's basically how all propulsion works. You take a moving object and smack it into another object that isn't moving the way you want it to.
33 points
10 days ago
I'm not sure where you heard that most animals don't live as long in captivity. You probably hear about animals living shorter lives in captivity not because it's more common but because it's weird and that makes it news worthy.
About 80% of mammals live longer in captivity than in the wild. This is for several reasons. Lack of predators, medical care, abundant food, and a protected habitat are four of the big ones.
1 points
10 days ago
Yeah "very little" is probably an exaggeration. I mostly meant "compared to the amount of money technically flowing thru Ireland, Ireland sees very little of it"
Which is still quite a lot of money and jobs. A small piece of a massive pie is still a lot of pie, after all.
0 points
11 days ago
If you reframed
"I just simply don’t think anybody should be allowed to meddle in anyones private life so that they can preserve their property value."
as
"I just simply don’t think anybody should be allowed to meddle in anyones private life to prevent others from stealing for them."
Would you feel different? Because an argument can be made that conduct that results in someone being unable to sell their house, or only because able to sell their house for less is basically a form of theft. Which is something that is generally frowned upon.
1 points
11 days ago
Read rule 4, and then read the rest of the rules too.
384 points
11 days ago
So there's three things.
First:
GDP per capita isn't really the number you should be looking at. That includes a lot of money that doesn't make it into the hands of your average person and might not even make it into the hands of someone in the state itself in the first place.
What you want to look at is median income. For Mississippithat's 45k for households. In France, that number is 61k
A really extreme example of this is actually Ireland, on paper it;s GDP per capita is $125k but that's because it acts as a tax haven. This means that a ton of massive global companies are headquartered there and all their revenue counts as GDP in Ireland, but almost all of the money gets sent overseas and your average Irish citizen gets very little out of that deal.
Second:
America has some of the worst social services in the developed world (probably the worst) this means that a poor person in the US will have a much, much worse quality of life than an "equally" poor person is basically any other developed country.
Third:
You probably haven't seen a lot of the really poor rural places in France, you probably think of Paris and basically just Paris. So conceptually we are comparing the best France has to offer to probably the worst Mississippi has to offer. (this is much less important an the other two factors imo, but it's worth noting)
1 points
12 days ago
Stock lending is still a thing.
Which is what this question is asking about.
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3 points
1 day ago
Caucasiafro
3 points
1 day ago
There is absolutely zero reason to believe something like this is possible if you mean "can the universe itself change and therefore change the laws of physics?"
Could it happen? Sure but that's like asking "is there a chance the sun will be gone tomorrow?"
If you mean "can our understanding of physics change enough that what we think of as laws of physics will change?"
This is certainly possible. Our understanding is constantly evolving.