Or mom's just taking the opportunity to teach the kid how to swing.

In all seriousness though, my mom broke her ankle last year just falling backward while gardening. Bad angle and poor bone density worsened the fall. So even a feet or two could cause major damage.

Yeah, 20000ft is roughly 6km. The air density is about 1/2 but from what I can determine that doesn't equal 1/2 air resistance, but something more like 90-95% air resistance of sea level.

Having said that, I haven't studied aerospace engineering, so I might be getting the details wrong.

There are definitely some minor advantages to building on a mountainside, but I don't think they outweigh logistical difficulties under normal circumstances.

The idea has a good bit of scifi (and probably scientific) history behind it though. I believe Heinlein used a railgun cargo launcher from the moon in Moon is a Harsh Mistress and a mountainside sled rocket in one of his earlier books.

Project Rho is a great resource for hard scifi and rocketry research for writers. http://www.projectrho.com/public_html/rocket/surfaceorbit.php is the link to a page that discusses maglev, railguns and rocketsleds.

Using a mountainside might help with structural integrity, but it's not likely to give much air resistance advantage if I'm reading the math correctly. The 5 highest peaks in the US are all in Alaska and and range from just under 5km to just over 6km. Commercial jets using air resistance/density for lift fly at about 10km and even at 38km aerodynamic lift still carries 98% of the weight of the plane (https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line)

Air density is halved at 5km compared to sea level, but air resistance doesn't diminish as quickly (due to it being multiplied by velocity squared and drag coefficient), and only becomes irrelevant (for short-term purposes) around 100km at the Karman Line.

If we had a 5km peak in Florida, the lack of logistical costs might make the benefits worth it, and if we could build on one of Equador's 5km peaks, then there's the further advantage of equatorial location for optimal rotational advantage (part of the reason we launch from South Florida)

This shitshow is Trump's America, and a result of his lack of leadership. You and he seem to think he's only the president of Republican led areas.
Cities were run by the same party under Obama, did we have this slow burn civil war simmering then? No, we did not.
Q) What changed? A) Trump's in charge.

Cities are almost exclusively led by Democratic mayors. Cities have high crime rates because they have high population density. Per capita crime rates aren't that different from rural areas.

Republican led areas have much higher poverty rates and way fewer services. By your logic, republican leadership leads to high poverty and an MIA government except at tax time (actually, it does historically and by design).

Edit: Downvote for the blatant lies in the description. Democrats have not promoted violence they've constantly denounced it, and are blaming Trump for the dissolving union, the division, hatred, and violence he promotes including the murder of protesters and unarmed black men.

Human terminal velocity is around 120mph when falling in breathable altitudes in a belly-down (flat) position. Pulling in your limbs will get you closer to 200mph, which is roughly what a peregrine falcon hits in its dive and in the ballpark of what a .30-06 round in freefall (ie, after being fired straight up) would reach. Professional speed skydivers fly head-down and reach 330mph. The higher you start, the lower air density and thus higher terminal velocity you get. Felix Baumgartner jumped from 128,000 feet and reached 840mph.

Source: https://en.m.wikipedia.org/wiki/Terminal_velocity

It’s very important to note that drawing direct parallels between countries when it comes to crime is very murky, as these difference could be due to differences in laws, the way the criminal justice system is set up, how policing is done, how crimes are reported, and much more.

Quoting this: Harold Pollack, co-director of the University of Chicago's Crime Lab, called Zimring and Hawkins's book "an excellent source." In a 2015 phone interview, he pointed to a number of more recent studies that fit the pattern it identified.

"There's no question the United States faces a number of distinctive social policy challenges, some of which affect the crime rate. But many other OECD countries face their own distinctive problems that affect their crime rate," he told me. Western Europe, for example, has a major problem with drug use. Canadian cities have "very high" rates of property crime like car theft. And yet, the US still stands out on murders.

"I think that Americans have this view of Western Europe, or Toronto for that matter, which is very stereotypical and doesn't take into account the challenges that many of peer industrial democracy problems face," he points out. "There's a lot of drug sale, a lot of ethnic stratification and conflict, there's a lot of just general crime."

Crime rates in Canada aren't that much lower than the USA, there are just fewer violent crimes, like homicides.

In addition to this, a major factor might be considered in regards to Canada. Population and population density. Canada is lower than the USA across the board, 36.71 million to 325.7 million and density of 3.9 people per km to almost 90 people per mile (last census data).

I don't support the NRA, btw. I think they are idiots. I do support logical gun laws. I don't care for fake news.

I also think I was civil in my response to your original comment. I have tried to remain that way even though one could classify your response to mine as hostile and provocatory.

Can be! It depends on the contents of the container and how air-tight its construction and materials are. Generally materials packed for transport are supposed to be strapped or otherwise held in place so that they don't shift and upset the transport vehicle (see the 747 that crashed in the Middle East when its cargo shifted...). But that's just the stuff that was meant to be in the container. Every ship has to contend with the risk of water ingress. Un-contained water in a vessel forms a "free surface" and the so-called free surface effect applies. That's where that material can and will move based on gravity, often making a bad situation much much worse. Imagine water in a tank (itself a free surface) vs. water sloshing around the cabin of a plane. This is what usually causes ships to capsize: water gets in and isn't contained, so it can move tremendous amounts of mass anywhere it wants to go -- usually in the direction it's already going. Calculations of ship stability for things like cargo loading and ballast assume minimal free surface in the ship, because you have to. That's how ships stay upright and afloat.

How does this apply to lost containers? Depending on how watertight the container is and how well strapped in the contents are, some amount of water may get in and form a free surface. This free surface will move around until the container finds its equilibrium which may or may not be watertight and less dense than the water around it, which defines whether it floats or sinks and what direction it faces when it does.

A container with a lot of weight on one side but otherwise watertight will stand upright and perhaps still sink (like the one at the end of this video). A container with well-distributed weight would tend to end up flat. Whether it sinks or not depends on whether it's watertight and what its density is -- the weight of the container displacing ocean vs. the weight of the ocean it displaces.

Sadly, a significant number of containers end up at the worst possible density/displacement where they float just at or near the surface and lay in wait to devastate passing ships, regardless of the orientation of the container itself.

Let's be extremely optimistic and figure that these things work in a 25 meter radius, with 100% kill rate to any mosquito inside that zone for 30 seconds+. That's plenty to put in or near a house and drastically reduce the mosquito population in (and a little bit around) that area. But just a short distance away, the mosquito population will be completely unaffected.

Animals that prey on mosquitoes will find a small dead zone and move on.

Lets say they worked extremely well, and we decided to cover an entire city with a grid of these things. Maybe New York (800 km^2). Would the local ecosystem be affected? Sure. Some species of birds, bats, etc. would move upstate -- but overall there would probably be way less impact on the ecosystem than simply having a gigantic city there in general.

It would probably be better to set them up covering small villages in area with high risk of malaria, in which case any affects on ecosystems would be very small and contained. But on the other hand, first world people like New Yorkers with high population density and more $$$ to burn might be plenty happy to chip in (tax dollars?) for these things if they never got any mosquito bites again. And that would probably help the economy of scale kick in and make it much cheaper to set them up in places that would really benefit...

It's a good thing someone just invented a new lithium battery (not lithium ion) with a plastic electrolyte that can't short out and explode and can produce 3 times the energy density of lithium ion batteries. I hope they go into production soon.

I would say that Stalin, the Kin Jong's, Various African Tribal Genocides, and Pol Pot might disagree with your account of wholesale slaughter being reserved for the 'white' Europeans and their descendants. That is just to name a few. Also, what is a 'white' European? I mean the southern Europeans have quite a bit of Moorish blood in them, do they still count as 'white'?

All sarcasm aside, your argument is extremely flawed. Conquerors tend to lay waste to the societies they conquer, not always in terms of total lives lost, but in terms of cultural death. The reason why 'white' people are vilified for this lately is because for the past several hundred years they have been the ones expanding and taking over the regions you speak of. This is not exclusive to a skin color or originating locale, it is absolutely a core of our human nature.

I gave some examples earlier of non-European conquerors, but they are fairly recent. If we look in history at other groups, we find the same meme. The Steppe Horse Tribes were BRUTAL to cities and countries that did not capitulate. Look up "Measuring against the linchpin". That saying came from the fact that if you resisted Mongol rule, they would slaughter every male taller than the linchpin of a wagon wheel. The Aztecs and Mayans ruled southern American empires through great brutality, including human sacrifice for 'religious' purposes. Recent discoveries even indicate that it was considered a good omen if the sacrifices were crying in pain before they were to die. Remains recently found showed "All shared one feature: serious cavities, abscesses or bone infections painful enough to make them cry."

Slavery originated as early as human recorded history, if not sooner. Slavery can be traced back to the earliest records, such as the Code of Hammurabi (c. 1760 BC), which refers to it as an established institution. Slavery is rare among hunter-gatherer populations. Mass slavery requires economic surpluses and a high population density to be viable. Although slavery in some form or another existed in most European countries, it wasn't until after contact with the Arabic African slave traders that it soared in the 15th and 16th centuries.

tl;dr

You are referring to recent history to make an example while completely ignoring THOUSANDS of years of similar history. All humanity is flawed, narrowing it down to a singular group with cherry picked data is not going to persuade anyone with a brain.

To be fair, you were taught this in school if you were taught wave particle duality and the double slit experiment. Look at this. Now imagine a particle bouncing along in very small steps (quantum leaps if you will), and the direction it goes depends on the strength and orientation of the wave where it lands. You may never have been told to think about it like that, but that's what makes physics so amazing that sometimes all it takes is for someone to think about it slightly differently. The information was there all along, but who would imagine the 'particle' bit of an electron interacting with the 'wave' bit - the electron interacts with itself?

I absolutely love it, it's amazing, and simple and beautiful. It may provide insights into new ways we can model quantum behaviour, it might open up new questions to ask.

There's things I'd like to know. First, if the standing waves generated at each step in the droplet's progression interact with each other, the droplet is reacting according to waves it made in the past - what implications does that have for the notion of real particles in a spacetime continuum? For the double slits experiment to work in that model - in the ball on a rubber sheet sense - the sheet would have to stay warped to some extent after the ball had passed. In the quantum sense of the real double slits experiment, we would say it IS a wave, passes through both slits and appears according to statistical probability (the diffraction pattern).

Presumably several droplets released along the same path would go on to take a different route through the slits, to create a diffraction pattern as it must. Perhaps because of fluctuations in the temperature or density of the water at different locations? Is that a limitation of the model or an indicator about the nature of the fabric of spacetime? Perhaps even due to quantum fluctuations in the water particles - the water is never the same twice even if its perfectly still each time - which would potentially mean we're cyclically using quantum mechanics to explain quantum mechanics and we actually haven't explained very much.

The philosophy bit: But this reaches to the heart of the issue with quantum mechanics and perhaps science in general. How accurately can we model reality? The reality is beyond our ability to see, so we can only recreate simpler versions that are always wrong in some way... our idea of what happens - our models - can never be 100% because only a particle in spacetime can perfectly represent a particle in spacetime.

Scientific results and definitions are always defined with limits - "it works like this, within these confines, under these conditions, with these assumptions." There are always error margins. We are always only ever communicating an idea between different consciousnesses, and that idea will never be as true to life as life itself.

Sorry for the wall of text, it's a great and provocative experiment.

Tags for this video have been changed from 'geography cities' to 'geography, cities, Paris, New York, population density, europe, america, history' - edited by eric3579

Desal can be awesome ... for islands with a high percentage of revenues coming from tourism (lots of Caribbean examples), or for City-States that have high population density and lots of money-making industry (Singapore).

California is *huge*, with lots of revenue coming from agriculture. Not enough tourism per square mile to pass the costs on to visitors, like with Caribbean islands, and not really enough population / commercial density to make it an ideal solution for those uses either.


...On the other hand, economy of scale can't start kicking in until you get some early adopters. By throwing some money at this now, California might be making a smart investment towards having better and cheaper desal options that could fill a higher percentage of their water needs in the future.

I did this a while ago, but different dice have different densities so with the materials available to me I was only able to get a portion of them to float.

You should follow my example and, having discovered that some are balanced and some are not, put them all back in the same jar and ultimately learn nothing.

Ice has lower density than water, so no.

If you meant the fire, wood doesn't conduct heat terribly well and hot air rises so the main mechanism for heating the ice will be radiant heat... so this isn't a terribly efficient way to make a hole in the ice with fire.