CaptainPanic

The polystyrene will dissolve, not depolymerize. No reaction. What did you plan on doing with a solution of a polymer in acetone? Isn't that even more harmful, and creating more waste (which I measure in kilograms, not cubic meters)? I think you'll need the same amount of acetone as you'll have polystyrene... so you might double the waste. And in stead of having a nice solid waste, you'll end up with a liquid... (which you should throw down the sink). I believe that law (over here) states that styrofoam is normal waste, while acetone is considered chemical waste. Finally, if you really plan on using lots of acetone to save one or two garbage bags, then I want to point out the risk of explosion when working with a highly volatile solvent. Make sure to play with it in a well ventilated area (preferably outside!). My question is: how much foam waste can one have after Christmas? Surely not more than 1 m3? Who cares about that? It's negligible compared to all the trash you produce the rest of the year! (Or do you pay for trash per volume?)

I know that in making steel, the steel used to get beaten. In the old days, they used hammers... Hammering it (slightly) changed the chemical structure, and the crystal structure. This possibly changed the electron configurations of some elements present in the steel. Perhaps you can find more when you search about making steel. I am no expert in this field, I just wanted to give an example and new keywords.

Yep. If supersonic air is compressed enough, it becomes subsonic. This compression can be achieved with a stagnant design, such as in the Blackbird (SR-71). Read wikipedia's first line about the air-inlets in the Blackbird article.

When designing any airplane, you must specify which speed you want it to have. Propulsion is more or less efficient at different speeds. This swimming thing can be efficient at low speeds, but different designs might be more efficient at higher speeds. Therefore, make sure not to compare two things that cannot be compared. Apples & Oranges or whatever other fruit. I think that's a nice statement that is asking for a discussion. I postulate that in case of movement against a current (wind or current of a river) walking is the more economical, because ground does not move and you can push against a stagnant medium rather than a moving one. I think it's logical that airplanes have more drag than something that floats. Airplanes get their lift because of the drag. However, if you plan on swimming 900 km/hr (speed of commercial jets) then I'd rethink using an inflatable airplane. It's very bulky, and drag does go up with increasing frontal surface area. Your comment about swimming being the lowest cost of transport of any mode of animal locomotion seems weird: swimming takes place in a fluid called "water". When I walk, the fluid I am in is "air". Comparing the two seems silly (for example: the viscosity differs by a factor 1000). Also, the presence of the solid medium called "ground" has a large influence on our locomotion because of the potentially high friction that occurs when a moving object comes into direct contact with the "ground". Therefore, a lot of energy is being spend in avoiding such direct contact and in having only specifically evolved movement organs (called "legs") in contact with the ground while the bulk of our bodies move through the air at rather constant speed. Fish just float and never seem to worry about hitting the bottom of the ocean. They also don't seem to spend a lot of energy to avoid a collision with the bottom of the ocean (I exclude flying fish from my comment here!).

Step 1: Find out the Reynolds number (Re) for the water flow. Step 2: From the Reynolds number, find out whether it's turbulent or laminar flow. In case it is laminar flow, you'll need to choose a model for calculating the temperature profile... there exist several... and all are a pain in the ass on maths. I never work with these because a good heat exchanger has a turbulent flow. In the case of turbulent flow, you can either: look in detail at the temperature profile at the wall (can't really help you with that) , or assume constant temperature through the liquid, and calculate the Nusselt number (Nu), which in turn is a function of other dimensionless numbers. That number can then be used to determine the heat transfer on the liquid side. Step 3: Find the heat transfer of the metal. The only mechanism is conduction. You'll be needing Fourier's Law for that (look up heat conduction). And in addition, I'm not sure whether any heat is also generated in the metal to complicate things. I also don't know the dimensions of the metal. I'd simply assume a constant temperature because compared to a liquid interface, metal is a pretty good conductor. Please note: I'm trying to work towards a solution, and I am not working towards a complete set of equations that you might want... that set of equations is a lot of work

Assuming you're either at 37 deg C, or colder (so: not heating up inside), then the vapor pressure of the water inside you is 60 mbar. I think your body can withstand that kind of pressure if it's inside. (I mean that the skin and muscles provide enough pressure in a similar way as a balloon has slightly higher pressure inside than outside - the pressure will not be less than 60 mbar inside, so water will not boil. In addition the vapor pressure is actually lower, because the water is not pure water, but it's inside cells, or in the blood - those have a higher boiling point). The gas in your lungs will want to force a way out, but probably just through your mouth and nose. I'd worry more about how to get back into the spaceship after you jumped out and found out you survived. There will be nothing to push against to move back into the direction of your cozy spaceship I do also agree with npts2020's point: the decompression sickness can have an effect. Hadn't thought of that.

I hope this sets an example. Smaller countries are known to follow the big ones. I also hope that there will be some money left. With this kind of people at the top, you'd want them to be able to execute new policy, in stead of having to clear up the mess left behind.

Then build the turbines at sea. There are (almost?) no bats there. Off shore wind energy has more benefits. You need lower towers, you get more wind, the wind is more stable, less turbulent... and you have a tough job doing the maintenance, although even that is being solved as we speak... I'm assuming you're talking about CO2 storage underground in empty gas fields? Perhaps you can address the issue of safety? In gas fields, small earthquakes occur because the pressure of the gas is reduced. The surface actually sinks a bit during these quakes. If we can increase that pressure again, then won't there be new earthquakes? Would it be possible that we eventually create a leak through which the gas can escape again? A big cloud of CO2 in a densely populated area would be lethal for many people.

Why am I not surprised about this? He also started several wars to bring peace and democracy. (I like the saying that fighting for peace and democracy makes as much sense as ****ing for virginity).

For some the goal was "to know". Those people were closely followed by those who had the goal "to conquer, plunder and possess". I'm sure that once we get a settlement on Mars, the first thing we bring there is scientific equipment... and the second thing we take there is weapons.

That I don't know... but I guess not? How heavy can an engine be? Airplanes can carry quite a lot of stuff (passengers, cargo, fuel, and unfortunately sometimes bombs) - so if you remove some of the stuff, and add an engine, then it does not become more heavy... but you can carry less. I'd worry more about the differences in aerodynamic design for subsonic flight, low mach numbers and high mach numbers... but I am no expert in aerodynamics.

If the world would be more full of cameras, and they'd record, and they'd be able to recognize (automatically) who is on the movie, and what he's doing - then before you know 50% of the youngsters are in jail. In a completely transparent world, either one of the following things must happen: 1. people really change (for the 1st time in history) and everybody becomes truly good. 2. people don't change and prisons become the worlds best investment 3. punishments must become much lower because so many more people are caught - many minor things must become tolerated - like: crossing a red light is a fine of 0.10 euro - but you are caught for it 10 times / day (that's my average as a student when I went everywhere by bike, possibly more)... meaning you pay a daily fine of 1 euro for crossing red lights. In our current system, I'd have lost my drivers license and I'd be in prison for all the minor traffic laws I broke... but I never endangered myself or other people... We're not discussing whether this whole camera / internet thing is illegal at this moment. It is allowed in most cases. We're discussing whether it should become illegal in the future. I am just trying to say that you don't have to accept all technology just like that. Sometimes we don't have to use it, or even have to make it illegal. Can everyone who has never done something stupid in public please raise their hands? My estimation is that it's gonna be quiet. Perfect people don't exist, but internet has a near perfect memory. Illegal business doesn't diminish because cameras are linked. No matter how many cameras you place, you can always find or even create/build a space that is not filmed... and in that space people will do illegal things. Camera pictures can be stored with all the details, and data can be stored forever, while human eyes will only store important parts needed for a memory and will forget again if it was not so important. Camera pictures can be digitally searched for faces. Cameras don't get tired. They're not the same, because they don't have the same possibilities.

I think that many governments, including the US government, underestimated the crisis and thought therefore that this first bail-out would be the only bail-out. By now we realize that 2008-2009 is the period that all the dirt of the financial system will become known (the 50 billion fraud at Wall Street is the newest one adding to the misery) and logically governments realize they cannot bail-out their entire country... so after a few months of bailing out everything, this has now come to an almost complete stop. The car companies are just too late.

I enjoy watching the errors. Shows like "really big things" or whatever they're called regularly state numbers that are a factor 1000 off. (tons in stead of kilos or something). Also, expressing energies in watts, or power in joules. Or the worst of them all: expressing weight in elephants (Indian or African, male or female?), or area in "football fields" (soccer? Us-football? ). Horrible how accuracy is wasted to make sure that the world's stupidest people also watch the show. In short - they're better off showing the bike-buildoff shows. At least there they don't explain anything, and you just see grown up men discuss their projects the way 10 year olds talk. (Always makes me jealous - our meetings are more boring!). These are the worst shows, with the least information, and ironically also with the least errors.

The specific heat of water is 4.18*10^3 J / kg K. It takes 4.18*10^3 J to raise the temperature of 1 kilogram by 1 degree (Celsium or Kelvin). If you don't specify how much water you heat with the energy, then you're not making a correct statement. So, the correct question would have been: If it takes 1 calorie (4.18 J, please use SI units!) to raise the temperature of 1 gram of water by 1 degree Celcius, will it take 100 calories to bring the same amount of ice to a boil? Answer: no. You first need to melt the ice and turn it into water. It would take 100 times the energy to raise the temperature of liquid water of 0 deg C to 100 deg C. Melting ice takes additional energy, so it will be more than 100 times the energy. But that's a physics issue, not math.

Well... I could write a long story, but as so often, wikipedia has an article that is already giving all the answers. It lists a lot of methods to make hydrogen, including a number of chemical methods. To learn the most effective way, you must include the production of the chemicals too. I think the most simple way is electrolysis of water. Please note that none of the processes will be 100% efficient.

What I meant to say is that if the salt concentration gets as high as in the ocean, then your sweet water fish will eventually die from the salt water, even in the totally unlikely case that they survive a short exposure to the NaOH. I agree that I could have expressed myself a bit better there

So, a shock wave can travel faster than sound (supersonic). But: have a read here (again wikipedia) about the Chapman-Jouguet condition. Among some other things which I am not sure I understand, it states that due to a compression, the speed of sound changes. Inside a shock wave, there is a part where the wave becomes subsonic, even though the wave as a whole travels supersonic. I am not sure at all if this can be applied in a solid material.

Salt matters to fish. Sea fish cannot survive in sweet water, and sweet water fish cannot survive in the sea. However, I think that the NaOH is much more dangerous to fish... so if the NaOH spill is so small that the fish survived so far, then the little salt will do no harm I think.

My horror scenario starts the moment that Google earth, Picasa's face recognition and surveillance camera's are combined... Just some examples of how things could be (has nothing to do with 1984): Your boss can find out that you go out a lot really late, and really often. Despite the fact that you do your job well, your boss might conclude that you are irresponsible and you don't get a promotion. Imagine all the English guys having to explain their girlfriends what they were doing in Amsterdam on their weekend trip? You can't hide anymore in areas where people go out. Imagine Youtube videos of you - with your name attached to it so it can be "googled". There are a lot of cameras in areas where people go out. But I don't think those will be linked to the internet soon. Much more likely that webcams will be in this scenario, and those are not all in areas where people go out, but more in random places.

Well... it seems like that Detroit's Big 3 need a new plan. The Bail Out has failed in the Senate (link to BBC). In a opinion article in a Dutch magazine (De Ingenieur), the writer suggested that the crash of the car market was actually merely an "inflation correction". He suggested that the new cars that people buy have no added value. They essentially do the same as the old cars. Therefore, if the consumption of cars would drop, then no wealth would be lost. He also argued that therefore there are too many people working in the car industry. I wish I could link, but my reference is printed on paper, and I could only find older articles online. Well... It's in Dutch anyway. Another interesting remark, again in a Dutch newspaper (I should start reading English papers if I want to post here, lol) says that the car companies have "hundreds of billions of debt" (link to Dutch article). How can that be possible? How can any company of such size have a debt several times the worth of the company and the yearly production? I understand that investments can have a large pay-back time... but this seems a bit extravagant to me. Regarding the near future: Place your bets. Will one of the Big 3 actually go bankrupt soon?

Apart from all regulations, at most you could sustain a ballistic flight. That's the same as intercontinental ballistic missiles do (the big nasty ones with nukes). That means: the rocket will fall back down to earth at the gravitational acceleration. that will take minutes, not days. And if you plan on using a single moment to release all the pressure... well... that we call an explosion. I believe they tried that once with the Space Shuttle Challenger (sorry, bad joke) - anyway - cannons also use this technology, and they focus the energy inside a barrel. They cannot shoot something into orbit either. Single blast of pressure will not be enough, and it will almost certainly destroy any rocket. And finally, if you would be able to make it into orbit, then yes, your rocket would burn up on the way back down. But that would be irrelevant, because you would never be able to find it back anyway. Unless you also included a guidance system (GPS and whatnot) you would lose track of the rocket in the first minute anyway. In short: experiment on a small scale first. Then you'll soon realize how difficult it is to put something in space. I always advise people the very safe version of rocketry: water bottle rockets. Safe, simple, legal, and environmentally friendly. You will learn about propulsion. Then you can start playing with things that burn later.

What do you mean by "Effective (in the 1st post)"? Do you mean: "the most H2 with the least energy"? Or do you mean: "Most practical: the least problems to do, fool proof, and if I use 2 cents worth of electricity more than strictly necessary, I don't care?" It's quite a different approach.

"Speed" should be "speed and mass", or "kinetic energy". Kinetic energy: E = 0.5*m*/v^2 Sound energy can be estimated from a formula found here on wikipedia. (Gives W/m2 = J/(s*m2) as result). I think that the Krakatoa blast was a lot of different types of energy, and the sound was just one small fraction of that.

Bah. I hate to discuss statistics. I still don't agree with you. If 50% of the Americans live in those densely populated areas, and if they would travel as much by train as for example the Dutch (also densely populated), then the average number (which is on the wikipedia site) should be half of the Dutch traveled kilometers, not less than 1/10th. I think we're not understanding each other. I think you put all things on rails in the category "trains" while I agree with wikipedia that a tram and a metro is no train. It is probably true that New Yorkers take the metro all the time. We have no data about this (yet, I cannot find any), so if we want to include it, we need assumptions. Please note that the metro/tram are not counted also for the European numbers (and we do have similar infrastructures). There is never a problem, merely a challenge. (Sorry - crappy remark). I don't blame Americans for not taking the train. You obviously need an infrastructure first. And that was my first point: If you leave it up to the market to build an infrastructure, there will be none. The investment is too high, and payback time too long. You will need some kind of Michael Moore plan where the state steps in, and takes initiative (and Obama will do just that, I hope). It is up to a state to build the infrastructure, and possibly even to run the trains at low costs (non profit, or even subsidized). Once you get intercity trains running between major cities every 15-30 minutes (this is the Dutch system - cities can be >200 km apart) then it is convenient also for business. Business is often situated in downtown areas close to main railway stations. Trains allow you to actually work while you travel, and they might serve coffee on board. I call that convenient. However, it is true that you need to go to the station first. It's a matter of taste perhaps. I'm completely used to our system, and even though I have the money, I don't buy a car. I use trains all the time. As far as I'm concerned, most has been said. I should apologise for hijacking the thread... but a disagreement about numbers should always be settled.