CaptainPanic

The nearest star is 4 lightyears away. To get there within a professional lifetime, which is about 40 years, you'd need to travel at an average 1/10th of the speed of light. Since the main problem is likely to be acceleration (and delivering the energy in the first place), I propose that we accelerate half the time, and decellerate the other half the time. In other words, our desired top speed is 1/5th of the speed of light, or nearly 60,000 km/s, to be reached after 20 years. The necessary acceleration for that is: V(t) = a*t + V(0) 60,000,000 = a*(3600*24*365*20) a = 0.1 m/s2 So far, it seems quite reasonable... In terms of kinetic energy (assuming a super lightweight 1000 kg spacecraft), that is: E = 1/2*m*v^2 = 0.5*1000*(60,000,000)^2=1.8*10^18J, or 1.8 EJ. If we express that in terms of fuel, it's the equivalent of 12.6 million metric tons of hydrogen... which shows that we at least will require a different propulsion. Either we provide the energy from the earth (earth consumes 474 EJ per year), or we go with Mr Skeptic's plan: And indeed, it may be easier to invent new laws of physics. Until then, I think we'll be stuck here for a little longer.

This website gives an idea of the debt - the money owed by African countries, and the trend that can be observed in that debt. I believe that the money spent on the wars in Iraq and Afghanistan topped a trillion dollars? That would suggest that it's at least in the same order of magnitude as the total debt of a continent such as Africa. I never said that there is no corruption in the 3rd world. I also never said that Western countries aren't self-sustaining regarding food. At least I know that the Netherlands is self sufficient... but our climate, just like the USA, does not allow us to grow every type of crop on our own soil. What I did claim is that we import many goods from poorer countries, and that we pay a price for those goods which would be considered unacceptable if it was produced within a Western country.

I am not sure "bottom waves" exist. Also, I am not sure how this will work. The hydrostatic pressure in the cylinder at the place of the valve seems unrelated to the setting of the valve itself. In short: it doesn't matter if the valve is open or closed - the pressure doesn't change at the location of the valve... The only thing that will change the hydrostatic pressure in such a column of water is a (big) wave. Then more water, and thus more pressure is pushing on the column of water.

It helps to draw a 2-dimensional picture (from the side obviously). Or play with a 3D version, using a lamp, and something spherical with the equator and earth's axis painted on it, and at the right angles.

Phones have several inputs: they obviously can receive certain wavelengths from the phone/internet/text network. They can also receive sound (microphone). They can sometimes receive GPC signals. They can receive visible light (the camera). They can receive touch signals (touch screen and buttons). They can sometimes feel acceletration, or know what it up and down. Special cameras exist that can see temperatures (IR), so that can be built into smart phones too. The phones have a processor which would not look silly in a desktop PC. They have a screen with a similar resolution as a television or computer screen. And the amount of apps for the phones is immense. Also, some phones run open source operating systems, allowing anyone to write applications (at least, I think so). What I just described above sounds like the perfect tool for scientists and engineers. Yet, when I think of a smartphone (such as the iPhone or the Android), then I just see kids playing games, or adults watching a movie and reading their email... and obviously using it for communications. I would like to see smart phones to become a real scientific tool... something like the tricorders used in star trek. How long until phones can be just that? How close are we already? What is still missing, and would it be practical (and safe) to give this technology to the average normal person?

The CO2 partial pressure on Mars is high enough for plants. There is about 600 Pa of CO2 partial pressure (or 6 mbar). We have about 40 Pa of CO2 partial pressure. The use of greenhouses can raise the temperature (a bit), which may be enough for plants that are resistant to cold temperatures. That leaves only the issue of water, and the possible need for N2 and O2 for plants. I believe that the nitrogen is not necessary? And can plants survive with much lower oxygen concentrations present?

Poverty in poor countries is for a large part to be blamed on the rich countries. All the agricultural products grown in poor countries (sugar cane, maize, coffee, tea, tropical fruits, soy, etc) are sold to us at a low price. Our own farmers would all be bankrupt if we paid them such low prices for their products... and we all refuse to allow prices to more than double. The same goes for other bulk products, from mining, fishery, forestry. We buy stuff for low prices, and we like it. Poverty would be partially solved if we would just pay a fair price for products... but the entire world economy is build on the inequality of income. We outsource work to poor countries because the people get paid much less... and that's considered a sane and smart way to run a business, rather than pure extortion or coercion on a continental scale! If you want to solve poverty... then I completely agree (no sarcasm here) that space mirrors are probably the best option... because I cannot see humanity learning the lesson.

If the goal is to achieve just high latitude (they say that space starts at 100 km altitude), then the idea of a balloon is quite good, because the rocket launches at 20-30 km, and the balloon shortens the distance by 20-30%. If the goal is to achieve orbit, then the balloon seems utterly pointless, because the goal is to achieve a high velocity, not high altitude. For practical purposes, it also seems the wrong technology. Even the largest airships (zeppelins, for example the LZ 127 Graf Zeppelin) had only a payload capacity of 15000 kg. The Space shuttle has a payload (to low earth orbit) of 24,200 kg... and that's excluding the weight of the vehicle and all the fuel. My point is: there is no balloon large enough to lift a big rocket. I know I sound negative here. However, I think it's a pretty cool project. I think that the real value of such projects is in the fact that we learn to think simple about rocketry again. Everything related to space sounds complicated and expensive... and that's perhaps not strictly necessary.

Hmm... Scaling up a torus: we increase diameter, then the length of the torus increases linearly (length = 2*pi*r) as a function of the diameter. Assuming that we don't make the torus any thicker with increasing diameter, then it only becomes longer, so the weight also increases linearly. Assuming we build spokes (like on a bicycle wheel) to keep it together, the amount of spokes that we can build also increases linearly. The only non-linear aspect that I can find off the top of my head is the weight of the spokes. Those increase in number, but also in length. So, unless we're talking about some ridiculously large monster torus, I see little limitations to scale up a simple ring to a large scale. The only factor that I dare not say something about is the thickness of the ring itself. You propose a 100 miles thick ring, which makes it larger than almost anything man made. How would you solve the force balance of such a ring to see if it can keep itself together? Afinite element analysis of the forces involved?

For what age? And in what country (I guess in English)? Sesamestreet is a good start?

A global government is only useful for global issues... The climate, our oceans, overpopulation, and possible aliens are about the only issues that I can see that are really global. I just fear that a global government wouldn't be democratic (or rather that the democratic system would fail) because people will regard their local situation, and use that for voting for a global government. Also, I would definitely fear a police state where a government has too much control over the population. If I see how most governments worldwide get their priorities wrong, then I have little hope that a world government would do any better.

Hmm... I should have chosen my words more carefully, as I can see they are misunderstood. What I meant to say is that you can beat the system (and for example go through the bureaucracy a lot faster), but that it takes some skills which a student needs to learn first. And once you have learned more about the system, it's even possible to change it altogether - as you pointed out, history has numerous examples. But someone needs certain skills to be a leader, or an innovator. To some, it comes naturally, to some it doesn't. But I sincerely believe that struggle is a good teacher in this case... and that is the value of a stupid slow bureaucracy: the struggle itself teaches students some important lessons in life. The struggle itself may even motivate people to do something about it. Of course, too much struggle, and students may just give up. If you can't beat it, join it. What you describe here, is a system that is no longer a useful struggle... but is instead a system that hampers innovation. And I agree that society (at least the one I am familiar with) seems to go towards this. The university was a useful struggle, and a single student was able to make a change. But the bureaucracy created by massive institutions such as governments cannot be changed by me - not yet at least.

I agree with Marat in a way... although my personal experience is that I was taught about the bureaucracies only at university, and my teachers were not so insane. But the real lesson is a lesson in attitude, not simply getting around a bureaucracy. The lesson is that if you lose your temper, or if you try to beat the system all by yourself, you lose, and you spend only more time. However, if you play with the system, and you try to find your quickest way through it, you will be rewarded. The lessons are not the practical issues that Marat described. They are the deeper lessons you learn: how you as a young person have to deal with these things. While I agree that what's in the books isn't taught very efficiently, the school system prepares kids for the real world. If we change the school system such that kids can choose their own topics, then we must be careful not to make a gain (for example) in teaching maths or languages while losing a lesson in discipline and obediance.

"Ceterum censeo Carthaginem esse delendam", said Cato the Elder. (English: "Furthermore I think Carthage must be destroyed".) And it was destroyed. A whole city razed to the ground. Most of its people killed. An empire wiped off the map. Its culture either absorbed or neglected. The Romans made an effort to all but completely erase Carthage from history. It is claimed (but not confirmed) that the Romans even plowed over and salted the earth of the city of Carthage. And today, nobody remembers Carthage, while most know the Roman Empire. At the same time, we know the Romans from cartoons such as Asterix, and from some movies. But what does the average person really know about them? Most is forgotten. The victors are always right in history. The Roman Empire grew to be a political and cultural power for centuries after. A lot of our modern culture and languages are here because of the Romans, but in the every day life, people don't think about the Romans when they speak Latin languages... so the Roman culture is undoubtedly of value to us, but also mostly forgotten... But, if an ancient Roman (a senator from 50 BC for example) could be here today. If he could look back to the Punic Wars, would he say "it was worth it", or would he wonder why they made such an effort to practically erase a culture from history, given the fact that the Roman Empire is also gone for about 1600 years (and the East-Roman empire for 557 years). Its way of living does not exist either today, and that only parts of their culture remain in an adapted form. p.s. If Carthage was not destroyed, then history would undoubtedly have been different... this thread should not be a long speculation on how the world could have looked if Carthage hadn't been destroyed. There is no way to know.

Replace Belgium with Poland, Czech Republic, Romania, Bulgaria, Slovakia, and you're pretty much on the money. Those are all European Union countries, and therefore the people have the right to work in any other country in the EU. Completely open borders. In addition, there are millions of people from outside the EU who want to enter. I have no idea where you got the idea that the USA is the only country in the world that attracts immigrants. You're very wrong about it. It's not the USA. It's money and wealth that attracts immigrants... In a way, the rich countries have created the immigration problem themselves, because they've used other countries for so long to acquire a lot of wealth (we all know that people in poor countries produce products for the rich countries, and don't get paid nearly as much as us). And now that mass transportation has become global, it's logical that people try to come to the wealth, if the wealth doesn't come to them.

I fail to see the comparison... Do you honestly think that hundreds of thousands of guys and gals back in those days investigated the laws of nazi Germany in detail? Hell no. They just got a gun, did their training... but they were essentially in the blind what was going on. It was just a matter of "Germany is bad, m'kay?". The fact that I don't read a lot of text (after actually looking it up too, and taking a glance) does not mean that I wouldn't fight if there would be injustice in America. In fact, I am online on this politics subforum of SFN exactly because I think there is some injustice in the world (including the USA). I think I will stop the discussion right here. We've godwined this thing to death by now. And you haven't answered any of my questions regarding the differences between federal laws and Arizona state laws - which I maintain is the actual issue we are discussing here, or at least is the actual topic of the movie. Yes, it's within. Yes, there is a " us" and "them" (inside the borders, outside the borders) kind of thinking. But I still fail to see how that relates to the other racist remarks. "American" is not a race. It's a culture, and a nation. You can feel culturally dominant, or you can be nationalist about the place... but to be a racist, and proud of America as a country at the same time doesn't seem to make much sense to me. It's like being proud of a country, but hating some of your countrymen... but it's the people that make a country, nothing else. You can't even see most borders in real life. They exist only on maps, made by man. It's the only illegal book in the country. For the rest, we're pretty free here. I think if you look up the book online, nobody cares. Essentially, it's just illegal to sell the book. I've never heard of a police officer with a warrant to search for the book in someone's house.

No, it was the guy in the movie who brought up the Jews and Polish. I commented on the movie, nothing else. And yes, Mein Kampf is really illegal in the Netherlands... There are more countries where it's illegal, btw. As far as I know, nobody has ever been arrested for just owning a copy anyway. It's the only book that is illegal over here... Historical reasons, I'm sure I don't need to explain. I still fail to see how the whole racist discussion, to which you keep steering back, is related to the topic of the movie... The issue discussed in the movie is whether the US federal government is allowed to discuss a state-law, and whether the federal laws and state laws may contradict (because apparently someone in the federal government thinks there's a problem with the Arizona law). - Shall we discuss this bit, rather than the legality of racist books?

Curiosity driven education would be the best. I agree. The practical problem is that every kid will be curious, but interested in different topics at different times. So, this puts an enormous burden on the educational system. Now, a single teacher can educate up to 30 kids (in a rather inefficient system from the kids' perspective, I admit, but effective from a school's and a short-term profit point of view). If we go to a curiosity driven education, then we may need twice the amount of teachers, or even more! Also, I believe that kids should then be able to specialize much sooner into a field that they are interested in... but important other fields should not be neglected (for example, personally I would have loved to specialize into the exact fields such as physics, chemistry and engineering much earlier, but now that I am older, I enjoy the fact that I was forced to learn languages - although I despised them at the time).

Oh, I'm sorry. I hadn't realized that it has to be an invention. Internet is indeed much older than 10 years... but if you compare the internet of 10 years ago with the internet today, then that's a huge difference.

It's against the law to own a copy of Mein Kampf in many countries in Europe. I am not sure what you are suggesting here, and I am not sure I wish to know. I don't need a book to confirm that racism is an outdated and dangerous way of thinking, and I only need to look around in the world to find that places with the most hate are often also the places with the most racism. The two go hand in hand. I live in the Netherlands, which is at the end of the river Rhine (and not in Germany, as you seem to suggest?). It's also a melting pot. Just like many other European countries. In fact, the amount of foreigners in the Netherlands is pretty close to that of Arizona, except that the Netherlands seems more diverse.

Regarding the movie Please note that in my previous post I neither agreed nor disagreed with the statute. I did not give an opinion about immigration. I just wrote down phrase after phrase what the guy in the movie said, and what type of argument that was. I merely commented on the narrative techniques used by the speaker. His techniques seem to be aimed to convince a listener without having to use any facts or coherent reasoning. In short: it's all very emotional, and not founded on facts. If the speaker had chosen a more objective way to communicate the issue, then I may have been able to form an opinion. Instead, all I was able to form an opinion on is the guy himself. And I think he's a nut. And the movie wasn't worth the 5 minutes of my life that I gave it. Regarding "races" Now, in reply to your post: I always get a little angry when I see people talk about races. First of all, because it's the reason racism exists, and history has proven that racism isn't a good idea. Second of all because races aren't well-defined, and therefore are a subjective thing. Thirdly, many people are half-bloods, or are just genetic mixes. The world is one giant mix of genes. It makes sense to talk about apples and oranges... as long you can be sure about every apple and every orange in which category they fit. It says enough that Obama is considered "black"... while his skin color indeed suggests that, I believe that genetically he's not all that black... is he? Americans, as far as I am concerned are not a race anyway. Americans, at most, are a culture. Genetically, Americans differ way too among themselves much to be called a race, and that might be because America in its current form was formed by immigration. Almost no native genes survived if I am not mistaken. You see, there were people living in North-America before Columbus arrived. The first discoverers and settlers mistakenly called them "Indians" first, now they're called native Americans. That already gives a clue that anyone who is not a decendant of the native Americans is logically a decendant from immigrants. Other countries, such as places in Europe also have lots of immigrants. This was something that was established a few days ago in another thread here (link to relevant post). Wealth simply attracts immigrants. It always has, already since the days of the old Roman empire, or even before that... so I don't know why you complain that only America has to allow millions of immigrants, when it's not just America. Regarding immigration Now, on the topic of immigration: it's acceptable to set a limit to the amount of people, or to have other selections at the gate, so to say. Or, at least, other countries do that too. But, the issue here is that we're not talking about the existing immigration law. We're talking about whether it's acceptable for the federal government to test the validity or legality of a new law of one of the states of the USA in court when it is suspected that the new state law breaks a federal law. At least, that's what the movie was about. The movie said something like: "Hey, we're stopping drug cartels, so why is the federal government trying to stop us??". ... I expect that a new law may be tested against federal laws in court. In fact, a court is probably the best place for a law to be tested, because lawyers, judges, etc., are the experts regarding laws. So, I don't see the problem to be honest. Regarding the statute itself I tried to google for the statute... and I found that it was a lot of legal gibberish. I'd gladly leave it to the experts. Too long to read anyway. And I have no opinion at all regarding the Arizona statute itself. I don't care. I don't live in the USA anyway.

Internet.

Must be the tarsier's hypnotic stare. It's the eyes! Anyway, the 2nd post already gave the answer. The animal is a tarsier, and in my opinion, looks quite different from a chameleon...

Took me at least 5 minutes playing with the website, clicking little dropdown boxes with my mouse. I just didn't get it. Couldn't see it. Then I got annoyed with it, got pen and paper, and solved it in a minute, using letters (a,b,c,d).

In the pipe, the methane is probably pure: no air, no explosion. In the air, the methane is probably too dilute to explode. The lower explosion limit of methane is 5%vol, the upper explosion limit is 15%vol. Somewhere in between those two, it goes through its explosive concentration range. And that is probably under ground. All you need then is a spark, or enough heat, and it explodes. So, there must have been a leak... that's all you need for an explosion, or at least a fire. I found this link which may be an interesting read.