K^2

I'm guessing you copy-pasted that typo? Should read km/h rather than km/s. Oh, and you have an extra zero in that first line. Answers look good, though.

*Cough cough*

It's not "inverse". I don't know where this myth originated, but there is nothing like that related to FTL travel.

Sorry, that was uncalled for. It basically did exactly that. Yes, we've overshot the mark, but the increase in temperature certainly predates any effects of human activity. Why it got even warmer than during Medieval Warm Period and whether we have something to do with it is a separate discussion, but at least half of that temperature change is clearly due to the end of Little Ice Age. We've seen temperatures level off, which is exactly what you'd expect from a dynamic system responding to this sort of input. I'm not saying it's a sole factor. But end of the Little Ice Age has given us the agricultural boost needed to go from agricultural economy to an industrial one. You can't build a factory if all of your labor force has to be in the fields in order to feed the population. I'm not positioning end of Little Ice Age as the cause of industrial revolution, but rather as a trigger that set up the timing. Technology to begin industrialization was already in place and population densities sufficient long before that. Some people need to learn a bit of math and physics. Even today, most of the third world doesn't produce enough CO2 output to be of any concern. United States produces 20% of anthropogenic CO2, in contrast. An agricultural society doing anything sufficient to change climate? In middle ages? That is absolutely laughable. Sure. I'm the only person here who has done any numerical analysis of the problem and provided at least some hints at why certain models work or fail. But no, that's all drivel, according to you. We should trust information from propaganda pamphlets instead, which carry absolutely no references, let alone explain any analysis. Yeah, lets go with that as our reliable source of information.

Little Ice Age. Please, educate yourself. It has now gotten warmer than medieval warm period, so one might argue that this bit is anthropogenic, but the latest warming trend since 1800s started long before humans had anything to do with it. In fact, I would argue that it's likely the end of Little Ice Age that has jump-started the industrial revolution. Furthermore, whatever effect we have on the environment, we are pushing on the upswing. If the temperature overshooting its equilibrium is due to human efforts, it's still likely that it's the outcome of us pushing with the main driving force. And we don't know how long that's going to last. In fact, as Sternface pointed out, there is indication that this trend has ended.

Yes, a brochure from a website whose name, "climatechange2013," suggests no bias whatsoever is certainly the definitive proof of consensus within scientific community. How about something that, at least, cites sources, so we can talk about where the numbers are coming from and whether they are reliable?

Our agriculture is dependent upon farming machines. We have neither land nor human resources to produce sufficient food for the population without burning fossil fuels. Ditto the distribution networks. In large cities, the cost of food is directly tied to energy costs. As gasoline prices increase, so do the prices at the store by almost the same fraction. So the costs of completely taking out fossil fuels right now? Complete and total devastation. Just petroleum? That would account for roughly a third of emissions, and we would end up without sustainable agriculture or transportation. Transportation accounts for over 70% of petroleum consumption in U.S. We can talk efficiency. US is really bad in that regard. Liberally, energy consumption percapita in the US can be roughly halved. This requires a total rehaul of the infrastructure, however. If we start now, we can roughly balance off the consumption growth rate with improvements in efficiency. It will cost a lot of money, however. So yeah, halting growth of CO2 output would cost a lot to the economy, making it more difficult to spend money on research we need to switch to other energy sources. Trying to reduce CO2 output would result in food cost inflation and starvation even in the U.S. I'm not even going to bring up third world where food is already a problem. But then again, they don't contribute as much to the total output, so we really can limit discussion to U.S., Europe, and China. No, we do not have consensus. Criteria for consensus require an established model, which we do not have. The fact that there is still a significant percentage of publications being made in peer-reviewed journals that show lack of anthropogenic cause to global climate change is a direct reflection of the lack of consensus. Try to understand, scientific community doesn't work by majority vote.

We do know the cost of not putting any more CO2 into atmosphere. It's worldwide starvation. We can maybe, maybe, stop the rate of output growing. And that would still be at a great cost to economy. You are putting potential long term dangers of going along the route we are in against absolutely real and devastating short term costs of veering off this path. And to support it, you put forward research you yourself do not understand. Now tell me, how in the world does that make sense? Do you understand that when you place additional regulations on CO2 output, you effectively increase cost of all energy resources? Do you understand that it translates to scarcity of food? Do you understand that it leads to immediate cost of lives worldwide? That's what you are advocating based on second-hand data you got from people who make careers on scaring people with global disasters. Damage we can do in a decade, if it's real, can be fixed without cost to human lives. We'll be in the position to understand the environment and to switch some of our infrastructure to alternative energy. This is not where we are right now. We don't know if the problem is real for sure, we certainly do not understand how extensive it is and how to address it, and we are just starting to build the infrastructure for alternative energy. The absolutely best thing that everyone can do right now is sit tight until we know what we are dealing with.

We absolutely should be investing in alternative energy sources. Even if we don't run environmental risks, and even if we aren't risking running out of fossil fuels any time soon, which with development of hydraulic fracturing seems more likely now, we still can't rely on fossil fuels indefinitely. Most of our technology is energy-density limited, and energy density of gasoline is fixed. The problem is that fear mongering can be used to harm the oil industry directly. If we develop better energy sources and oil industry dies, good riddance. But if we start suffocating it now artificially, we are suffocating entire economy, doing loads of damage to the technology sector, and that's where almost all of our money for research is coming from. This is simple strategy. Like it or not, we are relying on oil too much right now to do absolutely anything without it. If we give up burning hydrocarbons, most of the world's population will simply starve to death because we cannot sustain agriculture without this input. If this damages the environment, well, that's too bad, but we simply can't stop it. What we can do is try to get past this phase of oil dependence, and the best way to do this is to have as much money diverted to research as possible, which requires a strong, healthy economy. If stimulating economy means relaxing some of the restraints and producing more CO2 emissions in the short term, I say it's worth the risk. Fossil fuels are pretty much the only shot our civilization has of making a leap from agricultural society to a true post-industrial, and if we screw this up, the next opportunity will be millions of years from now.

Yup. Thermodynamics, statistical mechanics, fluid dynamics. I'm not an expert on weather or ecology, of course, but I've studied all the necessary basics as part of my curriculum. That's why I can actually read these papers and gauge their reliability. And like I said, I have not seen anything that would convince me that we have good evidence of anthropogenic climate change. Don't get me wrong, there is no solid evidence to the contrary, either. But lacking good evidence either way, I can't recommend an action against status quo. So for the time being, I would say we should look after local environment, assume that's what is good for local environment is good for global environment too, and not panic until we have good enough models to address the issue directly. Going by how the computer models have been evolving, we'll know for sure in ten to twenty years, because we'll be able to model global environment with sufficient precision. There is definitely no way in hell we'll manage to do irreversible damage in a decade, so lets just wait.

Yeah, but I don't see the point of scaring population with a dubious global problem when there are very real local problems that can be identified and fixed directly. Effects of human population on local pollution are easy to test. Which means that not only do we know for sure that these problems exist, but we know which actions are causing them, and how bad the impact is. So we know what we should do differently to have a much better local environment at minimal impact to economy. With global effects, even if I fiat you that we are causing significant damage to global environment, how do you decide what reasonable limitations to our activities are? No two models agree on how much is too much, and as I've pointed out, many models suggest that we aren't even close to doing significant damage. These are the models that I find more believable. So how do we decide on the plan of action? Environmental movement should have stuck with local climate. That's where they have done a lot of good, and where a lot of good can still be done. Not even close. Evolution was predicted based on general taxonomy, then confirmed with archaeological findings, and beyond doubt confirmed with genetics. Moreover, there are controlled experiments in the field of genetics that test evolution. You will not find a serious biologist, who is not a complete crackpot, that has doubts of evolution. Environmental community is split. Yes, over 90% of publications are saying that humans are causing global climate change. Unfortunately, very few of these are in agreement on exactly how this effect works. Most of these papers are just total tripe. Lets do it this way. You point me to a specific paper, and we talk about the specific claims of the paper. That's how scientific debate works. Saying, "97% of scientists agree..." sounds like a toothpaste commercial. I've looked for good papers on climate. I have not found a single analysis that holds water both computationally and in terms of its assumptions that suggests that we can currently cause significant change to global temperatures. If you find me such a paper, I will do a 180° turn on the spot. I am a scientist, and as a scientist, I'll only change my position based on evidence. Not peer or political pressure. Unfortunately, this is a dying trend among scientists these days.

That's mean lifetime, not half-life. Half-life is closer to 10 minutes.

What evidence? Seriously, we wouldn't be having a debate if there was good evidence of anthropogenic climate change. There are fluctuations. There are some suggestive correlations. There are models that suggest that we can cause global climate change. But nothing conclusive on whether it's already happening or if it will happen in near future. I understand hat it's difficult to meet criteria of rigorous scientific proof when you have no way to control the experiments, nor anywhere near the capability to do a proper simulation, but that's exactly why you shouldn't be writing it off as something we understand. We don't. And the fact that you are under the illusion that it's something that has been established is just another indication of how much the politics has rotten the debate on the topic.

They look at stuff that comes out when a particle decays. By looking at product particles, you can identify mass and quantum numbers of the source. This tells you that what you are dealing with is a very heavy boson. Then you want to make sure that it's an elementary particle and not just a bunch of already known particles clumping together. There are some meson excitation that could be mistaken for Higgs Boson, for example. However, these have completely different decay modes, so if you observe enough decay events, you can exclude this possibility. So finally, what we see is a very massive elementary boson with decay modes consistent with Higgs mechanism. Looks like a duck, quacks like a duck, and there are no reasonable alternatives.

178m2Hf decay is a strong process. It has nothing to do with weak decay.

The point isn't just to accelerate the crew, but to accelerate the crew without killing everyone with over-G. Gravity would do the trick, indeed. But yeah, it would be extremely wasteful for many reasons. No. In fact, electric resistance is also a purely quantum effect.

The reason I'm going with toy models is because I can run through all the algebra in a post. Anything more complicated would require heavy numerical integration. I do have resources to run something significantly more sophisticated. I do not have resources to run a simulation that realistically takes into account global temperature distributions and weather. But then again, nobody else has these resources either, so everything we have to go on comes from models that make some very restrictive assumptions. But if you like, I can run some simulations of heat exchange in atmosphere that take into account altitude density and temperature variations and show that they give you the same results. I'd only be able to give you the model and the output, however, which would require you to take my word that I ran everything in between correctly.

We already have relativistic quantum physics. It still says that speed of light is the local limit. Without warping space-time, there is no way to travel FTL. Warp drive and wormholes are the only known ways around it. In terms of normal space-travel, however, there is something called proper velocity. It's the map distance covered in unit proper time. From perspective of the crew of the ship, that's the true velocity. And that can go as fast as you like. Better yet, once you are going fast enough, it becomes easier to speed up. At proper acceleration of 1G, it's possible to make a round trip to Andromeda in a little over 50 years of ship time. So speed of light isn't that big of a problem for crew of the ship. On Earth, however, millions of years will pass, which might be a problem depending on what the goals of the voyage are.

The reason it's not often pointed out is because every time it's brought up in intelligent debate, the other side immediately reminds the speaker that geothermal output of our planet was significantly higher then, and we were loosing geothermal at a faster rate than we are gaining in Sun's output. Decrease in geothermal output explains most of the temperature decline. By now, of course, geothermal output is almost insignificant on average. Which is still only about a tenth of the rate at which carbon from atmosphere is bound by the biomass. That's something to keep in mind for perspective. Which is why cloud layer has a stronger effect, since it can dramatically increase absorption in mid to upper troposphere. And yes, CO2 absorbs near peak of our IR output. Even in lower stratosphere, however, absorption specturm is completely saturated with H2O, leaving only a small window. And we are talking here about affecting some fraction of that. H2O is by far the dominant effect in greenhouse effect we currently experience, and the overal atmospheric effect is still under 30°C. Of that, only fraction is greenhouse in IR. Of that, you have a small window where it's not saturated, and of that you'll be able to affect a small fraction with CO2. Saying CO2 can contribute to a degree or two increase would be generous. Besides, like you yourself pointed out, all the fossil fuels we burn used to be CO2 in atmosphere. So if we have to picture an absolute worst case scenario, we don't have to go far. And guess what, there was no runaway effect then, either. Ecosystem can cope with these CO2 concentrations as a matter of empirical fact. It already did. It can kill any number of modern species, sure, but again, Earth has recovered from worse. Several times. Humans can survive even that drastic of a climate change, along with enough of our food crops for us not to starve. (Don't forget that we can modify our crops if necessary.) So we'll have food and habitable environment even if somehow we manage to make Earth into what it was a billion years ago. In fact, direct CO2 poisoning is the only thing we have to worry about with the CO2 output, and we are nowhere near capability of getting to that point.

If I recall correctly, two objects that are traveling faster than light and can communicate with eachother can allow for time travel. But such possibilities are almost always excluded for reasonable FTL setups. So the only way to time-travel still remains traversing a closed space-time loop. Though, FTL can allow you to traverse some paths that you could not otherwise. Anything sub-light preserves the causality.

Where are you guys getting this nonsense? For matter fields, Higgs mechanism provides a tiny amount of current mass. The chiral symmetry is dynamically broken anyways. 99% of mass is due to kinetic energy of quarks and gluons in nuclei. How are we using weak and color fields? These are way more accessible than Higgs field, and we are doing nada with these. Heck, our use of gravitational field is rudimentary. The only reason we make good use of electromagnetic field is that it has such strong coupling, infinite range, and the two charges can cancel eachother out. Other fields don't have such nice, convenient properties.

Satellite: [#]O[#] Polish Satellite: O[#][#] Reverse Polish Satellite: [#][#]O (Had to be done.)

There are, of course, plenty of competent people in climate and atmospheric sciences. They have their share of nutjobs, too, and lately, it's been popular to make some of the more exagerrated and less reliable claims into sensationalist news. All of it is best illustrated with some toy models. Lets pretend, for a moment, that Earth was a perfect sphere of constant albedo and had the uniform temperature across the surface. Things are obviously way more complicated, but it's a good picture to start with. Earth is roughly 200 times further from Sun's center than Sun's own surface, and Earth is going to receive solar radiation with cross-section area ÀR² and radiate in IR from its total surface area 4ÀR². In other words, it radiates energy from 160,000 times greater surface area than area of Sun's surface from which it receives radiation. Since radiation of heat goes like T4, Earth is roughly (160,000)1/4 = 20 times cooler than the Sun. This is in the ball park. If you do all of the algebra correctly and take albedo into account properly, you end up with a temperature that's a bit low, leaving room for various atmospheric effects. Now, spectrum of radiation we receive from the Sun and spectrum Earth radiates back into space have almost no overlap. See the graphic I posted on the last page. So we could envision, in our toy model, a shell around the Earth that is perfectly transparent to Sun's radiation, and completely opaque to Earth's. Since energy flux in has to be equal to energy flux out, the total IR radiation outside from this shell has to be equal to the Sun's total radiation going in. So this shell will now have the 1/20th of the Sun's surface temperature. However, it radiates out and in. So Earth now receives twice as much radiation and has to radiate twice as much. To double the radiation output, Earth's tmperature has to increase by a factor of 21//4, or by roughly 18.9%. Taking Sun's effecive photosphere temperature, that would make for over 50°C increase. That's a lot. And this is basis for a lot of fearmongering. Things are quite a bit more complicated, however, because we don't just have one layer of dense, IR opaque material. We have an atmosphere. First, note that adding another IR opaque shell makes absolutely no difference. The outer shell must still radiate the same amount, and the inner shell(s) end up in thermal equilibrium with an outer one. So the temperature of each shell is 1/20th of Sun, and Earth is still the same 18.9% hotter. What's interesting here is that we can have as many shells as we like, spaced any way we like, and onlly the shell closest to the Earth is going to matter. So radiation and re-radiation in upper atmopshere is pretty much irrelevant. We also know that this 18.9% jump isn't just going to happen right next to the surface. It can't, because we have air currents carry heat between layers of atmosphere as well, so things are going to get more interesting. But lets look at something else. Now, lets suppose that shells are not 100% opaque. Lets compare two simple models. In one we have just one shell that's 75% opaque, in another we have two shells at 50% each. Note that the total is still 75%. For a single shell, denote Earth's radiation as x and shell's radiation as y. We know that .25x + y = Sun's total. And Earth is going to recieve the total + y = x. So now Earth has to radiate 8/5 the energy of the original model, and that means temperature is increased by a factor (8/5)1/4 or about 12.5%. For the two spheres, .25x + .5y + z = total is going out, total + y + .5z = x is what Earth receives, and x/2 + y = 2z is what outer shell receives. So we get x = (3/2) of total, which gives us temperature increase of 10.7%. So multiple layers of partially opaque shells are much better than a single shell. There is one more thing I pointed out. Upper stratosphere has an inverted temperature distribution. Lets see if we can model some of that. The reason for that inverted layer is the UV radiation absorbed by upper stratosphere, which doesn't reach lower stratosphere. Since we are playing with toy models, lets say that 1/2 of the Sun's total output, which I'll now abbreviate as t, is going to be in UV that is absorbed by the outer shell. Again, that outer shell is opaque in IR. So Earth recieves x = t/2 + y, while the outer shell still has to radiate the total t = y to the space. So Earth ends up being only (3/2)1/4 or 10.7% warmer in this model. In other words, if we allow the UV-absorbing portion of the atmosphere to radiate that heat in IR, Earth ends up being somewhat cooler. The overall system is far more complciated, of course. In these toy models I completely neglect the air currents carrying heat between the layers. And because there are changes in pressure, atmosphere can actually function as a heat pump. This is most severe in troposphere, and ends up being a dominant effect on the temperature down here. This is why I started out my previous post by pointing out that IR absorption beyond troposphere makes very little difference.

And if you understand anything about how the "thermal blanket" effect works, you should realize that it's only relevant in the troposphere. "Greenhouse" is a terrible misnomer, since the actual greenhouse works completely differently. Upper troposphere is not particularly moist either, but still well within water vapor saturation. They are balanced. They cannot be imbalanced. If they were imbalanced by a tiny fraction, we'd be cooked already. And again, CO2 concentrations in stratosphere are irrelevant, and these are the main contributions to the IR lines. Temperature there is inverted, so if anything, IR opacity can help cool the planet. There is a correlation between CO2 concentrations and temperature. That's all the records show, and nobody's arguing about it. And peats help bind carbon how? Amazon jungles are a factor, and yet every measurement done shows that total biosphere mass has been growing in the past decades. Take a look at pretty much any NDVI data to see that we've been increasing amount of land vegetation despite what we do to the forests. Ocean biosphere is a bit harder to estimate, but indication is that we aren't doing any worse there either. "Changing patterns" and "weather disasters" are different things. You might as well say, "If we aren't wiped out by an asteroid," and blame that on greenhouse gasses too. Yes, because there is such great evidence for looming "weather disasters"... People who claim that stuff don't even understand enough thermodynamcis to know what can and cannot change global temperatures. All I'm saying is that we aren't doing anything worse than this planet has already been through and thrived.

You are asking a theoretical question based on assumption that violates core assumptions of said theory. Therefore, the correct answer to your question is pink elephants.