CaptainPanic

When talking about climate, a reasonable point is, by convention, 30 years ago. conveniently, this 30 year period encompasses more than 2 solar cycles, so that any fluctuations from the 11-year solar cycle are included. It also averages out severe weather. Taking 1998, or 2001, or 2000 as starting point is wrong, from a statistics point of view. Any discussion about climate should be just that: statistics.

Then I guess the question is: Do yo want to design airplanes (involves lots of math and physics, and design is determined by aerodynamics more than by making it look pretty) or do you want to design buildings (drawing pretty pictures, possibly with some maths and physics).

That's carbon-storage, not carbon-reduction. (They don't react carbondioxide to a fuel, they just simply put all CO2 in an empty gas field, where it will stay... for as long as the gas field is stable). Per kg of CO2, this is much less costly than reacting. But obviously, this also doesn't solve anything. While other sustainable technologies really solve a problem (energy independence and global warming), this carbon storage is used only to prevent greenhouse gas emissions.

Hehe, I think you are talking about (chemical) Engineering... not chemistry.

What kind of engineering are you thinking about? Aerospace engineering? Civil engineering? Chemical engineering? Electrical engineering? Applied physics? Applied maths? Something else?

In fact, modern fax/modems almost never make noise anymore. But I remember my first old dail-up modem. I am exaggerating when I say that I needed ear plugs.

The underwater turbines may still kill fish, and they reduce the depth of the river, so larger ships can get into trouble (if there are any ships on a river). Solar panels obviously reduce space for plants and nature. Wind power, to me, seems one of the best options... but even wind power does not have zero ecological impact, and people complain that windturbines are ugly (personally, I disagree with that - then again, I'm Dutch, and us Dutch have a thing with windmills ) But in the end: if all 6.7 billion humans want energy, something else has to go away so that we can construct something new. Zero ecological impact is just not possible.

But why does a fax or a modem have a speaker? Many faxes and (dial-up) modems actually make the screeching noise even when you use it properly. I mean, while the signal is in the phone line, it's just some electrons (current & voltage). Why convert it into sound at all?

Yep. I think that's the only option if you want to build something "into the river bed" (as written in the 1st post). You cannot block the flow, so you must convert kinetic energy, rather than potential energy.

http://en.wikipedia.org/wiki/Brocchinia There are more, but it's really hard to find out the name of a plant if you don't even know in which country it grows. I am not sure that any plant actually collects water from the top with the purpose of using it for photosynthesis (or for even absorbing it at all). I think that if water is limited, it's better absorbed through roots, and then stored inside. Somehow I have the feeling that this will be more efficient because it will limit the evaporation. Plants may be capable of absorbing some water through the leaves though.

Thanks. You're right. Wavelength and temperature are related there... and they don't radiate one very specific wavelength, but more a temperature (and material?) dependent spectrum. But here on earth, IR is the major contributor to cooling. Once the earth would cool more, indeed other radiation would become more important.

About the water-vortex-plant Per volume and head (head = difference in height) of water, hydro dams are close to optimal. Hydro dams run at 80% efficiency (the rest is friction). You simply cannot get much more out of it... You can get the 20% extra if you use frictionless moving parts and superconductors and such... it's all a bit science fiction. So, I'm not sure of this water-vortex-plant, but I saw different data to start with: # Presently used falling height 1,3m # Presently used flow rate 1m³/s # Diameter of the rotation tank 5,5m # Hydraulical power 13kW Which is all correct: [math]Power = flow * head * g[/math], so [math] Power = 1000 * 1.3 * 9.81 = 13 kW[/math] Apparently these guys have zero friction... although later they claim that their effectiveness is "over 70%" (i.e. not 100%), which puts it at the same efficiency, or slightly lower, as standard hydro dams. The "150 kW" was another value, for another system, with another flow and/or head. Still, I am not sure about the ecological impact of this thing: it still has large steel pieces moving around, effectively blocking the path of the fishes. About the topic in general Any system that has a less severe ecological impact will also run at lower efficiency, because they all have a bypass of some kind. Whenever water is just flowing past the power station without pushing on some rotor, wheel, turbine or propeller, its potential energy goes to waste. Of course, the fish like this, because heavy steel equipment and fish never combined very well, unless you want fish-soup. But the bottom line is: hydro dams are so popular because they're the most efficient. Please note that the other type of hydro-power (using propellers under water) is also used: as tidal energy. Why? Because at the coast you have no constant difference in height like in a river. The available energy is kinetic energy, not potential energy.

Apart from the fact that we'll never reach the absolute zero... because cooling is happening asymptotically (we would get closer and closer to zero, but earth (or any other object) would never really get there). The issue is of course heat transfer. We know the current rate of cooling/heating. We know that we basically radiate as much heat as our sun sends to us. Once there is no sun, the outside of the earth will initially cool at the current rate. Once it's cold, it will still cool (relatively) fast. The atmosphere would cool, oceans would freeze. And then the inside of the earth is still hundreds / thousands degrees. This heat from inside would need to go through all the layers and finally radiate into empty space (as infrared radiation). It was already mentioned that radioactive decay will actually heat the planet. In addition, the heat transfer that I just described takes place below the surface. We don't know what's going on there... and I don't even want to make a start at estimating all the parameters.

The extension of physics that deals with ... the study of matter and the changes it undergoes. The more you learn about chemistry, the more the line between physics and chemistry fades away.

You might try a university library. You just need to read the book (you might even do that at the university, without actually borrowing the book). And indeed, any silly computer program will plot the data once you have the numbers. Excel can do it. I prefer Octave (which uses a code identical to Matlab, but it is for free). Useful keywords to find this type of data are: - Vapor liquid equilibria (VLE) - Bubble point, dew point

Once you reach the nano-scale, or even before that, you have to re-design your robot. Scale-up and scale-down are specific fields, and it's not just a matter of making things smaller or larger. You also have to scale the forces that your robot exerts, the electric circuits, power. Many aspects of scale up and down are not linear. And that means that your "robot creator machine" needs to be able to not just copy-paste itself on a small scale. It needs to be able to actually design.

ROFL! You have a 3 m3 helium balloon floating around in your room, and you worry about the ceiling? I bet you can't even see the ceiling with such a balloon in the room (Or your laptop is just really tiny). I don't even have a laptop. I have one of those desktops, with an old CRT screen. It is about the size of a continent, and I don't care. If I want to optimize the space in my house, I'll just clean up all the other junk But I did consider to publish a paper on how to effectively prevent anyone working on a desk by covering it with as few bananas as possible.

How much data does an account contain? Looking at my profile, including pictures, avatars and all, that's about 2 MB? Assuming that's the average: On a 50 euro, 500 GB harddisk you can store 25.000 accounts. That means that 1 account represents a whopping 1/5 of a cent (0.002 euro). I guess that's how much motivation there is to delete stuff.

Data like that is often found in tables, not in graphs. Books like Perry's Chemical Engineer's Handbook, or Ullmann's Encyclopedia of Industrial Chemistry might be helpful. Sorry for not giving actual data...

Ah, so they live in a tube? Hmm... I tihnk I'll just apologize for replying to a (fictional) topic that I had not sufficient knowledge about. If you guys think this is a fun book to read, I'll add it to my yet-to-read list (which unfortunately always grows - I cannot read fast enough).

Mine is suspended on a long elastic from the ceiling.

BLOG? What's this "blog" thing I hear so much about. It sounds like an interesting concept. Does it have anything to do with this other concept that they call "internet"?

Just a thought: why not go for a helicopter? Then you only need to worry about the propeller and the rpm's... no wings that will cause any trouble. Did you calculate the energy stored in the spring? It's not much anyway, so I wouldn't worry too much about flight time. Just lift off is an achievement. To overcome the gravity, you need to create a force (however brief) that is greater than the gravitational force. Since your spring contains so little energy, you'll have to focus on releasing this energy in a very short time (a matter of seconds). Since this is a school project, I think your teachers would be pleased if you actually work out how much energy you can store in your spring.

Regarding gravity and the whole thing being torn to shreds: we had a discussion here about a year ago about the rings of Saturn. I'm assuming that this ring world is positioned around the sun: you might want to look at the Roche limit. It's an interesting law. I'm not sure if it applies though, since you said it orbits at the same distance as the earth. And I agree that even if the Roche limit doesn't ruin the fun, then the ring might collapse into several spheres that will all have the same orbit. You also mentioned the day/night cycles: it's possible to create night with some disks moving around the ring. But how does one create day on the backside of the ring? Mirrors? However, I think that the greatest challenge is indeed the weather system and/or the water system. I have no clue about that actually... but with such a massive surface area (the mass of Jupiter, but in the shape of a ring will create an enormous surface area) the place will have an astonishingly large amount of atmosphere which will have some funky day night cycles, possibly some "pole" on the back side where it's always dark and freezing... Does the ring in the book have oceans? That seems like an incredible risk in the design: water can move! Therefore water will be attracted by whatever gravitational imbalance there is and gather in 1 place, and form a sphere somewhere on the ring (and that will most likely destroy the thing).

I'm no expert, but if I remember the formula to calculate the force in an electric field well, then the particle must have a (net) charge. If it has no charge, then there is no force. A polar particle might align its internal charges with the field. I'm awaiting our experts to give feedback. And we're fighting this out in this forum, whether you like it or not.