CaptainPanic

Where did the forefathers of the dog become mammals? That Cynognathus looks like a mammal: ears, fur. Is there any scientific evidence of those features? Or perhaps the squirrel that's not a squirrel was the first one? Nice video.

Wikipedia's page about torque starts with the sentence: "A torque (τ) in physics, also called a moment, ..." http://en.wikipedia.org/wiki/Torque

I'm not sure I understood your point / question... The viscosity term in the formula above is that of the liquid, not of the gas. [math]V_s = \frac{2}{9}\frac{\left(\rho_p - \rho_f\right)}{\mu} g\, R^2[/math] [math]V_s[/math] = terminal velocity of bubble in m/s [math]\rho_p[/math] = density of particle (in this case that's a bubble!) in kg/m3 [math]\rho_f[/math] = density of fluid (the soda, so take that of water) in kg/m3 [math]{\mu}[/math] = viscosity of fluid (water) in Pa s [math]g[/math] = gravitational acceleration (m/s2) [math]R[/math] = radius of particle (radius of bubble, half of the bubble diameter) in m It is true that the gas in the bubble will move, this is induced by the outside of the bubble. (Simplified: the liquid outside of the bubble is stationary, and the gas tries to move upwards through this). There is indeed a boundary layer, both in the gas phase and in the liquid phase. Movement will reduce the thickness of this layer, which enhances mass transport (and perhaps heat transport). So the bubble moving through the liquid already reduces the boundary on the liquid side. Additionally, the turbulence that might be created increases mixing. Inside the bubble, the movement of gas will increase mixing. But in the case of soda bubbles, this is just 1 single molecule (CO2) so mixing in the gas phase is irrelevant for mass transport. I don't understand how you see the equations. But I think you are right: if the liquid viscosity would be zero, there would be no drag. It's kinda theoretical though.

Pity that no fridges exist for cars that can be connected to the car itself (other than to the 12 V battery). Combustion engines have lots of heat that you could use.

If you remove some air at the top, then less air is pushing down... which is exactly what happens in a low pressure. (Low pressure, less pushing down). Low pressure means lower density.

That is true... fridges don't have a constant electricity demand either. I overlooked that for a second. But 400 W power (while doing sports) is a total. That includes heat... it's not quite mechanical output (to drive a compressor)... So, I conclude that you still need a significant and annoying amount of time to have a cold beer. Then again, there are people who bike and have a beer, and actually enjoy that...

I can see that solar winds (very high speed particles) can strip a planet of its atmosphere. I think it'll be a slow process, but one by one atmospheric molecules are hit by high speed particles and thus accelerated. Some might escape earth. If this happens enough, then the atmosphere will be gone after sufficient time. Can anyone comment: is this process more likely to occur at the geographical poles of a planet (regardless of the magnetic field), because the solar winds are almost parallel to the surface? What is keeping the molecules / ions in our atmosphere? The magnetic field is vertical at the poles, and horizontal elsewhere (ok, I like to simplify things) and the upper atmosphere is essentially a very thin plasma with both positive and negative particles. The solar winds are the same: thin plasma's. I understood that solar winds are reflected. But the ionosphere is not reflected... and this all got me quite confused

A decent approximation is Stokes' Law: [math]V_s = \frac{2}{9}\frac{\left(\rho_p - \rho_f\right)}{\mu} g\, R^2 [/math] It does assume that you have a single perfect spherical bubble. However, bubbles are not spherical. The fact that they rise up with many friends joining them influences the terminal velocity significantly (much more than the change in pressure). The bubble in fact does grow a lot (which is obviously not taken into account in Stokes' Law), but not because of the change in pressure, which is minimal as D H already said. It's due to more CO2 coming out of solution and into the bubble. [edit] Here's a link to some bubble shapes. It's a bit of a weird link: the page won't open (you gotta pay) but Google images does find the pictures. I guess linking to Google pictures cannot be copyright infringement.

Indeed, 2 plates will work better than 1... because then you make a capacitor. Bigger plate = more electrons stored. But higher voltage will also store more, so putting the 4 AA's in series will work better than when you put them parallel: [math]Q = C*V [/math] More about capacitors and capacitance on wikipedia.

I found it tricky to find the power (peak power and average power) for a refrigerator. But here are a few results: http://hypertextbook.com/facts/2001/SambitMishra.shtml I do know that humans can do about 150 W average power, and about 400 W when doing for example sports. I think that a fridge will easily consume 50W average... but all depends on size and outside temperature of course... To produce 50W constantly is not hard-core sports, but it does mean that you are busy with it a lot. I propose a small wind turbine or a solar panel.

Every reaction has a heat effect. Some heat up, some cool down.

I found this on Slashdot today: http://arxiv.org/abs/0808.2386 Seems that somebody did find stellar spots (or at least a dip in the brightness), and mistook them for a giant Jupiter-like planet first.

Capitalism is reposible for war in a way that weapons manufacturers have lobbies for selling things that are purely designed to kill people or destroy things. Their purpose is to sell more, and have a growing market. They have a benefit from war, because their revenues go up. And the USA spends about 10% of its money on weapons and its army. But we really shouldn't rule out religion's influence. More people were killed in the name of god than in the name of capitalism.

As I showed, both are quite small. We're talking tenths of a degree temperature differences here. I can adapt parameters such that droplets cool, and also so that they warm. I think I also showed that there are so many parameters which are not fixed (such as the weather: temperature and air humidity) that it's really difficult to make a prediction. Additionally, a lab experiment is already difficult to model: A decent model would take into account: Drops heat from conversion of kinetic energy into heat Water evaporates from surface (droplet velocity (not constant) and droplet shape (function of velocity)) Other droplets influence the speed of each other, and therefore the shape of the droplets which in turn influences the mass transfer Air and water are not of the same temperature, and even if they are at the top of the waterfall, the previously mentioned effects will change the temperatures of the particles, so that there will be a temperature gradient. This means there is also heat transfer. composition of surrounding air is not constant, which influences air density, and heat and especially mass transfer Evaporating water influences the droplet size, and that influences everything mentioned before Input parameters: Temperature (both water at the top and air) Air pressure and humidity droplet size at the top (distribution, if you want to make life even harder) Then you integrate the whole thing with respect to height, and pray. I don't see how you can take things as landscape (rocks and such) into the model without spending weeks or even months or years on it. Therefore macroscopic air turbulence is not put into a model easily. If rocks influence wind, and create an updraft (countercurrent system) or a downdraft (co-current), that's a massive difference. Therefore I conclude that I think it's easier to take an airplane and go there to measure it, rather than calculate it with a really decent calculation. Might save you a lot of time anyway.

In other words, we can make it as big as the sun (on a picture) but it'll be a bit of a blur?

Responding to your comment means I risk hijacking this thread (apologies! Mods, perhaps we can move my previous post, Sayonara's reply and this post into a new thread somewhere in Computer Science?)... ... but I am curious how I should use Facebook then. I have as a boundary condition that some people who know me in reallife know I am on facebook... they are the ones filling in all the details. I haven't filled in any personal details about myself at all... and I don't want anyone to know my buying habits (although Google, my bank, my supermarket and probably my government already know it).

They invented the Darwin awards.

I've never seen that word before, but... Perhaps: A german loan word that's become half-English for hardening (like tempering steel)? To be honest, it looks more like a massive spelling mistake than anything else, when I look at Google's 4 hits. It looks a little like "uitharden" which is a Dutch word for tempering / hardening. This is how I got the idea.

Not even our nearest neighbors? Alpha Centauri is only about 287,000x as far as the sun... rather disappointing I must say. Sun = 8 light minutes Alpha Centauri = 4.37 light years = 4.37*365*24*60 / 8 = 287,000x distance earth - sun The sun is big enough to see sunspots with the naked eye (ok, with a filter, but no telescope needed) and we have equipment that can magnify things more than 287,000 times... At least, that's what I thought.

Have you searched Google/wikipedia and this forums search?

You (and us too) have spent the better part of the century building up the infrastructure over and over again. Every bit of the infrastructure is replaced within 10-40 years... most of it rather 10 than 40 years. The same goes for housing, roads, etc. Therefore I am convinced that going for electricity is not necessary to take any longer than 2050... and then we can have 100% of it, if we want to. Batteries are one option, but trains, trams and trolleys have overhead cables, and that could be option 2 (especially for the long distance trips on the highways).

In my country, the two are actually quite different. Engineering focuses very much on the practical side of chemistry: how to make a factory, how to do that efficiently. Chemistry focuses on the electrons and atoms much more than the engineer does. After you finish your degrees, you can switch once you're working. In universities it might be possible but it kinda depends on you, the university and what you exactly want. There are certainly fields that are covered by both educations, but some that are not. It might be necessary to do a few extra courses in order to be able to switch... All in all, I think it should be possible, but it's not very common.

nitric, You're very enthusiastic and not very familiar with the whole topic of chemistry... I want to express my worries about that. I fear that the forum is helping you to make some explosives, which I am not sure is such a good idea for a newbie in chemistry.

Another card game: One student gets a number of acids on a card. Other students gets a number of bases on a card (none of them strong, or perhaps 1 strong one). Then student 1 plays a card, which is countered by student 2. The one student with the acids owns all protons, and must keep as many. The other with the bases must try to steal them. Example: student 1 has 3 cards: H3PO4, NH4+ and HCO3- student 2 has 3 cards: IO-, CN-, SO4(2-) student 1 plays the NH4+ card, which gives student 2 the choice to win it by playing his/her IO- card (NH4+ + IO- -> NH3 + HIO) , or to hold on to that, and lose the round by playing for example the SO4(2-) (NH4+ + SO4(2-) --> no change). It's similar to a 2-person card game where you just win 2 cards when you have the highest of the 2. Same thing might work for redox-half reactions... stealing electrons. One electron keeper, one electron thief. You can also come up with an "expansion set" as any good game maker does. Start off with just a few cards, but expanding this fast as students will need but a few minutes to get used to the first cards... To make it more unpredictable, as with other card games, students draw only a number of playing cards from a larger stack. I am not sure if the equilibrium constant should be mentioned on the card... at first it might be best, but students learn fast.

Alpha Centauri A and Alpha Centauri B orbit each other, with Alpha Centauri C (also known as Proxima Centauri) orbiting those two. Alpha Centauri A and Alpha Centauri B circle around each other in 79.91 years. The orbit length of Proxima Centauri is not known, I think, because according to wikipedia (where I got all this from) it's not even 100% certain that it is in a stable orbit around the first two stars. source: http://en.wikipedia.org/wiki/Alpha_Centauri A comment: I try not to be rude, but I link so often to wikipedia where one can find all the answers in simple language, that I don't understand why people ask these questions. How do they find their way to this forum, when the answer is almost pushed in their face by our omnipresent search-company Google? In 3 steps: 1. Open your browser 2. Go to Google, Type "Alpha Centauri" or "Proxima Centauri" 3. Click first hit and read It's almost always hit #1 in Google... that goes for this one, but also for a lot of other questions. Now, once again, nothing wrong with posting. Not all info is on Google/wikipedia and you're silly if you accept those as your only source, but it's a good start. And in fact, the questions make me search for it, and learn something too (15 min ago I didn't know anything of what I just posted)... so let that encourage you