timo

- I don't understand your answer to question 1. - For the 2nd question, I would straightforwardly express the energy via the simple canonic sum, take the derivative wrt. to T of this expression and hope to get the desired result. Did you try that and what did you get? - There is no constant A to be seen in the expression for C. Did you mean D? Sidenote: You can use TeX on sfn by enclosing the code with [ math] TeX-code [ /math] (without the blank). It makes expressions a bit more readable.

Transdecimal, Just hit quote on a post using the feature you want to use; you'll see the code within the quote tags, then.

So what does that mean in English? He voted against a new law banning torture practices because in his opinion torture is already illegal, anyways?

Things that spontaneously come to my mind: - Times when Dave still showed up. I somehow remember the math section being more interesting back then - the correlation might be either way round, though. - Severian's post about potentials with a massive field (related to the measurement of the photon mass), one of the best sfn posts ever: http://www.scienceforums.net/forum/showpost.php?p=212536&postcount=14. - Some of the best people leaving because they underestimated the power of the word "forum" in "science forums". - The old politics and religious forums, how they made carbon emissions look negligible in heating the atmosphere, a lot of discussions what to do with regards to that and a staff member going rouge starting similar threads to ongoing staff discussions in public areas.

I had similar problems as 1) and 2) some time ago. Although the freezing on graphics-intensive applications makes the graphics card highly suspect for being the cause I think in my case it was the processor which overheated. Take a look at your cpu (mainboard cpu) temperature.

I already find it strange when 11 year-old girls worry about their weight. I find it even more strange when the parents of an 11 year-old girl worry about it (except in cases of overweight). What makes me very suspicious is that you worry about gaining weight from 45 pounds to 47 pounds (we are talking about 1 pound = 1/2 kg, are we?). That sounds like very little to me. Next-best internet page sais Judging from that I would naively (I neither know you nor do I know to what extent the numbers above make sense) say you most likely do not have a problem with being overweight.

I don't think this very oversimplification is helpful. Effectively, understanding that energy is a property of an object, not an object itself should not be much more complicated than understanding that a red car is not "pure color" but a car with a certain color. I'm not a pedagogue but I think that sometimes oversimplifying things to the point that they are wrong can often make things harder to understand rather than easier.

Nope. Two hydrogen nuclei (you don't really have atoms in the sun I think, the stuff is most likely ionized) have a much lower mass than one helium nucleus - just look it up. Not knowing the reaction myself my guess is that you take four hydrogen nuclei (=protons) where two of them are converted into neutrons, which then is also where the positrons and neutrinos mentioned by Kaytie come in. You hereby volunteered to reply to the next three "I have a theory that everything is made of pure energy"-threads .

Ok, first of all: Please do not use abbreviations like "u" for "you", "wut" for "what" and so on. Some people (e.g. me - but at least I am used to that slang from computer games) in this forum are not native English speakers. And even those that are might not always understand internet slang. Using capitalization of nouns and consistent use of punctuation greatly helps understanding a post. That said, now for your question: - I think you possibly cover a wider topic than your teacher wants you to. Of course, I do not really know what your teacher expects, but starting a report on "how the sun works" with Big Bang and formation of the first stars seems a bit too far-fetched to me. Perhaps just take the current state of the sun as granted and explain how it produces light and heat. - The process you are probably looking for is nuclear fusion. As you already found out yourself, it is the fusion of hydrogen nuclei into helium nuclei and some other stuff that I don't know without looking it up. Positrons and neutrinos seems to make sense. There are probably some photons (particles of light) involved, too - after all, shining light on earth is a primary function of the sun. Some specific comments on what you wrote: It's basically not gravitons but simply gravity that makes the hydrogen clump together. Gravity, in case you do not know, is the effect that objects with mass are attracted towards each other. Gravitons are supposed to be related to gravity but you can safely forget about them. Elementary particles, their correct names being "positron" and "neutrino". - Light is definitely not matter. What you probably meant is wave vs. particle, not wave vs. matter. It is both, wave and particle. The layman explanation is that light can act like a wave or like a particle, depending on how you look at it. - Waves can react to gravity, no problem with that. - No object with non-zero mass can move at the speed of light. That has -in principle- nothing to do with whether the object is matter or not. - Energy is a property of something. A volume is neither a house nor a car (see below). No. Energy is no thing, it is a property of things. Those lifeforms "made up on pure energy" from Star Trek are misleading because ... well, energy is not a thing but a property of things. What the equation means is that mass contributes to the energy or alternatively that mass is a form of energy. Note: Mass also is no thing but a property of things. What you can do is converting something with mass into something with less mass and some other energy (like kinetic energy, the energy related to the motion of things). That also is what happens in the sun. Not really. You can turn non-matter with some energy into matter with the same energy. But energy is just a property of matter and non-matter, just as volume is a property of houses and cars (and you might possibly turn a car into a house but not volume into a house). The energy transferred from the sun to earth is mostly electromagnetic radiation, I think. In this case, you can think of electromagnetic radiation simply as light rays or light particles travelling from the sun to earth. And yes, light rays hitting an object tend to warm it up.

C does not naturally support large integer numbers, as far as I know. So you either have to write the structures for large integers yourself, get some module doing that from the internet or switch to a programming language that supports large integers.

Why do you think your were doing something wrong? Everything looks fine; including your result, which is [math]m= \sqrt{3.25}-0.5[/math]. EDIT: Well, not completely. When taking the root, you'd not only get m+0.5 = sqrt(3.25) but also an additional solution m+0.5 = -sqrt(3.25).

There is no such theory, but the term you are looking for is "axiom of choice".

They do say gay people cannot donate (except if you assume the gays not having had sex in the last 30 years are a relevant group): So that does indeed sound as if the test is not fail-safe. Source: http://www.redcross.org/services/biomed/0,1082,0_557_,00.html

Perhaps you should aim at symmetry in physics rather than symmetry breaking. Sounds like a prequisite anyways, so you can still cover a bit of symmetry breaking if you really want to.

You'd possibly better mail it to him, because:

The force due to gravity is unchanged in vacuum. You still have the same problems for building a long vertical tube as you have for building a long vertical tower when it comes to the stress on the material.

Nucleus diameter is roughly [math]10^{-15}[/math] m, atom diameter around [math]10^{-10}[/math] m. So yes, unless that resolution is a well-disguised 100000x100000 pixels, then the nucleus shouldn't be larger than 1 pixel if you want to keep it in scale.

It's a TeX (a typesetting language) plugin. TeX mode is enabled by the tag [ math] (no space) and closed by [ /math]. Most of the commands are quite straighforward, e.g. the sum symbol is \sum, a greek capital gamma is \Gamma. You can click on the images of the mathematical term to get a pop-up window that shows the code. A simple tutorial should be lying around somewhere in these forums, too.

I am not completely sure what you mean but I suppose you want to know if and how you can do calculations when the appearing values are expressed in scienfic notation rather than written out as a single number with all the zeroes? Let's take an example: Assume the mass of earth was [math]6 \cdot 10^{24}[/math] kg (didn't check the value and used 6 rather than 5.9... so I can do the calculation in my head and don't need to look for a calculator) and that Jupiter was 318 times heavier than earth. What is the mass of Jupiter? Surely it's mJ = 318 * mE, so let's plug values in: [math] mJ = 318 \cdot \left( 6 \cdot 10^{24} \text{ kg} \right) [/math] The term inside the parentheses (the mass of earth in scientific notation) is just a normal product between two normal numbers. For a product of three of such numbers, it does not matter in which order you perform the multiplication (a*b*c = (a*b)*c = a*(b*c)). This means you can simply multiply the 6 and the 318 first, and then the exponent term. [math] mJ = \left( 318 \cdot 6 \right) \cdot 10^{24}\text{ kg} [/math] 318*6 = 1800 + 60 + 48 = 1908, so as an intermediate result we get [math] mJ = 1908 \cdot 10^{24}\text{ kg} [/math] Now let's convert that back to standard scientific notation which uses only one decimal digit before the comma by rewriting 1908 as 1.908 * 1000. [math] mJ = 1.908 \cdot 1000 \cdot 10^{24}\text{ kg} [/math] The factor 1000 can be absorbed into the term with the exponent. 1000 = 10*10*10 = 10³ and [math]10^{24}[/math] = 10*10*...*10, meaning [math] mJ = 1.908 \cdot \underbrace{10\cdot 10 \cdot 10}_{3 \text{ times}} \cdot \underbrace{10 \cdot \ldots \cdot 10}_{24 \text{times}}\text{ kg} [/math] Taking together all the factors of 10, you get to [math] mJ = 1.908 \cdot \underbrace{10\cdot \ldots \cdot 10}_{27 \text{ times}} \text{ kg} [/math]. Rewriting the product of 10s in scientific notation you end up with [math] mJ = 1.908 \cdot 10^{27} \text{ kg}[/math]. Note that this is the super-pedestrian way. In reality, it's actually a one-liner if you are used to the scientific notation.

A note ahead: Saying what level of education you are in can be very non-saying to people not living in <whatever country you live in> unless it is an internationally-comparable level (e.g. a PhD course is roughly comparable all over the world), age might be a better indicator for lower levels. Anyways, a very simple example that hopefully helps you: I'm going to drive to Göttingen tomorrow. The distance is 250 km. Suppose I leave home at 10:00 and arrive at 13:00. - What will be my average velocity (including units) and why? What would be my average velocity if I left at 11:00 and arrived at 14:00? - Can you see how this question, specifically the times and velocity, relate to your problem, specifically to the heights and the pressure gradient? - Bonus question: Does an average velocity of whatever mean I travelled with that average velocity all the time?

I take that your actual question is where the 3 km came from? That is indeed the difference 3 km - 0 km = 3 km, the upper boundary minus the lower one (which in that very case happens to be 0 km). The reason for that is the keyword "average". I don't know what level of math to expect from you but I'll save myself time to give an intiutive explanation - if you're not sufficiently familiar with calculus, just ask for further clarifications. Here we go: Taking an average <V> of N values [math]V_{1\dots N}[/math] is done by [math] \left< V \right> = \frac{1}{N} \sum_{i=1}^N V_i [/math]. If you have a continuous distribution f(x), its average over some interval [math] \left[x_0, x_1 \right] [/math] is [math]\frac{1}{x_1-x_0} \int _{x_0} ^{x_1} dx f(x)[/math]. In your case, you have a pressure field with the P(h) depending on height h. The pressure gradient, g(h), is the derivative of the pressure with respect to height, i.e. dP(h)/dh. Hence, the average pressure gradient between height [math]h_0[/math] and [math]h_1[/math] according to above is [math] \left< g \right> = \frac{1}{h_1 - h_0} \int_{h_0}^{h_1} dh \ g(h) = \frac{1}{h_1 - h_0} \int_{h_0}^{h_1} dh \ \frac{dP(h)}{dh} = \frac{1}{h_1 - h_0} \left( P(h_1) - P(h_0) \right) [/math].

I think the only titles given for being naughty are "suspended" and "banned", so no custom titles for that, either.

Yes, it's arrogant and elitist (except if iNow is a climate scientist in which case it's only elitist). But to be realisitc, most people in the world are much more elitist than only demanding someone to know basic school physics before taking their contributions to modern research seriously. It's a capital W, btw.

The subname (official term is title, I believe) is a function of the number of your posts, only (except for staff members). As a rule of thumb, the more posts you have made, be bigger the object of the title. So the only way to change it into a different term is by making more posts (which still limits you to the titles given by the system) or by becoming a moderator or admin.

Watt per square meter.