timo

- No. If the charge was at rest relative to you, then you wouldn't detect a magnetic field. - You get the answer either directly from the Maxwell equations or, if you prefer it more "relativity-like" by transforming the field-strength tensor [math]F^{\mu \nu} = \left( \begin{array}{cccc} 0 & E_x & E_y & E_z \\ -E_x & 0 & B_z & -B_y \\ -E_y & -B_z & 0 & B_x \\ -E_z & B_y & -B_x & 0 \end{array} \right) [/math] according to the normal transformation rules for tensors.

You can create wave pakets of pretty much any shape. However, the most common base for photons is [math] A_i \exp(\pm ikx) [/math] with [math]A_i[/math] being the photon polarisation, k, being the wave-vector, and me not being completely sure about the sign, atm (doesn't matter for my statement). That's a plane wave and neither a wavefront, nor spherical. Yes and no. In QM, the size of a particle usually refers to its sub-structure, like the extent of the electron cloud around an atom which defines the size of an atom. Being elementary particles photons do not have a sub-structure and are therefore considered having a size of zero. @YT: I'm currently thinking how to construct a coherent reply. Might take some time, though. The short answer: When you define size as a sub-structure of a particle, then the photon-size is zero. When you define it as the size of its wave-function, then it can have pretty much any size but the size is no longer a property of the particle-class "photon", but a property of the specific photon you're talking about. Analogy: Mass is a property of the particle class (all electrons have the same mass), kinetic energy is a property of individual particles (different electrons can have different velocities and hence different kinetic energies).

The good-old pV=NkT with p being the pressure, V being a sample volume, N the number of particles in this sample volume, k the Boltzman-constant and T the temperature should work well here. You get T from your assumed energy-distribution of the particles. Do a few sample-calculations to see if you can get any relevant pressures with such a low density at all. Then, you'll have to qualitatively explain why the pressure distribution in the universe is such that pressure of your small particles is bigger outside the galaxies.

I'd also assume it's the heat that is blown away that stops the flame. I really doubt that the CO2 in the breath air has any measurable effect: - Why should CO2 have any effect at all? - Since what you probably meant was "the lack of O2 in your breathing": There´s quite a lot O2 in the air you exhale. That's one of the key points why CPR works.

For sending him a PM, klick on his name and select "Send a private message to Klaynos".

The fact that you used the term "often" gives me hope that other reactions do exist ("me too, which field are you in?" doesn't count). Imho, finding good replies to these two reactions should be added to the list of most important questions in modern physics. Finding those probably has more impact than knowing the mass of the Higgs-Boson. @Diana: Yes, and it really, really sucks. Depending on my mood and the people asking me I sometimes claim to be an ambulance driver. On topic: Physicists being arrogant towards other sciences/scientists and especially towards students of other sciences pretty much fits my perceptions which are not limited to physicists' behaviour towards them but also physicists' talking with each other about other sciences or people doing other sciences. That's not limited to biology. In fact, people in biology have an advantage over engineers in that they at least are considered nice persons .

Can you explain what "absolutely universal education" means?

Similarly to abskebabs, I´d recommend you to use an existing engine. I would, however, strongly recommend that you simply play around with its tutorials a bit before you even think about starting your own project. If you still have to learn the language, you won´t even know what is possible and what will turn out to be complicated, otherwise. A very nice java engine with -iirc- nice documentation and available tutorials is the jmonkey engine (http://www.jmonkeyengine.com/).

Not something the admins could do anything about but perhaps this is a suitably-public place to mention it: I dislike people refraining from posting because... - they are afraid of being wrong: Who cares? If what you think is wrong and you post it, chances a good that you'll know better, afterwards. Chances are much smaller if you don't post and hope to get it right from the other replies. - they think someone else could explain better. a) what if everyone thinks so? b) how you´re gonna learn explaining stuff to others when you're not trying? c) again: who cares? I dislike people posting... - claims about the lack of intelligence of certain named or unnamed members or groups thereof. It is, in principle, ok to tell someone that he's simply lacking the background knowledge currently required but again you should probably restrict that to topics you´re fit in, yourself. - stuff like "I am too <add excuse here> to give a complete answer right now. In short <add incomplete or unnecessarily bad reply here>". I probably also belong to that group sometimes, so as a tip for all the other sinners: For me, the best times on sfn were those when I really put some effort into my posts, sometimes taking 2-3 hours to write a reply, browsing some books to back up what I was about to post, sometimes even replying to questions that I didn´t know the answer to before I started looking things up (and sometimes not even after posting ).

I think he was a physicist...

To avoid Klaynos getting sad because no one want to participate in his awards: 1. ajb 2. D_H 3. abskebabs 4. 5. 6.

Well, keeping the links in could possibly count as citing the sources used .

Don't do so, it looks terrible. Write /** *quick learny thingy */ class TestApp { public static void main (String[] args) { System.out.println("I have written a thingy! :-)"); } } if you absolutely need the parentheses to be in the same column (I consider it a waste of lines but that's just my personal preference).

I don´t see what´s so hard in understanding the question: If you get your money for working in a lab, then you´re a professional. If you´re employed as a scientist, then you´re a professional scientist. If you´re employed as a lab assistant, then you´re a professional lab assistant. If you´re employed as a student, then you´re a professional student . In other words: The answer should be written in your contract.

Basically, that happens when you call the energy of a particle "mass" (some factors of c let aside). This alters the energy [math] E = \underbrace{m_0 c^2}_{=E(v=0)} + E_{kin} [/math] with [math]m_0[/math] being the (rest-)mass of the object and [math] E_{kin}[/math] being its kinetic energy into [math] E = m_\gamma c^2 [/math] with [math] m_\gamma = m_0 + \frac{E_{kin}}{c^2} [/math] being the "relativistic mass" and dependent on the velocity of the particle. Due to being dependent on the particle's velocity, the relativistic mass is not a property of the particle anymore (velocity of a particle depends on the frame of reference), which is one of the reasons why it's less convenient to use than the rest-mass which is a particle property. Another reason is that [math] m_\gamma [/math] simply is the energy divided by c², wherefore it's simply another term for energy and a pointless concept (just call it energy!). Is short: If you call the energy of a particle "mass" then if you understand that energy increases with increasing velocity (because of the increasing kinetic energy) it's pretty obvious that the so-defined mass must increase. Afaik, that does, strictly speaking, not make any sense. The term "matter" lives on a completely different meaning-category than "energy" and "mass". Energy and mass are kinematic properties, whereas matter and non-matter are just classifications of particles. Particles being or consisting of leptons or quarks are called matter, other stuff (like light/photons) is non-matter. Both can have mass and energy. So energy being converted into matter doesn't make much sense. Non-matter particles can decay into matter-particles. But what you probably meant is "is energy converted into mass?". This question also doesn't make much sense, since, as you can see from the 1st equation in my post, mass already is a term contributing to energy. One thing that can and does happen is that the different contributions to energy transform into each other. The/one point of colliding particles in large particle accelerators is to give the colliding particles are large kinetic energy so that during the collision heavy particles (particles with a larger mass) can be created. So kinetic energy transforms into mass, there. Different forms of energy transforming into each other is nothing really new. You already know that from things falling down where potential energy transforms into kinetic energy or things being thrown up where the reverse process happens.

No, that´s imho completely wrong. Some questions, especially very broad ones or questions where the OP simply doesn´t know the correct term to look for like yours, can be best answered by a quick search on the net. That´s in fact the reason why only gave you the key word without elaborating - whether you look it up on wikipedia or google simply depends on your personal preference. However for information beyond looking up some facts, questions geared towards understanding some concepts, I believe that "personalized answers" are much more appropriate and helpful than general information which are constructed on a design sheet without a clear target audience in mind. That´s also the reason why I usually don´t like people replying to questions on sfn with a link to the wikipedia articles - I think it´s a bit of an insult to people's intelligence to give them relies they could have found within five minutes themselves.

Not having an acceleration I don´t know if you really can get a real analogy to the sonic boom. What you might have meant is Cherenkov radiation.

A straightforward solution would be plugging the equation into a computer and play around with different starting conditions; the system will probably go into a state that´s independent of the intial conditions after some time, anyways. You'll most certainly need a guesstimate of the interior's total heat capacity, though. You can get that from the heat capacity of air (shouldn´t be too hard to find on the net) and the volume of the interior. There´s a few other small issues that might need to be cleared up before you can simulate it on a computer, such as the question what the minimum and maximum temperature actually mean (is it mid-day vs. midnight? how does the temperature behave inbetween? what time-scale do you simulate on? ect.). Could be fun to simulate if you like programming, but if you´re not used to numerical simulations you should not underestimate it as a "done in an afternoon" issue.

You're way off the track. Where do you think Klaynos got his avatar from?

I think we simply ran out of ideas very quickly. I wanted to add "and no one liked mine" but I just looked it up and saw that I had missed a reply by Capn' <whatever word I always have to look up> on the issue which resulted in the discussion dying off (because I didn´t reply to it). I'll rethink about it and maybe post the challenge in the "computer science" section (it´s a little programming task).

I can´t answer how to (analytically) get the inside temperature as a function of time, atm. But, no offense meant, I am not entirely sure if that´s what you´really looking for. So allow me the question: What kind of engineer are you? Are you a civil engineer that looks for a material with suitable thermal properties to isolate the house (why is the material given, then?) or are you a mechanical engineer that wants to know the energy energy consumtion of a climate control system? In the latter case, the inside temperature would be dictated by the residents of the house and probably be constant => you just have to know the energy flux via heat and compensate for it.

I think typical room temperatures are around 20°C. But what would keep you from keeping the inside-temp as a variable and obtaining the necessary specification of your climate control system as a function of the demanded inside temperature?

Can you expand on what you mean with that statement? Gravitational interactions certainly isn´t part of the Standard Model so what would you expect from finding or not finding the Higgs boson? And please don´t use ugly colors .

- We have a TeX implementation in here that you can use. Usage is [ math] <tex code here> [ /math] without the spaces in the brackets. - I assume you meant [math] L_1 + L_2 = 0 [/math]. - A natural start is to convince yourself what 0 is/looks like. - You might (I did) need one of the conditions for linear transformations, namely L(ax) = aL(x).

The main problem is that you attribute physical reality to a coordinate system which, from a standpoint of relativity, is simply a tool for humans to put reality into a form that you can do calculations in. The two paths in my example about travelling to another town above "have a reality" (exist, are unchanged regardless of, ...) independent of the way I use to describe them. Whether I use GPS coordinates to describe the path or describe it via informations like "... after 3 km turn right on route B26, follow that route for 10 km, then ...". I´ve seen that on physicsforums.com someone gave you a similar classical example about two lines on a piece of paper. I´ve not completely read it but you could try to follow the steps he presented. The key point is, that the two lines on the piece of paper exist regardless of whether you draw a coordiante system on the piece of paper to describe the line-points via their coordiantes or not.