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timo

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Everything posted by timo

  1. If the wave was small, could you distinguish it from a small particle ?
  2. timo

    Binary

    Mathematical: The standard system used is the decimal system which has ten letters {0,1,2,3,4,5,6,7,8,9}. Now, if you start to count you can count to 9. Then you run out of letters. Thus, you write the next integer as 10. Binary system only has two letters {0,1}. In the binary system you then count 0, 1, 10, 11, 100, 101, ... .In both systems the combination of letters is simply a representative of an integer and 6 decimal would equal 110 binary, for example. Realization for computers: You could think of a lot of other representations than letters. {"Voltage on", "Voltage off"} is used in computers, afaik. So, the decimal 6 from above could be written as OnOnOff.
  3. timo

    Sound waves

    Yes. Also, sound waves travel faster in water, for example. And to tackle what might be your next question: Lightwaves do not need a medium to travel in. The mathematical description of both light and sound as waves led to the assumption that there would also be a medium that light propagates in. This medium was called aether. It, however, turned out that the assumtion of such a medium leads to problems and so the current view of lightwaves does not imply this.
  4. timo

    Why ?

    In what frame of reference and why? I´d simply doubt that statement because for an outside observer for example the mass actually stops before reaching the event horizon and because a time-like vector cannot turn into a light-like. well, again: Why so? In what coordinate system? What does "mass beomes infinite" actually mean to you? Oh well, I really don´t get your post. Doesn´t "mass increases" and "energy is released" contradict a bit? Didn´t understand your question sorry. Might either be because I don´t know the word "accreted" or because of the things I didn´t understand in your first sentences.
  5. Probably most known effect: Pair production: Photon -> electron + positron. Problems might arise with your definition of energy and matter and their differences. For example: Photon. Is it energy or matter?
  6. Adrenaline is a hormone naturally produced in an organ whose name I certainly cannot translate to english (look it up) which is spread though the body by the blood circuit. Effects are mostly what you´d expect of it: Increased heartbeat, increased breathing, widening of coronar veins (to support the increased heartbeat with the sufficient energy), widening of the bronchia (sry, didn´t know the english word for "Bronchien"), contration of peripheral veins and reduced peristaltis. Medical applications that I know of are (name of the drug is "suprarenin", at least in germany): - It´s the most common drug used in reanimations (because of the increased heart activity I´d think). - Can be used as a last resort (just before cutting the throat which noone would do these days except in movies) in case of allergic reactions that result in the patient being unable to breathe anymore. I think that´s because the widening of the bronchia and the reduced blood flow through peripheral veins counters the effect of the swelling. Problems I´d see: - Increasing heart activity over a point where the heart is unable to cope with it might result in cardial arrythmics and in the worst case to the heart failing to work. - Extreme narrowing of the peripheral veins over a longer period of time might result in peripheral areas (fingers) to have insufficient supply of oxygen. Dying off of these areas might be an effect. - Reduced peristaltis over a longer period of time might be uncomfortable, at least. Not sure if that case ever appears in a clinically relevant form. Sry if my english is bad. I´m not used to use english medical terms. Also, above is only what I recall from having worked as an amulance driver (that´s a two month education, so hey: What do you expect?!) some years ago. A physican or biologist will probably know better.
  7. That´s mostly correct although it´s already starting to change and will certainly continue on (if a state has the possibility to charge you it´s most certainly going to sooner or later). Nevertheless, I can top that: Finnish people get money for studying...
  8. no, it´s 42 ... sry, I couldn´t resist yes: 1+4+9 = 14
  9. It means that [math] \sum _{q=0} ^2 (q+1)^2 = (0+1)^2 + (1+1)^2 + (2+1)^2 [/math] because what dave said is correct.
  10. Heard a speech about quantum computing but since that was at least one year ago I can´t remember much. If I remember correctly the professor holding that speech (don´t even know where he came from) was experimenting with an atomic quantum computer (dunno which kind of atoms or even if it was single atoms - was defenitely not photons). They used 4-6 atoms each of them most probably a single qbit. I don´t think many of the algorithms written for quantum computers have yet been implemented (if the factorization of large numbers had been done one would have certainly heard about it) because it´s quite easy to design an algorithm theoretically when one doesn´t have to care about the huge problems in implementation. Interaction with enviroment for atomic Quantum Computers and lack of ideal optic materials for photonic ones would come to my mind, here. Since I can´t tell you much about this topic I can at least give you a link that might help you: http://theory.caltech.edu/people/preskill/ph229/
  11. timo

    Photons

    No that´s correct. Replace "shells" by "quantum states" and you almost got what I was saying. Electrons can switch to an energetically higher state (conservation of momentum let aside for now) by absorbing a photon and switch to a lower state by releasing a photon. Since the energy differences (the ammount that is absorbed from a photon or released as a photon) between the electron's possible quantum states are different for different atoms you can identify atoms by the wavelength of the photons they emmit (-> spectral lines).
  12. timo

    Photons

    My answer refers to a single isolated atom. YT refered to solid bodies consisting of many atoms/molecules. Explaining solid state physics would lead a bit too far, I think, but: - sooner or later an electron will take the place that became free (usually by emmiting a photon in this process). - "conductive layer" is a certain subset of states in which electrons are not bound to an atom and only bound to the body as a whole. - Energy can DISplace charges. It cannot REplace them. EDIT: Even though I don´t think I´m able to explain solid state physics correctly and in an easy way I should add that several effects (like solar cells) of photon<->matter interaction can only be discribed within the scope of solid state physics. The princliple "particles are sent to a different quantum mechanical state" (usually by absorbing part of the photon´s energy and momentum, but also by releasing other photons as in lasers) remains the same.
  13. timo

    Photons

    @5614: - how are atoms made (on an atomic scale)? Atoms consist of a positively charged nucleus (whose structure is on a subatomic scale and thus irrelevant here) and electrons bound to the core due to electromagnetic interaction. Due to boundary conditions (electrons with a low energy can´t get away from the nucleus) the electrons can only be in certain states with definite energy. There is only a valid state for certain "quantitized" energies. On an atomic scale it seems best to treat the electrons with QM and the atom as a whole as a classical particle. - what happens when the photon hits the item? As someone said in your thread about that topic a lot of things can happen. That´s most probably why no1 gave you a definite answer. In above picture imagine the photon as a packet of energy and momentum. Energy and momentum can be transferred to the atom as a whole which causes it to move. Energy (and no momentum) can be transferred to an electron to transfer it in an other bound state with higher energy. Also, an electron can be given enough energy to become free of the nucleus and move away (it´s also given momentum, then). All mixes of those effects that conserve energy and momentum can happen. At higher energies photons can also interact with the nucleus resulting in the additional option to put the nucleus in another state (energy differences of the nucleus-levels are bigger than those of electron-levels). Also the usually not very important, yet interesting, effect of pairbuilding (is that the correct english expression?) can happen: That´s when the photon "decays" into an electron and a positron (anti-electron).
  14. timo

    Photons

    Wave equation of a free particle is given by: [math] \Psi (\vec x, t) = C \cdot \exp \left( \frac{i}{\hbar} (\vec p \vec x - Et) \right) = C \cdot \exp \left( i (\vec k \vec x - \omega t ) \right) [/math] with k being the wave-vector and omega being the frequency of the wave (times 2 pi). The relativistic relation between momentum and energy of any particle is: [math] E^2 = p^2 c^2 + m^2 c^4 [/math] Since for a photon m=0 it follows that: [math] E = |\vec p|\cdot c [/math] So for the speed of the wave it follows that regardless of E and p: [math] v = \frac{\omega}{|\vec k|} = \frac{E}{|\vec p |} = c [/math] Sorry that I can´t really understand your problem but I hope above helps you. EDIT: Corrected sign-error in 2nd equation
  15. timo

    Photons

    - photons all move with the same speed. - energy is inversely proportional to the wavelength of the photon. Incresing it´s energy reduces it´s wavelenght.
  16. LaTeX is like TeX (look up the latter when searching on google ). Generally it´s a tool to write texts. It´s especially usefull for scientific texts (I don´t know a single scientist that does not write his/her texts with LaTeX/TeX) because it allows quite easy implementation of mathematical formulas, including figures, making tables and generally has a lot of features to format your text or assisting you in creating a well formatted text on your own. Firgures, chapters, subsections and formulas are numbered automatically, for example so you can insert a new formula anywhere in te text and don´t have to care about increasing the numbers of the following equations. Texts tend to also look very nice (ever wondered what scientific books are written with? -> TeX). TeX compiles your raw-text into a .pdf or .ps. You can download it for free (dunno where - beware: My distribution was about 130MB packed). Raw-texts can be written with any ascii-editor but there are specialized editors available. I use TeXnicCenter - it´s freeware and comes close to the more famous TeXEdt. To use TeX in this forum I think you don´t have to download anything. You can simply write TeX-code between math-tags as dave said (it´s somewhere in the FAQ, i think). If you´re an ongoing scientist or want to write good-looking essays involving formulas for school it might be a good idea to get used to TeX - most love it.
  17. 1) I´m not going to E-Mail you because I don´t give out my address to people I don´t know. The fact that I received about ten spam-mails in the last five years backs up that attitude. Hope you come back here and read my post. 2) I don´t really know how cross-posting is handeled in here but it´s usually not a good idea to post the same thing in different sections. The desire to reach a maximum number of people is understandable but usually the interest of everyone posting in the internet. They don´t cross-post and one should really stay off the arrogance to think "but my post is more important". 3) I filled out the form but I ran into serious trouble at almost every question. Dunno if that´s due to my limited knowledge about stem cell research or because I try to only answer questions I really understand (and have a decent answer to choose) or because you put little effort in creating the form. Let me give a few examples: - Do you belong to a religion? I´m not sure if that asked if I´m member of a religion (yes, I even pay taxes to the church) or if I feel associated with one (no). I answered "yes" because it´s technically correct. Not sure if that question helps you, though. An estimated 96% (just a guess) of the people are member of a religion, technically. - Q6-8, Q10 I didn´t have an idea about any of the questions except those that left a lot of room for interpretation. That was the point where I thought: "Maybe I´m not the audience that survey is targetted towards". - Q13+ Was there anyone that didn´t answer "a),14:Yes" or "b),15:Yes" ? - Q19c: "Do you think the goverment is more influenced by the biotechnology industry?" I´m not a native english speaker so it´s possible I simply didn´t understand the question, but: More than what? Do not phrase such vague statements except if it´s to test the intelligence of the reader. I didn´t see typical things like questions asked twice with a different wording so I don´t think you were up to this, here. - Q5: Don´t know what your thesis will be about but I was very surprised that I wasn´t asked about my lvl of knowledge on the topic. 4) I was very surprised not to see a question were I was asked wether I work in the field of stem cell research. Or was that what the mysterious "professional qualification" in Q3 was? 5) I don´t know if the software you created the survey with allows it but it would have been a good idea to add a notepad where people could write comments. For example I had been able to write this post there and knowing you´d read it, then. 6) Well, hearing you are doing your master you most probably already know that but I think it´s good to add it in a post that sounds as negative and pedantic as this one: Take this as an advice not an attack! I´m quite aware that you might know about the problems with surveys and a limited number of choices. GL&HF with your master thesis!
  18. @Robertson: Oh my. To a point I´m really quite sorry that I had trouble understanding your post again but on the other hand I think if you should have put more emphasis in content (was there any?) than in fancy wordings. Well, assuming your post wasn´t only a flame post (little things indicate this but I always think people should be given a 2nd chance): -- You were asking why I said Kelvin is wrong: That was refering to "That [0K] is when all molecular and even atomic and subatomic motion stops ('would stop')". Answer should be obvious since you seem to have read my post quite extensvely (hint: subatomic motion). -- You asked why I say his physics is outdated: Because he based his point of view on classical mechanics. QM wasn´t known at his time. QM is also the "today's standard" I was talking about. -- About my mentioning/not mentioning uncertainty: I put this in so that people knowing QM could follow my argumentation (stop of movement => delta-peak in momentum-base => no bound state). For people not knowing QM that point is absolutely unimportant since they have to believe my words without being able to understand the reason anyways. I don´t feel responsible for uncertainty being prostituted by pseudo-scientists (yes, I agree with you that some people bring it in whenever they want to sell you some obscure pseudo-science). -- About your rantings I didn´t stay on the subject: You have said yourself that you can´t access this forum correctly. Where the hell do you take the arrogance to tell me my posts are off-topic? My post was refering to Jordan´s post about "What happens when the electrons stop moving at T=0" not to yours. Most of your flames thus become pointless. -- My 1st post: As you asked for it, here´s the URL: http://www.scienceforums.net/forums/showthread.php?t=4634 it´s post #18. One last thing: Might I ask you upon what authority you judge the things I said (which you basically didn´t even reject - you just seemed to randomly flame around) and my mental state? From the style of your post you seem more like a columnist or historian than a scientist. EDIT: From the E-Mail (was it an E-Mail?) you posted in your last post it seems that the quote in my post between "[...] occasion to repeat more explicitely what I already said:" and the rest of my post is missing. This might explain your confusion.
  19. Thermodynamics doesn´t refer to single atoms :]. If all of your 10^23 atoms are at rest and all of their electrons are in the ground state, then yes: That´s T=0 (<=> "absolute zero"). Also (getting tired of repeating it) excited electrons do not play a role at low temps. It is sufficient to only consider the movement of the atoms. Forget about your electrons!
  20. . No, I think you didn´t get my point. I was talking about T=0 not a point close to that. The closer you get to T=0 the more electrons go to their energetically lowest state. At T=0 all are in their lowest state. Simple as that. A rough approx I just made tells me that even at room temp most electrons would be in their lowest state (assuming difference in energy-levels to be in the eV-Range or even greater which I´m not certain of).
  21. ^^ I didn´t really understand much in above post (but I didn´t really try hard) except the reference to Kelvin - and he is wrong on the subject which is not too surprising since his physical knowledge is a bit outdated (a hundred years) for today's standards. Nevertheless I´ll take the reactivation of this debate as an occasion to repeat more explicitely what I already said: EDIT: uh, oh, reading my previous post again it seems I actually didn´t say that. Well, that´s even better: Quantum Mechanics doesn´t allow a bound electron to stop moving. QM tells you that bound atoms can be only in certain states. None of these states is associated with stop of movement (*resistthetemptationtostressuncertainty). Each of these states have an energy associated to it so if for example an electron changes to a lower-energetic state the differrence in energy will be released as a photon of characteristic energy. At absolute zero all particles will be in the state with the lowest energy. But since there´s no state allowing the bound electrons to rest they won´t do so. I can imagine that eating "there is no state where everything is at rest" isn´t that easy but that´s the best answer I can give you assuming you don´t know QM (you might want to read it up; the Hydrogen atom and it´s quantitized states is not too hard to understand - non-relativistic). And to repeat it once more: Temperature is no physical quantitiy. It´s a statistical variable. I don´t think there´s much point thinking about it and speculating what this tells us of the world if one hasn´t really understood that and can tell statistics from physics.
  22. you don´t need energy to cancel out a force (gravitational force octing on the magnet in this case). You need force. You examle with the magnet is essentially the same as with the cup of coffee standing on my table in front of me: If doesn´t fall down eben though gravity works on it. That doesn´t mean the table puts infinite energy in it over time. It simly means the force of the table acting back on my cup of coffee cancels out the force of gravity. The reaction would be: - Force Fg tries to pull the magnet down. - Frictional force Ff caused by the magnet being pressed against the kitchen fridge (due to magnetic attraction) cancels out the force of gravity: Ff = -Fg. - Total force working on the magnet: F = Ff + Fg = 0. - Force is change of momentum (basically speed - I dunno about your lvl of physics) over time. Since F=0 the speed of the magnet doesn´t change over time => magnet remains where it is. - Note that energy never appeared in above. To sum it up: Forces only have an effect on energy when applied over a distance. Since there´s no change of poisitions involved in a static setup energy becomes irrelevant (I´m not 100% sure if that statement is correct for all cases but it applies for your question and I wanted to keep my answer as simple as possible).
  23. you think that seconds, minutes, hours, etc. are time ?
  24. timo

    quantum states

    What´s a hydrogen-like Boron ion? An ion with only one electron around the core? What do you consider a quantum state? Only looking at the state of the electron and ignoring the quantum state of the core, maybe even treatening it as a positive point-charge? If 2 x "yes": Without even looking at the equation I´d say you can safely assume there are as many possible states as in a hydrogen atom: Infinite. if 3+ x "yes" ... you did something wrong Or if you want a more pedantic answer: Each object has/is in exactly one quantum state ... one out of all those that are possible.
  25. Do you have any sources on that? According to two of my books and my notes of the lecture on GR I heard R is the smallest r of the trajectory´s points and not the impact parameter. I might try pluging the impact parameter in there as 4M/b and see what I get but since b>R the prediction values will be even worse (predicted values are too small in case I didn´t explicitely metion it before). Validity for M<<1 is essentially the same as validity for R>>1, here, so your 2nd statement is just what I said. What I need (better: Could use) is a source that explicitely shows me I´m right or wrong - with an explanation why so! Thx for the answer, anyways. Maybe you can tell me why the approx is only valid for M<<1 or what better approx you´d suggest ? EDIT: No need to further think about it if you don´t know a good answer. As i already expected in my 1st post I found a sufficient answer myself
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