mooeypoo

Of course they are. Engineers all over teh world would much prefer building equipment based on theory rather than actual specific numbers. Go unified verbal theory.

Mathematical equations for everything so we can plug in "time" and see how the universe will look like at that time.

There's no need to wonder, Bear, you just need to learn about it a bit. The comparison you're making is totally unrelated to what goes on in the USA in so many levels, I'm not quite sure where to even begin. You can say whatever you want about what goes on in the fringes of the US government, but the US still has freedom of press, freedom of speech and freedom of movement - things that did not exist in Nazi germany. This conversations did not exist either; in fact,you would have been escorted quite forcefully to a "nice" work camp (in the good case, death camp in the more often case) for just voicing these opinions. I don't quite think we're thee yet in the US. Nor are we even getting close. There are fringes everywhere, and there are always people who go with the moment and get into the whole emotional-appeal argument. There's a big difference between that (statements, during protests/groups/etc of "USA! USA!") and mass murder and totalitarianism. No, the Nazis did quite a lot more than that; their methods were very different, and the social situation in Germany prior to the rise of the Nazi party was *VERY* different. There are many many reasons for the rise of Hitler to power. I really suggest you read it and get into it, it's a very intricate history that lead to this and I would - by far - not even suggest that the US is close to it; also, today, we have the Nazis to remind us of what not to do. That is, the "Never again" statement is a driving force for all the other groups to speak out and rise up against fringe-comments and attempted-actions by all those fringes who attempt to bring up racist or extreme atmosphere. Hitler played on the emotions of the people and used blatant propaganda in a state that stopped being democratic and turned to tyrannical totalitarianism. There's not much comparison here. It wasn't about balance, it was about incitement to racism in the name of nationalism, race and the crushed German pride (after the versaille accords, and the very very badly run Weimar republic). Far from the USA. *Far*. ~moo

I recently read a paper in a bio publication (I think it was "Molecular Ecology") with a Dr. Sullivan in it, who's from the university of Idaho. Interestingly enough, he has the same picture as you: http://www.uiweb.uidaho.edu/biology/people.html#Sullivan I am assuming you are one and the same. In which case, Hi Dr. Sullivan, welcome to scienceforums. Would you mind explaining this quote: In light of a quote from an interview, with you, made earlier this year: Question: And how do you think we should respond to the creationists? Fighting court battles require very different tactics than changing public opinion. To affect public opinion, there are two things we can do: 1. Publicly deconstruct the false dichotomy between macroevolution and microevolution. 2. Engage in a strong public outreach campaign over the importance of evolution in day to day life. (Source: http://treethinkers.blogspot.com/2009/04/dechronization-interviews-jack-sullivan.html ) And in light of the following publications: Evolution of the Mitochondrial Cytochrome Oxidase II Gene in Collembola (source: http://www.webpages.uidaho.edu/~jacks/Fratietal97.pdf) Within the genus Isotomurus, although three pairs of populations were consistently identified, these appeared to have arisen in a burst of evolution from an earlier ancestor. Isotomurus italicus always appeared as basal and I. palustris appeared to harbor a cryptic species, corroborating allozyme data. Evaluating Hypotheses of Deuterostome Phylogeny and Chordate Evolution with New LSU and SSU Ribosomal DNA Data (source: http://www.webpages.uidaho.edu/~jacks/Winchelletal.pdf) Among others. I'm just wondering, Dr. Sullivan, how do you research evolutionary trends if you are so admittedly antagonistic towards evolution? ~moo

No. At the very least, where are some resources? where's the statement of purpose and the methodological proof of said statement? where are the supporting *varying* documents (the bible doesn't count, and multiple versions of it are not 'varying' sources). It's not a doctoral dissertation, which explains why Hovind was reluctant to share it. This, btw, is another red flag; as I'm sure you know, Dr. Sullivan, doctoral dissertations *are* published for all to see, if not in a publication, then at the very least in the university library, and are *available* for anyone that asks. Kent Hovind's dissertation was held secret, no one was able to take it out of the library of the institute or look at it. That's not any form of doctoral dissertation.

Wow, I would hope so

http://c0122981.cdn.cloudfiles.rackspacecloud.com/091209KenHovindThesis.pdf Enjoy.

There's no need to build any false arguments about any other subject here, all one needs to do is read Kent Hovind's dissertation. Hovind insists to be called a "Dr", and when people ignore that ridiculous request (read his "dissertation") he gets very upset, claiming he's got credentials. Hovind dug his own little pothole here. ~moo

If your videos will also have a 'simple, yet not dumbed down' explanations to them, I'd be happy to feature them on my site (I do more physics-related experiments and articles, but I'd love to have more diversity). Obviously with full credit to you, of course. As for a name.. uh.. I'll think about it. "Chemicool" or "Awesomistry" ? it has "cool" and "awesome" in them, does that make it cool and awesome? ~moo

MAGIC!!!!!! Awesome demo, Bob_for_short

You know, seeing as the mind controls the body, it seems that technically, every time I move a chair I am moving it with my mind.

The need for a frame of reference starts because time and movement are relative. Think of it this way: You are sitting on a chair (presumably) reading this post in front of your computer. You're not moving. A car outside your window is moving relative to you. That is, the car is moving relative to your frame of reference. If I am inside the car, I am sitting down strapped to the seat. While I logically know that I am moving, I could also look at things from *my* frame of reference and declare myself as stationary and the road, streets, buildings and you in your chair to be moving relative to me. That would be perfectly true, and in fact when we calculate relative speeds we do that. Now look at some spaceship outside our galaxy, say. The person inside that spaceship looks at the Earth, and for him, the Earth is moving - around the sun, around itself, and along with the sun around the center of our galaxy. For the observer outside the galaxy, the Earth -- which we defined as 'stationary' before when we looked at ourselves in front of the computer -- is no longer stationary, it's moving. You are stationary in your own frame of reference, but you are moving relative to other frames of reference. When you go into relativity, those definitions get an even bigger meaning because we can calculate relative time dilation and length contraction based on the difference in reference frames. Also, in relativity, you *must* pick a frame of reference to discuss otherwise you are making no sense, because there's no such thing as "absolute" frame. That is, while you are stationary in your seat, there will always be infinite number of reference frames that will see you moving. We won't be able to speak of your state (moving or stationary, and at what speed) if we don't decide, first, that we are talking about the same frame of reference. Last example: If I am on a moving train, and I throw a ball accross the cart, I see myself as stationary, and can calculate the speed of the ball *relative to me*. However an observer on the ground, outside the train, will calculate a different speed for the ball, relative to him, which would also include the speed of the moving train. That is what we mean by "Frame of Reference". ~moo

"simply" ?

(+UnintentionalChaos) rubber stoppers for lab are EPDM, IIRC (+UnintentionalChaos) also, stopcocks are standardized, it's just harder to find info on it (@mooeypoo) are stopcocks rubberized too, UC ? (+UnintentionalChaos) no (+UnintentionalChaos) that's a stopcum (+UnintentionalChaos) or stopbabies

Watch the attitude, please. A question was asked, quite obviously because the poster does not understand. Instead of attacking them, it would be more helpful to explain. If you have nothing constructive to post, please refrain from posting.

?? What is this and where did this come from?

Yeah.. I think I'm starting to get the point, though. The equation I was dealing with had both lambda0 (initial photon) and lambda1(emitted photon), so the 'impossibility' was related to the emitted photon too. What I was having troubles with at first is thinking that the equation is only about the original photon and I didn't understand how we can make a determination about the emitted photon too based on that function alone... But yeah, I can see it now, I think. The equation is connecting BOTH the original and the emitted photon, that's why the end result being nonsensical can be related to the emitted photon. This, as much as it was frustrating, was actually quite a learning experience. Thanks, guys (ajb and timo on the chatroom and swansont on thread) for bearing with me on this one ~moo

I've had a long chat with ajb and timo on the IRC chan about this. What we did was equate the initial energy and initial momentum to the final energy and final momentum, and I saw that they create a nonsensical equation. That really hammered things home: Assuming 100% transfer of momentum: [math]p_{photon}+0=0+p_{e final}[/math] [math]p_{e}=p_{photon}[/math] Assuming 100% transfer of energy: [math]pc+mc^2=0+E_{e}[/math] [math]E_{e}=pc+mc^2[/math] And the equation of energy for the final photon should be: [math]E^2=m^2c^4+p^2c^2[/math] So, combining the above to see the final energy of the electron: [math](pc+mc^2)^2=m^2c^4+p^2c^2[/math] [math]p^2c^2+m^2c^4+2pcmc^2=m^2c^4+p^2c^2[/math] [math]2pcmc^2=0[/math] And we know that [math]m \neq 0[/math] and [math]c \neq 0[/math] so the only way this can happen is if [math]p=0[/math], but this is the initial photon momentum, which isn't 0 by definition, which makes this situation nonsensical. So, I do understand that a photon can't be completely absorbed by the electron judging by the conservation of energy. What I still disagree with is the statement that seems to be assumed from the question of the homework, that just because the final energy of my hypothesized emitted photon is 0, the entire situation is nonsensical. It just seems like bad physics-thinking to me. If we know in advance that the energies - initial and final - are unequal, and therefore can't be fully absorbed, that's one thing. But if I *only* take into account that the final photon has no energy, on its *own*, this statement can lead to 2 conclusions: either the entire process is nonsensical, *OR* there is no emitted photon. It seems to me that the professor expected us to assume nothing in the beginning (we weren't asked to equate the full initial/final energy conservation calculation) and just judging by the fact that a final emitted photon can't exist, we should conclude that the process can't happen. Isn't that backwards? I am being a bit pedantic here, but I am just trying to explain why I had such a problem with the request to set the photon energy to 0, and why it made no sense. The other exercise with the frames of reference (essentially asking whether an electron can "pop-out" a photon, which has larger energy and larger momentum out of it) makes much more sense in the judgment that this can't occur. The E=0 situation just assumes we have prior knowledge that the question doesn't give yet... Does that make sense?

swansont, why does the reaction has to conclude with a scattered photon? a scattered photon assumes in advance that the photon wasn't completely absorbed, no? If the photon *was* absorbed, then there's no scattered photon, which can also explain why the lambda is infinite (impossible, so it's non existing). I just have this feeling that I am going in the wrong direction here; I am trying to explain why something is assumed by assuming something that's assumed.. it makes no sense to me. If the collision was inellastic, the photon's energy (which is to say the photon itself) was absorbed completely in the electron, and there is no resulting photon. Why are we not assuming that to begin with? I do understand that an electron cannot travel at the speed of light, which means that if the photon was completely absorbed, there must be some excess energy that remains, and hence the electron cannot absorb the entire photon, but that can be explained with special relativity and 'simple' collisions.. It seems a bit weird to me that we are already assuming that there *must* be an emitted photon, but seeing as the lambda of that emit photon makes no sense, then instead of concluding that the emitted photon can't exist, we conclude that the absorption can't exist. Isn't that backwards? It's assuming on the assumption of the assumption. It's weird :\

It's not about thwarting your efforts. I, too, have a science education website, but I don't go around posting self-promoting posts on forums (usually those are treated as spam) and expect the forum to cheer as I collect SEO and take advantage of backlinks in a forum that's meant for a discussion. If you want to discuss something, go ahead, but do it in this forum, according to our rules, and with respect to the etiquette.

No, Lambda can't be infinite, of course not, I just don't see why I'm measuring lambda -- the question asks if the electron can absorb a photon while conserving energy and momentum; Why do I equate the photon's energy to zero? When the energy is zero, the lambda is infinite, which makes no sense. I think that the energy is set to zero to "imagine" a situation where the photon's entire energy passed to the electron, and now the photon has zero energy, and I am supposed to conclude that this can't be. BUT I don't quite understand -- a photon is made of energy, it has no mass, if it is absorbed in an electron, why do I even need to consider a photon that has no energy?? The photon 'vanished', there's no "resulting" photon after the collision, there's just an electron, because the hypothetical situation is that the electron took *all* of the photon's energy and momentum. Why can't the electron just get all the energy, in which case the equation of E=0 is meaningless.... The only reason I can think of why this can't happen is because the electron *does* have a mass, in which case it cannot move at the speed of light, which means it couldn't have taken the total energy and the total momentum from the phton, but (a) I'm not sure how to show it and (b) I'm not sure what this has to do with E=0. I am hoping I manage to explain myself clearly :\ it's a bit confusing. ~moo Merged post follows: Consecutive posts mergedErr, I just made my own case <sob> Part © asks to give another derivation of the answer in part (b) by considering the photon absorption process in a reference frame in which the electron after the absorption of the photon is at rest and 'play the movie backwards'. Does anything go wrong? So, in this case, I can see why there would be a problem (I need to work on the actual solution still, but it makes more sense) because the electron would have to be moving at the speed of light, and that's not possible to a particle with mass..... but why the E=0 situation?

Nitinol wire: http://www.youtube.com/watch?v=Y7jjqXh7bB4 Awesome trick, hehe but no, I don't mean that. The wire I mean turns flat/straight with *current*, not temperature.

Hey guys, I'm actually not sure which physics subforum this fits into, since I don't remember exactly what those rods were.. I'm hoping someone can help. A while ago a friend of mine from the department told me about a type of metal-like rod that can bend and flex, but retains its original shape when charge is passed through it. I don't remember the name, but it has one. I remember that I *did* find it online, but I can't, for the life of me, find it again. I also have no access to that friend anymore, so I can't ask again, sadly.. Does anyone know anything about this? Any help will be appreciated! ~moo Merged post follows: Consecutive posts mergedCorrection: When *current* passes through these wires, they straighten up. So if you had a loop, you pass a current through it, the wire straightens. Damn. I know those exist. I have no clue what the name is. So frustrating.

I thought about that in the beginning, but [math]\frac{d\lambda}{d\theta}=\frac{h}{mc}\sin{\theta}=0[/math] .... Okay, as I was typing it again, I answered my own following question. Theta=pi, and [math] \lambda_{1}-\lambda_{0}=\frac{2\pi}{mc} [/math] just like the graph says. Okay. Now for part b, though, I'm not sure why I even need to consider a case where E=0, but when I do, then [math]E=0=hc/\lambda[/math] and lambda is infinite. What does that have to do with free electron absorbing a photon while conserving energy and momentum? I am not sure I understand the connection between the question and the hint and the first part.

I started taking QM this semester and I am a bit confused with this question: "In the Compton effect, if the incident radiation has wavelength [math]\lambda_{0}[/math], what is the maxima wavelength that the scattered radiation can have, and for what angle will this happen?" So, maxima/minima is calculated using a tangent, so I figured I will differentiate the equation: [math]\lambda_{0} - \lambda = \frac{h}{mc} ( 1-\cos{\theta} )[/math] With respect to [math]\lambda[/math], but that made no sense (=0?). So, I figured I'll go a step back on the derivation of the equation and try from there: [math]\frac{h^2}{\lambda_{0}\lambda}(1-\cos{\theta})=mc(\frac{h}{\lambda_{0}}-\frac{h}{\lambda})[/math] But that doesn't come out well either (0=0) So I resorted to looking at the graph I was given, seeing that [math]\lambda_{1}-\lambda_{0}=\frac{2\pi}{mc}[/math] when [math]\theta=\pi[/math] (which is the max). But that strikes me as a bit of a cop-out. Is there a way to calculate this question algebraically? What did I miss? The next part of the question makes me think I am way off track here. It asks "Can a free electron absorb a photon while conserving energy and momentum? (Hint: think of part (a): what wavelength must the 'emitted' photon have if it has zero energy?)" Err the only connection i can think of is E=hv or [math]E=\frac{hc}{\lambda}[/math] but then if E=0, then lambda should be ... like.. infinity. Help!