xkcd

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So my friends and I are doing a project, and we need a DAC which has fairly good resolution between 0 and 0.3V (~100 values). First option we were looking at was a cheap arduino, but we found that it only had PWM outputs. Sure, you could voltage divide and then use an RC lowpass to get roughly the r...

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One week ago, at about 2 am on Friday the 24th, I was walking outside and up in the sky I saw a number of bands of very faint greenish blue light. They were vertical, covering 3-5 degrees of the sky. There were 4 in a group like claw marks in the sky to my north. One more was to the northeast and a ...

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My friend has a turtle, and it got me thinking... how do its eyes work? When diving underwater, I have extremely poor vision, which I assume is because the refractive index difference between water and the various parts of my eye are much smaller than in air. Do turtles and other amphibians suffer t...

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Yeah I suppose that would help, wouldn't it... I need the material to be a conductor (actual conductivity shouldn't matter too much), relatively cheap, low density, not violently reactive with water, and a melting point between roughly 200C and 500C. To me it sounds like a metal or alloy would fit t...

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Hi, I was wondering if anyone knew of a database or some software that would help me to find a material for a specific application I'm looking into. I need information like conductivity, density, melting point, cost, etc.

Thank you!

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I was wondering: do we know why it is that subatomic particles all have charges of 0, +/- e, or in the case of quarks, +/- 1/3 or 2/3 e?
Seems awfully convenient... Why isn't there a particle with 0.7982364 e as its charge, for instance?

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speising wrote:This is pretty nice, but deals only with one aspect of a lower c. It ignores the end of all the known universe which would probably occur when someone changes c. (cf. "well-tuned universe")

This is more along the lines that I was thinking of. Why, or in what ways would the universe end?

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So there would be no other noticeable differences in the universe, other than things would behave relativistically much more easily? That's a much more boring answer than I was expecting.

The fact that ε₀ and μ₀ are larger does nothing? The fact that gravity is slower has no effect?

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What if c was a smaller value? For our purposes, let c be both the cosmic speed... barrier, and the speed of light/massless particles. I get the feeling our universe would change dramatically at some point. I wonder at what point that would be. What if it was one 10th the speed, or one 1000th? Or a ...

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When in love, or upon experiencing emotional pain or excitement, many people will report a sensation in their chest, one which I can't find the words to describe, but I assume everyone knows the one I'm talking about. I imagine this is where the association of love and the heart came from. What I wa...

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True enough.

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Electroplating: I don't have access to the required equipment unfortunately, and I'm not sure, but it may be too expensive to scale up. Thanks for the suggestion though. Calcining: I can calcine up to 800 C, which is good enough for ZrO2 at least (the oxide is the goal in fact, the hydroxide and sul...

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Neil deGrasse Tyson, Brian Cox, Craig Venter

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I've been trying to do this for a few weeks now and it's frustrating as hell... I'm looking for a way to get relatively pure zirconium (sulphate, oxide or hydroxide forms are all okay) out from an aqueous solution of: 70 g/L Zr 40 g/L Mg 60 g/L S (as SO4) Free acid around 1 normal Addition of base f...

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it seems like most of the stuff you have to do in calculus (in undergrad anyway) a computer can do much much better than you. In fact, it seemed like the higher up I went with Calculus at university, the less I learned about actually doing maths, and the more I learned about how to use Maple TM . I...

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She's starting a business degree now. I'm not sure which applications that would suggest. Optimization as ThirdParty mentioned must surely be in there, though.
Thanks for your feedback!

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Okay. I love math, calculus especially, because it is so handy in so many ways, and so many fields use it extensively. It is no stretch to say that we wouldn't be anywhere near as advanced as we are today without the development of calculus. My friend doesn't see it that way. She took it once in hig...

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Hi, I'm taking a course on quantum mechanics, and we have a project which involves modelling some sort of quantum phenomenon using the numerical methods we've learned about. Basically, we've discretized the hamiltonian in the 1D case, and we've used Matlab to solve for eigenenergies and eigenfunctio...

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Hmmm. I think I'm beginning to grasp it, but it's still unclear to me why it's possible to slow down one component of a wave relative to the other..
Is there any analogous situation which I might be more familiar with that I could draw parallels to?

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I'm reading up on polarized light microscopy for one of my courses, and I am getting really confused by linear vs. elliptical polarization. Before when I was taught about PLM, what I got out of it was that light was polarized linearly, went into an anisotropic sample, its polarization was changed, i...

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This could allow you some interesting plot devices to use as well... For example, receiving these memories would mean that the chip (or a replica?) must exist at the point in time in the future in order to send those memories back to itself, or there would be a time paradox which the universe doesn...

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Indeed - you can even play with the fact that to the reader it might appear the characters were travelling backwards in time in an explicable way before dropping the bombshell... Another problem/interesting bit is the question of how these newtonian flash-forwards interact with each other... imagin...

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It's not that they are going back in time, it's that they get to see forward in time and then get a chance to change stuff. i.e. "show me what will happen if I didn't know what was going to happen." The only problem/difference is this requires you to decide before any particular event tha...

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Well at this point, they have knowledge in their heads about what happened once before, so this pretty much ensures that the course of events will not be the exact same as last time. But yeah, they're pretty much free to do what they want once time resumes its usual direction.

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Awesome, questions. This is very similar to the time-turner idea (I don't know why I never made that parallel... especially since I just reread all of them a couple of months ago), but in my mind, they would be able to see time play in reverse for a brief... period... of time? Though unlike in Harry...

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Okay so this is going to be far-fetched, but I can't think of anything that sounds remotely reasonable. For a story I'm writing, I need something which can be activated, and will reverse time to a set point in the past, but at the same time, will preserve all of the information in the user's brain. ...

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It's been a long time since I've had a good programming task to sink my teeth into, and I wanted to get into something different from what I've normally done. So I made some vector copies of the blueprints to each building in my university and I'm hoping to make a Google-maps type thing that will be...

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I believe some of the numbers in the OP's spoilered image where added by the OP, and others by the original problem. There is a bunch of verbage about "first quarter", "second quarter" in half-passive voice that I couldn't be bothered to decode that leads me to that conclusion. ...

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I have a question on an assignment which I've been working on for a while with a friend. We also have access to a copy of the solutions manual, but we disagree with it completely. It's not the first time that it's been wrong. Essentially we're given a section of circuit made up of only capacitors an...

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Awesome. Thank you again. I think I just have one more: 3) No, you aren't restricted to k values where n*lambda. So far we've used such wavevectors as examples because in those cases the real space situation is easy to visualise. But k can take any value. So how does it look when k corresponds to a ...

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How long would it take to engineer super-intelligent animals, perhaps an ape, crow, or dolphin? And when will we make a machine with human-like intelligence? Perhaps we don't need to go to other worlds to meet an alien intelligence. I view this as cheating. For me, this would be like discovering mi...

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I feel your pain, OP. But we can't . ... Our only hope is that of strings of future events, conceivable, yet so improbable such as to be, by any other name, a fiction. That was beautiful. In response to the OP, I'm not sure I feel as strongly about it as you do, but I would definitely feel an absen...

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Eternal Questionner wrote:Do you mean this video

Yup, that's the one. Thank you.

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From what I've heard, this is slightly different from the usual Meissner-effect demo's we've all seen. In one video (I'll post the link if I can find it) they explain that the superconductor is a few hundred nanometers thick and has dopants introduced into it so that it allows some flux to penetrate...

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I'm confused slightly about what you mean by the universe "caring." In my mind, to accept that physics can exist is to accept the universe "cares." It seems to me what you know and your intuition are at odds. I mean the universe has no concept of entropy, or lowering a system's ...

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Sooo... as far as I know, the universe doesn't give a shit about what entropy is, it's just something that happens because it ought to. It's ridiculously unlikely for all of the air in a room to be in one half of it, so it probably isn't. And if somehow it's made to be, it soon won't be. This makes ...

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Alright so both of those really helped . I'm going to address both answers separately as best as I can. Okay, well I don't think I can summarize a whole semester's class in one post (or want to!), but maybe I can help with the big picture. It sounds like you don't really have any physics background,...

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In one of my courses, we have been introduced to the concept of reciprocal space in order to figure out the band structure of crystal lattices. Between 98 and 100 % of the class does not understand what the hell is going on, and I'm not sure if it's the concepts being too hard, or that our professor...

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Bahhh! This is one of my favourites.

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... The reason not to slowly change from pi to tau is that the only benefit is dropping a factor of 2 sometimes. This is such a small benefit that it's effectively outweighed by even a very small cost or inconvenience of changing it. ... All of those changes would actually offer significant improve...

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