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psi20

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Everything posted by psi20

  1. Hey. I was wondering how to black out text when you're in a forum so that when you try to read the page, you just see it blacked out but when you highlight the words, then you can see what it says. Actually, I was more interested in applying this technique to Wordpress so that I can make tutorials for myself, by blacking out the words so I have to fill in the blank while I'm reading, but still have backup for myself in case I forget.
  2. Ah thanks for all the advice. I'll look into these things and ask professors around here.
  3. Hi. I was wondering if any of you are studying/doing research in seismology. What kinds of math are important in that field? Outside of calculus, I'd imagine partial differential equations, stats, and linear algebra, maybe some topics in real analysis. But undergrad math just gave me a brief overview of different branches of math. I'm wondering if there are specific topics/areas that seismologists find useful. Thanks.
  4. Hi. I used to ask questions on this forum maybe 6-8 years ago back in high school. Now I'm about to graduate college, and I feel like I've wasted not only much of my college career, but also much of life in general. You ever felt like that? I'm studying math at the university I'm at. But I'm not really engaged in it. I feel like I wasted my opportunities here and really haven't pursued any research opportunities that were available. I'm just having regrets I guess. What do you do when you're at that point where you don't know where to go? And you feel like you've wasted what was one of your best opportunities in life, potentially destroyed any career plans you have in the future, etc. I've talked to a few friends, and they might say things like, "What are you talking about? Wasted your life? You're doing well in your classes, you're graduating this year, etc." But I don't think they understand. I was wondering if anyone had advice or thoughts from another perspective.
  5. psi20

    Carcycle

    Someone invent the carcycle. With the transportation capacity of a car, but you pedal it. Like an upgraded version of the Flintstones car. You can advertise it to the environmentalists so that they can reduce pollution. Then the athletes so that they can get a good workout. Also people who want to lose some weight will want to get the good workout. People who want to diminish car accidents will support this, too. It'll make millions. Billions.
  6. Ah, ok. Thanks for clearing that up. So the scales I'm thinking of in the lab are made to read out in mass. I was thinking that scales were made to read out the weight of an object (like bathroom scales). The 9.8 is for 9.8 m/s^2 from acceleration of gravity. I was thinking that the number on the scale meant the weight and not the mass. "a mole of carbon atoms weighs 12 grams. there`s nothing complicated involved :)" I think the confusing thing is that the word "weigh" is used as a verb for "to find the mass of" and "to find the weight of".
  7. I'm a bit confused about this. I've read a few wikipedia articles and chemistry sections on this, but I'm still confused. If you had a mole of carbon atoms and weighed it on a scale, what would you see? I guess what I should ask is what does a scale measure, weight or mass? If you measured that mole of carbon atoms, would the scale read 12 or would it read 12 x 9.8 ? If it reads 12, does that mean that the scale automatically divides out the 9.8 to get the mass?
  8. Why not though? If a lion and antelope share the same ancestor, or shark and fish, or any other predator-prey pair, wouldn't that mean one day my descendents would be eating one another?
  9. I was thinking about it the other day. Does evolution and natural selection mean that one day my descendents will be eating and preying on each other? That's just weird.
  10. I don't get how an electric current can go through a conductor faster than the individual electrons flowing through. How can the electrons make a current go across a conductor at the speed of light when the electrons themselves aren't moving across the conductor at that speed?
  11. psi20

    Electron shells

    It's all good.
  12. psi20

    Electron shells

    On average, is the electron in a 4s orbital farther out than the 3d one? Or is it the other way around? Do electrons in the 5s shell tend to be farther out than the ones in the 4f? And also, can you explain how the electron's energy in each orbital fits in to this. Thanks in advance.
  13. psi20

    Expired Milk

    Sealed as in the cap was on the gallon. I opened the gallon to drink from it. But I left it in the fridge with the cap on top, and I had drank about half the milk in the gallon. Maybe it was just my brain playing tricks. We'll see.
  14. Spyman, when you combined the equations like in step II, did you subtract? Z" L+O+R+E+N+T+Z+99=Z+E+R+N+I+K+E+102 => L+O+T=E+I+K+3 If you did, shouldn't the L have a negative sign in front? This is too hard for me. I'm just going to accept that I'm a person of inferior intelligence.
  15. psi20

    That one game

    I remember this one game online but I can't remember what it's called. I think I first found out about it through SFN, but I can't remember that either. It's online. You are a person in a locked room and you can't remember anything. You escape through the room and do a lot of puzzles. It has about a dozen levels I think. You discover that you're a time traveler or something. There's one room with a lot of green tiles on the wall and you click the tiles. It's part of a puzzle. There are aliens on level 9 or so. What's it called?
  16. psi20

    Expired Milk

    I'm going to slowly stop eating cheese then. I'm going to see if I can repeat this. Doesn't it violate the law of conservation of mass, though? It was a sealed gallon. That's what's puzzling me.
  17. psi20

    Expired Milk

    I can't weigh it now, because I threw away the gallon. Yeah there was some funky gas building pressure inside. When I lifted the tab, it blew off. But I'm positive that it was a lot heavier. What poured out looked like water with cottage cheese chunks almost. But it was definitely heavier than a normal gallon of milk. It was a noticeable difference. That's why I'm confused.
  18. psi20

    Expired Milk

    A few weeks ago, I began drinking soy milk and stopped drinking cow's milk. Unfortunately, I didn't drink all of the cow milk from the gallon before switching to soy. I left the milk gallon in a small fridge, which doesn't really work. I opened the fridge today and found that the milk had expired a week ago. Here's my question. What happened to the milk? It's all watery for 9/10 of it and the top 1/10 is white, probably the milk fat. The gallon has bulged out. Is that because it's giving off a gas? Most intriguing of all, why is the gallon a lot heavier now? A gallon once half full now weighs as much as two gallons. Shouldn't it be the same weight?
  19. Is x = y = a since this is a cube centered at the origin? a^3 = V so 3a^2 da = dV. So the integral might be integral p(2a^2)(3a^2)da Which becomes 6/5 pa^5 +C M = pV = pa^3 Doing the calculations, I get 6/5 Ma^2 + C.
  20. psi20

    help with a proof

    b = r(r(b)) and a = r(r(a)) so they both must be of the form y(4x+y). k^2 - m^2 must be of the form y(2x+y). These y's and x's are different than the ones above. Might want to use different letters. I don't know, but try looking into the method of infinite descent.
  21. psi20

    help with a proof

    If r(b) is even, it too has to be a specific type of number. r(b) must be of the form y(4x+y) where x and y are positive integers. r(a) must be, too. Again, I don't know if this will help. *On the list of integers above, I shouldn't have listed 0 since we're talking about positive integers.
  22. psi20

    help with a proof

    I haven't got much from it either. Suppose that (2a)^2 + r(b) = k^2 and k is a positive integer. Then k^2 - r(b) must be a multiple of 4. k and k^2 are odd if and only if r(b) is odd. k and k^2 are even if and only if r(b) is even. If k is even, r(b) must then be a multiple of 4 since k^2 is a multiple of 4 (k is even, k^2 must be even evener) and k^2 - r(b) is a multiple of 4. If r(b) is odd, it has to be a certain kind of odd number. I haven't looked at this in depth. (2a)^2 is an even number. Again, if r(b) is odd, then k^2 is odd. Write out the first 10 squares. Subtract an even square (2a^2) from an odd square (k^2). There's a pattern to what kind of odd number r(b) can be. 0 1 4 9 16 25 36 49 64 81 100 k^2 - (2a)^2 = r(b) Here's a list of odd squares minus even squares. 1, 5, 9, 13, 17... Something like 4x+1 or 4*1x+1^2 9, 21, 33, 45... 12x+9 or 4*3x+3^2 25, 45, 65...20x+25 or 4*5x+5^2 49, 77...28x+49 or 4*7x+7^2 I'm thinking that r(b) must fit this pattern. Departing from this train of thought, (k+2a)(k-2a) = r(b). Similarly, if (2b)^2 + r(a) = m^2, then the stuff from above similarly applies. I've tried to find a contradiction by looking at the sum, difference, and product of k^2 and m^2. I've looked at just the evenness and oddness of the sum, difference, and product. I don't think it works, though, because r(b) and r(a) is even or odd like k and m. I don't know if this will help. Perhaps it will, perhaps it won't.
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