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Showing content with the highest reputation on 01/27/21 in all areas

  1. actually I have exactly 15 questions. I've done 10 of them, but I couldn't understand them and that's why I found this place. Maybe I expected the people here to understand them and show me a solution. You may have scolded or humiliated in your own way, but there was no need to humiliate that much because I uploaded it with an incomplete explanation. I'm sure more well-intentioned people will come across. have a nice day. actually I have exactly 15 questions. I've done 10 of them, but I couldn't understand them and that's why I found this place. Maybe I expected the people here to under
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  2. Hello Col and welcome. +1 for a good start, I look forward to further worthwhile contributions. I've been a member since 2012 and in that time I have seen many threads started discussing the question, "What is space ?" So it is indeed apressing question. So pressing that in fact we now need to separate what is meant by a physical space and what is meant by a mathematical space. Defining a mathematical space is easy. You need a set containing at least three (perhaps four) sets of objects. 1) A set of mathematical objects you wish to work with. 2) A set of co
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  3. I'm no expert either, so be my guest. And of course it would be nice that some of the local experts can give us a hand. Yes, DNA does get old. That's at the basis of cellular aging, and thereby the organism's aging itself, AFAIK. The replication mechanism is some kind of bi-directional zip assembly, so it's always imprecise at the ends. In one direction the replication process is very smooth, because the initial fragment (RNA primer) and the DNA polymerase work in the 5' to 3' direction, but in the opposite strand, primer and polymerase are forced to work against the uncoiling of the double st
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  4. 1. A topological manifold 2. The Levi-Civita connection 3. A metric with the correct signature 4. A local constraint on the metric which guarantees the automatic conservation of the Einstein tensor (=the Einstein field equations) This is pretty much the minimum structure required to get GR, as opposed to other models of gravity.
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  5. Cyanoacrylate adhesive ( superglue ) is often used to 'seal' open wounds, where stitches might be too obtrusive. Doctors don't seem to be worried about absorption and toxicity. And superglue might keep your hairpiece on for months at a time. Better yet, shave your head and grow a beard.
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  6. But the sister cells are just as old. Excepting cells that are manufactured (*), all bad (damaged, stressed) cells are replaced by mitosis of the remaining ones, all of which are essentially as old as you are. Maybe I'm wrong about that. Hardly an expert here. The DNA is also replicated this way, not manufactured from scratch, so all the DNA is effectively as old as you are,. Neurons can't just split since their connections cannot be reproduced, so they're intended to exist without replacement after their initial allotment is complete some months after birth. * Blood is a nice exampl
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  7. That goes for neurons. But I meant it --more in general-- in the sense that the cell --every cell, including neurons-- is the basic unit that carries out a particular function within the organism. In order to do that, they specialize down the line of cellular development. Cells have a finite life though, so when they no longer work, they are replaced by releasing stress signals that activate their destruction and further mitosis in other sister cells. As long as the cell is performing its function, it's important that it does it well --cancer being an example of how bad it is that a cell stops
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  8. New User here. Hi everyone. Please advise me where to go and what is appropriate, my apologies in advance for getting it wrong so far. 1. Thanks for pinning this post to the top of the board, it seems like a good one for newbies to start with. 2. It would help if the original creator(s) posted an update, so that we could see what the article looks like after 4 years of comments and editing. I've only had a scan through all the comments and that took a whole day. 3. Are you sure people often ask "What is space made of"? Have you got any surveys or other evidence for that?
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  9. @MigL Hope you don't mind, but I'm gonna take our PM exchange into the thread here (keeping your point unquoted, will share my reply here instead). We're still talking passed each other. While I said I can understand the underlying motivations, I have NOT made excuses for violence perpetrated in the name of BLM. There is violence happening as part of the movement. I don't agree with it. I'm not making excuses for it. I'm not pretending it doesn't exist. My primary point has been that the violence is the extreme outlier in BLM. It's marginal. It's super rare. It's uncommon. It's been
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  10. An alternative proof from direct Taylor expansion in the metric coefficients and counting how many parameters are left that I cannot set to zero by changing the coordinate system: https://www.youtube.com/watch?v=gf-G4QiAHLY&list=PLaNkJORnlhZnwjIXnOHrX50FEyoyiTh4o&index=5 Those must coincide with the number of independent components of the Riemann. \( \frac{1}{12}n^2\left(n^2-1\right) \) Uses Young tableaux, which allows you to count free parameters very easily.
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  11. Neither, the police are quite adept at inspiring violence at an otherwise peaceful protest. Like I said, the difference is the intent on the part of the protester's and I think there's little doubt the Trump army intended violence, when they descended on the capital, because they didn't get their way in the polls; so no, the two aren't equivalent. You can't/shouldn't just dismiss a legitimate protest because some of them defended themselves when attacked. Violence is never Ok, is more of an excuse to deny legitimacy in this context; I have every sympathy with pacifism as an idea
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  12. Umm, windows are one thing, Zap. Would you feel better if you were one of the 5 killed at the Capital, or on of the 18 killed during the BLM protests? And lets not confuse the issue with self defense; we are discussing perpetrating violence, up to and including the death of innocent bystanders. At both protests people were there by choice, and some ( not all ) willfully harmed ( and killed ) innocents. In my opinion, violence is violence, no qualifiers. I recognize that others may have a different opinion, as you've stated ( personally, I would have used hate crimes as an examp
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  13. Homework Help is where members guide other members towards deriving answers to their homework. It is not where members provide full answers to members too lazy or indifferent to at least make some effort to answer those questions. Perhaps, if you make an effort now to describe what work you have done to attempt an answer and what uncertainties you have, then some members may be willing to offer you help. That's "help", not "complete answers".
    -1 points
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