501–510 of 839 posts
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I hope this helps: https://www.youtube.com/watch?v=qPKj0YnKANw
Actually... yes, which just makes it worse that something about that presenter's style really rubs me the wrong way. Do they have their content in text format somewhere? Anyway, thanks!
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The thing I don't understand about qc is how on earth can you read values from qbits without breaking superposition.
You can't, it's a fundamental aspect of quantum mechanics (measuring any entangled system collapses it because you've forced the system into a state by measuring it). The idea is that you structure the QC system such that the computation is done using entangled states, but when it comes to measuring the qubits (to get the result of the computation) the state is such that you'll get meaningful results. This means the…
I would like to understand how cellular biology processes actually work. Like, how do all the right modules and proteins line up in the right orientation every time? Every time I watch animations, it seems like the proteins and such just magically appear when needed and disappear when not needed [0]. Sometimes it's an ultra-complex looking protein and it just magically flys over to the DNA, attaches to the correct sp…
I studied bioinformatics and found the standard textbook, Albert's "Molecular Biology of the Cell"[0] to be one of the most captivating books I've read. It's like those extremely detailed owners' manuals for early computers, except for cells. The amount of complexity is just absolutely insane. My favourite example: DNA is read in triplets. So, for example, "CAG" adds one Glutamine to the protein it's building[1]. The…
Note that the 4th edition is (sortof) freely available at the NIH website. The way to navigate through that book is bizarre though, as the only way to access its content is by searching.
• Magnetism. There are plenty of videos out there calling it the result of a relativistic charge imbalance. But I've never been able to use this point-of-view to practical use cases like understanding how permanent magnets work or how increasing the number of windings in inductors boosts the magnetic field strength. There were more situations I tried to put this POV into use but I can't remember them off the top of m…
I think this was a pretty neat explanation:
https://sites.google.com/site/butwhymath/m/convolution
The problem with convolutions, like many things in science, is that how you learn it, depends on what you're studying. Same theory, but with N different explanations, which can cause confusion if some of them are very different and tough to connect (i.e learning convolutions in a physics class vs leaning one in a statistics class)
Flight. How can a plane fly when it's thrust to weight ratio is less than one? It's like, if you can produce 10 pounds of thrust, who would look at that and say "ah ha, we can use this to keep a 100 pound machine miles in the air indefinitely"? I understand flight from a mathematical point of view. I've actually read a few books on the subject, and I could explain how flight works to someone. However, I'm still fishi…
Put another way, weight pulls it down, thrust moves it forward, the resultant lift keeps it up, and drag limits its speed. Only rocketeers and fighter/aerobatic pilots need to really worry about the thrust to weight ratio as a constraining factor, because the vertical flight regime matters to them. From your average bugsmasher to your commercial airliner, it's not a factor (to the disappointment of pilots everywhere).
Consider that a Cessna 172 has a glide ratio of about 9:1, so it can go 9 units forward for every 9 of altitude it gives up. If that's hard to intuitively grasp, consider that it's traveling through a fluid. Surfing, even. The interaction with that fluid is why it works.
That any more satisfying?
BlackHoles - where does the 'extra' mass/gravity come from? I've been watching a lot of documentaries lately, and I can't figure out how a star that _radiates_ light, collapses and suddenly light can't escape? Doesn't that mean the blackhole has more mass/gravity then the star that created it?
BlackHoles - where does the 'extra' mass/gravity come from? I've been watching a lot of documentaries lately, and I can't figure out how a star that _radiates_ light, collapses and suddenly light can't escape? Doesn't that mean the blackhole has more mass/gravity then the star that created it?
What they don't tell is that once inside the sphere the force decreases linearly, because the planetary mass ahead of you is partially balanced by the mass behind you.
With this you can see that the gravitational pull of a planet/start/spheroid is largest at its surface. So, if something happens to make a start shrink by some factor, the gravity pull at its surface is increased by the square of this factor, even if the mass of the star remains the same.
Actually I believe starts eject a lot of mass when they become black holes, and this is just a Newtonian argument for a phenomenon intrinsically relativistic, but I hope you get the gist of it.
Flight. Apparently "air flows faster on the top side of the wing, lowering the pressure" is an incomplete explanation; I even heard we don't completely understand why it works (?!?).
The now classic Bernoulli vs Newton debate. "Air flows faster on top" is the Bernoulli explanation. The Bernoulli principle tells us that fast air means low pressure, and low pressure sucks the plane up. Newton explanation is the idea that the wing pushes the air down, and by reaction, pushes the plane up. Based on Newton's third law. In reality, both are correct. The Bernoulli explanation is more specific and the Ne…
I want to go up. I want to use the thrust I have available to achieve that. Would not the most efficient use of the thrust available be the direct and naive approach, of pointing the engine straight up/down? Nope.
Instead, we point the engine horizontally; literally orthogonal to our desired goal. Then we use these "wing" things - they're not complicated, they're just rigid bodies with a shape, which honestly isn't even that unusual of a shape. Now we're not only able to go up (we finally achieve our goal), but we get to go fast in some horizontal direction as well.
I haven't found an explanation for this that feels satisfying to me.
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Very simplified explanation: If you understand Turing Machines, you probably also understand other automata. So you probably understand nondeterministic automata [1]. A quantum computer is like a very restricted nondeterministic automaton, except that the "do several things a once" is implemented in physics. That means just like a NFA can be exponential faster than a DFA, a QC can be exponential faster than a normal…
The thing I don't understand about qc is how on earth can you read values from qbits without breaking superposition.
I found an explanation of schor's algorithm by my colleagues quite helpful. In my experience math seems to be more useful here than computing science.
Flight. How can a plane fly when it's thrust to weight ratio is less than one? It's like, if you can produce 10 pounds of thrust, who would look at that and say "ah ha, we can use this to keep a 100 pound machine miles in the air indefinitely"? I understand flight from a mathematical point of view. I've actually read a few books on the subject, and I could explain how flight works to someone. However, I'm still fishi…
Consider the vectors of the four forces (thrust, drag, lift, weight). The thrust only needs to equal the drag at a given airspeed, not the weight of the vehicle. (Unless it's climbing vertically.) The weight is countered by the lift generated by the wings, which, given the efficiency of airfoils, is very more or less why it all works: they produce a positive lift-to-drag ratio. Put another way, weight pulls it down,…