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Ask HN: What scientific phenomenon do you wish someone would explain better?

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Re: Ask HN: What scientific phenomenon do you wish someone would explain better?

#241

Post by 7thaccount »

arkanciscan wrote: post #173

Quantum Computers. Not like I'm five, but like I'm a software engineer who has a pretty decent understanding of how a classical turing machine works. I can't tell you how many times I've heard someone say "qubits are like bits except they don't have to be just 1 or 0" without providing any coherent explanation of how that's useful. I've also heard that they can try every possible solution to a problem. What I don't u…

There is a comic (maybe SMBC) that covers the whole commonly false belief surrounding qubits.

Re: Ask HN: What scientific phenomenon do you wish someone would explain better?

#242

Post by drocan »

arkanciscan wrote: post #173

Quantum Computers. Not like I'm five, but like I'm a software engineer who has a pretty decent understanding of how a classical turing machine works. I can't tell you how many times I've heard someone say "qubits are like bits except they don't have to be just 1 or 0" without providing any coherent explanation of how that's useful. I've also heard that they can try every possible solution to a problem. What I don't u…

not quantum computers per se but I had my aha moment when I saw quantum computing as "linear algebra with probability coefficients". It's mostly working on superpositioned qubits while doing the calculation and then making them (with linear transformations) as likely as possible to collapse on the solution (when "measured").

Re: Ask HN: What scientific phenomenon do you wish someone would explain better?

#244

Post by AngryData »

tomp wrote: post #116
contravariant wrote: post #113

Earlier quoted context omitted.

It directs air moving horizontally downwards, by conservation of momentum the wing must get additional upwards momentum, called lift.

That can't be the explanation, otherwise wings wouldn't need to be curved - flat wings could fly, as long as they're tilted to redirect the air.

Flat wings can and do fly just fine, they are just a bit less efficient. The teardrop shape and camber/cupping underneath just make the winds more efficient at slicing through the air without creating as much turbulence and drag.

Re: Ask HN: What scientific phenomenon do you wish someone would explain better?

#245

Post by lbblack »

sloaken wrote: post #238

Avogadro constant - I can accept the number, if someone can show me how, over a hundred years ago, without having every really seen a molecule, this number could be derived. Obviously no one ever sat there and counted them but I find it hard to believe, they could have decided this without being able to see it.

"The charge on a mole of electrons had been known for some time and is the constant called the Faraday. The best estimate of the value of a Faraday, according to the National Institute of Standards and Technology (NIST), is 96,485.3383 coulombs per mole of electrons. The best estimate of the charge on an electron based on modern experiments is 1.60217653 x 10-19 coulombs per electron. If you divide the charge on a mole of electrons by the charge on a single electron you obtain a value of Avogadro’s number of 6.02214154 x 1023 particles per mole."

https://www.scientificamerican.com/article/how-was-avogadros...

Re: Ask HN: What scientific phenomenon do you wish someone would explain better?

#246

Post by harimau777 »

I don't know if this would be my "one question" if I could ask the most brilliant minds in science, but something that always bothered me:

When I took physics they basically said "at first scientists were disturbed by the fact that magnets imply that two objects are interacting without any physical contact, but then Faraday came along and said 'the magnets are actually connected by invisible magnetic field lines' and that resolved everything."

How does saying "but what if there's invisible lines connecting them" resolve anything? To be clear, I'm not objecting to any of the actual electromagnetic laws or using field lines to visualize magnetic fields. It's just that I don't get how invoking invisible lines actually explains anything about how objects are able to react without physical contact.

(Also, it is not lost on me I that this question boils down to "fraking magnets, how do they work?")

Re: Ask HN: What scientific phenomenon do you wish someone would explain better?

#247

Post by skanga »

na85 wrote: post #237
skanga wrote: post #223

Can anyone explain disc loading and solidity in a propeller and if there are any equations governing them?

Disc Loading is just the force on the actuator disc (such as a rotor, in which case the force is the weight of the vehicle the rotor holds aloft) divided by the swept area (pi times r squared). It's used when discussing propulsive efficiency, as it's a proxy measurement for how much "work" each blade is doing. Because propeller/rotor blades are just high-aspect wings, if you have high disc loading your blades are at…

Thanks na85

Let's take a contrived example. I have a 4 engine high wing airplane with 2 bladed 55 inch props on each engine with 100kg force (1 kg-f is equal to 9.8 N) thrust per engine.

Now, I need to make that a low wing airplane so need to change to 22 inch blades with the same thrust and I don't want to change engines. So I want to add more prop blades. How many more blades do I need to add?

Re: Ask HN: What scientific phenomenon do you wish someone would explain better?

#248

Post by Retric »

umvi wrote: post #119

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…

Cells are tiny and the speed of sound is how fast air molecules move. Proteins are also not bouncing around as fast but it’s very still quick relative to their size. Next, often there are multiple copies of each component. That’s half the story, larger cells also have various means to clump things together to improve the odds. https://en.wikipedia.org/wiki/Endoplasmic_reticulum

PS: Speed of sound is 343 m/s, diameter of a cell nucleus is ~ 0.000006m to give an idea.

Re: Ask HN: What scientific phenomenon do you wish someone would explain better?

#250

Post by sloaken »

druml wrote: post #214

Escape velocity

My dad was an aero space engineer, and I always had trouble with this. It is the speed you need to be going at, to not be pulled back by gravity. As a kid, I always thought, well big deal, if I am in a plane and just keep going up, eventually I will be out. The key I always missed was the velocity at that point was with no added power. So when the engine cuts off, what is your velocity? Is it enough to escape? Or do you need more power. Of course there is a good chance I still do not understand it.
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