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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?

#491

Post by Smaug123 »

sodafountan wrote: post #454
dreamcompiler wrote: post #398

Earlier quoted context omitted.

It's accurate. QC is just linear algebra with complex numbers, plus probability extended to the complex domain. Why that's useful is something I'm still struggling with as well.

I'd assume it's the speed advantage, but the only problem I can think of that would require that type of exponential speed is cracking hashing algorithms which just seems destructive and counterproductive, like building a digital nuclear bomb - and from my very limited understanding that's a long ways off from being achieved. I assume there's probably many more complex computational problems outside of my domain that…

Grover's algorithm lets you search an unsorted list of four elements with just one "is this thing in the list?" query. Classically, of course, it requires four queries.

More precisely, given f: 2^n -> {0,1} which is guaranteed to hit 1 exactly once, Grover finds the one input which hits 1, and it does so using about 2^{n/2} queries of f; but the constants happen to line up so that when n=2, exactly one query is required.

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

#492

Post by ramraj07 »

salawat wrote: post #350
mynegation wrote: post #11

Why tardigrades are so hardy, how their biology is so different? How immune system and medications work. Why some plastics are recyclable and others are not.

>Tardigrades: No comment. >The immune system: The most awesome thing ever. It's actually two systems. One called the innate that we have in common with most forms of complex life, and the adaptive immune system, something we've only seen manifested in jawed vertebrates. The innate immune system is a set of cellular signals/behaviors that are triggered by cells being exposed to damage and or stress. These responses ar…

Thanks for a detailed writeup, which seems for the most part in agreement with my understanding technically. But then you kinda tried to summarize janeways in a few paragraphs, and that means no one who doesn't already know immunology is going to find it helpful. In fact, Janeway itself tries to summarize their book in the first chapter and that chapter goes on for 50 pages iirc.

Some fundamental concepts that might fly over someone without a biology degree might include the absolutely fundamental requirement of protein binding for any biological process (akin to a transistors function for a computing device).

I'm thinking that step one of communicating the entire immune systems complexity is probably omission, of anything that's not absolutely required for comprehension of the basic concept. In that regard I'm not convinced there's any need for bringing up the innate system first (there's a reason we discovered it quite recently, perhaps?). Other details can also be similarly "omitted" for simplicity perhaps. What are your thoughts?

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

#494

Post by sangnoir »

nojvek wrote: post #466
atomicnumber3 wrote: post #410

Earlier quoted context omitted.

Disclaimer: I used to work in HFT Each exchange is basically its own world, with the exception of Reg NMS, which I'll get to in a sec. Let's task about order books. Each stock has its own order book. This might be an example of the book for AAPL: * SELLING 100 shares @ $10.02 * SELLING 200 shares @ $10.01 * SELLING 100 shares @ $10.00 * BUYING 100 shares @ $9.99 * BUYING 200 shares @ $9.98 * BUYING 100 shares @ $9.97…

Love the detailed explanation. Thanks. Once I saw Boeing at $120. I thought to myself. That’s dirt cheap and should buy. So I hit buy at market and lo behold I bought for $130. Wait! Whaaa! Did the exchange lie to me ? That day I learned a very hard lesson that there are infact two prices. Ask price and bid price. I wasn’t paying attention. Now I try to always put limit orders. I put sell for Boeing at $150 with “goo…

Also note that Robinhood (and possibly other apps) sell your trading data to HFT firms (in real-time), so market trades are not going to be in your favor

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

#495

Post by mech422 »

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?

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

#496

Post by sah2ed »

nojvek wrote: post #466
atomicnumber3 wrote: post #410

Earlier quoted context omitted.

Disclaimer: I used to work in HFT Each exchange is basically its own world, with the exception of Reg NMS, which I'll get to in a sec. Let's task about order books. Each stock has its own order book. This might be an example of the book for AAPL: * SELLING 100 shares @ $10.02 * SELLING 200 shares @ $10.01 * SELLING 100 shares @ $10.00 * BUYING 100 shares @ $9.99 * BUYING 200 shares @ $9.98 * BUYING 100 shares @ $9.97…

Love the detailed explanation. Thanks. Once I saw Boeing at $120. I thought to myself. That’s dirt cheap and should buy. So I hit buy at market and lo behold I bought for $130. Wait! Whaaa! Did the exchange lie to me ? That day I learned a very hard lesson that there are infact two prices. Ask price and bid price. I wasn’t paying attention. Now I try to always put limit orders. I put sell for Boeing at $150 with “goo…

> Shopify, Amzn, Zoom. WTF! Their charts seem hyped. Or may be I’m just plain wrong and don’t understand the fundamentals.

Since the outbreak of COVID-19, demand for the kind of services offered by those 3 Internet businesses have in fact skyrocketed. Increasing demand imply those businesses still have room to grow revenue. Shopify [1] for instance is now seeing huge Black Friday-like traffic during the shelter-in-place and a lot of these small businesses are first-timers on their platform who will likely stick around after the pandemic.

1: https://mobile.twitter.com/jmwind/status/1250816681024331777

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

#497

Post by Buttons840 »

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 fishing for an explanation that "feels" more satisfying though. Per the question, I still want it explained better.

EDIT: There's already a thread about flight. I asked the same question there, but phrased a bit differently: https://news.ycombinator.com/item?id=22993460

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

#498

Post by aeternum »

bollu wrote: post #381
aeternum wrote: post #160

Earlier quoted context omitted.

No, they are not really spinning. However the spin quantum property does make the particle deflect as if it were spinning when it moves through a magnetic field, thus the name. It is techinically a two-component spinor, which is why the direction of the spin 'moves' if you measure it along different x,y,z axes. It is also quantized unlike a normal vector: All fermions have quantized half-integer spin magnitudes and a…

Can you please formally define what a spinor is? Like, mathematically, what are they?

A quaternion is a (more-commonly known?) type of spinor which is often used in 3d graphics in matrix form to perform rotations.

Spinors are difficult to describe in an HN post since they require a good amount of linear algebra, but my favorite explanation is probably here: http://www.weylmann.com/spinor.pdf

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

#499

Post by mistermann »

GuB-42 wrote: post #322
vmception wrote: post #202

Has someone that thought they were taking LSD ever turned into a permanent schizophrenic zombie or in a mental institution, or is it all urban legend. If someone that didn't know they were predisposed to mental illness, is it applicable to dismiss their experience in order to maintain how safe LSD is? If any of this is true, are there any sources aside from "my friend's friend's brother took too much and now he is...…

When I looked up into illegal drugs, I found it very difficult to find reliable data. On one hand you have anti-drug people, usually backed by the authorities. Listen to them and all drugs will make your body rot, give you hallucinations like datura, and for some reason cause complete addiction after a single dose. Drug users on the other hand will tell you that it not as bad as alcohol/tobacco/coffee/... that concer…

> Drug users on the other hand will tell you that it not as bad as alcohol/tobacco/coffee/... that concerns are unfounded, that police is the only risk, etc...

Sure, some ("plenty", in absolute numbers) will tell you this, but I don't recall being in many forums where that attitude doesn't get significant pushback (as opposed to the anti-drug community). The modern "pro drug" community has a fairly significant culture of safety within it, unlike back in the sixties.

> The truth is almost impossible to find.

There is plentiful anecdotal evidence online. Any clinical evidence, if they ever get around to doing it in any significant volumes, will be utterly miniscule (and I highly doubt more trustworthy, considering what you're working with, and the size of the tests that will be done) to the massive volume of trip reports and Q&A available online, much from people who know very well what they're talking about, not unlike enthusiasts in any domain.

> Now from what I gathered about LSD (and psychedelics in general): these are very random.

Depends on one's definition of random.

> If you take a reasonable dose, you are most likely going to have a nice, fun trip and nothing more.

Effects vary by dose of course, but I've seen little anecdotal evidence that suggest high doses have a different outcome, and plenty that suggests the opposite.

> But it can also fuck you up for years, or maybe bring significant improvement in your life.

See: https://rationalwiki.org/wiki/Balance_fallacy

> The big problem is that there is no way to tell how it will go for you. There are ways to improve your chances, but it will always be random.

I believe this to be true, but don't forget the fallacy noted above.

That said, these things are not toys - extreme caution is warranted.

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

#500

Post by JabavuAdams »

eranation wrote: post #461
JabavuAdams wrote: post #308

Earlier quoted context omitted.

Sorry, don't have time to unpack all this, as some are things that scientists understand, but some are so deep that ... not. When talking about light or radio waves, you're probably talking about Classical Electrodynamics, which does not include the notion of a photon. In Classical EM, light is an EM wave in the sense that if you look at the electric field E or magnetic field B (of a plane wave) at a fixed point in s…

Wow, any chance with a few MooCs in physics I’ll be able to understand this better? Or it needs years of study. I’m worried about the math mostly (Ms in CS, but I got Bs in all the math classes :))

The math should be no problem if you go to the right sources. Some people like to play up the math, but it sounds like you're well prepared.
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