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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?

#191

1. Carbon dating. Sure, I get that carbon decays over time and this changes the proportion of isotopes. But why does this give you any information? That carbon didn’t come into existence just to be in that bone, it was made in the sun billions of years before that, so why does the age of the carbon tell us anything about organic matter? The key fact, which I think is not emphasized enough, is that the ratio of isotop…

Carbon dating can't say anything about dinosaurs (in the colloquial definition) because dinosaurs went extinct >>50k years ago and CD doesn't work after such long time spans.

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

#192

Earlier quoted context omitted.

I started to read the first one but his insistence that Many Worlds is true was too frustrating. Many Worlds Theorem seems specifically useful at saying "the variables aren't hidden because everything before wavefunction collapses actually plays out in different worlds. But, we specifically have no way of proving that theory. So now we're back to the essence of the original question - if these things seem random why…

Well, I'd recommend to read the whole series. It's not so bad as it sounds. There are so many steps from where you are to appreciating the utter weirdness of Bell's experimental result. Not the weirdness of any theory (or an interpretation, which Many Worlds actually is) but of the basic experimental result. If you are properly amazed by it, rejecting MWI or any crazy-ish borderline-conspiracy theory seems suddenly a…

To be clear, I don't reject Many Worlds at all and in fact consider it a promising candidate due to it sort of "falling out" of the Schrodinger's equations taken literally unless you add complexity.

But the fact remains that it is impossible to prove and it is conveniently well equipped to handle this situation. I'd prefer an argument that presupposes the Copenhagen interpretation as that is when my intuition fails.

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

#193
post #146

Earlier quoted context omitted.

This is definitely related, though not the whole story. Quantization did get rid of some infinities, but as GP kind of states, it also introduced others. My comment focuses on what we do for those.

> In the limit of d -> 0, the energy released -> infinity. I believe the poster's general premise to be false. While renormalization may be useful in resolving infinities in general, I don't think it's necessary for this one. You can't commute the dp*dx of a Hamiltonian to be zero in a quantized world, so if gravity has quantum properties, you don't need to worry about what happens when d -> 0. There is no "0" distan…

I guess, but it depends on how one parses the poster's setup. You're correct that for particles interacting under a 1/r^2 force, the energy turns out finite in quantum mechanics. My comment was referring to the fact that once you quantize the field that gives rise to that force, the infinities return, but for a different reason.

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

#194

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…

I recommend Computerphile's videos https://www.youtube.com/playlist?list=PLzg3FkRs7fcRJLgCmpy3o....

I had the same "problem" as you. What finally made me feel I sort of cracked it was those videos. The way I think of it now is: They let you do matrix multiplication. The internal state of the computer is the matrix, and the input is a vector, where each element is represented by a qubit. The elements can have any value 0 to 1, but in the output vector of the multiplication, they are collapsed into 0 or 1. You then run it many times to get statistical data on the output to be able to pinpoint the output values more closely.

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

#195

What happens when you actually fall inside a black hole and what is the singularity. I never really understood what happened really when the guy fell inside it in Interstellar and how come he started seeing all those photos. I just accepted it as Hollywood bs. I know my question is based on a movie but would still like to know what will someone witness (assuming of course they somehow live)

> I never really understood what happened really when the guy fell inside it in Interstellar and how come he started seeing all those photos. I just accepted it as Hollywood bs.

Coupled with people saying "but they had scientists on staff! they talked with scientists that makes it so cool and accurate, lets ignore that other part"

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

#196

Why does time slow down/go faster with movement compared to another object. The well known example that if you travel into space you'd gain let's say 5 years and people on earth 25 in the same time or so. I just don't get it and I can't find any logic explanation. For instance: Two twins who came to live exactly at the same moment in the year 2000 and both die on their 75th birthday at the same time. One travels into…

Just to nitpick for a second, you shouldn't feel compelled to believe something because "it's Einstein's point." Francis Bacon established the foundation of the scientific method when he argued that knowledge means the ability to predict or create some effect reliably. Now you probably do not have the ability to test special relativity experimentally, but you can read about the many successful predictions and applications derived from it. You shouldn't feel like you just "have to believe it," though.

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

#197
post #76

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 (?!?).

Aerospace engineer here:

What a lot of people don't know is that the wings are actually installed on a small upward incline, relative to the longitudinal axis of the body. Think of holding your hand out the window of a moving car, and then tilting your hand to catch air under your palm. In aerospace we call this the Angle of Incidence, and most aircraft have a small amount, usually in the 1-5 degree range. So while you might be walking on a perfectly horizontal path as you go to the bathroom over the Atlantic on your way to Paris, the wings keeping you aloft are actually angled such that the leading edge is higher than the trailing edge by a small amount.

Now google any picture of an airfoil and notice that many of them are slightly concave on the underside. This is called Camber, and in a nutshell it creates a "cupping" effect under the wing that intensifies the high-pressure area under the wing and correspondingly increases the amount of air deflected downward. Additionally, the teardrop shape reduces the tendency of air to billow off the trailing edge of the wing in favour of kinda sticking to the wing's surface and following its curvature. This also causes downwash off the trailing edge (i.e. more air going downward, which is a good thing).

That's really all there is to it, from a high level. The wings deflect air downward such that the total momentum change causes an upward force that is exactly equal to the aircraft's weight, and that equilibrium of forces keeps the aircraft aloft.

Obviously it gets more complex than that, because guys spend entire PhD careers researching edge cases, but there's no magic involved.

Note that wings don't have to be of the classic teardrop shape. There are plenty of research papers about lift forces on flat plates. In fact that's classic fodder for an undergraduate assignment. The airfoil shape is beneficial in several ways, some of them quite subtle, but you can think of the airfoil as being the most efficient cross-section for a wing known to science, whereas a flat plate is much less efficient (though it still works).

>I even heard we don't completely understand why it works (?!?).

I don't think that's true. For a while there was the meme about "science says bumblebees shouldn't be able to fly" but that was a clickbait headline because we didn't know enough about the structure and motion of bumblebee wings. That's about all I can think of.

There are certainly areas of ongoing research and exploration (I'm thinking hypersonic flight, novel means of propulsion, aeroelastic structures, etc.) but in general, the physics behind conventional aircraft are quite well-understood.

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

#198

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…

I had an aha moment with quantum computers a few months ago when reading an article that explained it as probability distributions. I don't think I have the complete understanding in my mind anymore and I wish I had saved the article, but looking into how quantum computers essentially serve as probability distribution crunching machines might help with your understanding.

So can they still do traditional deterministic(?) calculations? Or would that be somewhat akin to using machine learning to do your taxes; possible but just overkill?

I've often heard it said that Quantum Computers can crack cryptographic keys by trying all the possible inputs for a hashing algorithm or something handwavey like that. Are they just spitting out "probable" solutions then? Do you still have to try a handful of the solutions manually just to see which one works?

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

#200

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…

In short I'd say you need to understand the underlying mathematics to intuitively understand the operations that underpinn the algorithms. And since this is quantum mechanics...there's no real ELI5 version that can give you any useful understanding.
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