What are things you never understood.

[Alain De Vos]

- My specialty is calculating diffusion of electrons in semiconductors , as such i never understood quantum mechanics. But then who does.
- I never understood light. Is it a particle , is it a wave , is it both , is it none. Time does not exist for light . And then it has mass zero.

On programming,
- I never understood what is a monad.
- Java , i never understood inversion of control.



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Sidenote about light, if i was a photon,


1. Your Clock Would Be Frozen
Because photons travel at the speed of light

(c), time dilation reaches a theoretical limit of infinity.

• The "Zero Time" Paradox: Your clock would never tick. From your perspective, you are emitted and absorbed at the exact same instant.
• Instantaneous Travel: Even if you travel across the entire observable universe (a journey of billions of years from an external observer's view), for you, no time passes at all.

2. Your Meter Sticks Would Shrink to Zero
Length contraction also reaches an extreme at the speed of light.

• No Distance: The universe in your direction of travel would contract to zero length.
• Immediate Contact: Because the distance between your starting point and destination is contracted to nothing, you don't "travel" through space so much as you exist at both points simultaneously.

3. The "Non-Existent" Perspective
Physicists often note that a photon technically has no frame of reference.

• No Rest: In physics, a "perspective" requires a rest frame—a state where you see yourself as stationary. Since light is never at rest and always moves at
  cc
  for all observers, you cannot "sit" on a photon and look around.
• Mathematical Divergence: If you try to plug
  v=cv equals c
  into the standard equations of relativity (the Lorentz factor), you end up dividing by zero, which produces "mathematical nonsense" rather than a usable physical viewpoint.

In short, to a photon, the universe is timeless and dimensionless. You would not see a world "passing by" with your meter sticks; instead, your entire existence would be a single, instantaneous link between two points in space.

 

[doul]

What are things you never understood ? humain being.​

But then who does.

Me

I never understood light. Is it a particle , is it a wave , is it both , is it none.

That's because you're confusing the object or the fact—call it what you will—with the physical/mathematical model. Nature doesn't need models to function; humans need models to understand nature. Depending on the case and the desired precision, an applicable model is chosen.

 

[loveydovey]

I never understood

You are on the right track

But first things first. There are so many more questions that need to be asked and need to be answered. For example, do you understand why such a deadly habit like tobacco smoking is legal everywhere?

 

[Alain De Vos]

Indeed. But then just like Richard Feynmann would say, just do the math.
A very easy question is this. Try to imagine in your brain a 4-D object. No matter how hard you try you can't.
Yet space-time is a 4-D object.
A Fourier transform is an object with infine dimensions.
Or try to imagine curved-spacetime due to gravity

 

[Crivens]

Or try to imagine curved-spacetime

That can be done, but be prepared not to get all of your mind back after this. A part of it will find it much more fun to keep wandering.

 

[bgavin]

Women.
It took decades of study but at the end of my life time, I understand enough to get by.

 

[Zare]

- Java , i never understood inversion of control.

Dependency injection in Java allows easy decoupling of interfaces and code, which is important in enterprise context.

It allows something like Spring to easily plug in whatever it needs to do the brunt of the work.

When you do this, it's good to keep the mindset that you're not writing an application. You're writing pluggable code pieces to be consumed by Spring. That is the way, because you want Spring to do the lifting and boilerplate.

 

[ralphbsz]

i never understood quantum mechanics. But then who does.

I don't. Even though I passed the QM1, QM2, QFT1, QFT2 and GR classes in physics, and got a doctorate.

Is it a particle , is it a wave , is it both , is it none.

Yes.

Time does not exist for light

Only true in a mathematical sense. The better answer is: the whole concept of "passage of time" is not applicable to a thing of zero mass, because that thing can not have any internal mechanism to keep track of time, or know concepts like "yesterday, all my troubles were so far away".

if i was a photon,

You can't be. You have mass. You have a functioning brain, which can distinguish "happened earlier" from "happening now" from "may happen in the future". You may remember what you had for breakfast. A photon, by definition (being massless) doesn't have any of these things. Trying to reason about things that require dividing by zero is pointless.

On inversion of control: There are many aspects of that. One of them happens when a low-level function (probably in a low-level class) which was called from a high-level function (or class) calls the high-level class back. If you are using parallelism (and who isn't these days), that screams deadlock and race condition.

 

[Jose]

- Java , i never understood inversion of control.

Maybe this will help. I was once faced with the following problem:

• Our system depended on a very large store of small to medium binary files
• I had to test reads and writes from and to this store in a test environment
• The test writes should never, ever appear in the production store
• We could not afford to replicate the entire store in the test environment

What I did in essence was write a test reader/writer that had exactly the same interface as the production reader/writer. However, it diverted all writes to a test store. It tried all reads in the test store first, and fell back to calling the production reader for any misses.

The test reader/writer was injected into the system in the test environment. The production reader/writer was injected in the prod environment.

This is strictly a violation of the "test what you deploy and deploy what you test" principle, but by abstracting all of the read/write code I was able to reduce most of the change to a configuration value. The test environment exercised all of the read code and almost all of the write code.

Women.
It took decades of study but at the end of my life time, I understand enough to get by.

A labour of love!

 

[Alain De Vos]

Gone read this tomorrow

 

[Crivens]

Women.
It took decades of study but at the end of my life time, I understand enough to get by.

And once you get it, they call a secret meeting and change the rules. And Al Bundy says that is for the better.

What I don't understand is how people can be smart as a person but dumb as a brick as a collective.

 

[eternal_noob]

Why people kill each other.

 

[drhowarddrfine]

Even though I passed the QM1, QM2, QFT1, QFT2 and GR classes in physics, and got a doctorate.

Not to embarrass Ralph but, about a year ago, I stumbled onto a paper online and made the connection. It's good to have you here.

 

[Paul Floyd]

I've never had a good metaphorical mental model of how bipolar junction transistors work.

In calculus, the lack of systematic way approach integration bothered me. Then in complex analysis finding contour integrals bothered me to another dimension.

I wish that I understood much better how krylov subspace methods work.

 

[doul]

I've never had a good metaphorical mental model of how bipolar junction transistors work.

MOSFET transistors are much simpler to understand because we can use the hydraulic analogy; the MOSFET is simply a channel that can be opened or closed. The image is simple but accurate enough. The bipolar transistor is much more complex because its operation relies on the size, shape, and doping density of the regions. The counterintuitive thing is that current control is due to minority carriers, another thing that doesn't help is this totally false image that we see everywhere with three equal NPN or PNP zones.

A medium valued analogy is a narrow Venturi tube where the base is a controlled leak, open no current, partially open linear mode, closed saturation.

A more accurate analogy is a triode vacuum tube :

Vacuum tube ​	Bipolar transistor​
Hot cathode	Heavily doped emitter
Electron emission	Carrier injection
Gate	base
Gate current (low)	base current
Anode	collector
Electric field	Base-collector junction

 

[Paul Floyd]

MOSFET transistors are much simpler to understand because we can use the hydraulic analogy; the MOSFET is simply a channel that can be opened or closed. The image is simple but accurate enough. The bipolar transistor is much more complex because its operation relies on the size, shape, and doping density of the regions. The counterintuitive thing is that current control is due to minority carriers, another thing that doesn't help is this totally false image that we see everywhere with three equal NPN or PNP zones.

A medium valued analogy is a narrow Venturi tube where the base is a controlled leak, open no current, partially open linear mode, closed saturation.

I've always imagined it as being like a siphon, but was never sure if that is the best analogy.

 

[fmc000]

Politics, specifically one side (which I'm not going to mention of course).
People paying for sex.
Religious wars.
Conspiracy theorists.
Social media addiction in general.

And probably many more...

 

[Alain De Vos]

Interesting.But too bad guidelines don't allow me to go deeper into politics of sex.
Recently i was in a train station, everybody watching his smartphone. I was the only person just looking around. Looking at addicts

 

[Maturin]

Looking at addicts

Zombies.

 

[Crivens]

Zombies.

We call them "Smombies", some place even has the pedestrian traffic lights at the curb so they see them...

 

[fmc000]

Today at lunch I was with my mother and my brother and we were watching the news about the tragedy that happened in Crans-Montana. We were astonished seeing those kids filming their possible death with their smartphone instead of just fleeing the discotheque. As parents of young girls I and my brother are seriously concerned by this social media addiction.

 

[Maturin]

Today at lunch I was with my mother and my brother and we were watching the news about the tragedy that happened in Crans-Montana. We were astonished seeing those kids filming their possible death with their smartphone instead of just fleeing the discotheque. As parents of young girls I and my brother are seriously concerned by this social media addiction.

Yeah. Please, don't get us started with this tragedy. Best you can take out from it, is to see how quickly international help was provided. Actually humans stick together as a team. This needs to be seen, and not listen to some few egoistic assholes who want to drive wedges between humans, seduce them with their snake poison, only to satisfy their neverending greed, and personal bitterness.

But your point also bothers me for a long time.
When 2004 the tsunami hit the coast, some people didn't ran away but took a picture of it. I actually saw a video made with a cellphone directly from the shore line of the approaching wave until the camera drowned under water and the picture went black. The cell phone was found, of course. Its owner not. I couldn't help myself, but I just could only laugh, and rate this for a Darwin Award. But I think that's not really funny anymore, because people are so addicted to their smartphones, so tempted to "document, preservere their lifes" (instead of just live and enjoy it as it is. it's not a show. but life is live.) - feed youtube/WhatsApp/'The Cloud'/whatever (What does Google [or others] earn with videos made by people dying taking it?) - for such a long time that you simply cannot accuse them for their own stupidity anymore. As we also have those "TikTok"-discussions, and social media bans in schools, and countries we really need to reconsider of what we have done to our society.

And what can be done to steer in another direction.
For my part, I don't have no smartphone anymore.
This may not be the one and only solution, but maybe a way to keep options, to preserve other ways of life than having everything bound to that little mobile computer thingy, controlled by a few greedy companies.

 

[Zare]

Politics, specifically one side (which I'm not going to mention of course).
People paying for sex.
Religious wars.
Conspiracy theorists.
Social media addiction in general.

And probably many more...

There were a lot of conspiracy theories that came out as conspiracies in practice.
I'm not talking about hyper-popular ones like moon landing, WTC, COVID, etc, those are plain stupid, but ones that make sense from the get go, turn out to be true. Like Iraq not having WMDs, MKULTRA stuff, and so on.

Actually saying that USA has started some of these conflicts partially or wholly due to oil, back then could label you as 'conspiracy guy'.

Or better example would be that car industry is pulling strings of various world governments. It is nowhere-near 'theory', it is in practice, Volkswagen affair for instance, and the difference between French approach of high speed railway infrastructure vs German, where Germany had 'input' from automotive 'industry leaders' who 'supported' using high speed trains on normal tracks, in turn gimping the whole high speed transit thing.

And it is tied to your first point, politics. In my opinion, conspiracy theories appear when there are real conspiracies at hand, to muddy the waters, to present a mirage, a spin. For example I do believe the pandemic was real of course but lockdown happened as a staging, test to see how population in developed world will respond to a wide crisis...which is happening right now in geopolitical sense. Fact that covid/lockdown came to 'end' over night when first Russian troopers entered Ukraine plays along with my opinion.

I also dislike specifically one side. A conspiracy that I believe in, is that side is fueling extremism and violence on the 'our' side directly, funding, supporting, publicizing. As a sort of a embrace, extend, extinguish tactic.