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Infrared and visible light, plus radio, UV, microwave, x-ray and gamma radiation are all electromagnetic waves at different frequencies. So they are all also photons with different energies.
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That confuses me, as photons have mass. Also, the concept of light being a magnetic wave is new.
Any good tips on reading-material?
Bastard Programmer from Hell 
"If you just follow the bacon Eddy, wherever it leads you, then you won't have to think about politics." -- Some Bell.
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Thank you; added both to list, bought one. 
Bastard Programmer from Hell
"If you just follow the bacon Eddy, wherever it leads you, then you won't have to think about politics." -- Some Bell.
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Photons don't have mass. If they did, they couldn't travel at the speed of light.
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StarNamer@work wrote: Photons don't have mass. If they did, they couldn't travel at the speed of light.
Well, particles have mass. Somewhat more special than neutrinos?
"Photons are traditionally said to be massless. This is a figure of speech that physicists use"
What is the mass of a photon?[^]
Bastard Programmer from Hell
"If you just follow the bacon Eddy, wherever it leads you, then you won't have to think about politics." -- Some Bell.
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Years ago, I did postgraduate research in Nuclear Physics, hence I use the shorthand most physicists use.
The article you linked puts an upper limit on the rest mass of the photon at 7 x 10^(-17) eV which is about 1.2 x 10^(-49) gm.
Also, I can't recommend any books since this is all just stuff I learned 50 years ago and keep updated by reading the odd article.
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Sure, look up thermoelectric. The short explanation is there are certain materials when bonded together have an electrical barrier on the layer between the materials. The hot side is generally where the heat energy causes electrons to break away from atoms of the material and the cold side is where the electrons want to flow to. When the material absorbs enough IR energy the electrons from the hot side have enough energy to cross the barrier and enter the cooler side (they don't have enough energy to cross back over). They gather there and are available to use as an electric current. The Voyager 1 and 2 space craft have been using thermoelectric power for last 45+ years.
I honestly am quite skeptical that there would enough of a difference in the hot and cold side of the system that was represented in the article that showed them using the heat radiated at away to space. It only seemed to be a few degrees C, even given that space is very, very cold. You still need a hot side that supplies enough kinetic energy to rip the electrons from their orbits around the atoms of the material and send them across the barrier to collect on the cold side.
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Converting decaying plutonium?
So, it is using a fuel, not just relying on the cold of space to provide power?
Bastard Programmer from Hell
"If you just follow the bacon Eddy, wherever it leads you, then you won't have to think about politics." -- Some Bell.
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yes, that is true. However, the cold of space is the other half of the generator. The decaying plutonium provides the heat source and space is the cold side. There is no generation of power from the cold of space. It is the heat sink necessary for the thermoelectric effect. The article title was poorly chosen. The net effect of their patented emitter material was a 5 degree C drop in temperature with the narrow band IR emitter. This is simply not enough of a temperature difference to generate power. It can enhance terrestrial HVac systems though. I believe that is what that Sky... company was using it for.
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For Voyager, decaying plutonium provides the "hot" side, space provides the "cold" side; otherwise, the only source of heat would be how warm the craft was when it launched!
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jschell wrote: Is there something in that to insure that it actually 'reaches' space?
Yes.
As the article mentions, the radiation frequencies are chosen such that the atmosphere is completely transparent to the radiation. Hence it doesn't interact with the atmosphere and does actually radiate into space.
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StarNamer@work wrote: the radiation frequencies are chosen
Chosen?
https://www.skycoolsystems.com/technology/[^]
"The film reflects sunlight to prevent the panels from heating up during the day"
No choosing on that one. And the atmosphere does absorb sunlight.
"and also emits infrared heat to the cold sky"
Now that one is unclear to me and perhaps what you are referring to.
However infrared is in fact absorbed to some degree by the atmosphere.
And where exactly is the infrared coming from? Best I can suppose is it just moving it from the building (inside) to the outside. But that depends on how it moves and there will be a loss factor (not stated.)
Then that page also states the following
"When fully replacing an air conditioning system, we expect an 80% to 90% energy reduction for cooling."
If true then I don't understand why acceptance would not be instantaneous? That would cut total US energy needs by 8%.
Frequently Asked Questions (FAQs) - U.S. Energy Information Administration (EIA)[^]
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jschell wrote: Chosen?
From https://spectrum.ieee.org/energy-from-cold
Within the mid-infrared range, which is where heat radiation from typical earthbound objects is concentrated, the most applicable atmospheric transmission band is in the 8- to 13-micrometer-wavelength range.
Glass is a great material for an emitter. Its atomic vibrations couple strongly to radiation around the 10-μm wavelength, forcing the material to emit much of its heat radiation within the transmission window
So the material is chosen such that it's radiation frequency is in the transmission window, effectively choosing the frequency.
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There is no such thing as a "cold radiator". Heat always flows from the high temperature to the lower.
It might be possible to use the night sky as a heat sink for cooling (the radiator is hotter than the night sky), but that also seems like "handwavium" (love that word).
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.
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jschell wrote: Far as I can see the system is using heat radiation (versus conduction and convection) to disperse the heat. Is there something in that to insure that it actually 'reaches' space? Versus of course just being absorbed into the atmosphere?
One way to think of it is like an infrared pigment that has a "color" that matches up with the most transparent color range of the atmosphere, so that the substance deviates a little bit from a blackbody spectrum.
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I'm looking for an article I saw but did not keep. Every developer should read it. If you happen to know a link to it, I'd appreciate it.
I logged into Github after not being there for a while and for some reason it took me to an article in a repository by someone with a name starting with a 'Z'. I was thinking "what is this" and had some trouble getting to my home page, so I read it. I didn't really register it at the time, but it was amazing. It largely said that almost everything we've been told about programming best practices leads to excessive "cognitive load", meaning our minds are getting kicked by the intellectual demands. I've known this for a while, especially with the demands of cloud, security and DevOps.
I also liked it because it described practices I have done for decades, but never much admit to because they are not popular... I write really complicated stuff and need all the help I can get.
Consider, if I'm right, it popped up because the Github folks, very smart people, though that developers should see it. I agree.
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I read the article and, to me, seems like a long winded way to say "Everything should be made as simple as possible but not simpler" (an aphorism often attributed to Einstein). Each individual example can be ascribed to the "yes, but..." category: "Prefer composition over inheritance: yes, but...", "Too many small functions: yes, but...".
Conclusion: I'm still not sold to any particular design philosophy. There are many tools out there, pick the one best fitted for your job.
Mircea
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That's the one. Thanks a lot.
The more I thought about it, the more I liked it.
I did search on cognitive load and it didn't lead me to it.
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That github article makes a lot of sense about Cognitive Load.
Here's the flaw in it related to developers:
If you admit to having cognitive load while viewing some architectural phenomenon that most of the other team understands (because they use it every day) those developers will treat you as if you are dumb.
"Well, I understand it. It all makes sense to me," says lead dev while looking around the group and other followers nod their little heads.
So, unfortunately, no one says this stuff out loud.
Long ago (2002), we had a dev contractor working on a component for a web site.
He got a bit mixed up on understanding web session and how to handle it.
Some others got involved and everyone was confused.
They finally worked it out but it took them an extra week on a project running late already.
At the Post-Mortem, Dev Manager said, "Well, we know there are things we don't know."
"what don't we know," asked Dev contractor.
"Well, like the issues with session. We need to know more about that."
The dev contractor replied, "What don't we know about session? Ask me anything and I'll tell you the answer."
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raddevus wrote: So, unfortunately, no one says this stuff out loud.
I do. Annoys the h*** out of people when I tell them it doesn't make any sense.
At one company a contractor that one of the owners liked was brought in to solve problems. No idea what problems because I never saw anything he suggested (and company paid for) used.
But in one meeting he presented a solution that would handle several million users logged into the system at once. I sat through most of that, then question why he decided we would need that problem solved - specifically where he came up with millions of users. He answered by claiming that that was outside of my need to know space. Fortunately one of the other owners was also in that meeting and he immediately piped up to state that he wanted to know that also. The Consultant kind of nervously looked around and side stepped by suggesting he would send it later.
I never saw it.
At some point I sized the application using existing business data. From that if the application owned the entire market it would never have more than about 3,000 users. And most of them would never be using it constantly.
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I've never seen the article, but I have seen tools that purport to measure the "cognitive load" of functions.
I don't put a lot of stock in them because that metric simply doesn't work for me.
I have a neurological condition that leads to my short term memory being very unreliable.
As such, I tend to use a very large screen (55" at 4k), make my functions longer, and see as much code on the screen at once as I can. Lots of little functions means I have to remember how to call them and it slows me down and introduces bugs.
For me that's a much worse problem then being faced by a complicated function with a relatively simple calling footprint. So I tend to load my functions up with functionality. Why make 4 functions to do something when 1 will suffice?
I usually split off functions mostly to avoid duplicating code.
It's a Bad Practice(TM) that leads to functions with "high cognitive load" but it works around my particular disability, so those metrics be damned - they don't take my particular brain wiring into account.
Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix
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Github _IS_A_ Cognitive Load, in my opinion. 
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I've managed to survive on work that I liked ... The longest I've been "forced" to learn something I didn't need was 1 week (Java, Swing, Struts, Eclipse, Net Beans, Apache, JBoss, etc.) ... then they came to their senses (.Net).
"Before entering on an understanding, I have meditated for a long time, and have foreseen what might happen. It is not genius which reveals to me suddenly, secretly, what I have to say or to do in a circumstance unexpected by other people; it is reflection, it is meditation." - Napoleon I
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