My experience with MathOverflow was funny, the first time I posted a question it was almost immediatly downvoted and criticized by the moderators. Later the same day, I was surprised when my question was answered by Terence Tao, then the moderators quickly changed their opinion and people started to upvote the question.
Mathematics even worse than Software Engineering because lay practitioner can miss significance of question. If you have link to question, would appreciate. Just out of curiosity to see if I would realize why question is interesting. That in itself is a skill.
At first glance I was trying to figure out what this is about but, so far nothing. It's "like caniuse but for email content", ok but, what is caniuse? I don't know if it is worth but, before launching something new, I wish everyone consider to publish a brief section to explain to the average person what this is about.
Here in Brazil we use a system with copper pipes in an insulated "box" to heat water during the day using this energy from the sun. A couple of years ago, in a cold winter day with a minimum of 5 degrees (celsius), just after the sunrise the water froze, broke the pipes and the glass above it. I couldn't understand what happened because the ambient temperature was above freezing point, maybe it was something like this effect?
Fascinating! That does seem like the most likely explanation.
This reminds me of the ancient ice ponds that made ice thousands of years ago in Persia. I read somewhere that they were able to make ice through a combination of radiative and evaporative cooling at night temperatures around the same as you experienced, about 5C.
Yes, I like this explanation, when that phenomenon happened in our house I thought one of our neighbours was dumb because he just put a blanket over the collector on the roof, as he said, "to keep it warm". But now I think he was right. Now, I don't know if this exists but it would be nice if there was a kind of glass that let radiation pass only to one side and not the other way, a kind of "valve", this could solve the problem of water frozing from radiation in our solar heating.
>Now, I don't know if this exists but it would be nice if there was a kind of glass that let radiation pass only to one side and not the other way, a kind of "valve", this could solve the problem of water frozing from radiation in our solar heating.
This doesn't exist and can't even in principle because it would be a fundamental violation of thermodynamics. Basically, it would be a Maxwell's demon for radiation that would allow you to arbitrarily reduce entropy.
But, it might be possible to have a material that has different characteristics at different temperatures, as long as it's symmetric. If it's nearly opaque to IR in its cold state, hopefully sunlight at dawn would warm it rapidly enough that it would automatically "shut off" on cold nights, and still "turn on" shortly after dawn even on cold days.
Yes I think that'd be ok. You'd basically just be taking advantage of the thermal gradient between the radiating body and the object being heated. It'd be analogous to adding more insulation as it heats up and removing insulation as it cools down.
You'd be slowing the flow of heat into your reservoir just as much as you'd be slowing down the loss of that heat later though.
You might still get some benefit in preventing freezing at the expense of needed a larger area to get the same amount of heat flow in to your water system though.
I don’t think maxwells demon is impossible, it just is a device for converting información to energy. In theory, many such devices may be possible for the conversion of information to both energy and matter. This seems like it might be support the simulation hypothesis.
The handwavey explanation in my head is that “ambient” for this emitter is not just the immediate physical environment, but also deep space, which is very very cold. This wouldn’t work if the temperature of space and the air were the same.
An emitter is also an absorber so if space were as hot as the emitter then it would not shed heat.
Yeah, on a clear night the pipes radiate heat to space but nothing much radiates the other way as space is cold and dark. It's also why the tops of cars get frosty on clear nights.
I like footnotes, or in this case maybe we should call "endnotes". David Foster Wallace was known to use them a lot, sometimes he would put footnotes in footnotes.
I don't know about law exam, but Brazil has more undergraduate courses in law than all the rest of the world combined, naturally this comes with a lot of shit univesities and that means a lot of people with a law degree but don't work in the field.
You can add medical schools to that list. Plenty of shitty doctors being minted too. Unable to diagnose myocardial infarction levels of shitty.
The government basically thinks "education good" and starts making lots of crappy schools as if it was going to magically turn the country into a super power. I've literally seen politicians citing how many schools they created as a talking point. The result is of course overqualified Uber drivers.
Beats over here where the government basically thinks "education bad" and starts making lots of schools crappy out of a realisation that anyone who can add two numbers together wont vote for them come election time.
The result is of course a population that isnt qualified to do anything but sit at home watching propaganda on tv.
Everything you described is also happening here. I just avoided mentioning it so as to avoid derailing the thread into brazilian politics.
Truth is the primary purpose of our schools is to be the main government indoctrination tool. I still remember the asinine "sociology" and "history" classes taught by a socialist feminist teacher. I was literally forced to agree with marxist nonsense in her tests or fail the class. It was so blatant as to be comical. This also shows up in our SAT equivalent as rules about "respecting human rights". They force you to pick the "correct" ideological answer. Wrote anything even remotely controversial in your essay? You're not making it into any university. Even if you do make it, they never stop. Imagine a question about proper terms for trangender people suddenly showing up in the middle of a mathematics test at university.
I have videos of primary school teachers teaching children to sing worker's party songs. I wish I was making this up.
Without a Raspberry Pi, at least you can use the wolfram engine for free [0] and integrate with your applications, although without all the benefits of the wolfram notebooks environment.
I get recommendations in scholar.google.com based on my profile and sometimes browse arxiv.org to see the latest submissions. Also, I can say that https://www.quantamagazine.org/ is very nice. Other than that, I just follow my favorite scientists through their personal blogs or social media.
