Typical Quora stuff, many answers limit themselves to light as in the visible spectrum but of course the entire electromagnetic spectrum and gravity for that matter are there in the "darkness". That story BTW sounds like nonsense, "The interocitor the aliens gave me was destroyed in a fire so I can't make any more magic contact goop".
From edge.org's 2012 question: WHAT IS YOUR FAVORITE DEEP, ELEGANT, OR BEAUTIFUL EXPLANATION?
Nicholas A. Christakis: Physician and Social Scientist, Yale University; Co-author, Connected: The Surprising Power of Our Social Networks and How They Shape Our Lives
"Out of the Mouths of Babes, or, Why is the Sky Blue?
My favorite explanation is one that I sought as a boy. It is the explanation for why the sky is blue. It's a question every toddler asks, but it is also one that most great scientists since the time of Aristotle, including da Vinci, Newton, Kepler, Descartes, Euler, and even Einstein, have asked.
One of the things I like most about this explanation—beyond the simplicity and overtness of the question itself—is how long it took to arrive at correctly, how many centuries of effort, and how many branches of science it involves.
Unlike other everyday phenomena, such as the rising and setting sun, the color of the sky did not elicit much myth-making, even by the Greeks or Chinese. There were few non-scientific explanations for its color. It took a while for the azure sky to be problematized, but, when it was, it kept our (scientific) attention. How could the atmosphere be colored when the air before our faces is not?
Aristotle is the first, so far as we know, to ask the question about why the sky is blue, in the treatise On Colors; his answer is that the air close at hand is clear and the deep air of the sky is blue the same way a thin layer of water is clear but a deep well of water looks black. This idea was still being echoed in the 13th century by Roger Bacon. Kepler too reinvented a similar explanation, arguing that the air merely looks colorless because the tint of its color is so faint when in a thin layer. But none of them offered an explanation for the blueness of the atmosphere. So the question actually has two, related parts: why the sky has any color, and why it has a blue color.
In the Codex Leicester, Leonardo da Vinci, writing after 1508, noted, "I say that the blue which is seen in the atmosphere is not its own color, but is caused by the heated moisture having evaporated into the most minute, imperceptible particle, which beams of the solar rays attract and cause to seem luminous against the deep, intense darkness of the region of fire that forms a covering above them." Alas, Leonardo does not actually say why these particles should be blue either.
Isaac Newton contributed, both by asking why the sky was blue, and also by demonstrating, through his pathbreaking experiments with refraction, that white light could be decomposed into its constituent colors.
Many now-forgotten and many still-remembered scientists since Newton joined in. What might refract more blue light towards our eyes? In 1760, the mathematician Leonhard Euler speculated on the wave theory of light helping to explain why the sky is blue. The 19th century saw a flurry of experiments and observations of all sorts, from expeditions to mountaintops for observation to elaborate efforts to recreate the blue sky in a bottle—as chronicled in Peter Pesic's wonderful book, Sky in a Bottle. Countless careful observations of blueness in different locations, different altitudes, different times, were made, including with bespoke devices known as cyanometers. Horace-Benedict de Saussure invented the first cyanometer in 1789. His version had 53 sections with varying shades of blue arranged in a circle. Saussure correctly reasoned that something suspended in the air must be responsible for the blue color.
Indeed, for a very long time, it had been suspected that something in the air modified the light and made it appear blue. Eventually it was realized that it was the air itself that did this, that the very gaseous molecules that make up air itself are essential to making it appear blue. And so, the blueness of the sky is connected to the discovery of the physical reality of atoms. The color of the sky is deeply connected to atomic theory, and even to Avogadro's number! And this in turn attracted Einstein's attention in the period from 1905 to 1910.
So, the sky is blue because the incident light interacts with the gas molecules in the air in such as fashion that more of the light in the blue part of the spectrum is scattered, reaching our eyes on the surface of the planet. All the frequencies of the incident light can be scattered this way, but the high-frequency (short wavelength) blue is scattered more than the lower frequencies in a process known as Rayleigh scattering, described in the 1870's. John William Strutt, Lord Rayleigh, who also won the Nobel Prize in physics in 1904 for the discovery of argon, demonstrated that, when the wavelength of the light is on the same order as the size of the gas molecules, the intensity of scattered light varies inversely with the fourth power of its wavelength. Shorter wavelengths like blue (and violet) are scattered more than longer ones. It's as if all the molecules in the air preferentially glow blue, which is what we then see everywhere around us.
Yet, the sky should appear violet since violet light is scattered even more than blue light. But the sky does not appear violet to us because of the final, biological part of the puzzle, which is the way our eyes are designed: they are more sensitive to blue than violet light.
The explanation for why the sky is blue involves so much of the natural sciences: the colors within the visual spectrum, the wave nature of light, the angle at which sunlight hits the atmosphere, the mathematics of scattering, the size of nitrogen and oxygen molecules, and even the way human eyes perceive color. It's most of science in a question that a young child can ask.
"
Edge.org
I know you were joking ...
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Do we see the sky as blue, because blue is calming to us? (Why our eyes are more sensitive to it)
We're most sensitive in the green actually. 🙂
Color vision - Wikipedia
(Vision is so cool!)
There's some interesting language stuff around descriptions of color, but Rayleigh scattering does the blue midday, red ends of day. Pretty fascinating bit of physics. Does require some Maxwell Equations though. (please don't make me derive it)
http://www.physics.ohio-state.edu/~jay/657/blue.pdf
Color vision - Wikipedia
(Vision is so cool!)
There's some interesting language stuff around descriptions of color, but Rayleigh scattering does the blue midday, red ends of day. Pretty fascinating bit of physics. Does require some Maxwell Equations though. (please don't make me derive it)
http://www.physics.ohio-state.edu/~jay/657/blue.pdf
Sigh....
Another dead guy... Rayleigh.
Jn
Around and around we go..
Next, some guy will start spouting fermi velocity vs conductivity....
Jn
Another dead guy... Rayleigh.
Jn
Around and around we go..
Next, some guy will start spouting fermi velocity vs conductivity....
Jn
Nah but we could talk about propagation in a conductor with a defect such as a crack or noncunductive impurity.
I know this post is pretty ancient but I've just come across it and thought I could offer some insight. The first thing to understand is the method being used to produce a sound wave is different to the conventional one. They refer to their method as digital sound reconstruction, which essentially is combining the pressure produced by each micro driver in a particular sequence that reconstructs the sound wave required directly from a digital signal (so no DAC or amp required, or enclosure for that matter). A single micro driver can therefore create more pressure as on it's own it doesn't have to match the input signal. There's also something about the size of them that results in them producing ten times more pressure than what is typically expected. They break all this down in these videos:
YouTube
YouTube
I am not sure what 'directional' means. but cable construction can make the sound different one way vs the other. Shield at one end only, for example.
defect of crimp or contact may be like a diode in harmonic generation? diode effect changes with cable/connection direction??
I know its a stretch.
-RNM
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Anybody aware of any matter that has the speed of light? Higgs mechanism anomaly or failure? Or we have a new type of massless and/or volumeless matter? Or perhaps new definition we are not aware of.
It is not obvious (at least for some) that the absence of electron (a hole) propagates not at the same speed of an electron in semiconductors.
How does conciousness generate the universe, brain included?
😀 Murky water discussion.
Also pointless? Is it a problem for the scientific community to accept that some things will probably never be known?
There is no 'hole'* (except black ones ;-). There are photons (or electrons) or absence of them.
The time the last photon has took to hit your eyes or your censor is the time the "darkness" that follows ...has traveled.
...if my understanding of those mysterious laws of the universe is correct ;-)
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I have two radiation damaged diodes. One measures 4.2 volts at one amp, it's diffusion mate two inches away on the same brazed assembly measures 1.8 volts, both at room.
When I put them in liquid nitrogen, the 4.2 volt unit measures 1.9 volts at five amps, the other 1.5 volts.
Odd, I would have expected both to go up as temp goes down.😕
Any ideas?
Next is liquid helium.
Jn
When I put them in liquid nitrogen, the 4.2 volt unit measures 1.9 volts at five amps, the other 1.5 volts.
Odd, I would have expected both to go up as temp goes down.😕
Any ideas?
Next is liquid helium.
Jn
I don't think there is any fundamental reason why matter particles may not be massless. Until recently it was believed that neutrinos were massless.indra1 said:
No problem with neutrino mass but it can't travel at the exact speed of light. Because the neutrino mass (which is still unknown and only known through difference of squares related to the different flavours) its speed will be less than the speed of light. It might be a ridiculously small difference but that is and it is fundamental difference! Otherwise relativity is contradicted which cannot be because it represents the foundations....
No idea, does the damage increase the series resistance (which might have an opposite TC)?
This is from Bell Labs in the 60's when they were still worried about serious radiation damage to semiconductors. 😉
http://www.dtic.mil/dtic/tr/fulltext/u2/650195.pdf
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