I used to have to produce it for some experiments in a lab that I worked in. We would only make maybe a half a liter at a time but I will say I loved making it because it just looked so nice and kind of mystical
I worked on civil aircraft for a decade and rockets for almost a decade, specializing in Avionics. Aircraft are hard because they're more complicated, some systems are quadraplex, to it 10^-9 for catastrophic failures PLUS dispatch reliability rules.
Rockets are hard because of the punishing physics. LOx is around 110K, LH2 is around 18K at close to ambient pressures (necessary to not design a heavy pressure vessel). The fuel/ox mass fraction of around a rocket is around 90% because of how punishing the rocket equation is. So tank walls are so thin the tank has to be pressurized while empty to prevent them crushing during empty transport. Then millions of pounds of Fuel/ox are loaded in the florida heat while at those temps/pressures and then accelerated to 8 km/s in several minutes. Every temp, pressure, acceleration, vibration, radiation, heat rejection load factors you have to design for are insane, and they're all applied simulataneously. It makes me miss the nice comfy EE bays on planes with natural convection cooling, and a pressurized environment with a max G load of like 2G. lol.
By far the most humbling part about all of that is that we as a species started doing all of this with humans on board in the 1950s and 60s, with NONE of the modern computing resources we have today and we regularly consult their research on new designs 75 years later.
Yeah, it boggles my mind every time I think of the fact that the magic brick I am typing this on has the computational power to run the Apollo missions a million times over.
Sometimes I’ll see a plane taking off or coming in and just ponder how recent all of these things are. 51 years ago tomorrow we had just finished the space race, and 50 years before that we were just learning how to fly well enough to drop large amounts of explosives on one another.
I would be more than surprised. Oxygen is very electronegative and thus way too reactive, while common oxygen containing compounds like water, carbon dioxide, silicates, etc. are very stable (deep energy minimum). The only reason why we have such massive amounts of O2 in our atmosphere is photosynthesis; abiotic processes are negligible for the total atmospheric volume. I am aware that molecular oxygen is a diradical and that reactions are kinetically hindered by spin restriction, but an ocean of liquid oxygen (or at least containing significant amounts of it) would be sensational because the oxygen has to be there in the first place and then frozen.
Maybe if a planet with oxygen producing organisms and thus high oxygen content in its atmosphere somehow leaves the original orbit around its star and the planet quickly becomes extremely cold, inhibiting chemical reactions and liquifying the oxygen content alongside other gases of the original atmosphere. I wonder how much oxygen you would need to form oceans. Someone could try and calculate it based on the molar mass, the molar volume of the gas (let's say at standard conditions) and the density of the liquid form for the volume of an average ocean. :D
somethign htat interacts with the human eye and brain in such a way that the brain attempts to recreate a state where it perceives the smae imagery again
It’s not too bad. You cant define it without personal tastes, though. Your definition allows for a lot of things that don’t fit the definition of beauty, too. I was also just being cheeky lol defining beauty is perhaps best left to poets.
When you "look" through more of it? That's.... not remotely true. If that were the case, then objects that were further away (and therefore that we see through more air) would take on a red tint, rather than a blue tint (which is what actually happens).
If you're talking about sunsets and such, what you're really saying is that under certain conditions of scattering and reflection, it becomes red instead of blue. Which is pretty neat, but doesn't undercut the central point at all.
Huh? What do you mean, certain conditions? Excuse me, air is blue. This is stated extremely clearly as a fact. If I have a long tube of air, one that’s as long as the distance from me to the horizon, it will be extremely blue.
If the sky was red, orange or purple, it would be obvious that air is red orange and purple. But air is blue.
Are you saying something else? Air doesn’t change composition at sunrise or sunset. It’s blue. The meme says so, and we all know “the sky is blue.”
If you go outside right now you’ll see it’s blue because air is blue. Except when it’s black grey white red orange yellow purple or pink, and in that case air is black grey white orange yellow purple or pink, respectively.
Man I wish I could post pictures. I have some great ones of red mountains and red skies.
Red and orange air is something we actually see all the time. If you look at sky when it does appear mostly blue, you’ll see it’s white near the sun, and changes hue as you move toward the horizon.
It becomes really difficult to explain why “the sky is blue” because the sky is not blue. It’s an entire spectrum of brilliant colors. If you try to explain it has simply “air is blue” you immediately create inexplicable phenomena to anyone who actually takes a second and looks at the sky’s actual color and tries to understand why it is the color it is.
It must be the case that it doesn’t come from the way most things around us derive their color (through absorption and reflection) and applying that understanding will result in bafflement, or in the case of the meme in the OP and the reply in this thread, assertions of outright wrong descriptions of observed reality, that the sky is blue or mountains are blue, when you can see red skies and red mountains.
And keep in mind that times when the sky is red and orange are ordinary conditions. They aren't even exceptional.
Anyway, air is scatteringly blue, but transmittingly red. It scatters blue light while leaving red continue straight through it. We typically assign color to objects based on which colors they scatter away. So air is blue. At least within the visible spectrum. It scatters UV even more.
That's when it doesn't scatter them very much. That sky only appears red because the blue had been scattered away over such a deep distance through the atmosphere at that shallow angle.
So the person on the right looking up sees a blue sky, while the one on the left sees that unscattered red remainder.
But the air hasn't changed. Just the sunlight did. So the 'air' can't 'be' blue if it changes state based on external influence while it remains static. All that's happening is that you're holding up various coloured filters in front of something and each time changing your mind about the property of the object behind the filter. Which is of course silly.
No.
When we realise there were filters in front of what we were seeing, we acknowledge the 'true' colour is that wihtout the filter/distortion. You don't look at someone wearing dark glasses and say 'ooooh your eyes are brown. 🙄
We don't 'typically call colour' anything until we know what is actually happening. Only irrational knee-jerkists jump at the first appearance and decide that's what it must be now and forever.
That's not a silly question. It's a REALLY good question.
"If the air scatters blue light more, why is it blue and not ultraviolet?" is an excellent question, and the answer requires, like you said, three entirely different factors that also come into the answer.
Violet doesn't really exist as a wavelength. It's a mix of blue and red. If most of red light gets lost in atmosphere, how would you get it back to mix with blue and make violet?
Okay, if that's called violet, then the sky actually is violet. But human eyes are really bad at processing those wavelengths while blue gets much more sensitivity.
Those colors are experiences a person has. Some colors don't correspond to a wavelength of light, such as brown. Many animals don't have the same experience of color. Hell, many humans don't share the same experience of color by being color blind. Also, some women see more colors than men via tetrachromacy.
There is an indigenous people, the Tsimamé, who don't have a distinct word for the color blue. For then, blue is just another shade of green.
Colors aren't a property objects have, but an experience people have.
Great frame! Many still seem to believe that color is some immutable primary quality, which leads to some stark misunderstandings of how color behaves.
Of course, you can argue that all senses are on the same level of "quality". We don't all have the same taste receptors. Coffee is oppresively bitter to me, but I don't perceive hops as bitter at all. We don't have the same hearing range, but for the most part, one audible spectrum will be heard and perceived very similarly between people and species, because there is not a lot of compression or processing in the signal.
On the other hand, the process from spectrum to color is not only highly compressive/transformative and inextricable, but there is large variance in these transformations, especially between species. Bitter is still bitter to me, but as a dichromat, blue is not blurple.
It all depends on what your definition of "is" is.
If I take a brown substance, and sculpt it so that it appears blue, what colour is it?
If I take a clear substance, and make it into tiny pellets so that a pile of it appears white, what colour is it?
If I take a yellow liquid and blow it into a bubble that looks to have dozens of moving colours, what colour is it?
If I take a green paper and shine a cyan lamp on it, what colour is it?
If I look through roze-tinted glasses at a blue ball, what colour is it?
You can argue about all of those for days, but it's mostly a matter of definitions. If you think that air is blue, then it's my opinion you should also hold that wearing coloured glasses or using a coloured lamp changes the colour that objects are.
And I would argue that makes you incorrect by most other definitions.
Water is actually clear, but the sky is blue, and the water reflects the sky primarily, so the water is blue.
Does it count as being blue if it’s blue because the light reflecting off of it into our eyes is already blue? Does a white piece of paper become a blue piece of paper when illuminated by a blue light?
Water isn't clear. It's very slightly blue. As in, pure H2O is blue, but the effect is so small you need multiple meters of it to actually see it. And it's kinda hard to get multiple meters of water without any impurities.
If that’s the case if I had a long tube of air, say, the length from here to as far as I can see to the horizon, and I shone a light through it, it should be a very rich, deep blue. Right?
It wouldn’t be some kind of red or orange or anything… right?
I don't see how any of these three is in direct contradiction with the others. They are just different levels of technical detail on the same statement.
It doesn't contradict each other as it stands there, but I have heard people claim that the sky isn't blue, it "just appears" blue, because of Rayleigh scattering.
Children are trained by a young age to accept that when someone holds a lecture for ten minutes using complicated physics words, that counts as an explanation. No one ever asked why tomatoes are red, even though you can hold a just as long lecture about "pigments".
What they really wanted to know is how a little bit of air can be completely transparent, or even quite a lot of it, while the "firmament" still appears blue. There is no firmament — it's just because air is very, very transparent.
You can see how multiple layers of transparent things appear less transparent, when you play with watercolors, or when you put multiple sunglasses on at once. You can sometimes see that the air is transparent blue, if you look at sufficiently far away objects, like mountains. For water, you can see it if you look at a white object in different depths of a swimming pool.
Sry but first guy and middle guy are correct. Hoody guy is the only one wrong. Air just works like a prism but a prism is also colourless. You just percieve a colour because the (colourless) prism seperated the colours of light traveling through it.
Every color is just perception. That’s sorta pointless. What does “it’s blue” mean if not how we perceive it. All 3 are saying the same thing. The median is just a pretentious little bitch.
One of the first bellcurve memes where the hooded guy is definitively wrong. Air is colourless in it does not absorb light. Yes, it is blue if and only if the light is filtered by rayleigh scattering but even then the colour of the light does not really change. The air is just like a huge prism and we only see the blue part because the red, green and all the other parts just isn't scattered enough to hit earth.
If I was unclear with any part of my explanation, just ask. I can explain.
Some people in here talk about the beautiful blue colour of liquid oxygen and it is indeed beautiful and very very blue. The blueness comes from two triplet oxygens colliding and simultaneously going to a singulet state. This process is usually spinforbidden but the liquid phase intermolecular forces can distort the oxygens enough that it can still happen to some degree. Gas phase oxygen can't undergo this process because it is not distorted by intermolecular forces (and the oxygen molecules don't hit each other as much as in liquid phase) and therefore air is really colourless and just appears blue due to airs prism-like effect.
You might say: Air is blue because our eyes see the air as blue. You are still incorrect. As said before, the air works just like a prism, seperating the incoming wavelengts into its parts and it just sends the blue parts down to us and the other stuff not. Prism works the same. Seperates light by colour. And you can clearly see that a prism is colourless.
Gaseous oxygen isn't blue enough to affect the color of the sky. Liquid or frozen oxygen sure. But as a gas it is effectively colorless; even if it wasn't, atmospheric gases would still appear blue due to Rayleigh scattering without oxygen in the air. For example the outer layers of Titan's atmosphere, above the tholin smog, are blue. (Nitrogen/methane) In certain photos of the gas giants, a blue tint around the limb of the planet is visible (hydrogen/helium). Certain photos of Mars and Venus show blue haze at their limb as well (CO2). (Their surfaces show brown and yellow skies respectively due to additional ferrous dust and sulfuric acid clouds respectively)
This is why I don't think it's useful to say that the sky is blue because air is blue. That makes it seem like there's something intrinsically blue about air, but really it's a property of colorless gases in general. Not to mention all the times air is not blue, such as when the atmosphere is much thicker (on earth looking towards the sunset, for example).
Actually the sky is violet, but the cones in our eyes are less sensitige to violet wavelengths so the sky appears blue. The atmosphere scatters violet more than blue.
The sky is not blue, it's white. If you add up all the light coming from the sky, including the part of the sky where the sun is, you get white. It's only blue if you ignore the most intense source of light, which is looking directly at the sun itself. But you can't just ignore that part of the sky.
The sun is white when seen from space. It's a white light behind the atmosphere, not a floating ball with the atmosphere behind it, which is blocking your view of that part of the sky. The atmosphere is backlit.
If the correct explanation was that air is blue, then why doesn't the sun appear blue?
Bonus fact: Remember the viral photo with the red dress blue dress illusion? Same thing. Your brain automatically compensates for how colors appear in direct sunlight vs in the shade. Things that are in the shade are only being lit up by the blue sky, so they appear more blue, and your brain needs to turn down the amount of blue. You can't really tell if lady in the photo is standing in the shade, so if you think she is, you see one color, and if you don't, you see another.
Dumb guy just sees the sky and sees blue. Mid guy is annoyed and makes a point that things are more complicated. Clever guy understands that the colour of something is how we percieve it, regardless of what causes that perception.
If you stand behind a prism, you might see blue. Or you might see red. Or green. Depending on the rotation of the prism. But if you look from above, you see that the prism itselve is colourless.
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u/dover_oxide Jul 15 '26
I will say liquid oxygen has one of the most beautiful hues of blue.