371–380 of 517 posts
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I'm not american but still enjoyed the landing very much. They sent a freaking nuclear-powered jeep to the surface of another planet, they can gloat all they want.
I'm not saying anything bad about the landing. It was a great feat. I just find the chanting often done in US videos disgusting.
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My argument is a mm is too fine in that situation. 1/8ths and 1/16ths are ideal when working at those scales. In reality I use both systems all the time. It’s situational. > When I hear anything past about 1/8th of an inch my brain shuts down, and I give up. Realistically, same. 32nds don’t get used outside of some specialty wrenches. 16ths are a practical limit where other scales start to make more sense. Probably m…
So 3 mm is a weird measure but 1/8 of an inch is just perfect? You are like those guys who say that Fahrenheit is better because it feels "more natural and obvious"
I use both systems.
I do prefer Fahrenheit for HVAC (and weather) because it’s higher resolution and has reasonable values at human scales. Thermostats that lack half-degrees-c are never quite right IMO.
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It’s unfortunate that fractional measurements and the base size of units get conflated. Maybe metric users do use fractions and I just don’t hear about it. Is that table one and a quarter meters high?
There's something just right about 1/16th of an inch. About the same as a millimeter, and easy to do math with... it is weird though 1/8th, centimeter is hard to conceive, for me anyway. When more precision is needed, so easy to go to the 32nd
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Yes. Any one of these things would be a massive boon to our understanding of life throughout the solar system and broader universe, right down even to here on Earth. All three of them would arguably mark a new era in Earth's history.
we are very screwed if they find life on Mars. It means life is incredibly common and thus the Great Filter theory is true and we only have a few years left as a species most likely.
Or we're just ahead of the curve.
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From the JPL feed: "My computer was having trouble with Webex, I'll restart Webex and try the visualization again." Hope Percy isn't running Webex.
I mean, I'd be pretty impressed if NASA managed to get Webex to run on a 133MHz PowerPC CPU and 128MB of RAM.
EDIT: It's a 200mhz CPU alongside 256mb of ram. https://mars.nasa.gov/mars2020/spacecraft/rover/brains/
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we are very screwed if they find life on Mars. It means life is incredibly common and thus the Great Filter theory is true and we only have a few years left as a species most likely.
I find it extremely hard to believe you could kill every human being on earth at this point. We’ve reached critical mass, we aren’t going anywhere. When we had that few thousand individuals population bottleneck in the past was when it was dicey. What sort of event could kill every human and end our species? I can only think of planet-wide extinction events like massive asteroid impacts that sterilized the whole eart…
Yeah, but those individuals were presumably all in pretty close proximity to one another. If we were left with a few thousand individuals across the entire range of the human-inhabited Earth, we'd have one heck of a time continuing as a species.
In any case, the risk of an extinction event on Earth is exactly why I believe space colonization needs to be Priority Zero for humanity, from two different angles:
1. Living beyond Earth means that we as a species are that much more resilient against a literal-Earth-shattering catastrophe (and if we can get the bulk of Earth's current/future population off of Earth, then we might very well be able to avoid a couple different plausible extinction events).
2. If we can colonize entirely inhospitable worlds like Mars or the Moon (or my votes, Ceres, Venus, and Enceladus), then "colonizing" Earth is easy-peasy-lemon-squeezy even if it does become Venus 2: Greenhouse Boogaloo.
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would dust stay in the air longer or shorter than on Earth? also is it technically correct to call the Martian atmosphere "air"?
Yes, but it's not technically correct to call Martian seismic tremors "earthquakes". https://www.imdb.com/title/tt0080745/goofs Flash Gordon (1980) Goofs At the very beginning of the film, Ming and his henchman are discussing "an obscure body in the SK system", which the inhabitants refer to as the planet "Earth", pronounced as if the word is completely foreign to them. However, at that moment, Ming activates a butto…
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S/he already did. We just don't know yet.
You can just say "they". (Not trying to be judgy. People just seem to forget about the gender neutral use of "they".)
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Other posters have pointed out that it's the hazard avoidance camera, but they haven't said why the hazard avoidance camera is black and white. When you do computer vision, the first step you do is convert your color image into a black and white image, and run your CV algorithms on the black and white image. This is because when you're looking at objects and shapes and stuff, it's contrast that tells you where the bo…
Thank you for the explanation. That was highly interesting. Does anyone else know if the human eye does perceive color directly? Is this at all technically possible? And if yes, why aren't we doing it with cameras?
The human eye has four basic cell types, rod cells and cone cells, and there are three subtypes of cones, short, medium, and long. The three subtypes of cone cells sense blue, green, and red light more or less directly. Medium and long cone cells, which directly detect green and red light, almost entirely overlap. [0] It is more accurate to say that long cone cells detect yellow light than it is to say it detects red light. There is a brain system which measures the difference in response between the long (red) and medium (green) cells and uses the difference to say "aha! this must be red!"
The ratio of short (blue) medium (green) and long (red (yellow)) cone cells are roughly 2%, 2/3, and 1/3. The cells in your eye which detect blue light are more or less a rounding error. The cells which detect green light are roughly twice as numerous as the cells which detect red (well, yellow) light. If you see a thing and think, "man, that's awfully blue," it's not because your eyes are telling you "hey, this thing is awfully blue". The "blue" signal is barely noticeable in the overall signal; but your brain jacks up its responsiveness to the minuscule blue signal.
One of the side effects of the completely fucked ratios between the three types of cones is that your perception of the overall brightness of a thing is mostly down to how green it is. This shows up in lots of standards; NTSC, JPEG, the whole nine yards. If you've ever implemented a conversion between RGB and any luminosity-chroma colorspace (YUV, YCbCr, YIQ, NTSC, any of them) there's a moment where you'll go "wait a minute this doesn't make any fucking sense". You look at the numbers and the luminosity channel is just... green, and you know that the other two chroma channels are quartered in resolution. And you'll think that makes no sense. But that's how it works.
Then you'll remember that color sensors have their pixels arranged in groups of four, with two green, one red, and one blue channel. There must be some green conspiracy.
And there is. It's your brain. It's your eyeballs with 2/3 of its cone cells being green sensitive ones.
Those are your cone cells. Rod cells are entirely different. It's trivial to say well, cone cells see color, rod cells see black and white, but it's more complicated than that. Rod cells are excellent in low light conditions, cone cells not so much. Cone cells see motion very well, rod cells not so much. Cone cells can discern fine detail, rod cells do not. Rods and cones are not evenly distributed across the retina either; cone cells are densely packed in the center, rod cells are more common in peripheral vision.
Look at a colorful thing directly; take a note of how colorful it is. Now look away from it, so it's only in your peripheral vision; take a note of how colorful it is. Does it seem just as colorful? It isn't. That's your brain fucking with you. Your brain knows it's in your peripheral vision and all the colors are muted out there, so your brain exaggerates the colorfulness. Cone cells are 30 times as dense in the center of your vision as they are just outside the center of your vision. [1] That's why you can read a word directly where you're looking but it's very difficult to read elsewhere.
The reality is that your retinas give a fucking mess of bullshit to your brain, and the brain is the most incredible image processing system conceivable. It takes bullshit that makes no damn sense and -- holy shit I forgot to talk about blind spots.
Ok, so your rods and cones have a light sensitive thing, with a wire in the back, and all the wires get bundled up in the optic nerve that goes to the brain. Here's the thing: they're fucking plugged in backwards. The wires go forward, and are bundled up between your retinas and the stuff you're looking at. The big fat optic nerve therefore constitutes a large chunk of your vision where you can't see anything. Your brain just.. invents stuff where the optic nerve burrows through your retina.
Other weird stuff. If it's bright, the rods and cones send no signal, if it's dark, they send a strong signal. It's inverted. There's apparently a very good reason for this but I don't remember what it is. Also, the rods continuously produce a light sensitive substance that amplifies the light sensitivity but is destroyed in the process. It takes a long time to build up a reserve. This is why it takes time to "build up" your dark vision, and why it's so easily destroyed by lighting a cigarette. The physiology of "ow it's bright" as opposed to "it's bright" isn't just on your retinas, it's also on your eyelids and your iris, but more importantly, it's shared between your two eyes. This is why closing one eye makes it less painful when you go from a dark place to a bright place.
The point is, the study of human vision is not the study of the human eye. The study of human vision is the study of the human brain.
Much of what we do with color spaces and image compression is dictated by our stupid smart eyeballs and our stupid smart brains. Video codecs compress with 4:2:0 chroma subsampling because the brain's gonna decompress that shit better than a computer can anyway. Cameras have twice as many green sensitive pixels as blur or red pixels because the eye resolution is much sharper in green than other colors. More advanced image and video compression schemes will try harder to account for human eye-brain physiology.
[0] https://upload.wikimedia.org/wikipedia/commons/0/04/Cone-fun...
[1] https://upload.wikimedia.org/wikipedia/commons/3/3c/Human_ph...
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Can’t talk to the statute mile, but the nautical mile is sublime: one minute of latitude. The amount of math you can do in your head with a system with so many factors of 2, 3, and 5 is truly amazing.
I'm not aware of any tricks to make mile calculations easier but the fractional scale common with the inch is very useful for real-world mental calculation and practical exchange. Effectively everything is powers of two. Got something between 1/4 and 1/2 inch? Great, use 1/8ths. It's three. Not close enough? How about five 16ths? It infinitely scales to provide another unit that is suited to the measurement at hand.…
People who use metric units are perfectly happy rounding to the nearest 0.5cm or 0.25cm if that's what's needed, exactly as people do with inches. Why on earth would you imagine people use mm if something doesn't call for them?
