8 ms·

Depth of Field

89 points by moultano 5y ago

amelius 5y ago
What does "understanding" mean in this context?
- InCityDreams 5y ago
  Being able to visualise, and thereby.....comprehend?
  - amelius 5y ago
    But "comprehend" and "understand" mean the same thing.
    - dylan604 5y ago
      eh, maybe? I understand that a quadrillion dollars is a large number, but I don't comprehend exactly how large of a pile of cash that would be (assuming Benjamins and not Jacksons).
      - macintux 5y ago
        I think, at least in common vernacular, they are indeed different when placed side by side, much like “listen” vs “hear”.
        dylan604 5y ago
        or "hear" and "comprehend" being the same. Take the phrase "they don't hear that well". Does that mean they cannot actualy hear based on volumes and noise or some sort of hearing problem? Or does that mean they can "hear" just fine but don't comprehend what they are being told? Or that they do comprehend it just fine, but just don't like it being told to them? Now we're getting into idioms territory and less about definition of words and why have two words with the same, but different, meanings.
        daniel-cussen 5y ago
        When people actually talk about quadrillion dollars, I no longer listen, I only hear.
        dylan604 5y ago
        I hear that's common in the world of the peasants. Those of use in the 5 Commas club enjoy those reminders, as we try to comprehend what it would be like to have so little. It's beyond our understanding though
    - InCityDreams 5y ago
      And that was my point. I understand those numbers better as i have a better visualisation of them. We are going to a beach tomorrow. There are trees behind us. My kid, and his friends, have a better idea of the stars than ever before - they'll be even more impressed at the beach.
      - dylan604 5y ago
        I always liked the idea of "Look at all of the land you can see around you. That's just a fraction of the land. Of all of the land on Earth, it is just a fraction of the surface. The rest is water." From a kid's perspective, water just got huge.
- omnicognate 5y ago
  It means distinguishing intuitively between these particular large numbers and other large numbers. Once you get into the trillions, quadrillions, etc., it can be tricky to get a sense of the scale vs other large numbers that may sound similarly impressive but differ by orders of magnitude. These examples show that a quadrillion is smaller than I would have imagined without thinking about it, and I found they helped to get an intuitive sense of the scale.
hilbert42 5y ago
I don't think we should try, when scale is this large we should wonder and marvel in the numinous of this existence.
- omnicognate 5y ago
  Why not both?
mywacaday 5y ago
Deep field was pointed at an "empty" piece of space, what would the number be in the most populous piece of space?
- issa 5y ago
  Space at the scale being discussed here is uniform, so no one direction should be "more populous" than another. The "empty" here designates an area without stars easily visible from Earth. Our local area is denser in our galactic plane, in the direction of our supercluster, etc. But 13 billion lightyears in ANY direction should look about the same.
- supernova87a 5y ago
  One of the key findings of astronomy / cosmology of the modern age is that the universe is exactly so uniform in all directions, at the largest scales. In a way this is support for the notion of the big bang itself. There are density differences at some distance scales which have to do with clumping of matter (galaxies) as it began forming, but those differences are not a notion of "the universe being different depending on where you look". Funny how every subdivision / suburb looks kind of the same in the shape of the roads, density of houses. It is the nature of the laws that govern how these things get built. Btw, you could see a lot more stars (not galaxies) if you pointed the telescope in certain directions, but likely that would be because you're just looking at the direction of our own galaxy (which we're at the relative edge of), instead of looking out of our galaxy to see the rest of the universe, which is made up of the kinds of places shown in these images. These images are chosen to be taken in a direction far from our galaxy's disc (thing of us as sitting on the edge of a frisbee), because if you aimed at the disc, your image would be full of the giant overwhelming circles with spikes rather than tiny grains of sand, each of which is a galaxy far far away.
alecbz 5y ago
What exactly makes the light from these distant galaxies so “weak” that we need to point the telescope there for months to see it? Like, isn’t there a constant stream of photons? How does just waiting longer for them make them show up if they wouldn’t have otherwise? Are things blocking most of the photons? Things from within the galaxies they’re coming from, or things in between the galaxy and the telescope? edit: Ah, I suppose the further an object is the fewer photons from it are making it to the telescope, and so we need to wait longer for enough photons to arrive to be able to distinguish it from the random background noise on our end?
- photoGrant 5y ago
  Yes, it's called NOISE!
  - alecbz 5y ago
    But what specifically is it? Just random stuff in deep space between galaxies? I’d have thought most of the space between galaxies is mostly truly empty.
    - site-packages1 5y ago
      Isn't the paradox that if the universe is static in size or shrinking, eventually all the light would fill the sky into a blinding display, rather than dark. So it's a function of the universe expanding. https://en.wikipedia.org/wiki/Olbers%27_paradox https://en.wikipedia.org/wiki/Olbers%27_paradox
    - nprecup 5y ago
      The noise is inherent to our sensor technology... Very sensitive telescopes are cryogenically cooled to reduce the temperature of the focal plane, reducing the noise. As in an above comment, the light from distant objects is more spread out and appears weaker - fewer photos are arriving each second and hitting the focal plane than if the telescope were closer. At a certain point, the signal gets buried in the noise. I worked on the BICEP Array telescope at the south Pole - the light we are observing is actually extremely low energy and we can't see it unless our detectors are colder than the light source we are looking at (which is about 2.7K). We cool our detectors to 0.3K!
andybak 5y ago
If anyone missed it, the last paragraph is of interest in its own right.
whoisburbansky 5y ago
Pretty nifty how the example images of things like the sand grains (but make it Deep-Field-y) were made. I was hoping for an explanation, and the author didn’t disappoint.
- moultano 5y ago
  If you're interested in AI art, I've made a few more things built out of a series of generated images around a theme. https://moultano.wordpress.com/2021/08/23/doorways/ https://moultano.wordpress.com/2021/08/23/doorways/ https://moultano.wordpress.com/2021/07/20/tour-of-the-sacred-library/ https://moultano.wordpress.com/2021/07/20/tour-of-the-sacred...
  - copperx 5y ago
    I need this in my life; it would be great to create engaging lectures. Is there anything like MidJourney but public?
    - moultano 5y ago
      Nothing super user friendly. Most of the things people make right now are via various Google Colab notebooks. https://twitter.com/rivershavewings/status/1427580354651586562?lang=en https://twitter.com/rivershavewings/status/14275803546515865... https://colab.research.google.com/drive/1go6YwMFe5MX6XM9tv-cnQiSTU50N9EeT?fbclid=IwAR30ZqxIJG0-2wDukRydFA3jU5OpLHrlC_Sg1iRXqmoTkEhaJtHdRi6H7AI#scrollTo=CppIQlPhhwhs https://colab.research.google.com/drive/1go6YwMFe5MX6XM9tv-c...
      - refulgentis 5y ago
        GP, the links above are far out of date, you want reddit.com/r/discodiffusion and the Disco Diffusion v4.1 (note: I'm specifically saying 4.1 instead of 5.0, focused more on animation and trades off quality for speed of frame generation) They're very, very, easy to use if you have any familiarity with coding. The hard part is patience. Midjourney is (hand-waving) a Discord UI on top of that. Again, hand-waving, there's some secret sauce Midjourney does that makes it more likely to recognize your prompt. I assume they swapped out a model somewhere with one they trained on a wider variety of images
bobcostas55 5y ago
What causes that particular starburst pattern in the James Webb telescope image?
- zasdffaa 5y ago
  Search 'diffraction spikes' IIRC
- Aengeuad 5y ago
  The struts of the secondary mirror cause diffraction spikes on all 18 segments which combine to give the final pattern seen, the horizontal spikes are caused specifically by the top strut in particular. This video mostly covers how JWST was focused but from 01:15-04:00 it has an excellent of how the pattern is formed. https://www.youtube.com/watch?v=cWXTy_GeCis https://www.youtube.com/watch?v=cWXTy_GeCis
thriftwy 5y ago
Just a century ago, people thought there's infinitely many stars. Any real number of stars pales in comparison. It's not hard to think of a criteria where only a handful of stars in observable universe will fit. Or even none at all (but non-zero chance of).
frereubu 5y ago
I often think about these kinds of numbers when talking with my father-in-law, who's a marine geologist, and who regularly talks about time in millions of years. I wonder if he has a real grasp of the scale of what that means, in the same way that I might understand hours / days / months / years / decades. The only way he can explain it to me is by metaphor, which is what this post does. It's sort-of-effective, but what it mainly does it prove to me how little I comprehend numbers like that. I find even centuries are a little difficult to wrap my head around.
- DiggyJohnson 5y ago
  I think the answer is necessarily: he does and doesn’t. Analogy is probably the only way to try and make these numbers concrete, but he can develop a stronger intuition and respect for the time scale with domain experience.
gumby 5y ago
> The oldest of the photons that ended their life in the electronics of the Hubble had traveled from their birth star across the universe for 13.2 billion years. These photons had already completed half of their journey when the earth coalesced. Somehow this made me think of playing a video game in which you’re trying to steer between a bunch of obstacles and one magically grows right in your path.

Depth of Field

89 points by moultano 5y ago

amelius 5y ago

What does "understanding" mean in this context?

InCityDreams 5y ago
Being able to visualise, and thereby.....comprehend?
- amelius 5y ago
  But "comprehend" and "understand" mean the same thing.
  - dylan604 5y ago
    eh, maybe? I understand that a quadrillion dollars is a large number, but I don't comprehend exactly how large of a pile of cash that would be (assuming Benjamins and not Jacksons).
    - macintux 5y ago
      I think, at least in common vernacular, they are indeed different when placed side by side, much like “listen” vs “hear”.
      - dylan604 5y ago
        or "hear" and "comprehend" being the same. Take the phrase "they don't hear that well". Does that mean they cannot actualy hear based on volumes and noise or some sort of hearing problem? Or does that mean they can "hear" just fine but don't comprehend what they are being told? Or that they do comprehend it just fine, but just don't like it being told to them? Now we're getting into idioms territory and less about definition of words and why have two words with the same, but different, meanings.
      - daniel-cussen 5y ago
        When people actually talk about quadrillion dollars, I no longer listen, I only hear.
        dylan604 5y ago
        I hear that's common in the world of the peasants. Those of use in the 5 Commas club enjoy those reminders, as we try to comprehend what it would be like to have so little. It's beyond our understanding though
  - InCityDreams 5y ago
    And that was my point. I understand those numbers better as i have a better visualisation of them. We are going to a beach tomorrow. There are trees behind us. My kid, and his friends, have a better idea of the stars than ever before - they'll be even more impressed at the beach.
    - dylan604 5y ago
      I always liked the idea of "Look at all of the land you can see around you. That's just a fraction of the land. Of all of the land on Earth, it is just a fraction of the surface. The rest is water." From a kid's perspective, water just got huge.
omnicognate 5y ago
It means distinguishing intuitively between these particular large numbers and other large numbers. Once you get into the trillions, quadrillions, etc., it can be tricky to get a sense of the scale vs other large numbers that may sound similarly impressive but differ by orders of magnitude. These examples show that a quadrillion is smaller than I would have imagined without thinking about it, and I found they helped to get an intuitive sense of the scale.

hilbert42 5y ago

I don't think we should try, when scale is this large we should wonder and marvel in the numinous of this existence.

omnicognate 5y ago
Why not both?

mywacaday 5y ago

Deep field was pointed at an "empty" piece of space, what would the number be in the most populous piece of space?

issa 5y ago
Space at the scale being discussed here is uniform, so no one direction should be "more populous" than another. The "empty" here designates an area without stars easily visible from Earth. Our local area is denser in our galactic plane, in the direction of our supercluster, etc. But 13 billion lightyears in ANY direction should look about the same.
supernova87a 5y ago
One of the key findings of astronomy / cosmology of the modern age is that the universe is exactly so uniform in all directions, at the largest scales. In a way this is support for the notion of the big bang itself. There are density differences at some distance scales which have to do with clumping of matter (galaxies) as it began forming, but those differences are not a notion of "the universe being different depending on where you look". Funny how every subdivision / suburb looks kind of the same in the shape of the roads, density of houses. It is the nature of the laws that govern how these things get built. Btw, you could see a lot more stars (not galaxies) if you pointed the telescope in certain directions, but likely that would be because you're just looking at the direction of our own galaxy (which we're at the relative edge of), instead of looking out of our galaxy to see the rest of the universe, which is made up of the kinds of places shown in these images. These images are chosen to be taken in a direction far from our galaxy's disc (thing of us as sitting on the edge of a frisbee), because if you aimed at the disc, your image would be full of the giant overwhelming circles with spikes rather than tiny grains of sand, each of which is a galaxy far far away.

alecbz 5y ago

What exactly makes the light from these distant galaxies so “weak” that we need to point the telescope there for months to see it? Like, isn’t there a constant stream of photons? How does just waiting longer for them make them show up if they wouldn’t have otherwise? Are things blocking most of the photons? Things from within the galaxies they’re coming from, or things in between the galaxy and the telescope? edit: Ah, I suppose the further an object is the fewer photons from it are making it to the telescope, and so we need to wait longer for enough photons to arrive to be able to distinguish it from the random background noise on our end?

photoGrant 5y ago
Yes, it's called NOISE!
- alecbz 5y ago
  But what specifically is it? Just random stuff in deep space between galaxies? I’d have thought most of the space between galaxies is mostly truly empty.
  - site-packages1 5y ago
    Isn't the paradox that if the universe is static in size or shrinking, eventually all the light would fill the sky into a blinding display, rather than dark. So it's a function of the universe expanding. https://en.wikipedia.org/wiki/Olbers%27_paradox https://en.wikipedia.org/wiki/Olbers%27_paradox
  - nprecup 5y ago
    The noise is inherent to our sensor technology... Very sensitive telescopes are cryogenically cooled to reduce the temperature of the focal plane, reducing the noise. As in an above comment, the light from distant objects is more spread out and appears weaker - fewer photos are arriving each second and hitting the focal plane than if the telescope were closer. At a certain point, the signal gets buried in the noise. I worked on the BICEP Array telescope at the south Pole - the light we are observing is actually extremely low energy and we can't see it unless our detectors are colder than the light source we are looking at (which is about 2.7K). We cool our detectors to 0.3K!

andybak 5y ago

If anyone missed it, the last paragraph is of interest in its own right.

whoisburbansky 5y ago

Pretty nifty how the example images of things like the sand grains (but make it Deep-Field-y) were made. I was hoping for an explanation, and the author didn’t disappoint.

moultano 5y ago
If you're interested in AI art, I've made a few more things built out of a series of generated images around a theme. https://moultano.wordpress.com/2021/08/23/doorways/ https://moultano.wordpress.com/2021/08/23/doorways/ https://moultano.wordpress.com/2021/07/20/tour-of-the-sacred-library/ https://moultano.wordpress.com/2021/07/20/tour-of-the-sacred...
- copperx 5y ago
  I need this in my life; it would be great to create engaging lectures. Is there anything like MidJourney but public?
  - moultano 5y ago
    Nothing super user friendly. Most of the things people make right now are via various Google Colab notebooks. https://twitter.com/rivershavewings/status/1427580354651586562?lang=en https://twitter.com/rivershavewings/status/14275803546515865... https://colab.research.google.com/drive/1go6YwMFe5MX6XM9tv-cnQiSTU50N9EeT?fbclid=IwAR30ZqxIJG0-2wDukRydFA3jU5OpLHrlC_Sg1iRXqmoTkEhaJtHdRi6H7AI#scrollTo=CppIQlPhhwhs https://colab.research.google.com/drive/1go6YwMFe5MX6XM9tv-c...
    - refulgentis 5y ago
      GP, the links above are far out of date, you want reddit.com/r/discodiffusion and the Disco Diffusion v4.1 (note: I'm specifically saying 4.1 instead of 5.0, focused more on animation and trades off quality for speed of frame generation) They're very, very, easy to use if you have any familiarity with coding. The hard part is patience. Midjourney is (hand-waving) a Discord UI on top of that. Again, hand-waving, there's some secret sauce Midjourney does that makes it more likely to recognize your prompt. I assume they swapped out a model somewhere with one they trained on a wider variety of images

bobcostas55 5y ago

What causes that particular starburst pattern in the James Webb telescope image?

zasdffaa 5y ago
Search 'diffraction spikes' IIRC
Aengeuad 5y ago
The struts of the secondary mirror cause diffraction spikes on all 18 segments which combine to give the final pattern seen, the horizontal spikes are caused specifically by the top strut in particular. This video mostly covers how JWST was focused but from 01:15-04:00 it has an excellent of how the pattern is formed. https://www.youtube.com/watch?v=cWXTy_GeCis https://www.youtube.com/watch?v=cWXTy_GeCis

thriftwy 5y ago

Just a century ago, people thought there's infinitely many stars. Any real number of stars pales in comparison. It's not hard to think of a criteria where only a handful of stars in observable universe will fit. Or even none at all (but non-zero chance of).

frereubu 5y ago

I often think about these kinds of numbers when talking with my father-in-law, who's a marine geologist, and who regularly talks about time in millions of years. I wonder if he has a real grasp of the scale of what that means, in the same way that I might understand hours / days / months / years / decades. The only way he can explain it to me is by metaphor, which is what this post does. It's sort-of-effective, but what it mainly does it prove to me how little I comprehend numbers like that. I find even centuries are a little difficult to wrap my head around.

DiggyJohnson 5y ago
I think the answer is necessarily: he does and doesn’t. Analogy is probably the only way to try and make these numbers concrete, but he can develop a stronger intuition and respect for the time scale with domain experience.

gumby 5y ago

> The oldest of the photons that ended their life in the electronics of the Hubble had traveled from their birth star across the universe for 13.2 billion years. These photons had already completed half of their journey when the earth coalesced. Somehow this made me think of playing a video game in which you’re trying to steer between a bunch of obstacles and one magically grows right in your path.