[HN Gopher] Stacked images of the comet, photobombed by Starlink...
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Stacked images of the comet, photobombed by Starlink satellites
Author : _Microft
Score : 188 points
Date : 2020-07-23 12:42 UTC (10 hours ago)
(HTM) web link (twitter.com)
(TXT) w3m dump (twitter.com)
| Nikkau wrote:
| It's bad faith, a normal stacking would have made them completely
| disappear, it's one of main reasons to do stacking, remove things
| which are not on all images, and it's works flawlessly.
|
| You have to actively tweak your settings to create this kind of
| photo.
| vilhelm_s wrote:
| I guess the most basic way to stack (just add the images
| together) would leave them in, but
|
| > Almost every modern astronomical post-processing program has
| a rejection process (sometimes referred to as sigma-reject) to
| remove unwanted signals, though the exact sequence will depend
| on which program you use.
|
| https://skyandtelescope.org/astronomy-blogs/imaging-foundati...
| woko wrote:
| From your link:
|
| > The way this process works is that, while averaging all of
| the pixels in a series of, say, 10 images, the program
| mathematically calculates which pixels fall far away from the
| mean value because they're much brighter (or much fainter)
| compared to the same pixels in other frames. The algorithm
| then discards those out-of-range pixel values so they don't
| affect the final image.
|
| Wouldn't this process remove part of the comet trails as well
| as the satellite trails?
|
| I mean, I get how it works if all you care about is
| relatively static like distant stars, but would it work for
| this specific use case?
| Sharlin wrote:
| No, because the comet does not perceptibly move in the sky
| during the acquisition. All comet pixels are present in
| every image.
| [deleted]
| _Microft wrote:
| The comet does not change but its position in the sky
| does btw. Longer exposure times turn points into streaks
| if the object is not tracked to compensate for this.
| CydeWeys wrote:
| This is true of every single object in the night sky, and
| is why an equatorial tracking mount is table stakes for
| good astrophotography.
| Sharlin wrote:
| Yes, I assumed tracking as it's basically a mandatory
| requirement when you do telephoto astrophotography, and
| definitely used in the OP photo. The alternative is to
| shoot wider angle and align the images during stacking,
| but either way you have to get your subject's pixels
| aligned or the result is just blur.
| godelzilla wrote:
| The real question is why anybody would do a time-lapse
| photo of the sky without spending thousands of dollars on
| telescope, tracking, and corrective software. Do people
| really expect ELon to stop making billions for their
| photos? Fix the pictures, not the sky!
| sixothree wrote:
| Take a look at this
|
| https://photoshoptrainingchannel.com/remove-tourists-
| stack-m...
| spacemark wrote:
| The most common algorithm to manage airplanes, satellites,
| hot pixels, and other undesired photons in astrophotos is a
| process called Kappa-Sigma Clipping. It essentially rejects
| pixel values from subframes in your image stack that fall
| outside a user-inputted deviation from the mean.
|
| In other words, the process works wonderfully to get rid of
| the starlink-emitted photons, but you lose that subframe's
| signal, lowering your signal to noise ratio. Not the end of
| the world. But inconvenient and sometimes costly to
| professional astronomers.
| CydeWeys wrote:
| Yeah, but what % of subframes (small portions of large
| images) are ruined by noise caused by moving objects? Way
| less than 1% I'd imagine. It's just not a big problem.
| And certainly not worth outlawing new satellite launches
| over.
| [deleted]
| ipsum2 wrote:
| > You have to actively tweak your settings to create this kind
| of photo.
|
| No, the most basic stacking is just to add the images together,
| resulting in trails. I don't see this as bad faith at all.
| dvxvd wrote:
| im 100% against that commercial project is destroying my night
| sky.. its like building highway through my yard.. our already
| overglobalized world will be even more 'globalized' in the hands
| of few.. w t f..
| Alupis wrote:
| I find it astounding that just any old for profit company can
| decide to ruin a world-wide public resource just to turn a few
| bucks. In 2020.
|
| I'd expect that from something like the East India Company in the
| 1700's or something. Not a modern company in a modern society.
| oh_sigh wrote:
| Do you shake your fist at every airplane that flies overhead
| too?
| Alupis wrote:
| The country agreed to that. One day the country may decide
| against it. No-Fly Zones can be created.
|
| A US company airplane passing over my house doesn't impact
| people in India, for example.
|
| Airplanes have proven utility. Airplanes proved their utility
| before bothering people worldwide.
| oh_sigh wrote:
| The country agreed to the starlink satellites as well,
| considering they received FCC approval.
|
| The country can still decide against it and now allow any
| more launches, and the satellites that are up there will
| come down naturally in a few years time. You may even be
| able to forcibly deorbit them if they still have propellant
| left (not sure if they do or not).
|
| No-fly zones are almost always created for the government
| to do government things, and not for the direct benefit of
| the public (ie reducing airport noise for nearby
| residents).
|
| A US plane passing over your house doesn't impact people in
| India either negatively or positively(except for the
| consequences of global warming). These satellites passing
| over the US and India can equally benefit people in the US
| and India. It's not like starlink is a US only service and
| SpaceX is going to prevent anyone in India from having
| access.
|
| Satellites also have proven utility, as does the internet,
| which is why groups like the UN General Assembly HRC
| declared access to the internet as a basic human right.
| throw_a_fay wrote:
| > It's not like starlink is a US only service and SpaceX
| is going to prevent anyone in India from having access.
|
| I'm not sure this is entirely true. SpaceX is US
| corporation. They could easily decide to deny access, or
| otherwise limit what people can do, based on policies set
| by the US government.
|
| See also, the GP post, referencing the East India
| Company.
|
| EDIT: The point here is not whether StarLink is a net
| benefit or not. It's that it's a predatory capture of
| resources, fuelled by capital and advantages, which won't
| be passed down, but have a good chance of being used for
| further leverage.
|
| EDIT2: I'm not against advancement, far from it, but if
| there are no tools to manage it, then we end up with oil
| companies again.
| Alupis wrote:
| What is not proven is if Starlink will work the way it's
| been sold to you as an idea. What is also no proven is if
| it can be profitable even if it does work. People in
| these remote places of the world are unlikely to be able
| to afford internet... not have a need or desire for it.
| They have other priorities.
|
| Not to mention there's already ways to get very high-
| speed internet to remote villages that want it. The only
| barrier is cost - but for motivated villages and/or
| governments, it's not very expensive ($10's of thousands
| up front cost, trivial long-term costs). I've sat in many
| conferences with people building out wireless networks in
| remote regions - very fascinating work.
|
| There's some pretty non-trivial chance Starlink was only
| approved because of the Cult of Elon.
|
| SpaceX wants to put 1,584 satellites in orbit[1] to the
| cost of around $10 Billion USD, and will need to replace
| these routinely due to orbital decay.
|
| There's only 2,666 satellites in orbit currently[2].
| 1,327 of which are from the US[2].
|
| Re: No fly zones - they can be established for all sorts
| of things. There's no fly zones around many amusement
| parks, for example, and not just because of the remote
| possibility of some terrorist attack.
|
| > UN General Assembly HRC declared access to the internet
| as a basic human right
|
| That seems simply to be virtue signaling. Of course
| everyone should have access to information and knowledge,
| but that's not exclusive to the internet.
|
| It costs money to provide internet access. Basic Human
| Rights don't cost money to exercise. The Right to be Free
| doesn't require a monthly payment to some mega-corp. If
| it did, you would not be free, would you?
|
| [1] https://en.wikipedia.org/wiki/Starlink
|
| [2] https://www.ucsusa.org/resources/satellite-
| database#:~:text=....
| ortusdux wrote:
| Each starlink group is inserted at a low orbit, booted up and
| tested, and then they boost themselves to a higher orbit over a
| period of a month or so. During this boost, they orient their
| panels horizontally to minimize drag. Once they reach their final
| orbit, they rotate their panels vertically, at which point their
| visibility goes way down (mag 5 (prior to the new coating) down
| from a mag 0).
|
| I've seen plenty of people saying some variation of "there are
| only 600 of these now, imagine what it will be like when there
| are 42k of them..." If I understand correctly, the number of
| bright satellites will be proportional to the launch rate, not
| the total quantity in orbit. Going off Wikipedia, they have
| launched about 1/8th of their 2024 goal, and the majority of the
| remaining satellites are destined for much higher (and dimmer)
| orbits.
|
| https://en.wikipedia.org/wiki/Starlink#Constellation_design_...
| Rebelgecko wrote:
| >If I understand correctly, the number of bright satellites
| will be proportional to the launch rate, not the total quantity
| in orbit.
|
| Because the constellation needs constant replenishment, the
| launch rate (and hence the # of brighter satellites) will have
| to reach a steady state that is directly proportional to the
| size of the constellation.
|
| We can extrapolate that in the future this rate will actually
| be _significantly_ higher than it is currently:
|
| They currently have permission to launch around 12,000 sats.
| They're launching around 250 per year. The current launch rate
| is only sustainable if each satellite lasts for _50 years_.
|
| If you expand that to the proposed 42,000 constellation, 250
| new satellites per year is only sustainable with a MTBF of
| around 150-200 years per satellite, which is nigh impossible in
| low Earth orbit. Using a lower (but still very generous and
| optimistic) MTBF of 10 years, Starlink will need to launch
| 4,200 satellites every year, about ~15x _higher_ their current
| launch cadence.
|
| > the majority of the remaining satellites are destined for
| much higher (and dimmer) orbit
|
| Just about all of the satellites they've orbited so far are
| hanging out around 550km. SpaceX initially got permission to go
| as high as 1300km, but they've since changed their mind. The
| new plan (still pending FCC approval I believe) is to keep all
| of the satellites between 300-550km. So the future satellites
| will be as low or lower than the current ones.
| ianmcgowan wrote:
| Apart from all the comments about this being a bad faith post, I
| wonder about the utilitarian argument, if you take it at face
| value. If you could provide decent internet at low cost to large
| parts of the world that are underserved, at the cost of ruining
| ground-based telescopes, is that a good trade-off? What if it's
| just certain kind of telescopes, or certain classes of
| astronomers (as this seems to be)?
| CydeWeys wrote:
| This exactly. Satellites are _incredibly_ useful and enable
| trillions of dollars of worldwide economic output that would
| not be possible otherwise. This is a very meaningful
| improvement in everyone 's lives. We should not stop using them
| simply because they are visible in the night sky, and make
| astrophotography a little bit harder (though not much harder --
| removing satellite streaks is a default enabled option in
| astrophotography image stacking software).
| marcus_holmes wrote:
| I think this is useful if we also consider that part of
| SpaceX's plan is to make launching satellites cheap (in fact,
| launching anything cheap). So while ground-based astronomy will
| suffer, space-based astronomy will get cheaper and easier.
|
| Presumably to the point where people who want to can subscribe
| to a Hubble-like satellite service and get all the space photos
| their hearts desire.
|
| Also, we made a similar trade-off a long time ago - most people
| live in heavily light-polluted cities, because we value having
| street lighting more than being able to see the stars.
| simion314 wrote:
| But now if we are forced to move all ground telescopes on
| space SpaceX will make profit so is a win-win for SpaceX and
| the public will have to pay to replace working satellites on
| the ground with expensive and smaller ones on space.
|
| We should be fair and acknowledge all the downsides, and if
| you disagree I would ask to waste a bit of effort and explain
| why we should ignore this costs on the public(maybe the costs
| are worth it in the long run but we should not ignore them)
| HeadsUpHigh wrote:
| Space telescopes are vastly superior to ground ones. There
| is no competition, imo the decreasing cost of launching
| will enable incredible telescopes in the future.
| kergonath wrote:
| It's funny how many people who know nothing about
| telescopes have been saying that recently...
| simion314 wrote:
| If you have same size yes but the issue in space you can
| send only smaller telescopes, this ones are inferior on
| some dimensions versus the big ones we have on high
| mountains on deserts but sure a small telescope in space
| is better then a same size on the ground.
|
| Let me know if somehow I am wrong and for example Hubble
| is superior to all telescopes on the ground at the time
| it was launched. The best thing is to have it all, giant
| telescope arrays on the ground, telescopes in orbit, on
| the moon, on the other side of the sun/
| DiogenesKynikos wrote:
| That's a bit like saying that forks are superior to
| knives. They're good at different things.
|
| Ground-based telescopes have a number of very significant
| advantages over space-based telescopes. You can build
| much larger and heavier telescopes and instruments on the
| ground. If you want to observe faint objects, you need
| more photons. To capture more photons, you need a larger
| primary mirror.
|
| Space-based telescopes used to give higher resolution,
| but adaptive optics undo much of that advantage. In fact,
| because the diffraction limit is dependent on the size of
| the primary mirror, ground-based telescopes can achieve
| _better_ resolution than space-based telescopes.
|
| You can attach large, heavy instruments, such as
| massively multiplexed spectrometers, to ground-based
| telescopes. And you can switch instruments out and do
| periodic upgrades and maintenance.
|
| Space-based telescopes have advantages in certain
| specific areas. They can observe wavelengths that Earth's
| atmosphere absorbs or emits at (such as the ultraviolet
| and infrared). They can achieve much better calibration,
| because there's no atmosphere to calibrate out. They can
| achieve high resolution _across a wide field of view_
| (adaptive optics negates the effects of the atmosphere in
| a small field of view). Sometimes you need these
| particular advantages, so space telescopes are critical.
| Often you don 't, and ground-based telescopes are
| superior.
| marcus_holmes wrote:
| disclaimer: I know almost nothing about telescopes.
|
| Isn't there a way of multiplexing lots of small
| telescopes together to gather more photons and
| effectively emulate a larger telescope in software?
|
| If so, could you launch 1000 small telescopes into space
| and effectively have a (set of <1000) larger
| telescope(s)?
| Gibbon1 wrote:
| Multiple mirror telescopes are a thing. They can be used
| to gather more light or increase the angular resolution.
|
| See European Southern Observatory's very large telescope.
| justapassenger wrote:
| Cost of launch is not really main reason why we don't see
| more space based astronomy.
|
| 1. Space is a hostile place, and developing telescope that
| works there is much harder. 2. There are very real limits on
| size and weight of what can be put there right now, and
| rocket equation is ruthless. 3. Any type of maintenance or
| upgrades are basically impossible, compared to earth based.
| 4. Adaptive optics were such a huge breakthrough, that
| basically negated need for most of space based telescopes.
| gpm wrote:
| I would call cost of launch to space the _main_ reason,
| just not the only significant one.
| TeMPOraL wrote:
| Reasons 2 and 3 are big part of why launches of expensive.
|
| There's a feedback loop in space launches: they're
| expensive, therefore you launch less, so you need to add
| redundancies and spend more time ensuring the payload will
| work, which raises the development cost and increases mass,
| which makes launches less frequent and more expensive.
|
| Conversely, reducing the cost of access to space means you
| can send more stuff that's less robust, which shortens
| development time and makes it less expensive, and of course
| makes technological progress faster.
|
| Which translates to: suddenly space telescopes may be more
| affordable, and more of them will be launched.
| irthomasthomas wrote:
| Phased array ground stations cost about $10,000-$100,000.
| jeffbee wrote:
| That's a lot of money. Considering that the company has
| reversed course on almost every promise it has ever made
| about Starlink -- orbit altitude, inter-sat networking,
| service area, cost -- I think it's a good bet that Starlink
| will ultimately just look like a capital-intensive Iridium-
| like network without the ability to service mobile stations.
| I imagine the US military will end up being the main
| customer.
| paranoidrobot wrote:
| > Considering that the company has reversed course on
| almost every promise it has ever made about Starlink --
| orbit altitude, inter-sat networking, service area, cost
|
| All of these things are coming, in subsequent revisions of
| hardware.
|
| Everyone on HN should recognise the pattern - it's very
| much a launch of a minimum viable product.
| gpm wrote:
| If you're willing to take SpaceX at their word you are off by
| two orders of magnitude. I don't see why you wouldn't be.
| mooman219 wrote:
| Which is an order of magnitude less than a cell tower.
| sparker72678 wrote:
| Anec-data, but in my shots of the comets there were 0 satellites
| and about 12 airplanes with flashing lights that I had to remove.
| -\\_(tsu)_/-
|
| I get the frustration, and no doubt I'll be pissed when I have a
| shot that's more affected, but amateur astrophotography seems
| like the least-important reason to be concerned about Starlink.
|
| But then, the photo is going to get more attention, for sure.
| wl wrote:
| Anecdotally, I took about 100 exposures of the comet last
| weekend with shutter speeds ranging from 10-20 seconds. There
| were satellite streaks in every exposure! I don't ever remember
| it being this bad.
| autokad wrote:
| It doesnt matter the impact of amateur astrophotography's work,
| starlink doesn't have the right to take that from them. I do
| think we need to evaluate whether these costs are worth it.
|
| I go further.
|
| I myself think we need to take a second look at city light. I'd
| like us to begin working on making the milky way visible again.
| animal_spirits wrote:
| I agree. Vast populations of people can't know their place in
| the universe because they physically can not see it. What can
| we do to avoid that? In suburbs it seams feasible to stop
| building / start removing streetlamps in neighborhoods that
| don't necessarily need them, but I don't know how that would
| work in bigger cities
| kergonath wrote:
| Better, more directional street lamps help, even in large
| cities. We can tune their wavelength to be less blinding as
| well. They do not need to illuminate the sky. More of them,
| and less powerful, would provide better light where it's
| actually needed.
|
| The other side is to reduce emissions of aerosols and
| particles that scatter light in the atmosphere.
| TeMPOraL wrote:
| > _starlink doesn 't have the right to take that from them. I
| do think we need to evaluate whether these costs are worth
| it._
|
| Yes, but when doing that, let's also take into account the
| fact that Starlink exists to open up space access. Starlink
| doesn't exist (just) to provide Internet access, it exists
| primarily to fund Starship and further reduce costs of space
| missions. This makes it one of the most important thing
| happening _for_ astronomy.
| ganafagol wrote:
| Yeah, so it basically exists to bring FB and Google to more
| people on the planet easier. We're selling out our skies to
| the ad industry. For free! What a great idea.
|
| Textbook example for tragedy of the commons. Luckily we
| didn't do the same with earthly resources like water, air,
| wild animals, ... oh wait
| kome wrote:
| i can't believe people are suggesting to edit this away with
| photoshop... you are pointing at the moon and they are looking at
| the finger...
| tebruno99 wrote:
| It was caused by stacking incorrectly in photoshop to begin
| with.
| catalogia wrote:
| That the image tweeted is a product of photoshop in the first
| place should be obvious to anybody who _looks up._ Go outside
| tonight and look up. Does the sky appear as it does in that
| tweet? Obviously not.
| gus_massa wrote:
| It's the result of some image processing. For example, there
| are like a hundred segments in the photo, but if you look
| carefully, they are quite aligned in ~27 almost parallel
| lines (probably the 27 satellites in different frames?)and a
| strange almost parallel segment (probably another unrelated
| satellite?).
| asdfk-12 wrote:
| Perhaps to remedy the situation, SpaceX would do well to
| introduce a large fleet of freely-accessible amateur astronomy
| platforms with some kind of timeshare credit component? I ordered
| several images through a university terrestrial telescope as part
| of an astronomy course and it was a great experience to refine
| the object's orbital parameters based on the observations.
| shadowgovt wrote:
| That looks so cool.
| irthomasthomas wrote:
| It's trivial to erase these things from photos. The photographer
| no doubt knows this, but that isn't the point.
|
| It's perfectly reasonable for scientists to want to capture
| accurate data on the space surrounding the main subject being
| imaged. Simply erasing the satellites from photos does not
| recover the data on the space behind. Any data from behind the
| satellites is lost forever. This photo keeps the satellites in
| order to visually demonstrate this problem.
|
| Remember that astronomy today is often done on a single pixel of
| data. Starlink blocks multiple pixels, and even ruins entire
| exposures when they flare up. This will make astronomical
| research, like searching for exoplanets, far harder and more
| expensive than it is today. Space telescopes are, and will always
| be, orders of magnitude more expensive than ground telescopes to
| launch, maintain and operate.
| giantrobot wrote:
| For one a Starlink satellite, or any LEO satellite, is moving
| really fast relative to a ground based telescope. It'll occult
| any given star for a fraction of a second.
|
| If you're doing a narrow field long exposure with tracking,
| that will be problematic and you'll loose data. Most scientific
| observations don't do long exposures, especially measuring
| highly variable things like exoplanet transits.
|
| It's more effective to stack a large number of short exposures
| for scientific measurements. It's much easier to eliminate
| noise because everything that is not noise will be transient
| for a single frame in the stack. You can also remove frames
| with things like satellites, clouds, or airplanes without
| losing much data.
|
| Knowing the ephemeris of satellites also allows observations to
| time short exposures to _avoid_ occultations. Astronomers have
| been dealing with satellites, clouds, and airplanes for a long
| time. Amateur astronomers might have a harder time with
| Starlink satellites but they will adapt just like they did with
| the ISS and Iridium.
| irthomasthomas wrote:
| "Members of the LSST science team said last month that,
| assuming the full deployment of SpaceX's Starlink satellites,
| nearly every exposure from the observatory within two hours
| of sunset or sunrise would have a satellite streak. During
| summer months, when twilight times longer, there could be a
| 40 percent impact on twilight observing time, according to
| the Association of Universities for Research in Astronomy, or
| AURA, which manages the LSST project for the National Science
| Foundation.
|
| "Because of scattered light in the optics by the bright
| satellites, the scientific usefulness of an entire exposure
| can sometimes be negated," AURA said in a statement last
| month. "Detection of near-Earth asteroids, normally surveyed
| for during twilight, would be particularly impacted. Dark
| energy surveys are also sensitive to the satellites because
| of streaks caused in the images. Avoiding saturation of
| streaks is vital.""
|
| https://spaceflightnow.com/2019/12/09/spacex-to-
| experiment-w...
| LeifCarrotson wrote:
| They're trying to do a logical OR for all the light that
| comes in during a long exposure, as in an old film camera
| with a long shutter time.
|
| That may have worked with analog film before we had
| satellites, but Starlink is just the latest and brightest
| addition to the sky that makes that an increasingly bad
| idea. Change is hard, but it's not that difficult.
|
| Instead, AND a bunch of shorter exposures. Then, your
| streaks are not streaks, but a series of point sources that
| can be removed trivially.
| ganafagol wrote:
| And who will pay for all those necessary changes? Keep in
| mind that this is complex stuff, you don't just hack a
| perl script and be done with it. Anybody who thinks it's
| that simple is suffering full-blown Dunning-Kruger.
|
| If I poo in your front yard, would you be happy with me
| telling you simply "well you can just remove it, what's
| the big deal?" Or rather, pooing regularly somewhere on a
| lawn in a public park that you really like and visit
| daily.
| spacemark wrote:
| >Most scientific observations don't do long exposures
|
| Not quite the whole truth, I think you're speaking a tad
| beyond your expertise. While you're right that transient
| science generally does short exposures (TESS is 2 seconds,
| Kepler was 6.5, LSST will be ~20 iirc), the vast majority of
| astrophysical science I've been exposed to (mechanical
| engineer at an astrophysics research institute), 10 or 20
| _minute_ exposures are more the norm. Especially when looking
| at faint objects.
|
| Doesn't take away from your main point - astronomers will
| adapt. I think they're perturbed by this because Starlink
| makes their jobs even more complex, and thus more expensive.
| A cost that SpaceX doesn't bear at all.
| claydavisss wrote:
| Starlink will provide an immediate benefit to humanity, the
| astronomy performed otherwise, won't. Looking for exoplanets
| isn't a practical concern for humanity any time soon.
| ganafagol wrote:
| Odd perspective when defending technology from the same guy
| that wants to save humankind by literally colonizing other
| objects in space.
| kbenson wrote:
| If the images are stacked, doesn't that mean that there's
| plenty of images with the parts that are occluded in others not
| occluded?
|
| I understand for any specific image, there's going to be some
| lost background because of Starlink satellites, but that's not
| what this is showing, this is showing something that's not
| possible, right? Shifting all the satellites temporally so they
| appear together, _arbitrarily maximizing the problem beyond
| what is real_ isn 't an accurate depiction of the problem, IMO.
|
| Put another way, if you erase the Starlink satellites from the
| images _before_ stacking them, you then get a fairly accurate
| representation of the sky without any Starlink satellites, and
| you still have the data behind them (from the other pictures
| where that portion of the sky was not occluded). You can also
| probably fix the intensity of anything occluded in a few of the
| pictures but not others through some math.
| nsilvestri wrote:
| Exposures are generally taken frequently enough that any that
| would be problematic for data can simply be dropped. The
| satellites aren't permanently positioned in the sky.
| Geostationary satellites permanently lose any data behind them
| (although I haven't heard of a geostationary satellite being
| positioned precisely problematically).
| irthomasthomas wrote:
| Searching for exoplanets moving in front of a star, involves
| measuring the luminosity of a single pixel for ~1% change.
| Dropping frames ruined by a satellite train isn't going to
| work. E.g https://www.sciencealert.com/a-bunch-of-potential-
| tabby-s-st...
| nsilvestri wrote:
| You absolutely can drop those frames. Exoplanetary transits
| are generally in the range of 1 to 4 hours, and hundreds of
| exposures may be taken in that time. In my undergraduate I
| studied astronomy and some of my classmates did an
| exoplanet detection project with a 61" scope and had issues
| with satellites on a handful of frames. Sure, it sucks to
| lose 2 minutes worth of data, but it's not even lose to
| catastrophic when you have the data before and after as
| well.
| CamperBob2 wrote:
| Absolute bunk. As numerous people have tried to explain in
| this thread (along with its frequent predecessors),
| anything that moves across frames is by definition
| unimportant when stacking images. It's literally the
| difference between integration and differentiation.
|
| Satellites move _fast_. Not only that, but you know exactly
| where and when they will cross your field of view, and for
| how long they 'll remain within it. If the astronomy
| community can't muster the rudimentary image processing
| technology needed to reject satellites and other transient
| objects, I'm not exactly confident in their ability to
| finally figure out the whole origin-of-the-Universe thing.
| ViViDboarder wrote:
| So if someone decides to make money with a byproduct
| being messing with your day job, you'd just shrug it off?
| CamperBob2 wrote:
| If I were that incompetent at my day job, I imagine quite
| a few people would be "messing" with me, possibly for the
| sheer amusement of it.
| mlindner wrote:
| This is completely incorrect. The data is not lost, when you
| stack images the low signal of a single (or multiple)
| satellites in a single image disappears into the noise.
| dzhiurgis wrote:
| There's no sats up north...
| todd3834 wrote:
| What are some of the potential consequences of this? I'm curious
| if stars getting photobombed is a signal pointing to a greater
| issue? If they can coat them in a way to not be reflective then
| will most astronomers be satisfied?
| ardy42 wrote:
| > If they can coat them in a way to not be reflective
|
| _Less_ reflective. I don 't think there's a way to make them
| _not_ reflective, and many, many astronomical objects are very
| dim.
| webmaven wrote:
| _> > If they can coat them in a way to not be reflective_
|
| _> Less reflective. I don 't think there's a way to make
| them not reflective, and many, many astronomical objects are
| very dim._
|
| Vantablack[0] would probably be adequate for the timescales
| involved, at least for most terrestrial[1] observations:
|
| [0] https://www.sciencealert.com/this-object-has-been-
| sprayed-wi...
|
| [1] eg. I can easily imagine a similar but more severe
| problem for a lunar farside observatory if (when?) Starlink
| is expanded to provide internet coverage for the Moon's
| surface. Of course, the main reason for a farside observatory
| would be shielding from Earth's RF emissions, so just people
| needing and wanting internet access on farside is probably
| going to be a problem first.
| zaarn wrote:
| Any good astronomy imaging tool will remove temporary satellite
| flashes without much effort, provided you take a lot of
| exposures. If you naively stack them you get this of course.
| falcolas wrote:
| The greater thread has some data on the latter point - the
| latest satellites are coated, but it's not had much impact yet.
|
| Seems like this is light pollution taken to a completely new
| level.
| elliekelly wrote:
| I remember reading Musk had to get permission from some US
| regulator (the FCC and/or FAA maybe?) in order to launch
| these satellites but is there any sort of international body
| that deals with this?
| gpm wrote:
| To a first approximation it's just the FCC, but the FCC
| does listen to and evaluate issues pertaining to light
| pollution, space debris, satellites falling to earth and
| landing on peoples heads, and so on despite that not being
| related to radios.
| bryanlarsen wrote:
| SpaceX has abandoned the coating approach and is going with a
| shade approach, which works even better. The next set of
| satellites all have the shade.
| pmontra wrote:
| We will exchange white lines for black lines. We won't be able
| to see through the satellites.
|
| Actually maybe a white line is simpler to remove than a black
| one on a black background.
| gpm wrote:
| Presumably exchanging white lines for transparent lines not a
| color. For larger projects which don't move around this can
| be augmented further by removing known satellite tracks
| instead of lines, or even not imaging areas when satellites
| are going to be there.
| sp332 wrote:
| Black lines are far preferable because they do not contribute
| to the total amount of light collected. A momentary flash
| from a bright light can swamp the sensor, but a brief moment
| of blackness will leave the pixels' state much less
| disturbed.
| Kye wrote:
| This is why long exposure photographs of roads have light
| trails with no cars.
| jacknews wrote:
| exactly, paint them green
| [deleted]
| tinus_hn wrote:
| That's odd, I took a bunch of pictures of that same comet and saw
| no satellites at all. Did I do something wrong?
| zelon88 wrote:
| The OP posted this in the ensuing Twitter argument...
|
| > Why (on Earth) do you want to become a multi planetary
| species??
|
| That's just an un-neccesarily foolish question. Why does a dog
| swim when you place him in a lake?
|
| > Have you ever tried to live in Antarctica or in the Atacama
| desert (I have)? I support science, exploration, tech development
| but not foolishness. Do you surround your house with roads to
| explore distant locations?
|
| Isn't that exactly what we've done as a society already?
| dx87 wrote:
| We did that, realized it was a mistake, and have started
| placing emphasis on working around nature, instead of tearing
| it down because it's more convenient.
| marcus_holmes wrote:
| in the west, yes. In the places where real nature still
| exists; no, everyone's still happy to tear it down for
| convenience.
|
| evidence: Brazil's rainforest. Indonesian palm oil. Chinese
| mines. African, well, everything.
| shadowgovt wrote:
| I sometimes think the West overestimates how convenient or
| cohabitable nature is, because they were born into a tamed
| version of it.
|
| For most of human history, nature has been trying to kill
| us (if that's too anthropomorphic, we can go with the
| longer-form "The processes of nature are ambivalent to the
| survival of our species and individuals in that species,
| and there is no guarantee that the natural world is one
| habitable by humanity. Our species' history is shot through
| with plagues, floods, famines, and predation, and much of
| our technology was created to minimize that.")
| stinos wrote:
| I found that a bit of an odd question, besides the point, but I
| might be missing something. Is any of the purposes or uses of
| Starlink actually related to something multi-planetary? From
| what I read on it they seem to be there solely for
| communication on earth itself? Or does the commenter consider
| Starlink as one of the things further enabling technology to go
| multi-planetary? Which I still don't really get, since other
| types of communication are already which go _way_ deeper in
| space and send messages back and forth to earth.
| Ankaios wrote:
| A major ( _the_ major?) motivation behind Starlink is to try
| to earn SpaceX vast amounts of money that Musk can invest in
| settling Mars.
|
| See, e.g., this link for comments by Musk:
| https://www.space.com/spacex-starlink-internet-satellites-
| ma...
| _Microft wrote:
| > The OP posted this in the ensuing Twitter argument...
|
| "OP" refers to the OP of the Twitter thread.
|
| I'm just the submitter and do not share their view on being a
| multi-planetary species at all (I agree that it sucks to have
| streaks on your astro-photos, as I started taking them
| recently).
|
| _We have to boldly go where no man has gone before._
|
| Edit: changed wording to restore split infinitive.
| marcus_holmes wrote:
| or even go boldly
| _Microft wrote:
| Thanks, fixed.
| INTPenis wrote:
| For a different type of analogy, look at how long we had to
| sail around in wooden ships before that evolved.
|
| Without actually venturing out there, we might never develop
| viable star travel.
| kergonath wrote:
| I wish we would discipline ourselves to avoid ruining that one
| planet before we get delusions of grandeur and the urge to
| wreck another one.
|
| All these talks about "multi-planetary species" are bunk in the
| long term, anyway. We will probably have observation outposts
| scattered across the solar system, but that'll be about it for
| quite a long time. The only realistically reachable planet in
| the foreseeable future is Mars. We could fix our issues with
| Earth for a fraction of what it would take to make it
| inhabitable.
|
| We'll send our billionaire pioneers to the moon alright. With a
| scientific base as a side effect. It still won't improve
| anything that's wrong with Homo Sapiens.
| time4hn wrote:
| > That's just an un-neccesarily foolish question.
|
| On Twitter there seem to be a lot of people on who expect to
| _live_ in other worlds soon, and not just to explore and study
| them. He 's likely rhetorically responding to that idea. And I
| think it's worthwhile to confront those ideas critically. IMO
| as well, living off of Earth sounds hellish, given what we know
| now.
|
| The person the Twitter poster is talking with is now suggesting
| that many people will abandon their physical bodies, and those
| that won't will live in cylindrical space colonies. He's
| speaking fantasies.
| [deleted]
| crowbahr wrote:
| Twitter OP is also arguing that there will never be human
| settlements off this Earth, which is bullshit.
|
| Assuming humanity exists long enough, it will expand
| throughout the solar system. At very least to the moon.
|
| We can argue about how long that might take, but not about it
| ever happening.
| dhosek wrote:
| _> Assuming humanity exists long enough_
|
| That's a big assumption.
|
| There's also the _why_ question. What 's on the moon that
| would make it worth all the difficulty to get there? I
| suppose we might have a semi-permanent research station on
| the moon or even Mars, but colonization? Unless we make
| some really unlikely discovery like unobtanium is only
| found on Europa and it's really super useful, we're not
| going to have space colonies.
| dwaltrip wrote:
| The moon will be a good source of water for spacefaring
| endeavors of the future, due to the large quantities of
| ice it has at the poles. With 1/6 the gravity of earth
| and the appropriate infrastructure in place, it will
| likely be cheaper to get that water off of the surface of
| the moon than from the Earth. The most promising use here
| is actually for producing methane fuel from this water.
| An industrial base of sorts could develop around this.
|
| The other potential industry will be moon tourism. It
| could become something like the new Mt Everest. Obviously
| only for the very rich at first.
|
| Once it becomes a real possibility and not some crazy
| sci-fi project, governments may start competing, so as to
| not get "left behind", even if it is not immediately
| profitable.
|
| One way or another, unless we destroy ourselves, it will
| happen eventually. There's a percentage of people who are
| just absurdly curious and adventurous, and want to go
| where no one has gone before, even if the cost is
| immense. Hell, for some, I'm sure even just desire to get
| away from their situation on Earth will be a big part of
| why they go for it. People like this will build the first
| settlements and bases on the moon and elsewhere in the
| solar system.
|
| Edit: sorry for the constant edits. It's a bad habit -- I
| don't always get my thoughts out on the first try.
| dhosek wrote:
| So, going to space to the moon is useful because it
| enables going further out to space.
|
| And I'm not entirely sure how you turn water (H2O) into
| Methane (CH4). Granted I barely passed freshman chemistry
| 33 years ago so my chemistry knowledge isn't so good, but
| as near as I can recall, there is no process that will
| turn that input into that output.
|
| And again, even if the moon is a source of water, there's
| not a significant need for any water mining operation at
| the poles to have a colony around it or even any human
| staffing. Putting people there on even a semi-permanent
| basis would likely eliminate any gains to be had from
| using the moon as a source of water.
|
| Even the space tourism doesn't call for settling the
| moon. No one lives on top of Mount Everest either.
| gmanley wrote:
| Could you simply separate hydrogen from the water, using
| electrolysis, or other methods and then use the Sabatier
| reaction? [1] Carbon dioxide in bulk may be harder to
| come by on the moon, however.
|
| Also, the Lunar Gateway [2] is a key part of the plans by
| NASA/SLS. It's not about settling on the moon, it's about
| making it a stop off point to refuel or pickup supplies
| before going on to a further off destination like Mars.
| Instead of having to have all your fuel and payload when
| taking off from Earth, you can have a lot of your
| supplies and weight on the Moon. This means your trip off
| Earth can be cheaper. Getting out of Earths gravity and
| getting to escape velocity is the hard part. Getting off
| the moon is a lot easier.
|
| [1] https://en.wikipedia.org/wiki/Sabatier_reaction [2]
| https://en.wikipedia.org/wiki/Lunar_Gateway
| dhosek wrote:
| The Sabatier reaction relies on carbon dioxide. For the
| concept of using it to generate rocket fuel, there's a
| reliance on atmospheric CO2 which is viable on Mars but
| not the Moon (which is why the section in the Wikipedia
| article is called "Manufacturing propellant on _Mars_ ").
| And the Lunar Gateway is irrelevant to what I'm arguing,
| which is that there's not really any reason to settle
| off-planet.
| f00zz wrote:
| If we ever get functional fusion reactors the moon could
| be a source of helium-3.
| MrZongle2 wrote:
| > On Twitter there seem to be a lot of people on who expect
| to live in other worlds soon
|
| On Twitter there seem to be a lot of people who _currently_
| live on other worlds.
| peroporque wrote:
| Ah yes, the rich first worlder wants to be able to use their 5k
| USD camera to take pictures of the sky.
|
| What do they care if poor people in rural Africa can develop
| their farm with better and faster access to the internet, or if
| children in central Amazons will be able to get reliable internet
| at school.
|
| The level of egocentrism is unbelievable.
| dang wrote:
| Please don't fulminate or post denunciatory rhetoric to HN. It
| only degrades this place even further. Also:
|
| " _Please respond to the strongest plausible interpretation of
| what someone says, not a weaker one that 's easier to
| criticize. Assume good faith._"
|
| If you wouldn't mind reviewing
| https://news.ycombinator.com/newsguidelines.html and sticking
| to the rules when posting here, we'd be grateful.
| valuearb wrote:
| This is pretty much a cherry picked worst case scenario. The
| comet is only visible right above the horizon after sunset for a
| brief period.
|
| Starlink satellites are also only visible low on the horizon, and
| only for brief periods after sunset and before sunrise, because
| their low orbits keep them in the Earths shadow the rest of the
| night.
| asdfadsfgfdda wrote:
| Yeah its basically optimized to look bad. The satellites are
| relatively close to each other. In normal operation, there's no
| reason to have 30 different satellites in view. I suspect these
| satellites were very recently launched, so they are not in the
| normal sun-tracking orientation.
|
| Also, the comet is a wide object. A wide image is just more
| likely to have any satellite in view.
| toohotatopic wrote:
| Wait till we have the first moon bases and there will never be a
| new moon again.
| f00zz wrote:
| Can't wait!
| LeChuck wrote:
| I wonder if these things will have any effect on astronavigation.
| It would be sad to see such a cool practice become impossible.
| valuearb wrote:
| Starlink Satellites are only visible for short periods just
| after sunset and before sunrise, because most of the night they
| are in the earths shadow.
| LeChuck wrote:
| Yeah. That's the problem. Celestial navigation can only be
| performed during twilight, as you need to be able to see both
| the horizon and celestial objects.
|
| https://en.wikipedia.org/wiki/Twilight#Nautical_dawn_and_dus.
| ..
| shadowgovt wrote:
| I can't imagine it would; Starlink satellites are also
| moving. Quite fast. So don't do your celestial navigation
| by the moving thing and you'll be fine.
| catalogia wrote:
| I don't see why they would. The stars typically used for
| astronavigation are very bright; brighter than starlink
| satellites. A brief web search leads me to believe typical
| starlink satellites have a magnitude of around 5 or more, while
| the stars typically used for astronavigation have magnitudes of
| less than three
| (https://en.wikipedia.org/wiki/List_of_stars_for_navigation)
|
| Even if that weren't the case, it's easy for the human eye to
| distinguish a star from a LEO satellite; the satellite is the
| one that's moving fast. I see no reason the sailors couldn't
| simply ignore the satellites.
| LeChuck wrote:
| It was the brightness I was worried about, yes. Should've
| probably just looked it up myself!
|
| I don't think astronavigation is used in any serious capacity
| anymore, so in that sense it's a moot point. Still, it's a
| cool practice and it would've been too bad to see that go
| away.
| hombre_fatal wrote:
| How much sympathy can I really spare for a purely leisurely hobby
| like backyard astronomy vs. satellites, Starlink, and our space
| tech?
|
| To me it's like complaining that your photography hobby is harder
| now that more people can afford to travel and they get in the way
| of your favorite tourist shots.
|
| I'm sure there are good examples of trade-offs that matter here
| like the impact on terrestrial research telescopes, but a guy
| snapping a pic of a comet and ranting about it on Twitter frankly
| has the opposite effect on me.
| modzu wrote:
| it is a tragedy. what we have in the ever shrinking dark night
| sky is utterly breathtaking if you have ever seen it; light
| pollution is a bigger problem imo than starlink, but they
| relate. survey astronomers and astrophysicists and you will
| find for many it was being able to look up and see stars, be
| awed by them and wonder about them that got them into their
| field in the first place. i am scared to lose that..
| justin66 wrote:
| > How much sympathy can I really spare for a purely leisurely
| hobby like backyard astronomy vs. satellites, Starlink, and our
| space tech?
|
| Your sympathy or lack thereof is your business, but astronomy
| is one of the rare sciences where amateurs still do a great
| deal of work and make important discoveries.
|
| > I'm sure there are good examples of trade-offs that matter
| here like the impact on terrestrial research telescopes, but a
| guy snapping a pic of a comet and ranting about it on Twitter
| frankly has the opposite effect on me.
|
| It's a shame you would allow your opinion on an important
| subject to be swayed by a single tweet on an issue you
| apparently know little or nothing about.
| dmitriid wrote:
| True, because professional astronomers, lucky them, are
| provided a completely different sky devoid of satellites,
| debris and other man-made objects.
| marcus_holmes wrote:
| If we can make space travel cheap enough to get more Hubble-
| like telescopes up there, then yes, this.
|
| I believe that's part of the goal of SpaceX
| Alupis wrote:
| Hubble costs are estimated around $10 billion USD in
| 2010[1].
|
| The cost to put the thing into orbit is minuscule compared
| to the equipment and operation itself.
|
| Put another way - SpaceX isn't solving any problems here.
|
| [1] https://en.wikipedia.org/wiki/Hubble_Space_Telescope#Ch
| allen...
| simion314 wrote:
| I am sure we will not have the space tech soon that can
| build giant telescopes in space, Hubble is small compared
| with the larger telescopes on the ground, and from what we
| can see today it takes decades to send a new telescope in
| space because you can't go and tweak it. I just hope the
| benefits are larger then the costs and we the public will
| not have to pay SpaceX to send telescopes in space to fix
| the issue SpaceX created.
| wbronitsky wrote:
| Yes, but the point is that we should do that first before
| polluting the night sky.
|
| There are also reasons for humans and animals to not want
| new, moving stars for reasons other than pure utility. At
| the very least, these shiny beacons are an insulting
| advertisement for Musk.
|
| Next, people will be defending a Pepsi ad on the moon or
| something.
| https://www.theatlantic.com/science/archive/2019/04/pepsi-
| ad...
| supernova87a wrote:
| How about when satellite stray signals or signatures start to
| pollute not just amateur hobbies, but GPS, weather? It's all
| related.
| giantrobot wrote:
| Satellites have very constrained transceivers. This is not
| only for regulatory reasons but efficiency. It's a literal
| waste of power to leak noise into non-target bands.
| Everything from the transceiver electronics to antennas are
| tuned for target bands. Satellites broadcasting stray signals
| is rare enough to not be a thing.
|
| Interference with GPS and other signals overwhelmingly comes
| from _ground based_ sources.
| gpm wrote:
| Easily solved in software by removing the small part of each
| frame that has a satellite in it. Satellite tracks are completely
| predictable. This is not novel.
| [deleted]
| Kye wrote:
| Somehow I get the feeling people who do this professionally
| understand what's possible and what effect this has better than
| you.
| gpm wrote:
| They undoubtedly do, but this is an opinion formed by talking
| to people in person in the industry. Random twitter users who
| manage to get there tweet on HN is not even close to an
| unbiased sample of professionals in the industry. My sample
| undoubtedly also has its biases, but is not selected for
| sensationalist views at least.
| Kye wrote:
| This is "I talked to some people" vs the linked tweet from
| a person in the industry. I think you can understand my
| skepticism. I also understand you probably don't have a
| convenient way to prove your side of it.
| tenuousemphasis wrote:
| The person who posted this tweet? I don't think so. They also
| said this gibberish:
|
| >Space junk. There HAS to be another way to improve internet
| communications, does Humanity and planet Earth's livestock
| need this (5G)? Really?
| Kye wrote:
| Sometimes people with real domain experience on one topic
| try to have opinions on other things. It doesn't always go
| well.
| abduhl wrote:
| Yet another physical layer problem conveniently solved by a
| software solution (coded over the weekend, of course)!
| JBorrow wrote:
| Perhaps true for amateur astrophotography but not the case for
| professional astronomy. Please see reporting in e.g. [1] and
| [2].
|
| Note that simply putting telescopes in space is not a viable
| solution to these problems.
|
| [1] https://skyandtelescope.org/astronomy-news/starlink-
| astronom... [2]
| https://www.theverge.com/2020/3/24/21190273/spacex-starlink-...
| gpm wrote:
| A few particularly large and particularly sensitive
| telescopes will have problems not easily resolvable by
| software, the vast majority of telescopes will not.
| JBorrow wrote:
| Yes, these are massively important to professional
| astronomy and our understanding of the universe.
| dx87 wrote:
| That actually sounds worse. Large expensive telescopes will
| have issues, but amateur astronomers will say there isn't
| any issue because the pictures they take with their smaller
| telescopes are cleaned up with software.
| gpm wrote:
| Arguably so (I'm going to generally stay out of value
| judgments), but do note that it's not _all_ large
| expensive telescopes, it depends on the telescope.
| shadowgovt wrote:
| ... which has always been true.
|
| Several observatories were built near cities. As light
| pollution from terrestrial sources have increased,
| they've found their expensive optical telescopes become
| toys, and have moved their scientific collection utility
| over to radio.
| shadowgovt wrote:
| Such concerns should probably be balanced against the
| potential the launch capacity of Starlink represents.
|
| I'm looking forward to someone launching a satellite
| telescope network with the collection radius of an Earth
| orbit.
| kbenson wrote:
| Flipped on its head, I would say Starlink, or at least the
| underlying technology that makes it feasible (and it's all
| related, since it's all SpaceX) may be _good_ for astronomy...
| _eventually_.
|
| Space based telescopes give a much clearer picture than land
| based ones. You can't have ubiquitous and/or (relatively) cheap
| space based telescopes without a thriving launch industry that
| reduces costs. You can't have that without innovation and
| competition in the space launch industry. You are unlikely to
| innovation or competition in that industry the without a market
| need. Starlink _is_ the market need right now.
|
| Want lots of space telescopes to give you even better pictures?
| Don't kill off what's going to take you there before it begins.
| The astronomy industry needs to work with SpaceX to minimize the
| problem while also encouraging them (and anyone else working to
| drop costs to launch something into orbit) to succeed, not
| killing off or greatly delaying the oncoming age of ubiquitous
| and easy access to space telescopes because they are short
| sighted.
| rumanator wrote:
| > Space based telescopes give a much clearer picture than land
| based ones.
|
| Aren't those far more expensive to launch and operate?
| Robotbeat wrote:
| Not necessarily? Starlink represents an order of magnitude
| improvement in both launch and hardware costs.
| [deleted]
| vayeate wrote:
| Space man bad is the new orange man bad
| whoopdedo wrote:
| The truth is most people will never notice the Starlink
| satellites. Because light pollution obscures the night sky so
| much you can only see the brightest of stars and nearly nothing
| close to the horizon. How many kids are hearing about this comet
| in the sky, rush out at sunset, and are then disappointed to only
| see the haze of city lights?
| daveslash wrote:
| Truth is, _most people_ never look at the night sky, period.
| But this isn 't about _most people_ ; this is specifically
| about people who look at the sky _a lot_ -- and those people
| typically seek out darker skies anyway.
| catalogia wrote:
| > _Truth is, most people never look at the night sky,
| period._
|
| Truth is people never look at the sky _period_. Ask people
| when the moon is visible and most will say _" during the
| night."_ But about half of the time, the moon is actually
| visible during the day. Wouldn't people realize this if they
| simply looked up?
| cnity wrote:
| That's because what they mean is that the moon appears more
| brightly at night, and I suspect you know this. You don't
| _actually_ think these people have never seen the moon
| during the day, surely?
| CydeWeys wrote:
| I got into an argument with a second grade teacher (when
| I was in second grade) who insisted that the Moon was
| only visible at night. It still rankles me to this day
| how wrong she was, and how she could have easily been
| disproven simply by going outside and looking. Even
| worse, I think she was the science teacher or something.
| catalogia wrote:
| > _That 's because what they mean is that the moon
| appears more brightly at night, and I suspect you know
| this._
|
| No, I don't think that's the reason. The moon is
| frequently very bright during the day, not even remotely
| hard to see. Moreover, people are mostly outside during
| the day, meaning that most of the time they have the
| opportunity to see the moon will be during the day.
|
| I think the reason is that a supposed sun/moon -
| day/night dichotomy is perpetuated by culture (for
| instance, clock dials that use an image of the moon to
| symbolize the night) and that culture has a stronger
| impact on people's perception of the moon than their
| personal observations of the sky. I think they have seen
| the moon during the day, but the moon is very rarely the
| object of their attention. They see it, but rarely do
| they notice it.
|
| The reason for such a culture emerging seems obvious to
| me; the Sun's presence in the sky obviously correlates
| with daylight perfectly, making the sun an obvious symbol
| to associate with the day. But then what symbol would you
| use for the night? There's a clear day/night dichotomy,
| creating a demand for a symbol that's inverse of the sun.
| However there's no object in the sky that correlates so
| perfectly with the night. The moon isn't there half the
| time, but neither is any particular star. You could use
| generic stars, and sometimes that's done, but stars
| aren't necessarily visually distinctive. The moon is
| visually distinctive and so it's pressed into the roll of
| being the symbolic opposite of the Sun, even though a
| trivial glance into the sky reveals that it isn't
| actually opposite of the sun.
| dhosek wrote:
| I got into trouble with my fourth grade teacher over this.
| Sent to the principal's office even. Fortunately, the moon
| was new that day and I was able to take the principal
| outside and point at it.
| [deleted]
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