[HN Gopher] First images from James Webb telescope exceed expect...
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First images from James Webb telescope exceed expectations
Author : mooreds
Score : 722 points
Date : 2022-03-18 23:44 UTC (23 hours ago)
(HTM) web link (cosmosmagazine.com)
(TXT) w3m dump (cosmosmagazine.com)
| mensetmanusman wrote:
| In the Copenhagen interpretation of QM did James Webb collapse
| these distant galaxies because they were finally measured? :)
| gliptic wrote:
| The light from them was still hitting the Earth constantly and
| would entangle quickly with everything on Earth.
| deathanatos wrote:
| The NASA press release, which includes the same photo but at a
| decent resolution: https://www.nasa.gov/press-release/nasa-s-
| webb-reaches-align...
| WallyFunk wrote:
| Or just link to the _massive_ PNG here. Beware if your mobile
| plan has a bandwidth cap before clicking:
|
| https://www.nasa.gov/sites/default/files/thumbnails/image/te...
| Jap2-0 wrote:
| Only about 5 MB compressed. Interesting to note is that even
| though the extension and MIME type claim it's a png, Firefox
| claims it's actually a jpeg. Throwing it at a couple
| different pieces of software, they all appear to open it with
| either file extension (so presumably they're going off the
| file header rather than the actual extension).
| pp19dd wrote:
| Think this is the classical image of that star, taken in
| visible light:
|
| http://simbad.u-strasbg.fr/simbad/sim-id?Ident=2MASS+J175540...
|
| Click on fullscreen icon on right-hand side, then zoom out
| until FoV on bottom left says about 10.63' to 12.23'.
|
| Best I understood, that should be about the same field as the
| Webb image, based on the instrument definitions I read about.
| And I wasn't able to line up any dots visually - the new Webb
| image was taken with a red filter, so I thought it's likely
| showing photons no one's seen before.
|
| Paging any astros for corrections.
| seaish wrote:
| Looks like it's around 2.5' and the Webb image is rotated
| about 15 degrees clockwise from this one. The four blobs to
| the left form a quadrilateral that seems to match the four
| bright galaxies in the Webb image. It seems like the star has
| moved maybe 10" downward between the two, and used to be just
| below that round galaxy to the left of the top spike.
| ggm wrote:
| Any photon you see nobody has seen before.
| willis936 wrote:
| Photographs are funny like that. We can replicate once-
| unique information.
| [deleted]
| jcims wrote:
| Here's a nice comparison baggy_trough posted below:
|
| https://twitter.com/gbrammer/status/1504369779540480002?s=21
| the_lucifer wrote:
| Oh god that resolution.
| qbasic_forever wrote:
| Wow, that's almost exactly like seeing the world when I got
| glasses for the first time!
| idontwantthis wrote:
| Have you seen any articles on what was learned in the design and
| manufacturing and if NASA believes that similar cost and time
| overruns can be avoided on follow ups?
|
| Really curious if $10 Billion is just what it actually costs to
| build this incredible machine, or if the pioneering work will
| mean that we can do a better job making things like it now.
| mturmon wrote:
| The baseline take on what happened with Webb is that too many
| low-readiness technologies were included when the mission was
| approved and went into "Phase A" which means that development
| starts.
|
| The entire astrophysics community suffered as a result of the
| ensuing suckout of resources. Lessons have been learned because
| a lot of careers were impacted.
|
| There's several successors to Webb on the horizon, and current
| thinking is to mature the technologies needed before such
| missions enter Phase A and is in effect committed to.
|
| For a concrete reference on this, see the (very large) National
| Academies survey, which charts the course for NASA astrophysics
| over the next 10 years:
|
| https://www.nationalacademies.org/our-work/decadal-survey-on...
|
| A decent gloss on the above report is:
|
| https://www.aip.org/fyi/2021/astro2020-decadal-survey-arrive...
|
| which lays out the tech maturation plan under the " Flagship
| mission maturation program" heading.
| ElephantsMyAnus wrote:
| Yeah, it would make more sense to send several telescopes,
| each a bit better than the one before, but I guess it was
| easier to get funding for "this revolutionary telescope" than
| for "this would be like Hubble but a bit better."
| pkaye wrote:
| If they could get a bigger cargo bay on a rocket, a lot of the
| risky folding mechanisms could have been removed. They could
| have used a design closer to the Hubble, Spitzer or Neowise.
|
| The next telescope being planned out is LUVOIR which be even
| bigger so they will still need to continue with folding
| mechanisms given the bigger size. They may need to eventually
| think of modular telescopes that are assembled in space.
|
| https://en.wikipedia.org/wiki/Large_Ultraviolet_Optical_Infr...
| mkesper wrote:
| As far as I know there currently exists no bigger rocket
| cargo bay than that of Ariane V which also had to be modified
| for JWST.
| dtgriscom wrote:
| SpaceX's Starship is 9m in diameter, but it's not quite
| ready for prime time.
| perardi wrote:
| It really is worth pointing out, again, that it's $10
| billion...for the entire estimated lifetime cost of the
| project. Amortized out over 20 years? I'm not saying it's
| nothing...but given the US federal budget, it's kind of
| nothing.
|
| Compared to, oh, let's say, $1.6 _trillion_ dollars...
|
| https://www.nbcnews.com/think/opinion/air-force-admits-f-35-...
|
| But that's just petty to point that out.
|
| I too would like to see a debrief on "what went wrong"...if
| there is anything that really went wrong. I mean, there isn't
| exactly an off-the-shelf solution for an infrared space
| telescope deployed to a phenomenally distant orbit. One might
| reasonably expect a few cost overruns, when you're making
| mirrors that have no real precedence anywhere in human history.
| onelovetwo wrote:
| Well most of the cost is in building and launching the
| thing...
| runnerup wrote:
| Yes it's about $1.66 per US citizen per year during the
| 20-year development.
|
| I've already personally received way more value than that
| just following the "entertainment" of following along with
| the construction and launch. I would gladly pay that much
| again for a repeat endeavor.
|
| Now that it looks like JWST will be able to perform actual
| science, I think we'll all get a lot more than $1.66/year of
| value out of it.
| sethammons wrote:
| It would be amazing to get a list every year on how your
| personal taxes were spread out like this
| mkoubaa wrote:
| Even better if you could pick where 2% or so of your
| taxes go to
| omgwtfbyobbq wrote:
| It did cost $10 billion, and the cost overruns were exaggerated
| a bit.
|
| One example is comparing the final cost to the cost of the
| design phase. The starting point should be after the final
| design had been approved.
|
| Additionally, costs need to be inflation adjusted.
|
| I commented on this last year.
|
| https://news.ycombinator.com/item?id=27764547
| akira2501 wrote:
| We spent nearly 30 years planning, designing and deploying
| this. I don't believe there's an agency anywhere that can
| effectively cost out a project of that scope given that entire
| new industries can rise and old ones fall in that time.
|
| For perspective, $10 billion is like 1% of a single year budget
| in the US and I believe the estimate includes the entire
| lifetime operating cost of the instrument.
|
| If it did in fact just "cost that much" I would probably "not
| be that bothered."
| Gollapalli wrote:
| Hey, good for them! Congrats to all involved. One more joyful
| project in the world of technology.
| baggy_trough wrote:
| Comparison with the previous generation infrared telescope,
| showing the massive increase in resolution.
|
| https://twitter.com/gbrammer/status/1504369779540480002
| zamalek wrote:
| I am so relieved that it made it without hitting some debris, and
| that the hydraulics didn't fail for the unfurling. The unfurling
| was one insane piece of orchestration, which just means many more
| opportunities to see a piece of space dust or something messing
| it all up.
|
| This image is fantastic, even though we can easily see that more
| work needs to be done with the alignment. It hopefully proves
| that alignment is all that's left.
| ISL wrote:
| I believe that they have achieved diffraction-limited
| alignment. What about the image suggests that there is more
| work to do?
|
| The starburst pattern is part of the intrinsic PSF, not a
| signal of alignment error.
| frumiousirc wrote:
| > I believe that they have achieved diffraction-limited
| alignment. What about the image suggests that there is more
| work to do?
|
| Some of the remaining misalignment is rather obvious in the
| higher resolution image. For example, look left of the main
| star and notice an "echo" of the main diffraction pattern
| that is not centered on a star.
|
| Also, if you follow that pattern's downward arm to where it
| meets a diagonal arm of the main pattern you see a
| rectangular bar of increased brightness. Perhaps it indicates
| the need for calibrating that part of the sensor.
|
| https://www.nasa.gov/sites/default/files/thumbnails/image/te.
| ..
| chasil wrote:
| If one mirror's actuators fail, it's over.
|
| I hope they have long life.
|
| "The Webb telescope will use 132 small motors (called
| actuators) to position and occasionally adjust the optics as
| there are few environmental disturbances of a telescope in
| space."
|
| https://en.m.wikipedia.org/wiki/James_Webb_Space_Telescope
| cma wrote:
| If only one fails couldn't they do two-exposures with all the
| functioning ones making the smallest movement they can? Then
| the failed one's contribution can be decorrelated between the
| two exposures and removed since it stays the same throughout.
| kibwen wrote:
| AIUI if any one mirror fails then they can continue on with
| degraded performance, it wouldn't mean the immediate end of
| the telescope's usefulness.
| MerelyMortal wrote:
| Big Sky Theory, meet Space.
|
| https://en.wikipedia.org/wiki/Big_sky_theory
| darig wrote:
| kitd wrote:
| Kudos to everyone involved.
|
| I didn't realise there was a planet-spotting remit to JWST
| though. Looking forward to the results of that.
| ZYinMD wrote:
| The best news in a long time.
| [deleted]
| WallyFunk wrote:
| How fast is the JWT data transmission in mbits/s?
|
| And if it's fast, how is that even possible if it's so far away?
| junon wrote:
| Absolutely incredible. I can't wait to see what this thing shows
| us.
| gorgoiler wrote:
| This is the first time we've imaged these galaxies. Did we know
| they were there?
| kibwen wrote:
| Someone else linked an gif comparing against our previous best
| photo of that star:
| https://twitter.com/gbrammer/status/1504369779540480002 .
| Presumably astronomers knew those blobs were galaxies, but no
| details could be resolved.
| nullc wrote:
| The spitzer image is 3.6um IR, I think the webb alignment
| images are at 2um... pretty big difference in resolution just
| due to the wavelength.
| peter303 wrote:
| Its important that the Webb got this right because proposed 2030s
| successors to visible light Hubble or infrared Webb are
| considering as many as a hundred one meter mirrors due to the
| limited size of launch vehicles.
| srvmshr wrote:
| Honest question: Is the lens flare at the center to be expected
| or more corrections are underway?
| Sharlin wrote:
| It's an inevitable result of diffraction caused by the three
| arms holding the secondary mirror.
| willis936 wrote:
| Can this not be mathed out if we know the distance of the
| target? I know it wouldn't generate the missing information
| in the occluded regions, but it might look neater.
| Sharlin wrote:
| Distance to the target doesn't matter because to an
| astronomical telescope every object of interest is at
| optical infinity, but yes, if you know (an approximation)
| of the optical system's _point spread function_ , you can
| compensate for the effects of aberrations including
| diffraction.
|
| The JWST team knows the PSF from having designed,
| simulated, and now actually testing the telescope, and
| likely it will come useful in getting the last bits of
| scientifically valuable information out of the data, but in
| normal use those diffraction spikes in particular are
| unlikely to be any problem. They basically only show up
| because the star in the test image is highly overexposed.
| _xerces_ wrote:
| I believe most of the diffraction is due to the edges of the
| hexagonal mirrors, not the spider holding the mirror. The
| lens flare though I think is due to the spider.
| markus_zhang wrote:
| I'd really love to read a book about the design, engineering and
| project management of James Webb.
| ffhhj wrote:
| Which are your most expected objects that Webb should photograph?
| Here is my list:
|
| 1- M60 blackhole
|
| 2- Proxima Centauri b
|
| 3- Tabby's Star
|
| 4- some apparently empty space
|
| 5- Mars surface
|
| 6- Sagittarius A*
|
| 7- Mercury's craters with water
| qbasic_forever wrote:
| We can get some pretty nice photos of Mar's surface from the
| rovers and drone we have on the surface right now. :) There are
| almost daily updates here: https://twitter.com/NASAPersevere
| ffhhj wrote:
| Sure, but it would be cool to compare the resolution.
| pkaye wrote:
| Some of the priorities are earth like planets that we are
| already aware of and early galaxies close to the big bang time.
| The light from back then would have shifted to the infrared
| spectrum due to red shift.
| baggy_trough wrote:
| It can't image Mercury because it has to stay facing away from
| the sun. Probably probes have done better pictures anyway.
| j0ba wrote:
| TON 618
| 0xFFFE wrote:
| Trappist 1
| mysterypie wrote:
| I was wondering why the star has 6 crisp points and found an
| explanation here (a 3 minute video):
|
| https://www.youtube.com/watch?v=VVAKFJ8VVp4
|
| The most interesting part of the video explains why even your
| naked eye viewing the sky at night will cause this effect -- it's
| due to imperfections in the lens of your eye.
| Maursault wrote:
| I wonder what they would look like if stars _were_ pointed
| objects.
| yakubin wrote:
| To me it looks like this effect:
| <https://www.theclickcommunity.com/blog/creating-
| starbursts-i...>
| superjan wrote:
| I see 8. With the smaller horizontal ones likely coming from
| one of arms of the secondary mirror (check the "selfie" image).
| The linked video is nice, by the way.
| [deleted]
| k__ wrote:
| How do stars look like in animal eyes?
| staindk wrote:
| Good summary but I found it a bit weird how only 2 seconds were
| spent on the 'camera aperture' explanation - as AFAIK that's
| the main cause for photos of stars and lights to have 'points'
| - it depends on how many 'leaves' (? term) your camera/lens
| aperture has -> the more leaves the "more-sided" a shape the
| aperture makes (hexagon, octagon...) thus the more points you
| get when photographing lights.
| Green_man wrote:
| The number of rays is determined by the number of aperture
| blades, as well as whether there's an even or odd number of
| aperture blades
|
| https://phillipreeve.net/blog/best-lenses-for-
| sunstars/#The_...
|
| Interestingly, some modern photography lenses have achieved
| aperture mechanisms with much rounder geometry, sometimes
| with near perfect circles at multiple apertures. This can
| result in a more desirable bokeh, at the cost of well defined
| sun stars.
| blauditore wrote:
| The article fails to explain that, but round aperture is
| equivalent to infinitely many straight blades (and thus
| rays), so there is a light halo instead of distinct rays.
| Sharlin wrote:
| Which is essentially also why you get more diffraction
| limited as you stop down the aperture -- a larger and
| larger fraction of the light that gets through passes
| near the edges (and gets diffracted) rather than the
| central area.
| hatsunearu wrote:
| yup, but when you step down the aperture a lot (which is
| when the sun star effect becomes more pronounced), the
| aperture transitions from more circular to more polygonal,
| so with a lot of lenses, the behavior is that when your
| aperture is a few steps of fully open, it is basically
| circular but when you need the sun starts it's definitely
| there.
| arendtio wrote:
| Awesome video!
|
| Made me laugh and learn at the same time :-)
| [deleted]
| hatsunearu wrote:
| I think the wikipedia explanation is much better.
|
| https://en.wikipedia.org/wiki/Diffraction_spike
|
| One deficiency is why apertures (effectively, the support
| structure in a telescope is an aperture) observe this behavior.
|
| > No matter how fine these support rods are they diffract the
| incoming light from a subject star and this appears as
| diffraction spikes which are the Fourier transform of the
| support struts.
|
| Like why is that the case?
|
| https://en.wikipedia.org/wiki/Airy_disk
|
| Read this if you don't immediately understand why. This is the
| shape of the image you see when the aperture is circular. This
| is the Fourier transform of a circular aperture, which, in 1D,
| is a sinc function.
|
| I can't give a straightfoward answer to elucidate further, but
| if you've done signal processing stuff before you can probably
| handwavey explain that if there is a Fourier-transform
| relationship with one function, due to linearity and spacial
| invariance, you can say that it holds for all functions.
| Gatsky wrote:
| I wonder if this thing will see something which changes the
| course of human civilisation...
| JKCalhoun wrote:
| Considering these 'deep space' images that capture these myriad
| of little galaxies so far away.... The number of galaxies that
| must be out there is inconceivable to me.
|
| Spitballing.
|
| Might there be some space/time mechanism at play whereby we're
| actually seeing the same handful or so of galaxies? Like maybe
| some lensing thing.
|
| Or weirder, we're actually seeing right around the universe
| itself -- as though seeing the back of your head in a mirror if
| you look far enough. Not a topologist, but seems a toroidal
| universe would have a property like this: look far enough and you
| see the back of your head. So perhaps the same galaxies seen from
| multiple angles at the same time appear to be a greater number of
| galaxies than there actually are.
| jerf wrote:
| As well as what ISL said, if the universe is toroidial it seems
| like it's larger than our visible horizon. While images of an
| individual galaxy might be hard to tell if they are repeated,
| we can see enough of the structure of the universe that if our
| visible horizon was much larger than the real value of the
| universe and there was wrapping going on, we'd see it. This
| isn't the exact sort of video I'm looking for, but it's close
| enough to what I'm talking about:
| https://www.youtube.com/watch?v=rENyyRwxpHo Everywhere we look
| we see distinct structures.
|
| It is not a bad thought, though. It may well do some sort of
| wrapping around, just at a larger scale than we can see. It's
| an open problem.
| dm319 wrote:
| We're talking about being toriodal or curved in a 4th spatial
| dimension I assume?
| Keyframe wrote:
| _Everywhere we look we see distinct structures._
|
| This might be us being in an isotropic bubble where outside
| of the bubble is forever gone for us to see due to expansion
| of universe... Not sure how CMBR falls into that however.
| hnthrowaway0315 wrote:
| Watching that video will make anyone humble.
| idealmedtech wrote:
| It's been over a decade since my cosmology class, so forgive
| any errors, but isn't there a constant that describes the
| curvature of the universe [1], which so far has been
| calculated as "flat"? That's not to say we'll ever truly
| know, since you need infinite precision to rule out
| hyperbolic or spherical geometry, but in a flat universe, how
| can you have toroidal geometry?
|
| Per [2]:
|
| > The actual value for critical density value is measured as
| rcritical = 9.47x10-27 kg m-3. From these values, within
| experimental error, the universe seems to be flat.
|
| [1] - https://en.m.wikipedia.org/wiki/Friedmann_equations#Den
| sity_...
|
| [2] - https://en.m.wikipedia.org/wiki/Shape_of_the_universe
| justin66 wrote:
| > Might there be some space/time mechanism at play whereby
| we're actually seeing the same handful or so of galaxies?
|
| That strikes you as the sort of thing nobody would have noticed
| throughout centuries of study?
| colechristensen wrote:
| There are as many galaxies in the observable universe as there
| are stars in our galaxy or... as there are bytes in 100
| gigabytes. Within a factor of five or so.
|
| The universe is flat as far as our best measurements go, if it
| is curved, it is with a much larger radius than the ~100
| billion light year width of the observable universe.
|
| It is indeed difficult to conceive but it is how it is, the
| universe is very big and has a whole lot of unique stuff in it.
|
| Occasionally there is a lensing thing where we see the same
| galaxy twice or so, but not in any way to diminish the 10^11
| other galaxies out there.
| glenstein wrote:
| What's interesting to me is, relative to human scales, cosmic
| _space_ is so much more ridiculously vast than cosmic _time_.
|
| Our size as a percentage of the size of the universe is tiny,
| and our age as a percentage of the universe's age is still
| tiny. But the second number is gargantuan in comparison to
| the first.
| Trasmatta wrote:
| It always seemed odd to me that we're so close to the
| apparent start of the universe. 13.8 billion years isn't
| that long ago, given how big the future time horizon is.
| Jweb_Guru wrote:
| We are close to the beginning of the universe, but we are
| about halfway through the lifetime of our sun, which
| formed right around when 50% of all sunlike stars that
| will ever be formed, had been formed. So we're actually
| around average in many ways.
| Trasmatta wrote:
| Oh, that's interesting! That does make more sense. Most
| of the sun like stars that will ever exist are formed in
| the early universe, so it makes more sense that's why we
| exist when we do.
| grecy wrote:
| Does that mean that roughly around the time our sun dies
| that many more stars will also be dying ?
|
| And then will there simply be way less stars in the
| universe than there are today?
| vishnugupta wrote:
| Your comment reminded me of this story where a space program
| director decided, on a hunch or whim, to point Hubble at a
| seemingly empty space for 100 hours.
|
| The rest, as they say is history. Galaxies went from being rare
| things to abundant ones. Turns out the universe is teeming with
| them.
|
| https://www.nationalgeographic.com/science/article/when-hubb...
| supernova87a wrote:
| It wasn't _quite_ that dramatic a whim or lucky hunch as it
| 's made out to be.
|
| There was input from galaxy researchers on such an idea, and
| I think it was viewed as a bit of a calculated risk compared
| to other normal proposals to spend the telescope time on
| well-known targets visible with a few hours of observing.
| Especially when proposals outnumber available time by a
| factor of approx. 7, people will question why you should
| gamble on something unproven. Hence "director's discretionary
| time".
|
| But of course it was a smart move in setting up the field for
| "what's the next big thing", because if you were to find
| something interesting, it obviously drove the call for larger
| and larger telescopes to study farther and farther things.
| Just studying the crap out of brighter nearby things would
| have been relatively predictable/boring by comparison. (I
| exaggerate a little)
| rbobby wrote:
| Maybe it's a quantum observer effect and the galaxies only
| exist because there's an observer. Dark matter/energy is need
| to make things balance only because we haven't been looking in
| all the right places.
|
| The universe would be an odd old place if that was true.
| lamontcg wrote:
| > Might there be some space/time mechanism at play whereby
| we're actually seeing the same handful or so of galaxies?
|
| Nope. Current evidence is that space is infinite. Even if that
| was all wrong, then its incredibly large due to inflation and
| our past light cone is one tiny bit of it. As time goes on
| we're seeing more and more of it, and parts that used to be in
| contact before inflation are only just coming back into contact
| again (their past light cones overlapping). Those are all
| unique galaxies. An awful lot of physics would have to be wrong
| for that to not be true.
|
| "Space, is big. Really big. You just won't believe how vastly
| hugely mindboggingly big it is. I mean you may think it's a
| long way down the road to the chemist, but that's just peanuts
| to space."
| mhh__ wrote:
| You can reject some notions of repeating patterns / loops in
| space because it would violate Lorentz covariance. You could
| fire a laser in one direction and the opposite, then you know
| your absolute position in space.
| implements wrote:
| Perhaps it's all procedurally generated, and every time we
| build a new telescope there's a supernatural sysadmin out there
| going "Oh, ffs! - We need _more_ new hardware!".
| dom96 wrote:
| Surely if we do live in a simulation then the engineers just
| need to simulate our minds. It's easy to fake what we see
| then as an optimisation instead of generating a whole
| universe.
| mac01021 wrote:
| That assumes we're the object of the simulation rather than
| a byproduct. Maybe what they want to simulate is a universe
| and we've just happened to pop up in a small part of the
| simulation.
| mrtnmcc wrote:
| >> The number of galaxies that must be out there is
| inconceivable to me
|
| Don't worry, there are many times more galaxies in the
| observable universe than neurons in the human brain. Nobody can
| conceive of it.
| ggm wrote:
| That number nobody can conceive of... _add one to it_
| eldenring wrote:
| There's really only like 2 trillion galaxies in the
| observable universe which isn't that much more than the
| number of neurons.
| TaylorAlexander wrote:
| Yes but that's just the observable universe. My
| understanding is that the observable universe is only a
| fraction of the total universe. However that was something
| I found hard to verify so I could be wrong.
| willis936 wrote:
| We don't have an upper bound on the size of the universe.
| It's difficult to construct falsifiable models about
| things that can't be directly observed, but it may well
| be infinite.
| asah wrote:
| TIL there's about as many galaxies in the observable
| universe as trees in the planet.
|
| https://www.google.com/search?q=how+many+trees+are+on+earth
| stavros wrote:
| I don't need to be able to conceive of every individual grain
| to be able to make inferences about sand.
| grishka wrote:
| Back when they were launching JWST, I kept thinking that
| there's a non-zero probability of it proving wrong some of our
| essential assumptions about the universe. Like, you know, they
| keep saying "galaxies that formed just X years after the big
| bang", but what if it turns out there was no big bang? What if
| our estimations of the age and/or size of the universe turn out
| to be wrong?
| qbasic_forever wrote:
| If it proves there was no big bang then that's still an
| exceptional job well done and a huge accomplishment for
| science. Sure there will be more mysteries to solve, but it's
| not like we lose anything by proving something incorrect. It
| will be exciting no matter what they find!
| labster wrote:
| If there's no Big Bang then the origin of the cosmic
| microwave background needs a new explanation: why does it
| exist, and why isn't it more red or blue shifted.
| throwawaycities wrote:
| Even if there wasn't a Big Bang, let's say the universe was
| infinite, we would still have the CMB from the furtherest
| reaching photons from the edges of the visible universe
| that have been stretched to microwaves right?
|
| In other words eventually the nearest galaxies will one day
| become the CMB as the universe continues to expand until
| they are on the edge, until even they fall outside the
| visible universe and no photons/light outside our own
| galaxy will be capable of reaching us and the CMB
| disappears.
| cyphar wrote:
| That's not what the CMB is. The CMB is an incredibly
| uniform pattern which appears to have been formed by a
| very hot plasma at some point in the past. It's difficult
| to imagine an explanation other than the Big Bang (or
| some kind of expansion of a very hot plasma) because the
| uniformity means it was almost certainly concentrated in
| space.
|
| But yes, in the distant future, it will not be possible
| to detect the CMB anymore (and it's entirely possible
| that alien civilisations that evolve at that time would
| probably never have a model of the Big Bang because there
| would be no remaining evidence of it).
| throwawaycities wrote:
| > That's not what the CMB is. The CMB is an incredibly
| uniform pattern which appears to have been formed by a
| very hot plasma at some point in the past.
|
| I understood that the CMB is not photons from plasma but
| the first photons following recombination (when the
| universe cooled enough that electrons and protons formed
| first hydrogen atoms). In other words the universe was
| plasma just before the CMB.
| cheese_van wrote:
| ...and the galaxies will have drifted so far apart, that
| nothing will appear to exist beyond their own galaxy,
| except dust.
| XorNot wrote:
| The problem in an infinite universe is every possible
| location in the sky eventually terminates on a stellar
| surface - a star. So the night sky, if the universe is
| infinite, wouldn't be dark - it would be as bright as the
| sun - in fact the universe would be full of
| omnidirectional radiation coming from all directions at
| all times.
|
| I suppose though, that if space is still expanding but
| the universe is infinite, this might temper it out but it
| doesn't seem like enough - it would have to be an
| expansion precisely tuned to on average send radiation to
| 4 kelvin so we only see a cosmic microwave background,
| and don't wind up being bathed in an infinite amount of
| whatever frequency of radiation.
|
| Infinity is funny like that.
| Gupie wrote:
| > The problem in an infinite universe is every possible
| location in the sky eventually terminates on a stellar
| surface - a star.
|
| Isn't that only true if the universe is infinitely old as
| well as infinitely large?
| XorNot wrote:
| Sure, but postulating an infinitely sized universe (full
| of an infinite amount of mass) does ask the question as
| to why the universe would not be infinitely old?
|
| Particularly when you get into issues like entropy, which
| is the only real determinant of time even existing. A
| finite universe has a natural direction of entropy -
| whereas an infinite one does not, since there's an
| infinite amount of mass and energy and as such no
| possible lowest possible entropy state.
|
| It's actually worse then that though: an infinite massed
| universe by definition would contain every possible
| configuration of that mass somewhere within it. So you
| and I talking right now like this, our past and future
| conversations would also all be somewhere else in the
| infinite universe happening simultaneously.
|
| A universe with an infinite amount of mass and energy in
| infinite space doesn't really have any sensible notion of
| past, present or future - because all possible pasts,
| presents and future, exist at all times somewhere within
| it.
| gilbetron wrote:
| > A universe with an infinite amount of mass and energy
| in infinite space doesn't really have any sensible notion
| of past, present or future - because all possible pasts,
| presents and future, exist at all times somewhere within
| it.
|
| This is actually untrue for many reasons, but one is that
| there are different kinds of infinities. For instance,
| there are an infinite amount of real numbers between 0.0
| and 1.0, and none of them are pi. Just because something
| is infinite, doesn't mean everything is possible within
| that infinity. Again, there are an infinite number of
| integers, but none of the are pi or 0.1 or 37.5
| throwawaycities wrote:
| > So the night sky, if the universe is infinite, wouldn't
| be dark - it would be as bright as the sun
|
| You are inferring infiniteness also translates somehow to
| cosmic density and luminosity. By definition of an
| infinite universe the vast majority will necessarily fall
| outside the observable universe and never be visible to
| us.
|
| As to luminosity, even now when we look up and see dark
| patches in the sky, they are in fact are full of stars
| and galaxies. The most famous picture ever taken by the
| Hubble, the "Hubble Deep Field", was taken by pointing
| towards a dark patch revealing 10s of thousand of
| galaxies. These 10s of thousands of stars and galaxies
| still appear as dark patches in our skies because they
| are not sufficiently luminous to appear in out sky as
| light without the aid of telescopes to collect their dim
| light.
| willis936 wrote:
| Inside the framework of inflation this doesn't follow.
| You can have an infinitely large universe while still
| expanding and cooling over time.
| Keysh wrote:
| That's Olber's Paradox, of course, and it relies on three
| assumptions: 1. The universe is infinitely large _and_ 2.
| The universe is filled with stars _and_ 3. The universe
| has been this way _forever_.
|
| It turns out #3 is wrong, so it's still possible we live
| in an infinite universe.
|
| (Imagine an infinite, unchanging universe filled with
| stars that magically popped into existence a billion
| years ago. You wouldn't have a uniformly bright sky
| because even though every line of sight will
| theoretically terminate on a stellar surface, in most
| cases there hasn't been enough time for light traveling
| along that line of sight -- e.g. from a star 10 billion
| light years away -- to reach your eyes.)
| DebtDeflation wrote:
| The question I've always had is - what if the entire
| universe is not only unthinkably larger than the observable
| universe but also non-homogenous? In other words, what if
| the part of the universe that lies in our past light cone
| is nothing at all like the rest of the universe? The CMB
| and other remnants of the Big Bang could simply be remnants
| of something that happened in a large enough swath of the
| universe to cover our observable universe but still only be
| a tiny part of the entire universe and not represent the
| actual beginning. The parable of the Blind Men and the
| Elephant on a cosmological scale, so to speak.
| peter303 wrote:
| I predict astronomers will observe and catalog all trillion
| observable galaxies in a century. It was probably inconceivable
| a century that we'd observe and catalog two billion stars in
| the Milky Way by now. But with improving technology we have.
| throwawaycities wrote:
| On the scale of the universe you aren't just seeing far away
| objects but seeing the past. For illustrative purposes the edge
| of the Universe is the edge of time, where time has any meaning
| to us, and beyond that is inflation where light didn't travel
| freely.
|
| If somehow the Universe were as you propose and wrapping around
| itself so we were able to stare at the back of our heads, we
| would only see objects from the past to a point, and then the
| objects would begin to appear closer in time again until the
| furthest point where we would once again be looking at the
| present.
| Aerroon wrote:
| The universe was opaque up to about 380,000 years after the
| Big Bang. If the universe loops in on itself and is large
| enough then wouldn't we be blocked by that? And the further
| you go back from there the higher the density would be.
| throwawaycities wrote:
| Meaning we couldn't look straight out and see the back of
| our own heads. Eventually we would run into a point of the
| universe before time had any meaning (the opaque plasma)
| and there would be no looking past that back into the
| present.
| ISL wrote:
| People have looked for hints of this sort of thing without
| success so far.
|
| https://en.m.wikipedia.org/wiki/Shape_of_the_universe#:~:tex...
| .
| dm319 wrote:
| Yes, I wonder about this also. Wouldn't need to be toroidal -
| could just be spherical, but would need to wrap in a 4th
| spatial dimension. It would explain a lot of things, like the
| expansion not having a clear centre, the requirement for dark
| matter (expansion would happen in an orthogonal dimension),
| background radiation (which I never quite understood) and the
| size of the universe.
|
| But that was a high-school idea, and I'm sure some clever
| physicists and astronomers will tell me why this isn't the
| case.
| mensetmanusman wrote:
| " Might there be some space/time mechanism at play whereby
| we're actually seeing the same handful or so of galaxies? Like
| maybe some lensing thing."
|
| Good question. People have been wondering this and have studied
| whether it is possible a la periodic boundary conditions for
| example.
|
| https://aapt.scitation.org/doi/abs/10.1119/1.13499?journalCo...
| MontagFTB wrote:
| I really appreciate how NASA is handling the James Webb. Instead
| of waiting for everything to be _done_ done, they're bringing us
| all along for the setup, giving us "alpha" and "beta" images (if
| you will), and in so doing keeping interest in the telescope. I
| know it'll continue, and I'm all hype about it.
| spaetzleesser wrote:
| NASA has become really good at self promotion and exciting
| people. The JWST launch and deployment is being covered really
| well. I also thought it was great that they had cameras on the
| latest Mars Rover that showed videos of the landing sequence
| from several angles. ESA should learn from NASA.
| n00bface wrote:
| It makes me more confident that the right people are
| responsible for this project. The results for such a critical
| instrument are very important to the success of future
| research. To see them consistently exceeding mission
| objectives...how high can the Webb go?
| gotaquestion wrote:
| It's nice to not see NASA dragged through the mud for a change
| because "SpaceX is cheaper."
| dotnet00 wrote:
| SpaceX is cheaper for rockets, but they also aren't in the
| business of making space telescopes, so that's a complete
| strawman.
| ncmncm wrote:
| NASA's unscrewed exploration has long been top-notch.
| (Although, for the cost, arguably a series of initially less
| sophisticated 'scopes could have been lofted, leading to
| maybe a better one by now.)
|
| It is their crewed program that is completely screwed by
| politics.
| ncmncm wrote:
| *uncrewed
| dtgriscom wrote:
| ... maybe their crewed program is screwed?
| genocidicbunny wrote:
| They purposely designed some of the first experiments it will
| perform to produce aesthetically pleasing images, so they are
| definitely considering the PR angle. You should expect to see
| lots of pretty pictures from the JWST over the next year.
| foolfoolz wrote:
| nasas pr team has done an amazing job over the last 5 or 6
| years. something changed where they understood how to engage
| with people better
| pkaye wrote:
| NASA TV has been around since the 80s. I know they tried to
| engage the public with many MARS lander/rover missions some
| time back.
| overtonwhy wrote:
| They have a great YouTube channel
| sharkweek wrote:
| I love watching the ISS feed they stream on the app
| sometimes. It's fun to make the room all dark and have it up
| on the TV, it's super tranquil.
| trappist wrote:
| I wonder who they've been learning from
| https://www.youtube.com/watch?v=bvim4rsNHkQ
| chasil wrote:
| I really and truly hope for longevity.
|
| "The Webb telescope will use 132 small motors (called
| actuators) to position and occasionally adjust the optics as
| there are few environmental disturbances of a telescope in
| space. Each of the 18 primary mirror segments is controlled by
| 6 positional actuators with a further ROC (radius of curvature)
| actuator at the center to adjust curvature (7 actuators per
| segment), for a total of 126 primary mirror actuators, and
| another 6 actuators for the secondary mirror, giving a total of
| 132. The actuators can position the mirror with 10 nanometer
| (10 millionths of a millimeter) accuracy.
|
| "The actuators are critical in maintaining the alignment of the
| telescope's mirrors, and are designed and manufactured by Ball
| Aerospace & Technologies. Each of the 132 actuators are driven
| by a single stepper motor, providing both fine and coarse
| adjustments. The actuators provide a coarse step size of 58
| nanometers for larger adjustments, and a fine adjustment step
| size of 7 nanometers."
|
| https://en.m.wikipedia.org/wiki/James_Webb_Space_Telescope
| jcadam wrote:
| Any indication how many of those actuators they can lose and
| still maintain functionality (i.e., are any of those
| "spares")?
| chasil wrote:
| Good question. No idea.
| skykooler wrote:
| None of them are spares per se; if any of them fail they
| will have to use the other four on that segment to point it
| away from the sensor and disable that segment.
| oceanghost wrote:
| 3 points in a plane, so maybe half?
| TomVDB wrote:
| No, they require 7 axes of movement. See the video that
| somebody else linked to.
| TaylorAlexander wrote:
| The actuators control the XYZ position and the pitch,
| yaw, and roll, plus curvature. There is no redundancy.
| infogulch wrote:
| The actuator is a genius flexure design that is both
| mechanically simple and accurate. _Breaking Taps_ 3d-prints
| a working replica and describes the design. I highly
| recommend: https://youtu.be/5MxH1sfJLBQ
|
| The actuator breaking wasn't as concerning after seeing the
| design.
| tkluck wrote:
| Thank you for the link, that was incredibly interesting.
| For other people following the link: don't miss out on
| going into the comment section and finding the original
| designer of the mechanism complimenting the video and
| then sharing his own original model - in Legos!
| usrusr wrote:
| Slightly exaggerated paraphrase: "You YouTube kids with
| your fancy 3D printers, here at Ball Aerospace &
| Technology we didn't need all that, we had Legos"
| mywacaday wrote:
| Thanks for that video and channel. See what you mean
| about simple and accurate, strongly agree with the
| presenter calling it genius. Can't help but feel there is
| a strong lesson in there for software people.
| krisoft wrote:
| > Can't help but feel there is a strong lesson in there
| for software people.
|
| Hmm, can you elaborate on that? What is the strong lesson
| for software people specifically?
|
| Don't get me wrong it is a beautiful design, and I'm a
| big fan of flexure designes in general. There is this
| amazing open source project which uses similar flexure
| mechanisms for very accurate positioning of microscope
| samples: https://openflexure.org/
|
| But I fail to see any obvious takeaways which would
| generalise to software development. Other than perhaps
| "Think and work on the same problem for a decade and more
| and you might find a compact and elegant solution." Which
| is nice, when one has that luxury.
| aenis wrote:
| The takeaways are limited, IMHO. Yes, in software
| engineering ingenious, simple, sometimes a bit crude
| solutions exist and can solve otherwise complex problems.
| More often than not, overly complicated, endless stacks
| of abstractions are developed to solve relatively trivial
| problems. But, software engineering is usually about
| maintaining something as part of a larger, dynamic,
| distributed system (comprised of humans, other tech) and
| reliance of brilliance is a limiting factor, since
| brilliant engineers rarely want to support their
| creations for years. With age, I am growing more and more
| tolerant of bloated, verbose, boring code that can be
| passed from one individual to another without _too_ much
| trouble.
|
| I think the actuator is an equivalent of a very clever
| Perl one liner.
| ChrisMarshallNY wrote:
| We tend to make complex solutions to simple problems.
|
| The thing about any problem, is that "the devil is in the
| details." It may seem simple, from a high level, but,
| once we start to "drill down" into the issue, the "rough
| edges" appear.
|
| At that point, we start to break out the baling wire and
| bubblegum, to kludge our original "graceful" design to
| meet the facts on the ground.
|
| It doesn't just happen for software. Hardware suffers
| from the same issue, but software makes it easy to start
| coding before modeling the requirements and context
| completely.
|
| I actually leverage this, in my own work. I call it
| "Evolutionary Design"[0]. It's not for the faint of
| heart, because a big part of it is recognizing when I'm
| rabbitholing, and tossing out what may be weeks of code,
| wholesale. I'm actually going through that process right
| now, with the app I'm developing. I'm working on the
| final feature set.
|
| [0] https://littlegreenviper.com/miscellany/evolutionary-
| design-...
|
| _" There's always an easy solution to every human
| problem; Neat, plausible and wrong."_
|
| _" The fact that I have no remedy for all the sorrows of
| the world is no reason for my accepting yours. It simply
| supports the strong probability that yours is a fake."_
|
| -- H. L. Mencken
|
| _"When the map and the terrain disagree; believe the
| terrain."_
|
| -- Swiss Army Maxim
| jcadam wrote:
| Very cool. I know nothing about these types of actuators
| but you're right that they seem pretty robust. When I
| heard actuators I was thinking of the common types that
| definitely don't last forever :)
|
| Unrelated: reaction wheel assemblies (used for attitude
| control) typically would have one extra wheel as a
| "spare." Redundancy is important enough on spacecraft you
| expect it wherever it is practicable. I used to work in
| aerospace - spent enough time coding spacecraft
| simulation tools that I had to develop at least a working
| familiarity with how some of the common satellite bus
| systems are supposed to work :)
| binarycoffee wrote:
| Thanks for the video, flexure-based designs can be so
| beautiful.
|
| It reminded me of a collaboration I had with a small
| Swiss company that did wonders with electro-discharge
| machining such as this flexure-based mechanism machined
| from a single block of aluminium:
| https://i.imgur.com/PDAVDmJ.jpg
| arbitrage wrote:
| That is gorgeous. Well done.
| dtgriscom wrote:
| My guess: any single one of the actuators could fail, and
| the other actuators could compensate by moving the plane of
| the mirror(s). The exception would be the curvature
| actuators. (IANAL, or the appropriate equivalent...)
| LeifCarrotson wrote:
| Here's a simple video of the Lego prototype of the actuator
| that the inventor, Robert Warden, had on his desk:
|
| https://youtu.be/3WBrqUa_1yk
|
| The full paper describing it is an excellent read:
|
| https://www.esmats.eu/amspapers/pastpapers/pdfs/2006/warden..
| ..
|
| I think the latter was posted to HN a few months ago.
| asah wrote:
| Can someone explain why alignment can't be done in software?
| i.e. collect data from each mirror separately, then switch
| together in software ?
| TheOtherHobbes wrote:
| https://astronomy.stackexchange.com/questions/20605/instead
| -...
| asah wrote:
| Thx! Also this: https://astronomy.stackexchange.com/quest
| ions/20605/instead-...
| Asraelite wrote:
| I'm not certain but I believe to get a high resolution you
| need a large aperture, i.e. photons must physically
| interact from places that are far away from each other.
|
| Doing each mirror separately would observe the photons
| before their wave functions are combined and so it would be
| the same as many small low resolution cameras instead of
| one big high resolution one. It defeats the purpose of a
| large mirror.
| superjan wrote:
| Doesn't that imply that the incoming photons are spread
| out over the entire mirror, several meters?
| NavinF wrote:
| Yeah I was also surprised to find that photons can be
| really big: https://youtu.be/SDtAh9IwG-I
|
| Before I saw the experiments in that video, I assumed
| photons were about as wide as their wavelength.
| Maursault wrote:
| That guy is hilarious.[1][2][3] I'd like to know what
| would happen if the split beam was sent through fibre
| optics to Pluto and back, if the interference pattern
| would persist instantly.
|
| [1] "It's a golden oldie..."
|
| [2] "... just to give the setup a nice high tech look and
| feel."
|
| [3] "The physics behind this is pretty hefty, and not,
| like, youtube video material."
| baq wrote:
| From what little I know about quantum mechanics, the
| statement about changing the light source and expecting
| to not see an interference pattern is very surprising.
| I'd expect to see one.
| BobbyJo wrote:
| Woah. Thank you. This is nuts.
| nazgulnarsil wrote:
| amazing video. thanks.
| Sharlin wrote:
| Hm? Yes, that's how telescopes (and camera lenses) work!
| 4ad wrote:
| Because sensors in the IR and visible range of the EM
| spectrum can only capture magnitude, not phase information.
| At radio frequencies you could do this (in fact it's pretty
| common).
|
| Without phase information, you can combine different
| captures to improve SNR, but it won't improve the
| resolution. To improve resolution you need light
| interference, which requires phase information to be
| preserved.
| geocrasher wrote:
| Yes. It's the same reason you can't take 10 out of focus
| pictures of yourself and get one in focus picture. You need
| actual good data to combine.
| jfengel wrote:
| You can, with enough processing (and knowledge of how out
| of focus it is). It worked for Hubble. But you get more
| good pictures if you get it in focus in the first place.
| Keyframe wrote:
| Deconvolution. Haven't followed that in awhile, but
| getting to original function was next to impossible.
| Recording calibration image and/or recent AI developments
| might've taken that into something awesome. I'll go and
| catch up on material!
| toss1 wrote:
| We really need to watch it with trusting AI.
|
| While my example here isn't photo recognition, the same
| principle applies. I recently sat for a deposition where
| the stenographer used an "AI"transcription system. The
| result was literally pages of errata (vs the standard
| errata sheet that has space for about a dozen lines).
|
| The consistent error I noticed was that the erroneous
| words were (probably) the word most _expected_ in that
| position, and NOT the word that I said.
|
| So, at a glance, it seemed like a really good
| transcription. In fact, many errors were barely
| noticeable to me and I had to go back to the audio
| recording to confirm. And these were errors that
| substantially changed the meaning, or even inverted it.
|
| This is not merely information loss -- the least
| surprising/lowest information item was inserted instead
| of the real item -- this is actual information
| CORRUPTION.
|
| I'd fully expect parallel phenomena from image - "AI -
| filling in the item most expected from the training set,
| and actively corrupting the data by stripping out the
| highest-value info bits and replacing them with the most
| expected.
|
| Beware
| Keyframe wrote:
| Yeah, it's called signal reconstruction for a reason.
| There are classes of it where it's verifiable and decent
| enough however.
| toss1 wrote:
| Yes, I'm sure that with properly constrained and well-
| tested data spaces, it could produce outstanding and very
| helpful results.
|
| But accurate reconstruction in the wild is just sooo far
| away. And for good reason - it would need to have insane
| amounts of experience and exposure to every bit of
| unusual data that existed in the world to get it right...
| toss1 wrote:
| Yup
|
| A engineering friend of mine was working on hardware
| related to mil satellite imagery, and was sent to a
| course that covered all the kinds of post-processing
| techniques they had to improve resolution and what could
| help those techniques upstream. He said that at the end
| of the course, the instructor said the bottom line was
| that while they could do all kinds of 'magic' to improve
| & enhance the photos, the best input to all their
| techniques that would yield the best end result, was to
| take a better photo in the first place.
|
| So, yes, there really is no substitute to a good original
| image.
| dekhn wrote:
| as long as you know the point spread function you can
| focus out of focus images through deconvolution.
| https://imagej.net/imaging/deconvolution Basically, take
| a picture of a well-known object that should look like a
| single pixel, measure how spread out it is, and then use
| that to backconvert images taken from the same camera.
| geocrasher wrote:
| Would you prefer this approach over actually having the
| target in focus?
| dekhn wrote:
| It depends. Personally, I'd apply the technique even to
| focused images, after using a set of fluorescently
| labelled beads of known diameter to calibrate the PSF.
| simonh wrote:
| Other great answers, but if those things weren't an issue I
| think also you'd need one sensor for each mirror, and the
| sensor is bigger and heavier and more complex than a single
| mirror. Or you could just watch the same mirror for X times
| longer where X is the number of mirrors, but then you'd get
| 1/X as many observations.
| mensetmanusman wrote:
| Information theory. You can't fix information you don't
| have.
|
| Think of the csi 'enhance' meme and why that is physically
| impossible without introducing potentially fake
| information.
| [deleted]
| [deleted]
| quantified wrote:
| Between James Webb and Ingenuity, major kudos to things that
| actually work. Can't take any of these successes for granted,
| even if we spend $100 billion (!) on just one of them. Hope Webb
| is safe in its Lagrange point for a long life. Glad we actually
| had built the 100B of wealth to deploy.
|
| Now if we can only get those $800MM littoral combat ships to
| work, we're building like 53 of them and they don't launch up,
| they launch down a few feet. Not rocket science...
| pengaru wrote:
| > Hope Webb is safe in its Lagrange point for a long life
|
| JWST has a 5-year science mission requirement, with 10-year
| propellant life. Unfortunately it has a relatively short upper-
| bound on its lifetime, compared to say Hubble. Though
| apparently there's ~20-years of propellant onboard thanks to a
| precise launch, still a far cry form Hubble's 31 years and
| still ticking.
|
| Should we consider 20-years a long life for such an expensive
| instrument?
| ISL wrote:
| One should not value the time of operation as much as the
| total value of science returned. If JWST can engage in
| science operations for even a year, it will transform our
| precision understanding of the universe.
|
| This is like switching on the first electron microscope when
| everyone has only ever had optical microscopes. We will see
| new and surprising things with unprecedented fidelity. The
| big question has always been, "will JWST's engineering
| actually work?" So far, it looks like it is working very
| well.
| tux3 wrote:
| The glass half full haruspicy is that it might mean we'll be
| forced to start thinking about designing an even better one
| 5-10 years from now :)
| ianai wrote:
| I heard one option for addressing climate change is a huge
| sun shade between us and the sun. I figure that sounds like
| something that could be tuned into a radio telescope array
| or something. Maybe with the earth side being the side used
| for equipment? Idk.
| BurningFrog wrote:
| From memory, that sunshade needs to be many orders of
| magnitude bigger than any telescope.
|
| Which probably means it would have to be a "cloud" of
| millions of smaller shades.
| EZ-Cheeze wrote:
| If enough of a star's light can be blocked by polarized
| filters, data transmission can occur when they are
| switched on and off in a pattern. Maybe with the JWST
| we'll be able to download many different civilizations'
| Wikipedias if they're blinking their suns at us.
| kevin_thibedeau wrote:
| A radio telescope would perform best if it was shielded
| by the moon.
| quantified wrote:
| Let's get $5B/year out of it. Your $1K smartphone is
| expensive if it only lasts 1yr for fun and not so much if it
| lasts 5 years and you get business income via it.
| wolfram74 wrote:
| The Mission extension vehicles (MEVs) are demonstrated
| technology[0] for some geostationary orbit. I think I've
| heard some talk in the press releases that now they know
| they've got as much time as they do, and that it even got
| past it's 300+ single point of failures, they're chatting
| about what kind of maintenance missions they can carry out to
| extend JWST's life span.
|
| [0]https://www.northropgrumman.com/space/space-logistics-
| servic...
| _ph_ wrote:
| There are indeed some reasons, why it would be nice to have
| two JWST. Certainly, at least some costs would have been
| lower for building a second one. Though all the labor would
| have duplicated, and it seems a lot of labor went into just
| building JWST to spec.
|
| But what would buy us the money spent on a second
| telescope. One often named reason is protection against
| failure. That is not so straigth forward, as it sounds. If
| there is a random chance for failure, then a second
| telescope lowers the risk accordingly. However, if there is
| a systematic problem with the design, you would have two
| defective telescopes. That means, you would have even
| wasted more money.
|
| Then, if both succeed, you would have increased the
| "bandwidth", as they could be operated in parallel. But you
| wouldn't have added the capability to do things
| differently. With Voyager 1 and 2 and Spirit and
| Opportunity, they at least were sent on different mission
| profiles and thus justified the expense.
|
| The thing is, 10 Billion is a huge amount of money, if
| another JWST had cost like 5 Billions, thats a lot of
| scientific projects not done because of building a second
| space telescope. I would rather see the money spent onto
| different capabilities. Hubble for example is failing, we
| should have another telescope in the visual range ASAP. As
| soon as Starship reaches orbit, plans should immediately
| start to convert one starship into a humungeous Hubble
| successor.
|
| An instrument like the Thirty Meter Telescope costs just 1
| Billion. There is so much other science those 5 Billion
| would finance. Even if you look around only in the field of
| astronomy and cosmology.
|
| I really like what they did with Curiosity/Perseverance.
| They used a proven platform for a second mission with
| updated sensor and mission profiles. So in my eyes, it
| would be good to invest the money not spent on a second
| JWST to begin construction of a true successor, which
| should be operational before the end of the life time of
| JWST. With upgraded sensors and based on anything we learn
| in the first years JWST is used.
| WalterBright wrote:
| > extend JWST's life span
|
| I recall a thread here when it was launched where I
| suggested building a twin simultaneously, and that the
| increment in cost was likely to be 10% of the cost of one.
|
| One of the critics of this idea said there was no need for
| another, as there was only so much the JWST could discover.
| But it's hardly been turned on before people are trying to
| figure out how to make it last longer. Sigh.
|
| P.S. I found out later that in the past NASA would build
| probes in pairs, and made extra parts in case one was
| damaged or didn't work. So it really couldn't be _that_
| expensive to have built a twin.
| mturmon wrote:
| You have indeed raised this idea before. The replies in
| other threads, among people familiar with this design
| space, will be the same here, as they were before
| (https://news.ycombinator.com/item?id=29855830).
|
| Namely:
|
| These devices are one of a kind items, fabricated,
| integrated, and tested manually, not on some kind of
| assembly line. There isn't an economy of scale.
|
| Your conjecture is just not correct. It's remarkably
| hubristic to think the people who design these space
| telescopes have continued to do it wrong because making
| duplicates has not occurred to them.
| ericd wrote:
| When is the second copy of anything ever the same price
| as the first? That thread talks about the second being
| maybe 30% of the cost of the first. Is that not
| "economies of scale"? And I think that seems like a great
| deal, given how much universe there is to look at, and
| the potential for the first to not survive until the end
| of its expected lifetime. Hell, why not put 10 of them up
| there, and iterate on the design?
| WalterBright wrote:
| Even if building a 2nd one cost the same as building the
| first, how much of that $10 billion is design and
| development cost? $0 of that will factor in to the cost
| of the second.
|
| I've fabricated many things with my hands and machine
| tools. The second one takes dramatically less time, in
| every case. Even the 2nd set of materials cost less. For
| example, I ordered a needle bearing the other day for $7,
| but with shipping the total came out to $20. If I ordered
| two bearings, the total cost would have been $27, not
| $40.
|
| It took me 20 minutes or so to install it. If I installed
| it a second time, I could have done it in 5 minutes.
|
| The reason is simple. I had the right tools laid out, and
| I knew exactly what to do the second time.
|
| So, yeah, I was quite unconvinced in the last thread.
|
| P.S. I did not say they were doing it wrong.
| mturmon wrote:
| There is no reason a priori to believe that integration
| and test of one of a kind space cryocoolers scales the
| same way postage does, or batching out parts at a drill
| press.
|
| I'd suggest that it's on you to demonstrate why these
| analogies should hold.
| WalterBright wrote:
| > integration and test of one of a kind space cryocoolers
|
| The point is they wouldn't be one of a kind if #2 was
| built. Planning, designing, iterative prototypes,
| designing tests, designing test equipment, building test
| equipment, devising test plans, writing the enormous
| amount of software require for all of that, for the
| ground stations, etc., all add nothing to the cost of
| building #2.
|
| Normally, people take the cost of a program and divide it
| by the number of units built, and call that the per-unit
| cost. That's an accounting fiction. The first one costs
| the bulk, the rest cost far less per unit.
|
| > no reason
|
| The reason is I can't think of any endeavor where the
| incremental cost of #2 doesn't drop dramatically.
| pengaru wrote:
| I agree entirely. It's not like JWST components were
| built from diamonds or something where the material costs
| dominated the budget.
|
| It wouldn't surprise me if there were already more than
| one made for many of the bespoke components used in the
| telescope. Nobody makes a one-off component without some
| iteration and covering of their own ass in case something
| goes awry in shipping or assembly.
| bryanlarsen wrote:
| Perseverance was originally a twin of Curiosity, but it
| cost more than Curiosity. There's no way that a twin of
| JWST would cost only 10%.
| WalterBright wrote:
| > Perseverance was originally a twin of Curiosity, but it
| cost more than Curiosity.
|
| I can't imagine how that could come about.
|
| > There's no way that a twin of JWST would cost only 10%.
|
| It's kind of the way building things works. The cost of
| the prototype is enormous compared to the next one. For
| one thing, the additional R+D cost is $0. The additional
| cost of the software (and I bet the custom software is a
| big chunk) is $0. The additional cost of committee
| meetings to discuss competing alternatives is $0. And on
| and on.
|
| When cutting parts, the cost isn't in cutting the parts.
| The cost is setting up the machine to cut the parts. The
| cutting cost is trivial.
| stopping wrote:
| I still can't figure out why this "economies of scale"
| misconception is so popular on HN with respect to JWST.
| The major costs of building JWST are in the testing +
| validation + refinement phases, which must be done
| meticulously for every unit that is built. A JWST "out of
| the box" is guaranteed to fail: literally, you could
| launch a million "unrefined" JWSTs and every single one
| of them will experience a critical mission failure.
|
| Most components of the JWST are not within spec as they
| leave the factory floor; for many components, the
| precision required cannot be achieved with machining
| metrology alone. Remember that system error compounds
| with every new component that is incorporated. Components
| have to be constructed, integrated, and then
| measured/validated with sophisticated metrology equipment
| after full assembly. If you're lucky, you can modify the
| components you have to achieve the desired overall
| tolerances. But a lot of the time, you have to bin the
| same component a dozen times until you get a batch which
| happens to be correct (much like in microchip
| manufacturing).
|
| And this is just for physical manufacturing -- there are
| multiple other dimensions which are impossible to get
| right the first time, requiring multiple iterations until
| your integration tests pass. Many of these test scenarios
| are extremely expensive to simulate (e.g. full-size
| vacuum chambers, launch and zero-g simulators), and must
| be done to validate every single phase of a 5-year
| mission to an extremely high chance of success (from
| transport to launch site -> launch -> full deployment ->
| science operations). Something as simple as a wrongly-
| tensioned cable is enough to scrap an entire mission --
| the validation is absolutely essential to ensure that
| anything from a manufacturing defect to a simple human
| error doesn't make it through to launch.
|
| Even in spite of all the lessons learned from JWST 1, I
| would be surprised if JWST 2's cost was less than 50% of
| JWST 1 (realistically, I'd peg it at ~80%). The testing
| costs are a very high fixed cost that must be paid for
| every unit you make. There's no other way around it.
| WalterBright wrote:
| I remember seeing a documentary on designing the
| parachute for one of the Mars landers. JPL build this
| huge building solely for the purpose of testing the
| parachute designs. Design after design after design
| failed, and the engineers were worried that they'd never
| figure out how to make a working Mars parachute.
|
| But they did come up with a design that worked. Phew!
|
| The cost of that special building, the building's design,
| the special machinery that filled it, and all those
| months of testing various parachute designs must have
| been enormous, and all count for the cost of parachute
| #1. The construction of parachute #2, after all that, was
| likely insignificant in comparison.
| WalterBright wrote:
| Again, you'd have $0 in research and development and
| software and test rig costs of #2.
|
| > The testing costs are a very high fixed cost
|
| I'm sure they are. But you won't have to design the tests
| and build the test rigs and validate the test procedures
| a second time. Secondly, you'll inevitably learn from the
| first test runs to need less iteration.
|
| For example, the full-size vacuum chamber. You would
| already have it on hand, and not need to build another
| one. Having already just run #1 through it, you'd know
| just what to do to get #2 through.
|
| For example, the first time I took the heads off my
| Mustang it took 4 hours. The second time 2 hours. The
| third time 20 minutes. The procedure was already all laid
| out for me in the shop manual. But knowing just what to
| do cut the time enormously.
| jcranmer wrote:
| > When cutting parts, the cost isn't in cutting the
| parts. The cost is setting up the machine to cut the
| parts. The cutting cost is trivial.
|
| When you're building a one-off, you aren't setting up a
| machine to cut the parts. You're just cutting the parts
| more or less by hand. It'd be too expensive to set up the
| machine, and calibrate, and run all of the prototypes to
| make sure it works, if all you need is a couple of pieces
| out of it.
| WalterBright wrote:
| I've made parts on milling machines and lathes. The time
| spent is on the setup, not the cut.
| 41b696ef1113 wrote:
| 20 years of expected propellant, but other critical parts
| that could fail before that time.
| mulmen wrote:
| Maybe a shorter life is a feature if it adds capability. JWST
| was built to further investigate discoveries made with
| Hubble. Presumably whatever comes after JWST will similarly
| drill into discoveries we are about to make.
| mturmon wrote:
| Your $100B figure should be $10B, for Webb. Ingenuity was an
| about $80M part of Perseverance which was $2.4B in total.
| quantified wrote:
| Off-by-10 error, shame face here. Can't edit now that replies
| have rolled in.
|
| W.r.t the comparison to other science and engineering
| efficacy, defense spending is for total shit.
| nieve wrote:
| Shouldn't that be 10, not 100?
| quantified wrote:
| Yes.
| mulmen wrote:
| Military spending isn't like buying groceries. The US Military
| is a jobs program. Even a failed program fulfills this purpose.
| No amount of spending is "wasted".
| vgel wrote:
| This is the Broken Window Fallacy (https://en.m.wikipedia.org
| /wiki/Parable_of_the_broken_window) -- without the military
| spending, those same jobs could have been created by the
| government to do something _useful_ , like fixing our
| crumbling infrastructure.
| astrange wrote:
| The studies giving our infrastructure bad grades are mostly
| coming from the contractors we'd be hiring to fix them.
| Schiendelman wrote:
| A bridge just collapsed in Pennsylvania. In Seattle we
| have a major chunk of the city cut off because a bridge
| cracked. Every city's transit system is aging or needs
| expansion badly.
| willis936 wrote:
| I drive on our roads. I drink our water. As anyone who
| does these things can tell you: our infrastructure is a
| god damn trainwreck.
| quantified wrote:
| War is unfortunately real, if you read the papers. Our
| spending on stuff that isn't people is massively kickbacks
| and back-scratching.
|
| Look at wasted energy inputs and unrecyclable materials as
| the true wastes, and the offshored/oligarch-concentrated
| money as a time bomb for when it gets actually deployed from
| its base in Virgin Islands.
| coffeeblack wrote:
| That's awesome.
|
| Now let's mass-produce 50 of them and put them all over any
| Lagrange point there is, and on the dark side of the moon.
| Sharlin wrote:
| There's no dark side of the moon, unless you count some of the
| craters near the poles whose floors are in permanent shadow.
| dtgriscom wrote:
| What??? Pink Floyd lied to us???
| willis936 wrote:
| The dark side of the moon refers to the hemisphere facing
| away from Earth.
| gruturo wrote:
| But it's actually NOT dark, it's fully illuminated, just
| facing away from us. While normally this would be a nitpick
| (it's _far_ side, not _dark_ side!), it actually matters a
| lot for an infrared telescope.
| willis936 wrote:
| I'm letting you know what they meant. It's a common
| expression.
|
| https://en.wikipedia.org/wiki/Dark_Side_of_the_Moon_(disa
| mbi...
| Sharlin wrote:
| No matter what they meant, the point is that the idea of
| putting an infrared telescope anywhere that's _not_
| permanently dark and cold is a nonstarter. So it would
| only make sense to build one on the far side of the moon
| if it were _actually_ dark.
| willis936 wrote:
| JWST is never in the shade of Earth or moon.
| Sharlin wrote:
| Yes, but it has its own sunshade, with all the complexity
| and SPOFs it entails. The point is that at L2 it only
| needs a _relatively_ small sunshield to block the three
| way too bright things in the sky, without having to move
| a lot to keep them shielded. On the lunar far side, it
| would have to block _one whole hemisphere of the sky_
| (ie. the lunar surface) PLUS the sun, which moves in the
| sky, PLUS insulate the structure from conducting heat
| from the surface. Oh, and radio doesn 't work too well
| through 3000 km of rock so you'd need a relay satellite
| system just to communicate with Earth. _And_ you 'd need
| a non-solar source of power for the 14-day lunar night.
|
| But building an infrared telescope in one of the
| permanently shaded polar craters? _That_ just might make
| sense at some point, but likely not we have robust crewed
| infrastructure in place. The polar areas are very
| attractive from a crewed mission perspective as well,
| because we now know there are sizeable amounts of water
| ice there _and_ at the same time on the crater rims you
| can get continuous sunlight for solar panels.
| coffeeblack wrote:
| Because that was the important part of my post?
| Sharlin wrote:
| Yes, in this case it was, because there's no point in
| putting an _infrared_ telescope somewhere that's actually
| not in permanent shade and extreme cold!
| ck2 wrote:
| The endless dots as entire galaxies in that photo is just beyond
| mind-blowing.
|
| I wonder if the public can really grasp it, not just grains of
| sands on a beach but each one a beach with 100-MILLION grains of
| sand.
|
| If we can't have FTL travel in my lifetime sure would be nice if
| they figure out FTL communication.
| themeiguoren wrote:
| What were the expectations and what are they measuring that
| exceeds that? I haven't seen any comparison of the metrics. From
| my memory, the JWST was roughly a 10x upgrade relative to Hubble
| in each of spectral resolution, angular resolution, and platform
| stability. How are those numbers looking now?
| vgchh wrote:
| A bit poetic, but suddenly the universe feels a bit more
| approachable, more within reach, a bit more sane. As if, through
| JWST, you can extend your hand and touch and feel and socialize
| with neighboring galaxies. Truly a window to our galactic
| neighbors.
| sddat wrote:
| Is technology like the webb telescope design , or curiosity
| design open and public ? I mean eg CAD , components used , other
| details ?
| zokier wrote:
| In general, no. Individual elements of the design might be
| explained in some articles, and there are some overview
| articles like e.g.
| https://link.springer.com/article/10.1007/s11214-012-9892-2 but
| the actual engineering resources are usually not available to
| public
| marcodiego wrote:
| I'm relieved we don't have a new Hubble crisis.
| chaostheory wrote:
| Maybe this will start the transition from terrestrial telescopes
| to one's based in space instead? This should be good news for
| SpaceX and Starlink
| sizzzzlerz wrote:
| A universe of kudos to NASA, Goddard, and the hundreds, maybe
| thousands, of scientists, engineers, and technicians who
| designed, built, tested, launched, and now, run, this jewel. This
| is just the beginning.
| blenderdt wrote:
| Here a nice video that explains the mechanism that aligns each
| mirror:
|
| https://youtu.be/5MxH1sfJLBQ
|
| It is amazing that this is done with only a single motor.
|
| It works something like this: one direction of the motor sets
| which axis to align, the other direction sets the alignment of
| the chosen axis.
| krisoft wrote:
| > It is amazing that this is done with only a single motor.
|
| No. You misunderstood the video. There are 6 motors per mirror
| segment. Listen to video you linked at 9:11. It says:
|
| "There are 6 actuators per mirror segment, and they are
| arranged in a hexapod or Stewart-platform configuration."
|
| What you are confused about is that there is only a single
| motor per actuator. One could naively think "oh we need a rough
| adjustment, and a fine adjustment so we will need two motors
| for each of those". But they managed to make it more clever,
| and only use one motor for both the rough adjustment and the
| fine one. When they run the motor in one direction it adjusts
| the distance of the actuator roughly (minimum step size 0.058
| micron) and when they run it in the other direction it adjusts
| finely (minimum step size is 7.7 nanometer).
| blenderdt wrote:
| Ah yes, you are right. I was mixing up another video with
| this one.
| dtgriscom wrote:
| Pedantry: when the motor starts moving, it's a fine
| correction, but after one rotation of one of the gears it
| hits a stop and changes to a coarse correction. It then
| continues to do coarse correction as long as you rotate in
| that one direction.
|
| If you reverse the motor, you get fine correction again until
| that gear turns one rotation and hits the other side of the
| stop, reverting to coarse correction.
|
| Once you have things coarsely aligned, you back the motor a
| bit and then operate within the single rotation of that gear,
| staying with fine correction.
| ourmandave wrote:
| Like Hubble, are images taken with JWST public domain?
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