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Here's a Hubble vs JWST comparison zoomed into my favorite part: https://twitter.com/sprigland/status/1546633629236748294/photo/1 https://twitter.com/sprigland/

by darzu 4y ago

Here's a Hubble vs JWST comparison zoomed into my favorite part: https://twitter.com/sprigland/status/1546633629236748294/photo/1 https://twitter.com/sprigland/status/1546633629236748294/pho...

ncmncm 4y ago
To me, most remarkable is how little different they are. One is 140 hours, the other 12 hours. So, mainly this calibrates JWST as 10-20x Hubble sensitivity, with noticeably but not radically improved sharpness, but radically less noise. Presumably the actually important results will be the much longer exposures and the redder things Hubble can't see at all, or that would be obscured by noise. JWST depends very heavily on gravitational lensing and perverse perspective (where things far enough away look bigger because the space they were in grew) to get usefully detailed images. Which is a Good Thing, because we could not have lofted a big enough mirror to get such images directly. In The Future, when we loft hundreds of flat mirrors maintained in an array hundreds of km across, all this will seem pretty pedestrian. But those will have to be out by Neptune so the whole thing can be kept cold enough to be useful. Powering it will be a tricky affair: it will probably need beamed microwave power from a correspondingly large solar concentrator, or maybe D-3He FRC reactor if that can be got working. Then, getting the data home will be a project of its own. In the more distant future, civilization will have shifted major operations and population out there to take advantage of access to the thermodynamically most irreducible resource, cold. That probably cannot happen until after p-11B fusion is mastered. (To be clear: people won't move out there, much; rather, population out there will outgrow Earth's.)
- JohnJamesRambo 4y ago
  What will we glean from your Neptune array that would justify the massive cost? Won’t it just look like this but sharper images of galaxies and earlier and earlier in time? What are we trying to discover then? Surely almost everything about the universe that we can know from our location will be known then. Your Neptune array sounds like one of those bird watchers with the huge telephoto lens just hoping to capture a great shot of yet another bird the world has seen millions of times. “All science is either physics or stamp collecting.”
  - ncmncm 4y ago
    You could have said the same about JWST a hundred years ago. Many would have, and would have been as wrong.
  - oceanplexian 4y ago
    At a certain size it becomes possible to directly image exoplanets in enough detail to tell us what the weather looks like, atmospheric composition, perhaps even images of extraterrestrial cities.
  - sbierwagen 4y ago
    Ultralarge telescopes would let you directly image surface features of exoplanets. There's plenty of stuff we'd like to look at outside our solar system. We could send interstellar probes to local systems, but sending probes to stars thousands of light years away is still going to be pretty tough, even with far future technology.
  - meowkit 4y ago
    The hypothetical question to a hypothetical situation deserves a hypothetical answer. There would be no massive cost. It would be a project affordable by the curious humans/robots/organizations of The Future. Automation will construction and manage the array, and the civilization building such a structure will be post-scarcity to some extent.
- deleted 4y ago
  [deleted]
- darzu 4y ago
  You don't think this is radically increased sharpness? Look at the orange ones on the right: https://twitter.com/sprigland/status/1546633787030704129 https://twitter.com/sprigland/status/1546633787030704129
  - ncmncm 4y ago
    There is much less speckle noise in the JWST image, but the relative sizes of light patches roughly match. The lack of speckle noise is what will be important, because the dim stuff that doesn't show here is what will turn up in longer exposures, and not be obscured by it.
- blueblisters 4y ago
  > In The Future, when we loft hundreds of flat mirrors maintained in an array hundreds of km across, all this will seem pretty pedestrian. Or we use the Sun as a gravitational lens.

by darzu 4y ago

Here's a Hubble vs JWST comparison zoomed into my favorite part: https://twitter.com/sprigland/status/1546633629236748294/photo/1 https://twitter.com/sprigland/status/1546633629236748294/pho...

ncmncm 4y ago

To me, most remarkable is how little different they are. One is 140 hours, the other 12 hours. So, mainly this calibrates JWST as 10-20x Hubble sensitivity, with noticeably but not radically improved sharpness, but radically less noise. Presumably the actually important results will be the much longer exposures and the redder things Hubble can't see at all, or that would be obscured by noise. JWST depends very heavily on gravitational lensing and perverse perspective (where things far enough away look bigger because the space they were in grew) to get usefully detailed images. Which is a Good Thing, because we could not have lofted a big enough mirror to get such images directly. In The Future, when we loft hundreds of flat mirrors maintained in an array hundreds of km across, all this will seem pretty pedestrian. But those will have to be out by Neptune so the whole thing can be kept cold enough to be useful. Powering it will be a tricky affair: it will probably need beamed microwave power from a correspondingly large solar concentrator, or maybe D-3He FRC reactor if that can be got working. Then, getting the data home will be a project of its own. In the more distant future, civilization will have shifted major operations and population out there to take advantage of access to the thermodynamically most irreducible resource, cold. That probably cannot happen until after p-11B fusion is mastered. (To be clear: people won't move out there, much; rather, population out there will outgrow Earth's.)

JohnJamesRambo 4y ago
What will we glean from your Neptune array that would justify the massive cost? Won’t it just look like this but sharper images of galaxies and earlier and earlier in time? What are we trying to discover then? Surely almost everything about the universe that we can know from our location will be known then. Your Neptune array sounds like one of those bird watchers with the huge telephoto lens just hoping to capture a great shot of yet another bird the world has seen millions of times. “All science is either physics or stamp collecting.”
- ncmncm 4y ago
  You could have said the same about JWST a hundred years ago. Many would have, and would have been as wrong.
- oceanplexian 4y ago
  At a certain size it becomes possible to directly image exoplanets in enough detail to tell us what the weather looks like, atmospheric composition, perhaps even images of extraterrestrial cities.
- sbierwagen 4y ago
  Ultralarge telescopes would let you directly image surface features of exoplanets. There's plenty of stuff we'd like to look at outside our solar system. We could send interstellar probes to local systems, but sending probes to stars thousands of light years away is still going to be pretty tough, even with far future technology.
- meowkit 4y ago
  The hypothetical question to a hypothetical situation deserves a hypothetical answer. There would be no massive cost. It would be a project affordable by the curious humans/robots/organizations of The Future. Automation will construction and manage the array, and the civilization building such a structure will be post-scarcity to some extent.
deleted 4y ago
[deleted]
darzu 4y ago
You don't think this is radically increased sharpness? Look at the orange ones on the right: https://twitter.com/sprigland/status/1546633787030704129 https://twitter.com/sprigland/status/1546633787030704129
- ncmncm 4y ago
  There is much less speckle noise in the JWST image, but the relative sizes of light patches roughly match. The lack of speckle noise is what will be important, because the dim stuff that doesn't show here is what will turn up in longer exposures, and not be obscured by it.
blueblisters 4y ago
> In The Future, when we loft hundreds of flat mirrors maintained in an array hundreds of km across, all this will seem pretty pedestrian. Or we use the Sun as a gravitational lens.