How To Build a Telescope That Trumps Hubble 185
An anonymous reader writes "In cleanrooms around the country NASA and its contractors are building the James Webb Space Telescope, a marvel of engineering scheduled to launch in 2014. This gallery shows the features that will allow Webb to take the universe's baby pictures in infrared — most notably an 18-segment mirror and a 5-layer sunshield. I can't wait until Webb settles into its Lagrangian point way out beyond the moon and gets to work."
The universe is infinite (Score:2, Interesting)
So why do they thing that the universe isn't infinite? It seems that every time they get a bigger telescope the size of the universe gets bigger :\ Did they ever think that that big bang thing could have just been a localized event?
Re:The universe is infinite (Score:5, Informative)
Why do you think it is infinite, without any proof whatsoever? All evidence we have is that the observable universe is finite, and observations of the early universe (thanks to the finite speed of light) match what the Big Bang Theory predicted. Ergo, it's the best answer we've got right now, and the burden of proof is on those who have evidence to the contrary to produce it.
Is it possible there's an unobservable universe outside of the observable universe? Of course. But you can't do science with it because it is simply impossible to observe.
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I have just as much proof that the universe is infinite as they do that it's not. That is to say exactly none. We will never be able to prove that it is infinite by measurement just and we will never be able to prove that it is finite. Like I said a hunch isn't exactly proof with either argument. A year ago the "universe" was about ten times smaller than it is now. Once the new telescope is functional I'm going to make the wild speculation that to will get bigger yet.
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Re:The universe is infinite (Score:4, Informative)
You really don't know much do you? The radiation comes from the beginning of the universe, back when everything was a huge soup of particles. It's one of the greater proofs for the big bang theory, since there's no other reason for it to be there than to have one point where the universe was so dense it was irradiating in a nearly uniform manner. By studying the irregularities in the emissions, we can then learn more about that state in the universe's evolution, as well as what happened after that.
There's no distance to speak of because when those were around, they were everywhere and the universe wasn't of the same dimensions. We can measure that the universe is expanding, the big bang theory says there was a time where it was essentially a singularity, thus we can say (with good probability of being right) that the universe is finite.
Is it finite in the sense of a sheet of paper? Probably not. There won't be a wall with "the Universe ends here." written on it. Rather, it might very well be like the flat Earth theories: a loop that uses an additional dimension to complete. Whereas the Earth is a 3D object that was being represented as 2D (so you'd have edges even though they do not actually exist), it's very possible the universe loops around in another higher dimension.
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I did state that the near uniform radiation may only appear to be uniform because we lack the method to measure it with greater precision.
We already know that the cosmic microwave background (CMB) is near uniform not uniform. The perturbations in the CMB have been measured and are one of the attempts to say things about the parts of the universe that we can't observe (not being in our light cone), such as a minimum estimated extent of the current universe.
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You sound like Bill O'Reilly. Cosmic background radiation. You can't explain that.
Your argument is just like the arguments of people who disagree with evolution or AGW. You're just making stuff up to be argumentative. If you actually want to learn something, you can read about it [wikipedia.org].
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http://www.cracked.com/video_18254_bill-oreilly-teaches-kids-about-science.html [cracked.com]
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Who says you can't be skeptical about AGW? That's never been the argument.
The reason it appears so is because there is a vast imbalance in the two "sides" of the AGW debate regarding scientific knowledge and understanding of the way science works. On the one side you have actual scientists, on the other side you have people (often high profile TV and radio hosts) where the level of scepticism is on the order of "well, look at all that record snowfall we had last night! so much for this so-called "global war
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Actually mathematic proofs are based on assumptions as well.
Absolute knowledge is impossible since ultimately all methods of observation are subjective. But since all is subjective you have to sort of agree to accept the more obvious empirical data or reject *all* data.
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Actually, you're confounding the problem. The observable universe is always going to be finite until such a time as the observable universe and the universe are the same and the universe itself proves to have some sort of a limit in dimension.
I don't personally like the idea of confusing mass and energy with the dimension of the universe as you don't measure mass or energy with meters. If you're able to do that without any other units of measure, then you might have a point, but as it is there isn't any goo
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Maybe he's bounded in a nut shell?
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The observable universe doesn't "exist". It's just a construct, an abstraction we've created to describe what we, here on Earth, can see. It's not material. you could say it's just like a country's frontiers, something that matters for us humans but that doesn't really exist otherwise. The observable universe is finite because of the speed of light and the age of the universe. We cannot see what light cannot bring to us. With time, the observable universe will expand, since light from farther away will be a
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It all boils down to definition. What is the size of the universe? Is it the extent of space which contains matter? light? That is finite, according to our current knowledge, but is usually called "the observable universe." Is there something which prevents it from growing infinitely (aside from gravity and the potential "big crash")? Observations show the observable universe is still expanding, and there is legitimate argument that growth can co
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You can count to infinity (though it would take an infinite amount of time). That doesn't mean you are infinite or the number you are counting is. In the same manner, the universe can be expanding forever without ever being infinite.
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Then that is the fault of science.
In all the infinity that that is -- whether that be endless nothing beyond our 'universe bubble' (but why it wouldn't be equally likely to be an endless series of self-contained universe bubbles, is beyond me).
And that's where 'faith' can enter into science. Thinking that 'science' does anything other than predict conditions in the little speck of universe that we know about -- and nothing about the volumes beyond -- and that some people lean toward believing that our uni
Re:The universe is infinite (Score:4, Insightful)
Was space created by the Big Bang, or did the Big Bang happen inside of space that already existed?
Observe something that is more distant in space-time than the big bang, and settle the matter!
It is fine to speculate, but if you want coherent scientific models of the universe, you need to either assume the 13.7 billion light-year horizon or else show by observation or by theory that the horizon does not exist.
The ideas of an infinite theoretical universe aren't incompatible with a finite observable universe, but people who build telescopes are going to be concerned exclusively with the practical aspects of the latter, even if they believe in the former.
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Precisely, it's pretty well established that we can't view all of the universe. Given the speed of light and that we're using light or various waves that travel at or near the speed of light, I think it's pretty inescapable that we aren't seeing everything. For all we know just outside our range of observation is a giant window in some sort of even larger department store display case. Sure it's incredibly unlikely, but beyond the range of what we can sense all sorts of weird things could be happening.
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Was space created by the Big Bang, or did the Big Bang happen inside of space that already existed?
You ask it like it's some kind of unanswered question. Yes, space and time were created at the moment of the Big Bang. The question is HOW that happened.
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This is the part that always gets me..... the "nothing"
I understand that "nothing" is a concept that is very hard to grasp for a human being, but still...
As far as I understand the big bang is a series of events that led to the creation of our current universe. The part I can't get my head around is how "nothing" can turn into "something".
It seems to me that an event like the big bang had to be triggered by at least ''something". And that that "something" must have had some form of physic laws in order to t
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There's a lot of unclear and contentious issues at work here, I think; and unfortunately I don't know enough to gve an informed opinion on it all, but ...
Was space created by the Big Bang, or did the Big Bang happen inside of space that already existed?
Observe something that is more distant in space-time than the big bang, and settle the matter!
"Space" is only a convenient mathematical model of reality - mathematically a space is loosely speaking a set with some topological structure. In all our current models "space" is assumed to be a pseudo-Riemannian manifold - more or less - and as far as I know, any such thing can be embedded in an Euclidean space of higher dimension; don't ask me about det
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It does not really matter if it is infinite or not.
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So if there another big bang overlapped our Visible Universe we might see a big corner of space blue shift. You can bet a lot of papers would get written about that.
To defend Astro
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I actually want both. The hubble is awesome because it has multiple camera's and can view objects in multiple wave lengths.
Infrared is good, ultraviolet is good, but you can't get some of the stunning images the Hubble has produced without some visible wavelengths as well.
What was that comet? Levy 9 that hit jupiter years ago?? only the hubble got good images off of that. James webb won't be able to do such things. So we need both or even better, both in a binocular fashion. So we can see the same image
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IMHO, Astronomers forget to use the word visible, when they say universe.
I don't think they forget, I think they know it's redundant since traditionally "the Universe" (uppercase 'U') is everything, and "the universe" (lowercase 'u') is the visible universe.
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Did they ever think that that big bang thing could have just been a localized event?
I am willing to bet money that they do (I am assuming you mean professional physicists). This guy [wikipedia.org], for example, thinks that bangs may be happening inside black holes, and new universes are created all the time, with parameters "inherited" from parent universes. This is almost an evolutionary interpretation of the largest-scale cosmology, with the parameters of our own universe being this way because other sets of parameters caused premature death (say, a big freeze) before new universes could be created. Th
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So why do they thing that the universe isn't infinite?
Do you mean infinite in size, or infinite in age? Because the only implication of the summary or article is that the universe is finite in age. And there are pretty good theories with lots of observational support that suggest that the universe-as-we-know-it has a finite age.
It seems that every time they get a bigger telescope the size of the universe gets bigger :\
No, actually, that's not the case at all. Bigger telescopes have allowed us to see to points asymptotically approaching the theorized age of the universe, but it's been a long time since a bigger telescope has actually meant we had t
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Negative infinity makes my head hurt.
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For experimental/observational science 'the universe' and 'the observable universe' are the same thing, as by definition that's all we can know actually exists. If you think there's a distinction between the 2 terms you're the one making an assumption.*
* This is not necessarily a bad thing, there are many cosmological theories that feature the idea that there are vast areas of the universe beyond our current abilities to detect them. However all such theories are only at the hypothesis stage - currently wit
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Actually not. Suppose we can observe object A, which is influenced by object B. Then the light from B must have been able to reach A before the light that reached us left A. In which case that light could have got all the way to us.
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We have seen ligth (actually microwaves) from events longer ago and so more distant in space than the early galaxies Webb is targetting -- namely the cosmic microwave background. However there is a gap between that, and the most distant objects we can see in detail with Hubble. Webb is to look into that gap.
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It's only a sphere if it's finite in size, which is the problem. If you're defining the universe to be spherical then you're defining it to be finite in size. Which is largely fine at this point as we can't observe the furthest reaches that current theory predicts, but if we ever can see beyond it then we'll have to start really worrying about things like that.
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He's defining it to be hyperspherical. Not the same thing at all. The hypersphere, or 3-sphere, is the mathematical step up of a sphere from 3D space into 4D space. It's to a sphere what a sphere is to a circle.
A hypersphere would seem infinite by our measurements, despite being finite if you move into a higher dimension.
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True, but it's the same problem, he's defining rather than proving. And without some evidence to back it up, or even reason to take that view, it's pretty meaningless. I'm OK with speculation, but there does need to be some justification and or rationale involved. Given that we can't even see the edges of what we predict to be the size of the Universe, it's really hard to have anything intelligent to say about what might be really far out there.
Plus, the 4th dimension is time, and the fifth dimension defini
How To Build a Telescope That Trumps Hubble (Score:3, Funny)
Put a bad toupee on a telescope.
Budget Cuts and the JWT (Score:4, Informative)
While I recognize the U.S. is totally fucked, economically, this is a mistake. Throwing a minor budget item with huge potential like this under the bus in the name of pretending to become fiscally responsible is beyond short-sighted.
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While I recognize the U.S. is totally fucked, economically, this is a mistake. Throwing a minor budget item with huge potential like this under the bus in the name of pretending to become fiscally responsible is beyond short-sighted.
The reason that's happened is that the US is totally fucked politically as well as economically.
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No problem. They'll just save that money by skipping a few focal length tests on the mirror.... Oh wait...
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That's what we call being "fiscally conservative." You sign off on massive debt for wars and other pointless silliness even as you cut funding to tiny projects that are likely to lead to prosperity in the future. To put it into perspective, anything that costs less than about $15b isn't worth obsessing a lot over. That's about $1 a week per person for the year, sure it adds up but we're not going broke on that. We're going broke on big budget items like the overspending on the DoD and welfare for billionair
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I'm really curious as to how the JWT is expected to "lead to prosperity in the future". Off the top of my head, I can't foresee anything meaningful to our standard of living coming from IR pictures of the early universe.
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The Federal government is kinda fucked fiscally (though not irrecoverably so), but the U.S. itself is pretty well-off economically. Our unemployment rate is "only" 9% and we have one of the highest median household incomes in the world. Parts of Asia may have lower unemployment at present, but you really need to have everyone working when you make $2000/year on a full-time income.
I hope they're building several of these (Score:3)
I think just having "one" Hubble space telescope was a mistake. I hope they're building more than one of these new 'scopes.
I mean, it'd be a shame if a launch incident destroyed a unique capability. And it shouldn't cost anything like N times as much to build N of these at the same time, right?
--PM
Re:I hope they're building several of these (Score:4, Informative)
Of course not - the thing is a few billion Dollars to build and not exactly cheap to launch either.
In fact - if it does break, even if just in a minor way (e.g. the solar panels don't unfold because a space flea is jamming a gear), it's likely going to be a multi-billion dollar piece of space junk.
Why? Because it's going to sit at the Lagrange 2 point when it goes operational. That's far, far further than we've put humans (way beyond the Moon), which so far have been the only instruments adapt enough to do repairs on satellites (such as the ones for Hubble).
As it is, the James Webb Space Telescope is awesome - in infrared and -only- infrared. People suggesting it's a -replacement- for Hubble (IR, Visible, UV) are completely and utterly deluded.. or looking for additional grant money. They might as well claim it's a replacement for Chandra (X-Ray) as it's almost equally as idiotic.
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Your point is well taken, so don't take this wrong. It just bothers me how you're using "down" to describe going to smaller wavelengths from IR to visible, which conflicts with meaning of infrared which is "beneath" read just as ultraviolet means "above violet". There's already a pre-defined orientation for the spectrum where lower frequencies is "down". /nitpick :)
Re:I hope they're building several of these (Score:5, Informative)
Re:I hope they're building several of these (Score:4, Informative)
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It depends on how you calculate N.
If you look at the total cost of the satellite (cost to procure the bird + the birds amortized share of the R&D program), then yes - N drops considerably. But that's not really an accurate method of accounting in this instance because you're performing the R&D no matter how many you build.
If you define N as the opportunity cost (just the direct costs to procu
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That's true to some extent, but you still have to test, verify, and QA the new part - and that's where the real costs are in manufacturing a spacecraft. And not only do you do that to each individual part, you do it to assemblies as they are built up, and then to units built of th
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These things are insured. Yup, there is insurance for space missions- lots of money, but it pays back to have one.
In the unlucky event of an accident, a significant amount of the cost will be returned- sure, they won't launch again on the next day, but it's far better than loosing the craft and the money.
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They are certainly not insured. Commercial spacecraft are usually insured, but not government.
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They're not. Just the one.
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Ares and Constellation (Score:2)
JWST is great and I'm glad their building it. Prior to canceling Constellation, NASA was investigating this:
http://www.youtube.com/watch?v=2YsNvpVSzbI [youtube.com]
It wasn't all about space cowboys. In terms of cosmology, if this had been only thing Ares V had ever accomplished it would have been worth every cent.
Maybe China will get there.
Look at the price tag (Score:3, Interesting)
As a professional astronomer I hoped this thing would never have happened. It costs 6 billion and at this price tag a 5% overrun is $300 million, about six times the cost of the entire SDSS project, which has undoubtedly gave us more science that James Webb ever will. True, Hubble and JWST make great pictures, function as amazing PR machines, but most science at the end of the day comes from survey imaging and spectroscopic observations.
Re:Look at the price tag (Score:4, Insightful)
SDSS was good science, making great use of relatively humble tools. But, it takes an ecosystem - and heavyweight instruments like the Webb, or the LHC, will illuminate things that can later be confirmed with the broader toolset of more pedestrian instruments, things that would just be considered a wild theory unless they came with backing from observations on an instrument like the Webb.
You also need to face up to the reality that if the Webb were scrapped at inception, it wouldn't have meant $6B extra would have been supplied to general astronomy, only a small fraction of that money would have made its way around the community.
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DOUBLE ORIGINAL PRICE (Score:2)
Re:Look at the price tag (Score:5, Insightful)
Science isn't something you can measure by how many buckets you collect. Not all buckets have the same value.
If you honestly believe that all Hubble and JWST are doing or will do is collect pretty pictures, you're either hopelessly ignorant or hopelessly biased. But ff you want to talk spectroscopy - consider that four of the Hubble five main instruments are dedicated to spectroscopy, and two of JWST's three main instruments are so dedicated. If you want to talk surveys... Check out Hubble's schedule from Feb 14, 2011 [stsci.edu], or January 29, 2011 [stsci.edu] for some recent survey campaigns that Hubble is participating in.
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JWST has spectroscopy e.g. NIRSPec = Near Infra-Red Spectrophotometer.
The JWST is more about massive light gathering (seeing closer to the dawn of the universe than ever before) than pretty visible-light images.
There is no "do over" for James Webb (Score:5, Informative)
Not that I'm expecting some catastrophic screw-up on the scale of the Hubble, but if there is a problem with the JWST, once it is sitting out at the Earth-sun L2, we won't be able to go visit it and repair it. I haven't heard of any contingency to allow it to come back to earth, so they've really got one shot to get it right.
I'm hoping everything is nominal.
I was thinking the same. (Score:2)
Hubble didn't work out of the box. From the moment it was deployed there was a spacewalk to unfold one of it's solar panels. Then there was a famous 'set of glasses' fix to it's optics. There have been hardware upgrades and gyroscope fixes.
It takes only one small glitch for this to be an expensive piece of space junk. It would kill any future space telescope in the process.
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No. Not in the sense that it would sit in Hubble-type orbit for a year while it's tested, and astronauts go to turn wrenches and adjust things that aren't right. And yes, I suspect that would much more than "a bit of extra time and effort." It's probably completely at odds to being launched to L2, and would be an incredible cost and complexity adder.
But it has pre-flight testing and a lengthy in-space verification process as it reaches L2.
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Actuated primary mirror segments, actuated secondary mirror, and a wavefront sensor system enable it to self-align. While it's much more complicated, and unreachable for servicing, it's also much more flexible for on-orbit self corrections.
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La Grange point (Score:2, Funny)
They've got a lot of nice telescopes out there. Haw haw haw haw.
The future of telescopes. (Score:2)
The real future of telescopes will have no mirrors.
I'm not sure why no one has made a big deal out of this, but superconducting cameras have the potential to completely replace mirrors in telescopes, making them more robust and essentially eliminating complex alignment.
Why do I say this? Well, I reasoned this out myself, so maybe I'm wrong, but basically superconducting cameras are able to register every photon that sees them, sending off ~18000 electrons per photon hit. CCDs, on the other hand, send off 1
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Even with the most sensitive detector possible, you still need a lens to focus the image. Otherwise you've just got a very fancy flatbed scanner, and everything further away than a couple of inches will be a useless blur.
The lens can be virtual, like in synthetic aperture systems, but building something like that for optical wavelengths with literally *no* physical lenses involved (whether those lenses are glass, mirrors, or whatever) on a football-field-sized scale would be challenging at best. Each photos
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Even with the most sensitive detector possible, you still need a lens to focus the image. Otherwise you've just got a very fancy flatbed scanner, and everything further away than a couple of inches will be a useless blur.
The lens can be virtual, like in synthetic aperture systems, but building something like that for optical wavelengths with literally *no* physical lenses involved (whether those lenses are glass, mirrors, or whatever) on a football-field-sized scale would be challenging at best. Each photosite on each of your supercooled sensors would need to capture phase information as well as amplitude. The system would also have to store timestamps for each pixel with atomic clock-level accuracy in order to use the phase information. I think some day, the human race will build something like that, but it's probably going to be awhile.
Ah. Yeah, I was wondering about optics.
Well, it would still allow much smaller mirrors to be used, right? So something like a (relatively cheap) 30" mirror with an S-CAM sensor would be able to outperform a much larger telescope with a CCD?
Even if there are optics involved, making the sensor 18000 times more sensitive seems like it would be immensely more helpful than just making bigger optics.
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You still have to contend with the diffraction limit though, 100% efficiency be damned if you can't resolve anything. Also, CCDs are not as ineffecient as you are purporting them to be; they are as efficient as ~90% at some wavelengths (http://www.astronomy.ohio-state.edu/MDM/MDM4K/qe.jpg); therefore, getting 100% effeciency is not going to increase your signal as significantly as you seem to think.
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I missed a point here, you seemed to be implying using these for optical interferometry. However, we cannot currently digitize an optical signal and current optical interferometers use analog methods to create interference fringes. At radio wavelengths we can simply downconvert the signal so something more manageable and then calculate the antenna-antenna the interference.
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Well, it would still allow much smaller mirrors to be used, right? So something like a (relatively cheap) 30" mirror with an S-CAM sensor would be able to outperform a much larger telescope with a CCD?
Even if there are optics involved, making the sensor 18000 times more sensitive seems like it would be immensely more helpful than just making bigger optics.
You need a lens/mirror to focus, but the reason they have to be so big is to collect more light. The problem is not so much that the CCD doesn't detect all of the photons, but that there aren't many photons to detect in the first place! A sensor 18000 times more sensitive can still only detect photons that arrive.
The objects being imaged are reeeally far away, so you want to collect light from as large an area as possible to reduce the exposure time you need. A quick google says that some hubble exposures a
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That's not how optics work. You need to image what you want to see onto your detector.
To test this: remove the lens from your DSLR and take a photo. You'll get nothing but blur.
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That's not how optics work. You need to image what you want to see onto your detector.
To test this: remove the lens from your DSLR and take a photo. You'll get nothing but blur.
Yeah I was wondering about that. Some of the other replies cleared that up earlier.
I still imagine that investing in those sensors would have a great payoff.
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Because it's an AC, and ACs start at zero.
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Building it is the easy part. (Score:2)
Building one is the easy part, launching it into orbit is another matter entirely.
Are La Grange points safe for satellites? (Score:2)
Seems like a natural gravity pit wouldn't be the best place to hang out.
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L1, L2, and L3 are not stable (if you stick a rock there, it will fall away in "no time"). JWST is going to be placed at L2 (though it will move around a bit in a halo orbit). Only L4 and L5 are stable.
Aikon-
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It's my understanding that only L4 and L5 are actually gravitational minima. The other LaGrange points are actually saddles. This means that the point itself isn't stable, but stable orbits around the point do exist.
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The L2 point (which is where JWST is headed) isn't a gravity pit - it's a gravity hill. It's a long-term unstable orbit, but it takes minimal delta-V to stay put there with active correction.
L4 and L5 (60 degrees ahead and behind the orbit of the lighter-mass object) are the gravity pits, and lots of miscellaneous stuff does collect there. But even then, it's still nearly empty space and whatever has collected there isn't moving fast relative to you.
"trumps Hubble" (Score:4, Funny)
OK, I have no productive contribution here, but the phrases "Hubble trumping" and "trouble humping" are now echoing through my head.
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Up close and personal... (Score:2)
I've been lucky enough to have had a peek inside one of the cases (as it was being built and having the kinks ironed out) they're going to use to transport the reflector sail things from the manufacturer to the assembly plant, one case per sail. My friend is the shop's computer guy. The case was enormous and had to be perfectly air tight so it could be filled with nitrogen to protect the sail during transport. I saw it in July so I'm pretty sure they've finished and shipped them all by now.
Granted, it wasn'
Weird diffraction spikes (Score:2)
This won't be the case with the James Webb Space Telescope, however. Once it begins operations, we're going to have to get used to seeing diffraction spikes around stars in the images it sends back to us at s
If you want a comparaison with hubble (Score:2)
If you want a comparaison with hubble go there : http://www.jwst.nasa.gov/comparison.html [nasa.gov]
Am I alone in thinking (Score:2)
That naming the telescope after a NASA administrator is possibly the lamest thing they could have done?
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Meaning no offense, but have you ever actually submitted a story? Titles are limited to 50 characters. It leads to terrible, terrible headlines.
"How Scientists are Building a Telescope That Trumps Hubble!" gets truncated to "How Scientists are Building a Telescope That Trump"
Many of the bad headlines here are actually the result of trying to get something like "How scientists are building a telescope that is superior to Hubble" in a headline field that basically only allows "Science cool! They build'um H
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JWST's optics and sensors have to be kept very cold, something that is difficult to do in LEO thanks to all of the Earth IR and albedo. Putting it at L2 means the Earth's disturbances will be in line with the Sun's, and they can use a single stationary shield to protect the optics and sensors.
But yes, you are right, it will be significantly more difficult (impossible with current technology) to service it.
Aikon-
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Nope- the idea is that it expanded at an exponentially increasing speed, far, far, far faster than the speed of light. Look up the theory of inflation [wikipedia.org] for more
The only way I can make this sound as non-sci talk as possible, is to say that space itself expanded. Then again, "expanded" is not exactly the correct word, because we would expand with it and not have a clue. More like, when space expands (and it does so for reasons unknown) then more space is created in between to fill the, uhm, gap.
I don't know ma