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James Webb Telescope

I think of pure scientific research as akin to music or art - we do these things to enrich our minds, not our material welfare. It's what makes us civilised, makes us different to the animals from which we evolved. Any practical benefits which eventually emerge are just an added bonus.
 
Pixel42 said:
I think of pure scientific research as akin to music or art - we do these things to enrich our minds, not our material welfare. It's what makes us civilised, makes us different to the animals from which we evolved. Any practical benefits which eventually emerge are just an added bonus.
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And, don't forget the other difference, we use cutlery. ;)
 
Pixel42 said:
I think of pure scientific research as akin to music or art - we do these things to enrich our minds, not our material welfare. It's what makes us civilised, makes us different to the animals from which we evolved. Any practical benefits which eventually emerge are just an added bonus.
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I think it was Feynman who said physics is like sex: it has practical results, but that’s not why we do it.
 
Ziggurat said:
Sure, but they don't have the budget for two of these. And with the budget they do have, any telescope they could build two of wouldn't be as good. And they'd rather have less time on a better telescope than more time on inferior ones.

ETA: I can see a use case for multiple identical space telescopes, though. With radio astronomy, building multiple telescopes to form a giant array allows you to get vastly better diffraction limits on your signal than you can with a single telescope.
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Is that possible for Visible Light telescopes as well? Or it it not practical enough for that frequency band of the spectrum?
 
erwinl said:
Is that possible for Visible Light telescopes as well? Or it it not practical enough for that frequency band of the spectrum?
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I don’t think we can do it for optical band. You need to be able to accurately time the phase of the signal between your different detectors, and I don’t think we really have that capability for visible light in the same way.
 
erwinl said:
Is that possible for Visible Light telescopes as well? Or it it not practical enough for that frequency band of the spectrum?
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The other thing is that using multiple telescopes as a giant interferometer only helps overcome the diffraction limit on angular resolution, it doesn't really amplify the signal strength. So if you've got a bright source that provides plenty of signal and you just need better angular resolution, using this can help a lot. If you're limited on signal intensity, this won't help much.

But it turns out I was wrong, there are actually some optical interferometer telescopes, for example:
https://en.wikipedia.org/wiki/Navy_Precision_Optical_Interferometer
But in general, it's not used as much for optical as radio. For one, I think it's easier with radio. Two, radio benefits more, since the diffraction limit is much worse for a single radio telescope dish than for an optical telescope. And three, optical telescopes are often signal limited anyways, so you need big dishes anyways, and that helps with the diffraction limit as a side effect.
 
Ziggurat said:
The other thing is that using multiple telescopes as a giant interferometer only helps overcome the diffraction limit on angular resolution, it doesn't really amplify the signal strength. So if you've got a bright source that provides plenty of signal and you just need better angular resolution, using this can help a lot. If you're limited on signal intensity, this won't help much.

But it turns out I was wrong, there are actually some optical interferometer telescopes, for example:
https://en.wikipedia.org/wiki/Navy_Precision_Optical_Interferometer
But in general, it's not used as much for optical as radio. For one, I think it's easier with radio. Two, radio benefits more, since the diffraction limit is much worse for a single radio telescope dish than for an optical telescope. And three, optical telescopes are often signal limited anyways, so you need big dishes anyways, and that helps with the diffraction limit as a side effect.
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Thanks! :thumbsup:
A bit as I suspected.
But I had no idea concerning present capabilities and/or benefits so I thought, I’d ask.
 
Belz... said:
Er... no it isn't.

What do asteroids have to do with the telescope???
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Samson said:
I bet T rex would wish even a suboptimal device like James Webb had warned him.

(Honey i shrunk the kids)
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I'm not sure how the "Honey, I Shrunk the Kids" remark figures into Samson's post, but he's alluding to programs such as NASA's Near-Earth Object Observations Program, which scans the sky looking for things on a collision course with Earth. Of greatest concern something like the object that caused the Chicxulub crater and also wiped out the dinosaurs, which is what Samson was referring to when he mentioned T. Rex.

As humans we're also interested in smaller objects like the one that caused the Tunguska event back in 1908: imagine the carnage it could have caused had it occurred over a populated area instead of remote Siberia.

See also the Chelyabinsk meteor, and other modern impact events.

I'm not sure the JWST will help with near Earth observation programs, but we do have Earth based telescopes that are continually searching for potential impact objects.
 
Blue Mountain said:
I'm not sure how the "Honey, I Shrunk the Kids" remark figures into Samson's post, but he's alluding to programs such as NASA's Near-Earth Object Observations Program, which scans the sky looking for things on a collision course with Earth. Of greatest concern something like the object that caused the Chicxulub crater and also wiped out the dinosaurs, which is what Samson was referring to when he mentioned T. Rex.

As humans we're also interested in smaller objects like the one that caused the Tunguska event back in 1908: imagine the carnage it could have caused had it occurred over a populated area instead of remote Siberia.

See also the Chelyabinsk meteor, and other modern impact events.

I'm not sure the JWST will help with near Earth observation programs, but we do have Earth based telescopes that are continually searching for potential impact objects.
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It won't. It has nothing to do with it, which is why samson's post is puzzling. That's what I would say if samson's posts usually made sense.
 
Belz... said:
It won't. It has nothing to do with it, which is why samson's post is puzzling. That's what I would say if samson's posts usually made sense.
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Exactly. And I actually pointed this out to Samson earlier, so it's weird that he keeps bringing it up.

I suppose it's possible that if a potential problem asteroid or comet was noticed with some other instrument, JWST could be pointed in that direction and potentially give a more accurate measurement of its orbit. I'm not sure if JWST would be better than other telescopes for that job, or how much we could potentially gain from it in that use.

But, as you say, in general James Webb isn't involved in cataloging asteroids, so it doesn't seem to have much to do with the issues of potential impacts.
 
Roboramma said:
Exactly. And I actually pointed this out to Samson earlier, so it's weird that he keeps bringing it up.

I suppose it's possible that if a potential problem asteroid or comet was noticed with some other instrument, JWST could be pointed in that direction and potentially give a more accurate measurement of its orbit. I'm not sure if JWST would be better than other telescopes for that job, or how much we could potentially gain from it in that use.

But, as you say, in general James Webb isn't involved in cataloging asteroids, so it doesn't seem to have much to do with the issues of potential impacts.
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Radar is the best way to accurately track asteroids. But the world is a bit short on that now that Arecibo is gone.
 
Einstein ring captured by Hubble

Two galaxies with a distant quasar behind them.

Linky

And, the JWST now has an "official" launch date of December 18th:

https://www.bbc.com/news/science-environment-58498676

The $10bn James Webb Space Telescope is expected to launch on 18 December.

Yes, countless targeted lift-offs have come and gone in the past, but this one has a reality to it that the others didn't: the successor observatory to Hubble is now actually built.

All that is required is to ship the finished telescope to French Guiana, put it on the top of an Ariane rocket, light the engines and stand well back.
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Anyone know why it is being launched from French Guiana and not from KSC? (I know that there is European involvement in the project, but since the telescope was assembled in California, transporting it overseas seems like an unnecessary risk/expense.)

Sent from my LM-X320 using Tapatalk
 
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