# James Webb Space Telescope general discussion thread **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Tags:** science-math\ **Created:** [December 25, 2021, 1:18pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624 "2021-12-25T13:18:56Z")\ **Posts on this page:** 20\ **Page:** 16
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [January 23, 2022, 5:39pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/301 "2022-01-23T17:39:49Z")
Beryllium is a good conductor of both heat and electricity, so I don’t know what he meant. Heat conductivity but electrical insulation is an oddball combination, but it does exist – for instance, in the pastes used with heat sinks. But Be doesn’t do that. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [January 23, 2022, 5:43pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/302 "2022-01-23T17:43:31Z")
He’s talking about an oxide though, not the metal. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [January 23, 2022, 5:44pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/303 "2022-01-23T17:44:10Z")
Yes, I just realized that. He’s right about the oxide. ---
**Author:** ![DesertDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desertdog/32/11503_2.png) [@DesertDog](https://boards.straightdope.com/u/DesertDog)\ **Post date:** [January 23, 2022, 5:47pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/304 "2022-01-23T17:47:46Z")
> [@Riemann](#): > > Just did a double take on this… you mean electrical insulator and heat conductor, right? Correct. > [@wolfpup](#): > > Yes, I just realized that. He’s right about the oxide. It’s still toxic, though which is why I’d wash up with the grease and happy I’d never broken a ceramic. ---
**Author:** ![3AxisCtrl](https://avatars.discourse-cdn.com/v4/letter/3/ecd19e/32.png) [@3AxisCtrl](https://boards.straightdope.com/u/3AxisCtrl)\ **Post date:** [January 23, 2022, 6:06pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/305 "2022-01-23T18:06:35Z")
> [@Riemann](#): > > I think what matters is the strength of Beryllium for a given weight. I don’t see how low density is an advantage - quite the opposite, in fact. Well, the mirrors have to be large, which implies the need for a considerable volume of material to make them. And low mass is, for a rocket payload, highly desirable. It thus follows that any suitable real-world mirror material will be of low density. ---
**Author:** ![pjd](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pjd/32/3009_2.png) [@pjd](https://boards.straightdope.com/u/pjd)\ **Post date:** [January 23, 2022, 7:03pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/306 "2022-01-23T19:03:28Z")
I don’t see how it can be the website’s fault … wasn’t it always supposed to get to L2 today (Sunday) - day 29 ? (Sounds very suspicious to me !) ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [January 23, 2022, 7:19pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/307 "2022-01-23T19:19:39Z")
Precisely. But this morning they abruptly changed the “distance remaining” and added a “Day 30” to the timeline. ---
**Author:** ![pjd](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pjd/32/3009_2.png) [@pjd](https://boards.straightdope.com/u/pjd)\ **Post date:** [January 23, 2022, 7:23pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/308 "2022-01-23T19:23:38Z")
Yes, but that’s 'cos nasa told them it was going to be a day late for some reason. ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [January 23, 2022, 7:26pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/309 "2022-01-23T19:26:45Z")
They got out there, and found this sign. [![](https://www.macujo.com/wp-content/uploads/2019/05/sunday-deliveries.jpg) ](https://www.macujo.com/wp-content/uploads/2019/05/sunday-deliveries.jpg) ---
**Author:** ![pjd](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pjd/32/3009_2.png) [@pjd](https://boards.straightdope.com/u/pjd)\ **Post date:** [January 23, 2022, 7:30pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/310 "2022-01-23T19:30:00Z")
Well … i suppose that would explain it ! ---
**Author:** ![Bullitt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bullitt/32/5725_2.png) [@Bullitt](https://boards.straightdope.com/u/Bullitt)\ **Post date:** [January 23, 2022, 7:32pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/311 "2022-01-23T19:32:31Z")
As mentioned already, the total distance changed. When I calculated earlier that it was 95% to L2 the total distance was about 898,705 (from my calculator’s register) Now it is 911,131 For a difference of 12,426. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [January 23, 2022, 7:42pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/312 "2022-01-23T19:42:19Z")
> [@Bullitt](#): > > For a difference of 12,426. That’s approximately consistent with the amount that “distance remaining” changed this morning. Really, I think the whole thing was just a clerical error on the website. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [January 23, 2022, 7:49pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/313 "2022-01-23T19:49:23Z")
> [@3AxisCtrl](#): > > Well, the mirrors have to be large, which implies the need for a considerable volume of material to make them. And low mass is, for a rocket payload, highly desirable. It thus follows that any suitable real-world mirror material will be of low density. Nope. They need a large area, but _thickness_ is not a virtue. The material they are made from needs to be _strong_ (stiff) enough. The woman in the video said what’s great about Beryllium is it’s light weight. That was not wrong - it just left unstated the assumption that she meant light weight _to achieve a given strength_. You claimed that she should have said what’s great about Beryillium is it’s _large volume_ for a given weight. This is worse than an unstated assumption - it is wrong. They do not use Beryllium because (ceteris paribus) they want a large volume of material. ---
**Author:** ![3AxisCtrl](https://avatars.discourse-cdn.com/v4/letter/3/ecd19e/32.png) [@3AxisCtrl](https://boards.straightdope.com/u/3AxisCtrl)\ **Post date:** [January 23, 2022, 7:57pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/314 "2022-01-23T19:57:36Z")
> [@Riemann](#): > > They need a large area, but _thickness_ is not a virtue. The material they are made from needs to be _strong_ (stiff) enough. For essentially any material that could be used to make these mirrors (any structural material at all?), thickness and stiffness are correlated. > [@](#): > > You claimed that she should have said what’s great about Beryillium is it’s _large volume_ for a given weight. No, what’s great is its low mass for a given volume. (Along with its other desirable qualities.) ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [January 23, 2022, 8:02pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/315 "2022-01-23T20:02:11Z")
> [@3AxisCtrl](#): > > For essentially any material that could be used to make these mirrors (any structural material at all?), thickness and stiffness are correlated. So what if they are correlated. That does not imply that large volume is a design criterion. For a given strength and weight, if anything _less_ thickness is probably desirable. > [@3AxisCtrl](#): > > No, what’s great is its low mass for a given volume. (Along with its other desirable qualities.) No, what the designers cared about is its low mass for a given _strength_. You nitpicked the video for being imprecise in just saying that low weight is a virtue, yet your claim that low _density_ is the true design criterion is worse that being imprecise, it is wrong. ---
**Author:** ![3AxisCtrl](https://avatars.discourse-cdn.com/v4/letter/3/ecd19e/32.png) [@3AxisCtrl](https://boards.straightdope.com/u/3AxisCtrl)\ **Post date:** [January 23, 2022, 8:24pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/316 "2022-01-23T20:24:26Z")
> [@Riemann](#): > > So what if they are correlated. The point is that thickness is irrelevant, or if anything _less_ thickness is desirable. This is puzzling. If stiffness is (as you note) desirable, and if it correlates with thickness (which you seem to accept), then how can thickness be irrelevant? > [@](#): > > You nitpicked the video for being imprecise in just saying that low weight is a virtue … No, I objected to the narrator saying that beryllium is “super light weight”. A pound of Be weighs almost exactly what a pound of aluminum, steel, lead, or gold does. Its virtue lies in how much each pound can deliver in the way of mirror-base performance, as compared to other metals. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [January 23, 2022, 8:45pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/317 "2022-01-23T20:45:02Z")
> [@3AxisCtrl](#): > > This is puzzling. If stiffness is (as you note) desirable, and if it correlates with thickness (which you seem to accept), then how can thickness be irrelevant? Why is it puzzling? If larger X is a design objective, the fact that (for any given material) Y is positively correlated with X does not imply anything about Y. Y may be irrelevant, or it may often be a design objective to _minimize_ Y. For any given fuel, the total mass of fuel is positively correlated to the total maneuvering delta-V it can provide. Does this imply that having a large mass is a design objective? Of course not. It is desirable to find a fuel with _minimal_ mass for a given delta-V. > [@3AxisCtrl](#): > > No, I objected to the narrator saying that beryllium is “super light weight”. A pound of Be weighs almost exactly what a pound of aluminum, steel, lead, or gold does. That’s just ridiculous. The narrator never claimed that Beryllium was lighter than something with equal weight. She simply left unstated the fact that it is lighter than other materials _for a given strength_. > [@3AxisCtrl](#): > > Its virtue lies in how much each pound can deliver in the way of mirror-base performance, as compared to other metals. You’re so desperate not to concede that high strength (not large volume) is the design criterion that you are now circumlocuting with “mirror-base performance”? This is turning into a sidetrack for this thread. I’m done here. Feel free to have the last word if you want to be so stubborn. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [January 23, 2022, 8:52pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/318 "2022-01-23T20:52:25Z")
> [@Riemann](#): > > This is turning into a sidetrack for this thread. I’m done here. Thank you. I was thinking of starting a competitive derailing involving the obviously unwise decision to have the mirrors gold-coated, because it’s bound to attract alien space pirates! 😀 But it would be nice to get back to a discussion of the JWST for which I started this thread. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [January 23, 2022, 8:53pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/319 "2022-01-23T20:53:21Z")
I apologize, I should have stopped flogging this dead horse 3 posts ago. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [January 23, 2022, 8:58pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/320 "2022-01-23T20:58:11Z")
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