2564: Sunshield

|< < Prev Comic #2564 (January 5, 2022) Next > >|

Sunshield

Title text: RIP the surface of Mars

Explanation

This explanation may be incomplete or incorrect: Created by THE JWST - Please continue expanding and improving the explanation. Do NOT delete this tag too soon. If you can address this issue, please edit the page! Thanks.

JWST stands for James Webb Space Telescope, a space telescope launched about 2 weeks prior to publication of the comic. It has a sunshield to protect its instrumentation from the heat of the sun and to keep them below 40 K (-233 °C/-388 °F). The sunshield was deployed the day before the comic was published. The JWST has to undergo a sequence of deployment steps to unfold parts that had to be packed for launch. This sequence has some possible points of failure that would render the very expensive space telescope useless. Thus successful steps are widely celebrated. This comic is an example of such a celebration.

Ordinary cameras use a flash to take pictures in low-light situations. Outer space is very dark^{[citation needed]}, so this comic posits that the JWST has a very powerful flash to compensate for this. In reality, astronomical cameras don't use flash photography -- they depend on the light either emitted by objects themselves (e.g. stars) or from nearby very bright objects (e.g. planets in the Solar System reflect light from the Sun). A flash wouldn't work because A) take too long for the light of the flash to return to the telescope, and B) there would not be enough light returning, due to the scattering in all directions. There is, however, the Lunar Laser Ranging experiment which uses lasers, which are loosely related to flashes for photography, to measure the distance between earth and moon. Instead, mirrors and/or lenses focus the light, and long exposure times are used to collect enough light to form a decent image.

The comic assigns the sunshield a new, comical purpose of shielding the sun and earth (which is roughly in the same direction as the sun, due to the deployment at the L2 Lagrange point) from this flash, rather than the other way around. Of course space telescopes do not use flashes, since it would

The title text suggests that, due to the sunshield not being angled toward Mars, its surface has been badly scarred by the flash. This implies incredible strength of the flash, perhaps to ensure the light can return from its destinations, comparable to death-ray satellites in fiction.

Transcript

This transcript is incomplete. Please help editing it! Thanks.

[The James Webb Space Telescope is floating through space, a black background.]

JWST: Okay, universe-

JWST: Smile!

JWST: Click

[A bright flash glows from the telescope, turning most of the panel white. The left side is blocked and kept dark by the telescope's sunshield.]

Caption: Astronomy fact: The purpose of the JWST sunshield is to protect the Sun and the Earth from the telescope's powerful flash.

 add a comment! ⋅  add a topic (use sparingly)! ⋅  refresh comments!

Discussion

i thought this is common knowledge. 162.158.90.173 15:00, 5 January 2022 (UTC)

It's normally supposed to block sunlight from reaching the telescope. This comic turns this on its head by suggesting the telescope emits light instead of collecting it. The emitted light is claimed to outshine the sun. The title text means that the flash is bright enough to scar the surface of Mars, which is unlikely. 172.68.154.143 15:12, 5 January 2022 (UTC)

According to wikipedia it is about preventing heat from reaching the telescope and only secondary about the light. --172.68.110.139 15:16, 5 January 2022 (UTC)

The comic mentions the role of blocking light which is why I mentioned it's light-blocking property.172.68.154.141 15:34, 5 January 2022 (UTC)

Obviously, the comic distorts the facts to make it funny. --172.68.110.121 15:33, 5 January 2022 (UTC)

The point of the title text is that if the flash really were bright enough to serve its purpose, it would scar the surface of Mars (when Mars happens to be in that general direction). -- Barmar (talk) (please sign your comments with ~~~~)

SCAR? For the flash being bright enough, it would need to outshine supernovas. Mars would melt if not sublime. -- Hkmaly (talk) 00:24, 6 January 2022 (UTC)

Also, the JWST is drawn here to resemble the old Polaroid Land SX-70 Instant Camera (of just about 50 years ago.) Hmmmm. "Instant" raises issues of relativistic simultaeity....

Worse than that, shutter-click and then a flash (at least a frame of time apart) isn't that useful.

Trigger the flash and then the shutter around the time the flash returns. Depending upon distance and depth-of-field involved (also the duration of the flash and the movement of the subjects) you might have a longer shutter-open taking in passive light already, but only if you're happy mostly registering the 'bounce-back' from any given distance as the overwhelming flash gets there and back and don't mind the low amount of non-flash light leaching in, perhaps revealing motion.

(See various planetary nebulae photos where 'shells' of illumination, from subsequent flareups in the active centre, make it look like there's shells of matter, when it's more that these are volumes of debris that were in the right place at the right time to give us the current reflected glory. It makes for interesting mind-experiments.) 172.70.85.73 18:39, 5 January 2022 (UTC)

The JWST doesn't have a physical shutter, but makes a clicking sound so that it can't secretly take voyeuristic photographs of the universe.162.158.187.92 21:24, 5 January 2022 (UTC)

Searching for facts I found three comics with facts in the title, and also one other using facts like this ones Astronomy Fact. I have thus added this: Category:Facts, with Category:Fun fact as a sub category. I have only found 5 comics so far. But where "facts" is only used a limited time, then "fact" is used more than 500 times. And the two with fact that are not in the title only used the word "fact". So if you can remember any other comic with facts that are not fun facts, then please add them to the category. As I wrote on the fact page this reminds me of the Category:Tips under which Category:Protip now belongs. --Kynde (talk) 08:48, 6 January 2022 (UTC)

I have also added all JWST comics to Category:Space probes and wrote a bit about it in the collapsed explanation there. But may be with 6 comics (and more on the way?) it should have it's own category. What do people think about that? --Kynde (talk) 09:05, 6 January 2022 (UTC)

Wait, the JWST is NOT a space probe. It is a space telescope for imaging purposes. So I disagree with putting it in that category. It already fits in the category for telescopes. 172.70.214.43 19:01, 6 January 2022 (UTC)

Concerning the "click"-part in the explanation: If the JWST is using a reflex camera, the clicking noise is the mirror moving out of the way for the exposure, is producing a clicking noise far louder than a shutter mechanism and obviously happens before exposure/flashing. 162.158.89.180 07:45, 10 January 2022 (UTC)