2401: Conjunction

Explain xkcd: It's 'cause you're dumb.
Jump to: navigation, search
The IAU is sad to announce that at 00:39 UTC on December 22nd, Jupiter and Saturn did unfortunately come into contact, and appear to have blooped together.
Title text: The IAU is sad to announce that at 00:39 UTC on December 22nd, Jupiter and Saturn did unfortunately come into contact, and appear to have blooped together.


Cueball and Ponytail are observing the 2020 Jupiter-Saturn conjunction. This comic is similar to other comparisons between expectation and reality, such as 2176: How Hacking Works, 683: Science Montage, 2341: Scientist Tech Help, and 538: Security. The expectation is that the scientists will remain professional and serious throughout the event, testing Einstein's theory of General Relativity and using technical terms such as arcminute, a unit of measurement often used in astronomy. In reality, however, they are actually treating the event quite whimsically and are having fun with it, even jokingly commenting about the event. Other astronomical phenomena, such as solar eclipses, actually have been used to test Einstein's theories, but in this case the interest is purely aesthetic.

The title text references the misconception that the planets physically get very close at conjunction, rather than merely appearing to do so. The wording suggests a quick and uneventful merger, possibly alluding to the way drops of water merge when the surface tension between them is broken.

If Jupiter and Saturn really did come into contact and "blooped together", most of the mass would stay collected as an extremely hot and turbulent blob that would eventually settle down as a new planet (which Randall suggests might be called "Jaturn"), but more than a bit would be spewed outwards. The possible outcomes vary enormously, depending on factors such as how direct the impact was, and its alignment relative to the planets' spins. However, while such a collision would be preceded by a conjunction, a conjunction does not necessarily indicate an imminent collision, as Jupiter and Saturn, although on the same sightline from Earth, are still separated by 734 million km (456 million mi) at the time of the conjunction - almost five times the distance from Earth to the Sun.


Caption above the panel: What people imagine astronomers observing a conjunction are like
[Cueball and Ponytail are both looking through telescopes at the conjunction of Jupiter and Saturn.]
Cueball: 6.15 arcminutes!
Ponytail: Stupendous! This confirms Einstein!
Caption above the panel: What they're actually like
[The same picture with different spoken sentences.]
Cueball: Wow! Look how close they are!
Ponytail: It's so cool!!
Cueball: Now kiiiisssss!!
Ponytail: Dooo iiit!

comment.png add a comment! ⋅ comment.png add a topic (use sparingly)! ⋅ Icons-mini-action refresh blue.gif refresh comments!


It appears (depending upon how keen DgbrtBOT actually is) that this was posted at the significant time as mentioned. Though it's entirely within range of usual update time, I suspect this is not a coincidence. (Where I am, partly the weather but overwhelmingly the horizon obscured the moment of closest approach, but I did get a shufti earlier last night when there were fewer clouds in the sky for at least some of the time between sunset and planetsset. It took binoculars to key my eyes into where the dimmer Saturn was, but once I knew what I was seeing it was obvious enough.). Oh and, purely coincidentally, Happy Solstice everyone! 00:58, 22 December 2020 (UTC)

"...if they appeared to have boinked, it would have confirmed the weak cosmological constant, which we are very glad is not a thing." ocæon (talk) 14:23, 22 December 2020 (UTC)

I don't think this is really that interesting (in the technical sense) to astronomers. Although in theory there could be gravitational lensing of Saturn's image by Jupiter's gravity, I'm pretty sure the effect would be too small to bother even trying to measure. 14:49, 22 December 2020 (UTC)

Astronomers might not say that, yet people might say that astronomers might say that. (Astronomers thus aren't people. And the rules require no more than three fragments of astronomer per kilo of Soylent Green before the Food Defect Action Levels are invoked.) 15:31, 22 December 2020 (UTC)
The whole point of this cartoon is that lay people don't realize how boring something like this is to astronomers -- it's just a coincidence with little scientific import. But astronomers are people, too, and they can enjoy the esthetics and have fun with it. Barmar (talk) 00:33, 24 December 2020 (UTC)