Starship Asterisk*

Ann wrote: ↑Wed Jun 05, 2024 4:55 am

Sa Ji Tario wrote: ↑Wed Jun 05, 2024 3:34 am It looks spectacular but, what could this have been like? https://es.wikipedia.org/wiki/Gran_Cometa_de_1744

Fantastic! The Great Comet of 1744 looked like this:

Great Comet of 1744. Woodcut by Chéseaux(?)

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Imagine the dark skies of 1744! Look at the Milky Way above the comet's amazing tails. If I am not mistaken, the brightest star at upper right is Altair in Aquila. (All things considered though... I'm glad I didn't have to live my life in the 18th century.)

How did the Great Comet of 1744 acquire that amazing set of tails? According to Wikipedia, it may have been due to processes similar to those that led to the spectacular tails of Comet McNaught:

The Magnificent Tail of Comet McNaught. Image Credit & Copyright: Robert H. McNaught

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Wikipedia wrote about the Great Comet of 1744:

The tail structure was a puzzle to astronomers for many years. Although other comets had displayed multiple tails on occasion, the 1744 comet was unique in having six. It has been suggested that the 'fan' of tails was generated by as many as three active sources on the cometary nucleus, exposed in turn to solar radiation as the nucleus rotated. It also has been proposed that the tail phenomenon was a very prominent example of the "dust striae" seen in the tails of some comets, such as Comet West and C/2006 P1 (McNaught).

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The Formation of Striae within Cometary Dust Tails by a Sublimation-Driven YORP-like Effect by Jordan K. Steckloff and Seth A. Jacobson

https://www.researchgate.net/figure/Ill ... _281895985

Sublimating gas molecules scatter off of the surface of an icy body in the
same manner as photons (Lambertian Scattering). This means that for every
photon-driven body force, there should be a sublimation-driven analogue
that affects icy bodies. Thermal photons emitted from the surfaces of
asymmetrically shaped bodies in the Solar System generate net torques that
change the spin rates of these bodies over time. The long-term averaging of
this torque is called the YORP effect. Here we propose a sublimation-driven
analogue to the YORP effect (Sublimation-YORP or SYORP), in which
sublimating gas molecules emitted from the surfaces of icy bodies in the
Solar System also generate net torques on the bodies...

Yeah, yeah, yeah. I'll take you at your word.

Ann

Sa Ji Tario wrote: ↑Wed Jun 05, 2024 3:34 am It looks spectacular but, what could this have been like? https://es.wikipedia.org/wiki/Gran_Cometa_de_1744

Wikipedia wrote about the Great Comet of 1744:

The tail structure was a puzzle to astronomers for many years. Although other comets had displayed multiple tails on occasion, the 1744 comet was unique in having six. It has been suggested that the 'fan' of tails was generated by as many as three active sources on the cometary nucleus, exposed in turn to solar radiation as the nucleus rotated. It also has been proposed that the tail phenomenon was a very prominent example of the "dust striae" seen in the tails of some comets, such as Comet West and C/2006 P1 (McNaught).

Sublimating gas molecules scatter off of the surface of an icy body in the
same manner as photons (Lambertian Scattering). This means that for every
photon-driven body force, there should be a sublimation-driven analogue
that affects icy bodies. Thermal photons emitted from the surfaces of
asymmetrically shaped bodies in the Solar System generate net torques that
change the spin rates of these bodies over time. The long-term averaging of
this torque is called the YORP effect. Here we propose a sublimation-driven
analogue to the YORP effect (Sublimation-YORP or SYORP), in which
sublimating gas molecules emitted from the surfaces of icy bodies in the
Solar System also generate net torques on the bodies...

Ann wrote: ↑Tue Jun 04, 2024 7:20 pm

johnnydeep wrote: ↑Tue Jun 04, 2024 6:54 pm The best part of this APOD is the link to a crow having fun repeatedly sliding down a snowy roof. If that doesn't prove animals are conscious and sentient (are those even different things?), nothing does!
...

Amazing!!! The crow is even using a plastic lid as a sled!!! Crows are so smart!

I'm reminded of a picture of birds (hardly crows, what are they?) that are "jumping with joy"!!
...

Humanity is sometimes called Homo ludens, the "playful" humans. Well, maybe crows should be called Corvus ludens?

Ann

Homo Ludens is a book originally published in Dutch in 1938[2] by Dutch historian and cultural theorist Johan Huizinga.[3] It discusses the importance of the play element of culture and society.[4] Huizinga suggests that play is primary to and a necessary (though not sufficient) condition of the generation of culture. The Latin word ludens is the present active participle of the verb ludere, which itself is cognate with the noun ludus. Ludus has no direct equivalent in English, as it simultaneously refers to sport, play, school, and practice.[5]
...
Huizinga begins by making it clear that animals played before humans. One of the most significant (human and cultural) aspects of play is that it is fun.[7]

Huizinga identifies 5 characteristics that play must have:[8]

° Play is free, is in fact freedom.
° Play is not "ordinary" or "real" life.
° Play is distinct from "ordinary" life both as to locality and duration.
° Play creates order, is order. Play demands order absolute and supreme.
° Play is connected with no material interest, and no profit can be gained from it.[9]

johnnydeep wrote: ↑Tue Jun 04, 2024 6:54 pm The best part of this APOD is the link to a crow having fun repeatedly sliding down a snowy roof. If that doesn't prove animals are conscious and sentient (are those even different things?), nothing does!

Click to play embedded YouTube video.

Lee wrote: ↑Tue Jun 04, 2024 5:12 pm I love this picture! It looks like something tore the night sky and is letting light in.

macnenia wrote about his picture:

The anti-tail, apparently pointing towards the Sun, is an optical illusion. The comet sloughs off particles with a wide range of sizes. The really fine stuff is blown around by the solar wind, but the heavier material is largely unaffected and so stays close to where it was ejected by the comet, but maintaining the velocity of that ejection. Therefore it doesn't follow the comet along, especially as the comet, being pulled strongly by the Sun's gravity, maintains a curved (elliptical) trajectory. And so, behind where the comet has been, there is a curved line of coarse particles, holding to the comet's previous position, or perhaps having drifted but not too far. As the Earth passes through the plane of the comet's path, this thicker swathe of particles, changes from a diffuse curve, not so easily seen, to a thick line, where the areas of greater density are aligned behind each other.....thus we see a bright thicker line, surrounded by the diffuse and much more spread out smaller particles.