Starship Asterisk*

JohnD wrote: ↑Wed Apr 10, 2019 1:37 pm Interesting. Never thought of Mars' moons doing a solar transit.

The video of a Deimos transit at https://photojournal.jpl.nasa.gov/archive/PIA23134.gif (link in blurb) is a very much smaller (20 times?? He-he) image. But it looks as though I can see the moon rotating as it goes. Illusion, or real?
JOhn

De58te wrote: ↑Wed Apr 10, 2019 10:50 am I know that today's young people have the attention span of less than a goldfish, 13 seconds, but, was it really necessary to speed up the original transit time of 35 seconds to 2 seconds? I wouldn't have minded to have watched the entire original 35 seconds. After all that is just a wee bit longer than one super bowl commercial.

De58te wrote: ↑Wed Apr 10, 2019 10:50 am I know that today's young people have the attention span of less than a goldfish, 13 seconds, but, was it really necessary to speed up the original transit time of 35 seconds to 2 seconds? I wouldn't have minded to have watched the entire original 35 seconds. After all that is just a wee bit longer than one super bowl commercial.

geckzilla wrote: ↑Wed Apr 10, 2019 5:32 pm

De58te wrote: ↑Wed Apr 10, 2019 10:50 am
I know that today's young people have the attention span of less than a goldfish, 13 seconds, but, was it really necessary to speed up the original transit time of 35 seconds to 2 seconds? I wouldn't have minded to have watched the entire original 35 seconds. After all that is just a wee bit longer than one super bowl commercial.

You definitely could have written this without the ageism.

• Or Deimos's De58te's need to carp on Cypriniformes

https://www.bbc.com/news/health-38896790 wrote:

Fancy Celestial eye goldfish

---

Busting the attention span myth
By Simon Maybin BBC World Service, More or Less

<<It turns out that there is no evidence that goldfish - or fish in general - have particularly short attention spans or memories, despite what popular culture suggests.

I spoke to Prof Felicity Huntingford, who has spent almost half a century studying fish behaviour and just delivered a series of public lectures under the title, How Smart Are Fish? "Goldfish can perform all the kinds of learning that have been described for mammals and birds," she says. "And they've become a model system for studying the process of learning and the process of memory formation, exactly because they have a memory and because they learn."

She says there have been literally hundreds of scientific papers over the decades on goldfish learning and memory. I found a reference to a study on fish memory as early as 1908. "That a species that's used by neuro-psychologists and scientists as a model for studying memory formation should be the very species that has this reputation - I think that's an interesting irony," she says.>>

MarkBour wrote: ↑Thu Apr 11, 2019 1:45 am Because of my last name, some unkind people have occasionally given me the nickname of "goldfish".
... But anyway, what were we talking about?



Oh yes. Slowing down the video of Phobos.

If you follow the second linked word "Phobos" in the APOD caption, it leads to Wikipedia's Phobos article, https://en.wikipedia.org/wiki/Phobos_(moon). If you look down in that article under the section "Origin", at the right is a bit of media that Curiosity took quite a while ago, on 2013-08-20. It is satisfyingly slow, so Bruce and De58te, you might like it ... I do. It also repeats at 6x at the same stately speed. The direct reference to the video is: https://upload.wikimedia.org/wikipedia/ ... p.vp9.webm

The enlarged version shows the same kind of pixelation that caused JohnD to wonder if the Diemos video showed rotation. I agree, it certainly did look a lot like rotation, but as Chris pointed out, that cannot be. The above referenced video helps one confirm that it was an illusion, as the pixelation effects are consistent between this video and the Diemos video.

orin stepanek wrote: ↑Thu Apr 11, 2019 4:22 pm
When Phobos finally comes down to Mars! Will it be a crash or maybe a landing? Since it is in orbit; is it possible it may come in parallel to Mars surface and pretty much roll along the landscape until it comes to a stop? Still I'm sure there would be much damage!

https://en.wikipedia.org/wiki/Phobos_(moon)#Predicted_destruction wrote:
<<Tidal deceleration is gradually decreasing the orbital radius of Phobos by ~2 meters every one hundred years (as compared to our own Moon's orbital radius increase by ~3.8 meters every hundred years). Scientists estimate that Phobos will be destroyed in approximately 30–50 million years. Given Phobos's irregular shape and assuming that it is a pile of rubble (specifically a Mohr–Coulomb body), it will eventually break up when it reaches approximately 2.1 Mars radii (from it's current 2.76 Mars radii). When Phobos is eventually torn apart by tidal forces, a fraction of the debris will likely form a planetary ring around Mars, which may last from one million to one hundred million years.

Phobos' grooves were long thought to be fractures caused by the impact that formed the Stickney crater. Other modelling suggested since the 1970s support the idea that the grooves are more like "stretch marks" that occur when Phobos gets deformed by tidal forces, but in 2015 when the tidal forces were calculated and used in a new model, the stresses were too weak to fracture a solid moon of that size, unless Phobos is a rubble pile surrounded by a layer of powdery regolith about 100 m thick. Stress fractures calculated for this model line up with the grooves on Phobos. The model is supported with the discovery that some of the grooves are younger than others, implying that the process that produces the grooves is ongoing.>>

neufer wrote: ↑Thu Apr 11, 2019 6:00 pm

orin stepanek wrote: ↑Thu Apr 11, 2019 4:22 pm
When Phobos finally comes down to Mars! Will it be a crash or maybe a landing? Since it is in orbit; is it possible it may come in parallel to Mars surface and pretty much roll along the landscape until it comes to a stop? Still I'm sure there would be much damage!

https://en.wikipedia.org/wiki/Phobos_(moon)#Predicted_destruction wrote:
<<Tidal deceleration is gradually decreasing the orbital radius of Phobos by ~2 meters every one hundred years (as compared to our own Moon's orbital radius increase by ~3.8 meters every hundred years). Scientists estimate that Phobos will be destroyed in approximately 30–50 million years. Given Phobos's irregular shape and assuming that it is a pile of rubble (specifically a Mohr–Coulomb body), it will eventually break up when it reaches approximately 2.1 Mars radii (from it's current 2.76 Mars radii). When Phobos is eventually torn apart by tidal forces, a fraction of the debris will likely form a planetary ring around Mars, which may last from one million to one hundred million years.

Phobos' grooves were long thought to be fractures caused by the impact that formed the Stickney crater. Other modelling suggested since the 1970s support the idea that the grooves are more like "stretch marks" that occur when Phobos gets deformed by tidal forces, but in 2015 when the tidal forces were calculated and used in a new model, the stresses were too weak to fracture a solid moon of that size, unless Phobos is a rubble pile surrounded by a layer of powdery regolith about 100 m thick. Stress fractures calculated for this model line up with the grooves on Phobos. The model is supported with the discovery that some of the grooves are younger than others, implying that the process that produces the grooves is ongoing.>>

bcj_sf_nm wrote: ↑Wed Apr 10, 2019 5:20 am Really cool pic, but please, please, please, would people stop saying something is 150 times, or some such, smaller than something else? That is nonsensical. It may be 1/150th the size or Luna may be 150 times larger than Phobos. Thank you.

rstevenson wrote: ↑Thu Apr 11, 2019 7:20 pm

bcj_sf_nm wrote: ↑Wed Apr 10, 2019 5:20 am Really cool pic, but please, please, please, would people stop saying something is 150 times, or some such, smaller than something else? That is nonsensical. It may be 1/150th the size or Luna may be 150 times larger than Phobos. Thank you.

I agree. I find it distractingly odd to read something like "150 times closer". This may be due to my speaking a particular subset of English, or to my being a grumpy old man -- I can't tell. But I do feel that reductions should be expressed as fractions or percentages, and expansions as multiples. Using a multiple to express a reduction is just wrong. It says so right here in Rob's Book of Style.

Rob

Chris Peterson wrote: ↑Thu Apr 11, 2019 7:22 pm

rstevenson wrote: ↑Thu Apr 11, 2019 7:20 pm

bcj_sf_nm wrote: ↑Wed Apr 10, 2019 5:20 am Really cool pic, but please, please, please, would people stop saying something is 150 times, or some such, smaller than something else? That is nonsensical. It may be 1/150th the size or Luna may be 150 times larger than Phobos. Thank you.

I agree. I find it distractingly odd to read something like "150 times closer". This may be due to my speaking a particular subset of English, or to my being a grumpy old man -- I can't tell. But I do feel that reductions should be expressed as fractions or percentages, and expansions as multiples. Using a multiple to express a reduction is just wrong. It says so right here in Rob's Book of Style.

Rob

Your Book of Style is 10 times smaller than mine.

rstevenson wrote: ↑Thu Apr 11, 2019 7:31 pm

Chris Peterson wrote: ↑Thu Apr 11, 2019 7:22 pm

rstevenson wrote: ↑Thu Apr 11, 2019 7:20 pm

I agree. I find it distractingly odd to read something like "150 times closer". This may be due to my speaking a particular subset of English, or to my being a grumpy old man -- I can't tell. But I do feel that reductions should be expressed as fractions or percentages, and expansions as multiples. Using a multiple to express a reduction is just wrong. It says so right here in Rob's Book of Style.

Rob

Your Book of Style is 10 times smaller than mine.

Yes but I'm close to sea level, where the denser atmosphere allows for greater understanding of such niceties.

Rob