For Questions That Don't Merit Their Own Thread

[kerbiloid]

The more I know about astronomy, the more I believe that we live in a small room, full of funhouse mirrors.

Spoiler

 

[kerbiloid]

If take the Schroedinger's anti-cat box, and take a beholder as the observer.

Spoiler

Then put an eye tentacle inside the box.

Is the cat alive or not for the beholder?

Or will the beholder split into two parallel realities?

[Gargamel]

Since the eye stalk can see, the cat, and therefore the radioactive decay which triggers the poison release would have been observed.   The wave functions collapse, and one of the possible outcomes occurs.   The cat is only alive/dead if it is not observed. 

[kerbiloid]

2 hours ago, Gargamel said:

Since the eye stalk can see

But the vision can percept only the objects which definitely exist.
So, while the beholder outside of the box exists in the reality with undefined cat status, the same beholder's eye exists it the cat's reality, which should be defined for its eye.

Won't the Schroedinger's experiment cause an uncontrollable cell division of the beholders, that's the question...

[JoeSchmuckatelli]

This is probably an @mikegarrisonquestion:

 

I've been reading about toroidal propellers being used in drones and marine applications.  Trying to see if there were any advances in applying these to aircraft (traditional planes, not merely drones) - and I'm not finding much.

Is this because of an inability to change pitch of the propeller effectively with the toroidal shape, or are they simply too new?

[mikegarrison]

19 minutes ago, JoeSchmuckatelli said:

This is probably an @mikegarrisonquestion:

 

I've been reading about toroidal propellers being used in drones and marine applications.  Trying to see if there were any advances in applying these to aircraft (traditional planes, not merely drones) - and I'm not finding much.

Is this because of an inability to change pitch of the propeller effectively with the toroidal shape, or are they simply too new?

I am not an expert in propellers. And this is the first I have ever heard of "toroidal propellers". But I'm pretty sure that at least half of what I just saw in the first You Tube links I pulled up is wrong.

But to answer your question, you can't just slap any old propeller on your airplane and go fly with it. Propellers have to be certified by the regulators. (Unless, I guess, if you are talking about a plane with an experimental ticket. In that case, you probably have more latitude.)

[JoeSchmuckatelli]

1 minute ago, mikegarrison said:

this is the first I have ever heard of "toroidal propellers

New to me, too.  I'm guessing the main benefits are fuel efficiency in certain RPM ranges (Marine) and noise mitigation, drones. 

But, apparently they do fly 

[mikegarrison]

20 minutes ago, JoeSchmuckatelli said:

New to me, too.  I'm guessing the main benefits are fuel efficiency in certain RPM ranges (Marine) and noise mitigation, drones. 

But, apparently they do fly 

I strongly suspect they are less efficient. Very strongly suspect that.

Propeller efficiency drops with blade count, and in many ways these double the blade count.

Edited May 13, 2023 by mikegarrison

[magnemoe]

2 hours ago, mikegarrison said:

I strongly suspect they are less efficient. Very strongly suspect that.

Propeller efficiency drops with blade count, and in many ways these double the blade count.

How can it be less efficient if they make boats go faster with same power?
I think their benefit is that they reduce the wingtip drag on the propeller probably emulating an ducted fan. It did not work as an pc cooling fan since its ducted.
Downside is that you can not change the blade angle of attack who has been important to turboprop planes and the large diameter propeller will be very heavy. 
For motorboats would not an duct be more efficient? it also protect the propeller from damage. 

 

[kerbiloid]

3 hours ago, magnemoe said:

How can it be less efficient if they make boats go faster with same power?

Biplanes are used not because four (two) wings are better than two (one), but because construction materials are too weak to withstand the bending.

Say, originially monoplane OKA-38 became a biplane being grown into twice bigger An-2, but then the latter became back an experimental monoplane, when the duralumine had been replaced with carbon composite.

The propeller blades are also limited in length.

Edited May 14, 2023 by kerbiloid

[monophonic]

On 5/14/2023 at 1:51 AM, mikegarrison said:

I strongly suspect they are less efficient. Very strongly suspect that.

Propeller efficiency drops with blade count, and in many ways these double the blade count.

Indeed the originators don't list efficiency in the pros box in their brochure. Noise levels and 3D printability are the most important ones in my layman's opinion.

https://www.ll.mit.edu/sites/default/files/other/doc/2023-02/TVO_Technology_Highlight_41_Toroidal_Propeller.pdf

[SunlitZelkova]

I'm copying this from the Ancient History thread over in the lounge in case anyone wants to chime in here too.

How long does it take for a population to gain immunity to a disease?

I was originally thinking to have my alternate history where Zheng He goes east and winds up in America in 1407 lead to the Native Americans getting immunized by way of the Chinese being more cleanly than Europeans (I'd assume) and getting just enough exposure to become immune with triggering an epidemic. But I watched some videos the other day proposing it might take centuries or more for that to happen, so I thought I'd ask here. This kind of fits in the Questions thread in the S&S section too.

Or is that even possible? Just off the top of my head, it doesn't seem like it would be possible for a population to become immune to a disease without major losses unless they lived alongside that disease from its inception.

[JoeSchmuckatelli]

8 hours ago, SunlitZelkova said:

I'm copying this from the Ancient History thread over in the lounge in case anyone wants to chime in here too.

How long does it take for a population to gain immunity to a disease?

I was originally thinking to have my alternate history where Zheng He goes east and winds up in America in 1407 lead to the Native Americans getting immunized by way of the Chinese being more cleanly than Europeans (I'd assume) and getting just enough exposure to become immune with triggering an epidemic. But I watched some videos the other day proposing it might take centuries or more for that to happen, so I thought I'd ask here. This kind of fits in the Questions thread in the S&S section too.

Or is that even possible? Just off the top of my head, it doesn't seem like it would be possible for a population to become immune to a disease without major losses unless they lived alongside that disease from its inception.

The 'more cleanly' thing, at best, impacts waterborne pathogens like cholera or the prevalence of dysentery.  Respiratory ailments, blood pathogens etc rip through populations regardless of their beliefs about personal hygiene. 

Your best analogy to the NA experience with plague (disease process and population regardless of pathogen) is to look at the European / ME experience of the plagues we have records for.  Those that happened right before discovery of NA, especially. 

The answer is pretty devastating.  The population drops precipitously and then takes quite a while to recover. 

Ultimately - the answer you are looking for explains why NA looks like Europe after the experience of Imperialism/Colonialism and India / Africa don't.   India and Africa, being part of the same supercontinent as Europe experienced the same diseases at about the same temporality and so the populations all crashed and recovered together. 

NA's population crash came from multiple diseases they weren't ready for - and they never got to regain population before outside competition showed up.  You can extrapolate the numbers - but in Dee Brown's book, the statistic of 30 million Americans East of the Mississippi in 1860 compared to 300,000 Native peoples remaining in the West is telling. 

So - if in your story the Chinese don't rush back over here in numbers to colonize?  Yeah they might recover - but if nothing changes, meaning Columbus still sails in 1492? 

Probably not. 

If you take 1500 to 1600 for the population crash, it would take 1600 to 1700 for the recovery - and that's without external pressures and new diseases.  Functionally I don't think there is a way for the American and Eurasrica populations to interact back then that doesn't end badly for NA folks. 

[kerbiloid]

Afair the smallpox and leptospirosis were the most popular in North America. 

So, any cattle-herding people would bring it right inside themselves and the cattle,

[mikegarrison]

12 hours ago, SunlitZelkova said:

I'm copying this from the Ancient History thread over in the lounge in case anyone wants to chime in here too.

How long does it take for a population to gain immunity to a disease?

I was originally thinking to have my alternate history where Zheng He goes east and winds up in America in 1407 lead to the Native Americans getting immunized by way of the Chinese being more cleanly than Europeans (I'd assume) and getting just enough exposure to become immune with triggering an epidemic. But I watched some videos the other day proposing it might take centuries or more for that to happen, so I thought I'd ask here. This kind of fits in the Questions thread in the S&S section too.

Or is that even possible? Just off the top of my head, it doesn't seem like it would be possible for a population to become immune to a disease without major losses unless they lived alongside that disease from its inception.

Are you familiar with The Years Of Rice And Salt by Kim Stanley Robinson?

Edited May 16, 2023 by mikegarrison

[DDE]

12 hours ago, SunlitZelkova said:

by way of the Chinese being more cleanly than Europeans (I'd assume)

I'd keep a question mark by that assumption. European sanitary standards weren't that terrible before the initial urban sprawl of the Industrial Revolution, which hearded a lot of country bumpkins into cities that didn't have anywhere near the infrastructure or space. Arguably, compact urban cohabitation is where the Chinese had the advantage.

Exploring the New World was the opposite of that situation.

[sevenperforce]

On 5/13/2023 at 6:51 PM, mikegarrison said:

On 5/13/2023 at 6:35 PM, JoeSchmuckatelli said:

New to me, too.  I'm guessing the main benefits are fuel efficiency in certain RPM ranges (Marine) and noise mitigation, drones. 

But, apparently they do fly 

I strongly suspect they are less efficient. Very strongly suspect that.

Propeller efficiency drops with blade count, and in many ways these double the blade count.

The reason that propeller efficiency drops with blade count is due in part to things like turbulence and blade interference, which in turn is a factor of blade tip vortices, and so if the toroidal propellers more evenly distribute blade tip vortices to reduce noise, they might also reduce turbulence and interference, increasing efficiency in certain RPM ranges. Or at least canceling out losses.

But yes, I would suspect that they are most likely less efficient across aviation RPM ranges.

[mikegarrison]

1 hour ago, sevenperforce said:

The reason that propeller efficiency drops with blade count is due in part to things like turbulence and blade interference, which in turn is a factor of blade tip vortices, and so if the toroidal propellers more evenly distribute blade tip vortices to reduce noise, they might also reduce turbulence and interference, increasing efficiency in certain RPM ranges. Or at least canceling out losses.

But yes, I would suspect that they are most likely less efficient across aviation RPM ranges.

As I (and others) have tried to explain before, the idea that there are "tip vortices" is extremely over-simplified, and the idea that you can eliminate them with something like this is just flat out wrong.

A wing (or propeller) sheds vorticity as the lift distribution changes on the wing. So if it had a flat, constant lift distribution right to the tip, then yes, all the vorticity would be shed from the tip. But this doesn't happen (and would be a terrible way to design a wing if you could make it happen). Instead the lift decreases from root to tip, so it sheds vorticity all along the wing. This "rolls up" into one collected vortex on each side, but the explanation that pretty much every single youtuber "explaining" these toroidal propellers has for how they work is flat out wrong.

There are some ways that wingtip devices can help reduce left-induced drag, but these are in general much more complicated than people think they are, and for the most part they don't work the way that people think they work.

It is not clear to me that anyone is actually measuring any propeller efficiency increases from these things. But even if they were seeing some kind of significant, measurable, repeatable efficiency gain, then the obvious question would be "gain versus what?" As in, if you just compare against some random prop you bought off the internet, who is to say that prop was well-designed?

With rotating wings and propellers, one of the big sources of noise is chopping through the wake from the other blades. Most rotating fans and props and such have a strong noise signature at the "blade passing frequency" (that is to say, the frequency at which a blade moves through a given location on the circle). So the BPF is proportional to the number of blades and the RPM. Which means that you are certainly going to change the noise characteristics of the propeller if you change the number of blades. This, at least in part, is going to explain why they sound different.

Anyway, to answer (again) the original question, I doubt you are going to see these show up any time soon on airplanes.

[SunlitZelkova]

10 hours ago, mikegarrison said:

Are you familiar with The Years Of Rice And Salt by Kim Stanley Robinson?

No. But I just looked it up and it sounds very interesting!

9 hours ago, DDE said:

I'd keep a question mark by that assumption. European sanitary standards weren't that terrible before the initial urban sprawl of the Industrial Revolution, which hearded a lot of country bumpkins into cities that didn't have anywhere near the infrastructure or space. Arguably, compact urban cohabitation is where the Chinese had the advantage.

Exploring the New World was the opposite of that situation.

Yeah, it was a wild guess, but it sounds like factors other than that render it a moot point anyways.

[steve9728]

Fact is, the ancient Chinese wasn't 'that clean': Ming rule the empire for 276 years and had at least 168 years with pandemic. Deng Tuo, the historian expert found that, in entire Ming Dynasty there's 1011 time of disasters. There's including 196 times of flood, 174 times of droughts, 165 times Earthquake, 112 times hail, 97 times storm, 94 times locust plague, 93 times starvation, 64 times plague, and 16 times of snow. Ju Mingku, the author of Disasters and Ming Politics said that, in average each year there's 6.77 times of flood, 5.38 earthquake, 3.42 droughts, 1.61 hail, 1.17 locust, 0.99 storm and 0.32  snow. 

Which means, just counting these disasters by nature, would die HELL of people. When the dead body and any other waste couldn't clean up quickly, here we go, 168 years of pandemic in total. Then when there's not enough people to plant the food, starvation is coming. Then the next vicious cycle begins. Another fact is, in the county annals of the Ming Dynasty in many places in China, there are NUMBERS of cannibalism. So, if your Chinese buddy hellowing you is not "nihao" but "have you eat?", is for reasons: we know what's starving feels like.

The European epidemics of smallpox and bubonic plague did not bypass the Chinese, to give just two examples of  prince who contracted and died of smallpox: the three-year-old second son of Emperor Chenghua and the thirteen-year-old second son of Emperor Jiajing.

So, I think, if those guys get the world map a hundred years earlier between 1405~1433 for no reason, and they really want to "Hello America" make them at least 59 years earlier than Columbus, the thing happened next on those native American - by plague that those Chinese crew may bring, wouldn't better than what the reality history in this world.  If you want the native American can get proper antibodies before European arrived, I think you should give the map to Yuan's Khan not the Ming's Emperor. After all, there's someone point to the high probability that the plague in Europe in the 13th century began during the Mongol siege wars.

Edited May 17, 2023 by steve9728

[JoeSchmuckatelli]

@SunlitZelkova- I suspect you have moved on, but I found this informative:

"Different populations were affected at different times and suffered varying rates of mortality.

Diseases such as treponemiasis and tuberculosis were already present in the New World, along with diseases such as tularemia, giardia, rabies, amebic dysentery, hepatitis, herpes, pertussis, and poliomyelitis, although the prevalence of almost all of these was probably low in any given group.

 

Old World diseases that were not present in the Americas until contact include bubonic plague, measles, smallpox, mumps, chickenpox, influenza, cholera, diphtheria, typhus, malaria, leprosy, and yellow fever.

Indians in the Americas had no acquired immunity to these infectious diseases, and these diseases caused what Crosby referred to as “virgin soil epidemics,” in which all members of a population would be infected simultaneously."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1071659/#:~:text=Diseases such as treponemiasis and,low in any given group.

 

Edited May 18, 2023 by JoeSchmuckatelli

[SunlitZelkova]

5 hours ago, JoeSchmuckatelli said:

@SunlitZelkova- I suspect you have moved on, but I found this informative:

"Different populations were affected at different times and suffered varying rates of mortality.

Diseases such as treponemiasis and tuberculosis were already present in the New World, along with diseases such as tularemia, giardia, rabies, amebic dysentery, hepatitis, herpes, pertussis, and poliomyelitis, although the prevalence of almost all of these was probably low in any given group.

 

Old World diseases that were not present in the Americas until contact include bubonic plague, measles, smallpox, mumps, chickenpox, influenza, cholera, diphtheria, typhus, malaria, leprosy, and yellow fever.

Indians in the Americas had no acquired immunity to these infectious diseases, and these diseases caused what Crosby referred to as “virgin soil epidemics,” in which all members of a population would be infected simultaneously."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1071659/#:~:text=Diseases such as treponemiasis and,low in any given group.

 

I have not, thank you for this source!

——

Alright, now I have another question. Is the minimum viable population for humans known? I have looked around for this but have gotten answers varying between 14 and 14,000.

One last thing- would it make sense to build a giant interstellar ark or a fleet of smaller ships? Would there be any pros to building a single ship?

[steve9728]

Just now, SunlitZelkova said:

One last thing- would it make sense to build a giant interstellar ark or a fleet of smaller ships? Would there be any pros to building a single ship?

I would recommend the Wandering Earth on Netflix

Don't know did they put 2 on it because I'm no longer subscribe it anymore.

[JoeSchmuckatelli]

5 hours ago, SunlitZelkova said:

Alright, now I have another question. Is the minimum viable population for humans known? I have looked around for this but have gotten answers varying between 14 and 14,000

one that is commonly used in ecological investigations involves establishing greater than 95 percent probability of survival for more than 100 years. Since different species have different life spans, however, a time benchmark of 40 generations also may be used, especially when making comparisons between species

... 

They created the “50/500” rule, which suggested that a minimum population size of 50 was necessary to combat inbreeding and a minimum of 500 individuals was needed to reduce genetic drift. Management agencies tended to use the 50/500 rule under the assumption that it was applicable to species generally.  

(general rule, variable applicability based on mating habits and gestational trends - think multiple litters & parent combos per year for rats vs  long gestation plus preference for older, larger and dominant males among elephants (females stay in groups, prefer the same dominant male in any given year - although the available males change from year to year) 

 

Now... This article says the number is 98 - for humans specifically.  

https://www.google.com/amp/s/www.nbcnews.com/mach/amp/ncna900151

They do mention the 50/500 rule and your guy who came up with 14,000. 

[kerbiloid]

6 hours ago, SunlitZelkova said:

Is the minimum viable population for humans known?

A paleolitic family tribe ~20, a neolitic tribe ~100, the 80 kya humanity bottleneck is ~ 10 000 humans overall.

A couple of completely healthy humans with no chrosome aberrations yet = 2.

But it doesn't matter for interstellar ships, because everyone onboard will be irradiated and become a mutant spawner.

So, only frozen ovocytes and a sterilized or better female crew.

7 hours ago, SunlitZelkova said:

One last thing- would it make sense to build a giant interstellar ark or a fleet of smaller ships? Would there be any pros to building a single ship?

Some of many would survive.

Also, if the cargo is a GECK + ovocites, it would be a serial product, manufactured in great amounts (say, as the Earth Repopulation Kit), so anyway many ships are better.

And as the crew requires artificial gravity it would be ~200..400 m in diameter, so require a very powerful engine to start. It could be impossible to make even bigger engine to put all in one.