Counter-rotating propellers sparked my curiosity when I first saw them on a British Seafire Mk46 at a flight show in the early nineties.

So my amateur's answer would be that it's about the problem of turning the engine's power into thrust. With increasing power, you can either increase the propeller's RPM or its area. So you either a) spin it faster, b) increase its diameter, c) use a more favourable blade geometry, d) add more blades.

a) and b) both lead to blade tips moving faster, and once they approach the speed of sound, wave drag sets in and ruins your day. b) also runs into issues in terms of ground clearance. Thus the Kim Jong-un blades on planes like the An-70: short and fat.

c) is rather difficult to do in terms of manufacture -- that's why more pronounced blade shapes are a relatively recent development.

d) on a single propeller decreases the efficiency of each blade as it passes through the previous blade's vortex. That's why, for instance, German planes in WW2 almost exclusively relied on 3-bladed propellers with increasing blade size, whereas Supermarine went to four and even 5 blades rather quickly. You can work the issue to a certain degree by modifying the blade geometry, thus the 8 blade props on a modern A400M.

Adding more blades by adding another propeller gets around d), although the aft prop still loses efficiency compared to the front prop. On the other hand, counter-rotating props massively reduces problems with torque, which can be rather horrendous for single engine prop planes. The Bf 109, for instance, is (in)famous for being difficult during take-off as it pulls to the side quite violently.

I actually agree with you mostly, but you're not gonna like it.

One thing I will point out though - "I just don't connect gun regulations as an effective solution to mass murder."

We have data on this. Take Australia. In the 21 years leading up to Port Arthur and that massacre itself, which triggered the nation into heavily regulating guns, there were 16 mass murders of four or more people, totaling 137 murders. Since then, there have been 12, with a total of 76 murders. This despite there being population growth.

Violent crime rate has dropped from 1996 to now, mainly from reductions in robbery and a small drop in homicide rates.

There is very clear evidence that if most guns are removed from circulation, there are very real and likely benefits when it comes to reducing violent crime in general and murder.

I'm a political moderate and pragmatic. I go with what works. Don't care how liberal or conservative the solution is. I'm never in favor of regulation that is ineffective at solving problems.

And to that end, I'm against most gun control measures. I'm on board with banning assault weapons, fully automatic weapons, armor piercing bullets, but most gun control things like psychiatric evaluations, universal background checks? No.
Why? Because societal models we know that provided real progress on problems seemed to suggest one thing - it's the prevalence of guns that is the problem. If you make it marginally harder to buy guns by things like...

Three day waiting periods
Universal background checks
Psychiatric evaluations

They don't work. Banning guns works, though. It's worked time and time again. Australia, Britain, over and over and over, if guns lose prevalence, violence, murder, etc. decrease significantly.

At some point, society has to decide that giving up guns is worth it. But until that time, "common sense" gun control is a waste of time, and I quite frankly think it might do real effective gun control measures harm because when nothing gets better from these mild measures, they're going to point that out.

Not so much if you actually read (and comprehend) it, or listened to the authors.
They've said clearly that even using their revised estimates of CO2's effects that to meet a 1.5 degree rise (the tipping point where we loose all ability to mitigate the run away greenhouse effect and start the irreversible march towards mirroring Venus) we have to start decreasing CO2 emissions today and be at zero by 2040. They've also said clearly that anyone misusing their paper to imply climate change is a myth is a liar, a moron, or both, because it says and implies no such thing.

What we are doing is raising the amount we emit while people like you who clearly don't grasp the science argue, ignoring that the effects of warming are already being seen far earlier than predicted....effects like melting methane hydrates that make up the difference in CO2 effects and then some, effects like 3-500 year floods in under 2 years in places, effects like reefs bleaching worldwide.
So much for the climate science denier BS.

I'm torn by our pulling out of Paris. I think it's critical that we all cooperate to reduce our Co2 emissions. But I also understand that at least what China offered (not) to do is the single biggest factor in our future success (failure).

Their "reductions" are tied to points of GDP compared to 2005 levels, meaning that they can either reduce their emissions, or grow their economy faster than their emissions grow. The latter is what is happening.

Their contribution is to try to have their reliance on coal "peak" by or prior to 2030. At the moment, they are emitting over 30% of the world's Co2, with the US at about 17%. But even when and if China's Co2 emissions peak, they almost certainly won't fall...they will plateau. As we speak, China is building dozens of new coal-fired power plants...and these new plants, along with those already built, have life spans of at least 50 years. So when you hear talk of China's already reducing their emissions, they aren't speaking of real reductions, rather lowered percentages as a ratio of growing GDP. For example, China emitted over 5,800,000 kilotons of Co2 in 2005, and 10,600,000 kilotons in 2015. Yet China's nominal GDP was only US$2.3 trillion in 2005, and a whopping US$11.1 trillion in 2015. So as a ratio of GDP, China's emissions appear to have decreased. The opposite is true, and they'll continue this farce for as long as possible. Now, some will answer with things such as:

A. But America pollutes more per capita!
B. But China deserves to have a per capita GDP that rivals that of the US!
C. You should be comparing GDP per capita or PPP!

To which I answer...our planet's climate and environments don't give a damn about these abstractions. What matters is the TOTAL amount of greenhouse gases being emitted.

So, I guess we won't keep warming under two degrees Celsius. Because it's more important that China's per capita GDP of about US$8,000 grows to match the US$56,000 of the US. In effect, if populations stayed the same, and the US economy stagnated...we'd need to wait for China's nominal GDP to grow to US$77.7 trillion compared to the US's $17 trillion.

Let me just add that if China were allowed to grow that powerful, polluting all the while, then the free nations of our planet would have graver problems than climate change.

You may think that China is a poor country without the current means to effect a major transition. To which I'll answer that their government and state-run corporations could stop buying foreign businesses and real estate, as well as not building more missiles, planes, rockets, blue-water navies, and man-made islands...and perhaps put those funds toward an honest shift toward green energy.

*related https://videosift.com/video/Climatologist-Emotional-Over-Arctic-Methane-Hydrate-Release

It likely is too late, as soon as these short-lived but potent gases are released it will get unpleasant very quickly. I know dumping iron in the ocean to stimulate algae growth which then sinks as acts as a carbon sink has been discussed. Also, spraying aerosols into the upper atmosphere constantly can decrease warming, but that doesn't reduce the CO2.

Many, if not most, that oppose places like Planned Parenthood, and oppose most methods of birth control, oppose it, because they think it encourages promiscuity. Sex is of course limited only to marriage in their world view, which is why heavy red states have abstinence only education... which tends to result in them having the highest teen and repeat teen pregnancy rates. And some would argue that the only function of sex is for procreation. The Bible even forbid pulling out (Gen. 38:8–10), though one could argue that was for one guy in particular. Anyhow, basically they see pregnancy as part of God's design and purpose for sex. The fact it has physical pleasures, is a gift from God for the married couple.

In the case of IUDs, they believe the old myth that the IUD causes abortions, that it lowers the chance that a fertilized egg will implant. The reality is that it doesn't at all, at least for modern, non-copper clad IUDs. Once upon a time, the old copper ones did have a very small impact on the chance a fertilized egg could implant, and even modern ones that have far less copper cladding on a wire around it, can have a very very small chance of decreasing implantation. But those ones aren't really used that often. Basically, the IUD is the most effective form of birth control, but it is opposed to stereotypes and lies. Modern IUDs work to prevent fertilization in the first place, via the hormones in them and design, if an egg is fertilized, it still has the same chance of implantation... however the chance of an egg being fertilized is very low, as sperm mobility is seriously hurt, and of course the woman's body lowers egg release too.

Plan B also doesn't stop implantation, or if it does, it is near modern copper clad wire IUDs (and more recent evidence shows it is likely even far less than that). It prevents the women's body from releasing an egg... if an egg is released already, it won't do any good. However, once again, facts don't matter to those on the right, and they promote it as a morning after abortion pill.

Of course, a healthy young woman, who's optimally fertile, only 30-40% of her fertilized eggs will implant, meaning that God Himself aborts about 60-70% of babies (since they define it as a full baby and human life at conception) in optimally fertile women. Now.. you have to add to that, natural miscarriages for other reasons... and the odds of having a baby really are against you naturally. (There are links to medical journals here: http://ask.metafilter.com/203529/What-of-fertilized-human-eggs-die and in this Healthcare Triage video about IUDs: https://videosift.com/video/IUDs-Are-Pretty-Great-So-Why-Arent-They-More-Popular)

Trivia:

While not exactly proven (correlation is not causation), the wide spread introduction of refrigeration for food storage probably was the reason behind the gross decline of GI Cancer as a major source of death before the 1930s...

"Until the late 1930s, stomach cancer was the leading cause of cancer death in the United States. Now, stomach cancer is well down on this list. The reasons for this decline are not completely known, but may be linked to increased use of refrigeration for food storage. This made fresh fruits and vegetables more available and decreased the use of salted and smoked foods. Some doctors think the decline may also be linked to the frequent use of antibiotics to treat infections. Antibiotics can kill the bacteria called Helicobacter pylori (H pylori), which is thought to be a major cause of stomach cancer."

American Cancer Society...

The mechanism appears to have been the move away from pickling/smoking...and towards fruits/vegetables/etc which an in-home refrigerator let you use...

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1971721/?page=1

Look
If you had
One shot
Or one opportunity
To release all the energy you ever wanted
In one moment
Would you abuse it
Or use it for good?

They've armed the weapon
Countdown clock is set and
J. Robert Oppenheimer is sweatin'
Eyes are red and he's nervous
Cause on the surface this is armageddon
The shock bomb, but we're set upon and threatened
And with no sound the whole Alamogordo ground
Is glowing and cowed under one smouldering cloud
He's choked and wowed, everybody's open-mouthed
And over the ground the shock front blows, kapow!
Snap back to the alchemy
Hope before tragedy
Showed with bold math that we broke the whole atom
We choked; controlled action with poles of cold cadmium coat
To go capture neutrons and slow fracture
We broke, postponed that and we chose to go fashion
A most radioactive plutonium gadget then
Fat Man and Boy and Enola goes laughin'
As Nagasaki is blown and Hiroshima's blasted

You gotta choose, yourself how to use it
The knowledge you hold and
Don't ever let a letter go
You only get one shot to stop
And one chance to know
Responsibility comes once you're a science guy, yo!

Neutrons escaping from a source radiating
Merge and start atoms shaking; they begin
To unglue toward a decreased order
Entropic force distorts em
And supercharged with loads of protons they can only go farther
Cold war grows hotter--exothermal--Colorado to Joe Stalin
Coast to coast holes; silos but there's no farmer
Toe-to-toe drama
NATO and Warszawa in co-assured trauma
The globe groans everyone knows there's no calming
So show your foes and implode your core column
Quid pro quo Castle Bravo for Tsar Bomba
And move on and leave atolls exposed to gross doses of old fallout;
Slow-to-go toxins in shoals and so though we explode them no longer
Still the proof lives on in the blue lagoon water, father

You gotta choose, yourself how to use it
The knowledge you hold and
Don't ever let a letter go
You only get one shot to stop
And one chance to know
Responsibility comes once you're a science guy, yo!

When war games hit the stage of a gluon's rage
There's a military boot on the new doc's page
We were playing in the beginning, but grew up strange
Making radar and missiles, and new bombs blazed
And we kept grinding the lensed sights for the next sniper
Best believe son it'll pay to design fighters
All the gains of science analyzed by the
Man provide plans for sarin and cyanide
And our hands are blighted by crying
Eyes when dying lands are slammed if our grants expand the fire brighter
And there's no jury there's no sublime righter
This is our fight
And these minds are all ours so protect your pia mater
Try to feed and water good, seed trust, flee dishonour
Gotta be clean being Apollo stead of Vietnam and
Lay the armour down and be the one to stand up
And lead us on the trail of Spock
We'll elevate these motley progeny
To a future in a safer spot, an irrigated plot
Homicide a way forgot
Success is a lack of military options
Failure's not
Become a lover of a great and cosmic goal
We cannot condone these terror plots
So here we go it's our shot
Feel frail or not
This is the only world and humanity that we got

You gotta choose, yourself how to use it
The knowledge you hold and
Don't ever let a letter go
You only get one shot to stop
And one chance to know
Responsibility comes once you're a science guy, yo!

You gotta make your own mind up, man.

@bcglorf

i don't think using @drradon 's example of anarchy a good use as a rebuttal.

now may be larken rose's vision is an extreme example,taken from the von mises institute,and where they dreamily offer a counter to police with a "non-aggression principle".while cute and adorable,humans tend to be far more vicious and violent in nature,especially when desperate.

but again,i think our respective approaches to authority will not find common ground here.

i do not seek a leader,but i am ok with a representative,though i do not seem to have any in my government at the moment.

i find it curious,amazing and not a little disturbing just how easily people will quietly,and tacitly accept a police that has become more and more draconian,violent and aggressive while SIMULTANEOUSLY decreasing the citizens rights to protect themselves,defend themselves and resist unlawful police practices.

because they simply change the law to make what WAS illegal...legal.with a stroke of a pen.

and i simply cannot respect when an american says,without any sense of justice or history,to just sit down,shut up and do what you are told.

while claiming they are a patriot,waving their american flag made in china.

the history of law enforcement in this country reveals that their main job,their main focus and duty is NOT to the poor,the dispossessed or the marginalized.

the police's job is to protect those who hold assets,who have money and wield political power.

and before you say anything,i am quite aware that there are some,and they are the majority,who do their job with honor and distinction.my argument is not about singular police officers but rather the systematic problems inherent in the system.

lets take my city for example.
i am blessed enough to live adjacent to a very wealthy and influential housing development.

average police response time?=7 minutes.

right down the street,not 10 miles down the road,is a depressed area of town.industry and manufacturing abandoned that area 20 years ago.it is stricken with prostitution,heroin addicts and abject poverty.

average police response time?=22 minutes

yet the main police station is in THAT area.

or should i bring up the history of american labor movement?
where the coal miners in west virginia decided to strike,and because the owners of the mines were politically connected.the governor sent in the state police to...and this should send chills down your spine...shoot any miners unwilling to go back to work.

and they did.
they murdered any coal miner still willing to stand up against the owners of the mine,and this included women and children.

now lets examine that for a minute.
workers for a coal mine decided to strike for better working conditions (which were horrible) and actually have a day off,besides sunday (because:god).

the owner of the mine,who was losing immense of amount of money due to zero production of coal,called the governor to have the state police,a civil institution,sent in to put those people down.to force them to either get back to work or face violence.

*now the owner brought in his own mercenary group to assist in the process of intimidation,strong arm tactics and violence.

i will add one more story that is personal,and comes from my own family,and may possibly explain my attitude towards police in general.

my father was born in 1930,in alton illinois.
now that small town had been hit particularly hard during the depression.my father spoke of not having indoor plumbing until he went into the navy,and how the floors in his childhood home were simple boards over dirt.

he grew up extremely poor,and my grandfather struggled to find steady work,and i gather from what my father told me.my grandpa made bootleg beer out of the bathtub.so he and his 6 brothers and 1 sister had to bathe in the mississippi river while grandpa tried to make money by selling illegal hooch.

my father also regaled me with stories of the chores he had as the youngest of 8 kids.it was his job every morning to head to the train tracks and pick the coal that dropped from the coal carts.(which he admitted to being lazy and stole directly from the very full coal cart itself while his brother kept an eye out for the station master).

my point is that my father grew up in desperate and poor times.

but one story always stood out,and i think it is because it has a wild west feel to it that always transfixed me,and i made him tell me the story over and over as a child.

when times are tough,people will do whatever they have to in order to survive,so my grandfather making illegal hooch was not the only illegalities being played out in that small town.neighbor upon neighbor did what they had to,and most were considered criminals in the eyes of the state.

so i guess one of my grandpa's friends was on the run from the law,and sought refuge at my grandpa's home.which he allowed,because neighbors take care of neighbors,at least they used to.

well,in a small town everybody knows everybody,and eventually three police officers showed up at my grandpa's house,and demanded that he turn over (i forgot the guys name).

and i remember the pride on my fathers face whenever he retold this story....

my grandfather stood tall on the top of his stairs facing his front door,holding his gun he was given during WW1 and told the police officers (which he knew.small town remember?),that if they took one step into his home..he would blow their heads off.

now this is a story retold from a childs perspective many years later.i am sure my fathers memory was a tad....biased..but i would bet the meaty parts were accurate.

now my question is this:
how would that exact same scenario play out in todays climate?

well,we would see on the 6 o'clock news how a family was tragically shot to death for harboring a criminal and that the police had done EVERYTHING in their power to avoid this kind of violence.

i know this is long,and i hope i didn't lose you along the way,but i think we should not dismiss the very real slow decent into a society that silently obeys,quietly accepts more and more authoritarian powers all in the name of "safety",and that any form of resistance is to be viewed as "criminal" and "troublesome".

so while i agree that "when should we shoot a cop" should be in the realm of:let us try to never do that.

i also cannot agree to placing cops on a hero platform as if their job is somehow sacrosanct and beyond reproach.they are human beings,of limited intellect,whose main job it is to protect those who own property,have wealth and wield political power.

and with the current disparity and blatant inequality their job has been more and more focused on keeping those 30% undesirables down.

the poor,the destitute,the marginalized,the addict and the junkie and the petty criminals.

those are a threat to the "better" citizens.they are a blight on a community that should be cleansed from the tender eyes of those who are deemed more "worthy".

rich folk may wring their hands,and lament the plight of the poor and wretched,but for GOD's sakes! they don't want to actually SEE them!

so a police officer can do all the mental gymnastics they want in order to justify their place in society,but at the end of the day,they serve the elites.

and they always have.

Nice.
I wish they paid more attention to the combustion chamber. Most people don't know what a hemi is beyond a powerful motor. The hemispherical combustion chamber produces far more power than a normally shaped one. Even partial hemispherical combustion chambers (semi-hemi) can seriously increase the power of most motors....but also decreases the fuel efficiency.
I use a semi-hemi cut 1776 VW motor in my race buggy, and it outperforms much larger motors.

The only way I could see it working as described is if the Tesla really has that good of object-detection onboard, was already tracking all objects, and was just that accurate in determining the speed of the impacted SUV and the rate of decreasing distance between it and the car that hit it.
Even if that were the case, I suspect the sensors on these cars get exponentially fidgety at longer distances and with more extreme angles (like measuring changing distance between two 'overlapping' objects directly ahead), it's really unlikely it was predicting the collision.
All that to say: Yeah, I agree. You're most probably right.

Thanks for the pointer. Looks like his movie is available on Vimeo- https://vimeo.com/16598921
(24 min, b&w)

And I never said that nerdwriter (or anyone else) isn't allowed to criticize movies.

My point is that anyone looking for art in modern movies will inevitably be disappointed. The art in filmmaking has been replaced with business. And like @artician mentions above, creative work has to appeal to a large audience.

I'm not saying that there aren't any well made artful movies anymore, just that the ratio of those to hollywood-factory-churned-mediocre-fest movies is steadily decreasing.

The population is greatly decreased.
And now the odds are greatly increased.
That I may someday get a chance,
to kiss your lips.
I thank the lo-o-ord each day,
for the apocalypse.

Folks are mostly disfigured or dead
but, sugar, I wont let it go to my head.
My mama's face has dripped down into the dirt.

But I'm still chasin' chitlins, whiskey and skirt.

I am constantly flummoxed by folks' lack of understanding as to the 'why' of the electoral college. Its meant to prevent what's called the 'tyranny of the majority'. Has to become so lop sided that it should be recalibrated? Certainly. Population count increases and decreases should be reflected in the number of electoral college votes, while preserving the initial intent; making sure smaller states have at least some influence and power.

No, and that is a method to combat Slow Loris. You can also raise the number of concurrent connections, decrease the timeout on connection response, setting up reverse proxies, and other methods in a similar fashion.

The problem is that you can also modify Slow Loris to work around those methods. The only certain way to block it is to use a webserver software that is not affected by Slow Loris, but then you can encounter other difficulties.

Like he said, for large companies that are prepared, Slow Loris is not nearly as effective. But for smaller web sites or for shoddily put together ones (a LOT of government sites), Slow Loris is a nasty DOS attack.