For Questions That Don't Merit Their Own Thread

[Mad Rocket Scientist]

3 hours ago, Diche Bach said:

Uhh . . . given that nothing escapes a black hole, how could one consider it to be an "energy source?"

ADDIT: and going back to the question to which you responded "What is the most efficient way to use the sun?"

What about photosynthesis? Is anything actually "more efficient" than that?

Kurzgesagt made a video on one way to get energy from black holes:

 

[K^2]

4 hours ago, Diche Bach said:

Uhh . . . given that nothing escapes a black hole, how could one consider it to be an "energy source?"

Rotating black hole can be used to generate energy via frame dragging in the ergosphere. There are several variations on how exactly one would do it, but amount of energy you can extract from a black hole is truly astronomical in every sense.

[ARS]

I wanna ask something regarding black holes. Is it possible to achieve a stable orbit around it? Like a whole system orbiting a black hole? Kinda like solar system (minus the solar)

also unrelated, but how nuclear reactor are started in the first place?

[kerbiloid]

1 hour ago, ARS said:

I wanna ask something regarding black holes. Is it possible to achieve a stable orbit around it? Like a whole system orbiting a black hole? Kinda like solar system (minus the solar)

also unrelated, but how nuclear reactor are started in the first place?

Beyond its ergosphere.

[Mad Rocket Scientist]

1 hour ago, ARS said:

I wanna ask something regarding black holes. Is it possible to achieve a stable orbit around it? Like a whole system orbiting a black hole? Kinda like solar system (minus the solar) [...]

I can't think of any reason why not. There will just be weird relativistic effects from both the mass and the high orbital speed needed at low altitudes. Plus, the entire milky way orbits around a black hole.

 

[K^2]

3 hours ago, Mad Rocket Scientist said:

I can't think of any reason why not. There will just be weird relativistic effects from both the mass and the high orbital speed needed at low altitudes. Plus, the entire milky way orbits around a black hole.

Low orbits around black holes are unstable. If you start orbiting from within 3 r_s you'll fall in eventually if you don't make corrections. If you end up bellow 1.5 r_s escape is practically impossible. Above the 3 r_s there are stable orbits, though. So if we're picturing a Solar System with sol-mass black hole instead of the Sun, everything would work exactly as it does now.

5 hours ago, ARS said:

also unrelated, but how nuclear reactor are started in the first place?

Nuclear reactors exploit the chain reaction. When nucleus of suitable nuclear fuel decays, it produces neutrons. Or, at least, some products that eventually release neutrons. These neutrons have a chance of being absorbed by other nuclei, triggering them to decay as well. A neutron can, however, be absorbed by something that will remain mostly neutral, or escape the reactor core. So if the net probability of triggering another reaction is less than one, reaction dies out. If it's greater than one, it snowballs out of control. The point where the ratio is exactly 1 is the critical point. Nuclear reactor operates at that point of criticality.

There are several ways to control this. You can move rods of nuclear fuel closer together. That increases number of neutrons absorbed by fuel. You can put certain moderation materials in the way. They slow down neutrons, increasing the chance that they get absorbed by nuclei in fuel rather than just bounce off, or trigger a completely different decay mode. You can also put in materials that absorb neutrons and reduce number of them available for the fuel.

In its cold state, reactor is kept subcritical. To start the reactor, all you have to do is bring it to criticality. You do this either by moving fuel rods and/or control rods to change conditions in one or more of the ways described above. If you aren't designing a nuclear weapon, where things have to happen in an instant, it doesn't even matter where the initial neutrons come in. There's always going to be some radioactive decay producing neutrons that will trigger the chain reaction. So as long as you keep the reactor critical, it will basically start itself. Then you just want to make sure not to take it supercritical, and also to take away the heat produced by the reactor so that it doesn't melt.

You might find this video interesting.

 

[magnemoe]

12 hours ago, ARS said:

I wanna ask something regarding black holes. Is it possible to achieve a stable orbit around it? Like a whole system orbiting a black hole? Kinda like solar system (minus the solar)

also unrelated, but how nuclear reactor are started in the first place?

Far away it would be like any other gravity source, you are in part orbiting an black hole now
Stuff only got weird if you get real close and it would become very radioactive long before, 

[Nightside]

What's the deal with the crazy twisty roads NE of the shuttle landing strip at the KSC?

https://www.google.com/maps/d/viewer?hl=en&t=h&msa=0&z=14&ie=UTF8&mid=1VAskaWnNfx1r5UrYzvlRwq3vsfY&ll=28.610074555227815%2C-80.64845824555664

[GDJ]

1 hour ago, Nightside said:

What's the deal with the crazy twisty roads NE of the shuttle landing strip at the KSC?

https://www.google.com/maps/d/viewer?hl=en&t=h&msa=0&z=14&ie=UTF8&mid=1VAskaWnNfx1r5UrYzvlRwq3vsfY&ll=28.610074555227815%2C-80.64845824555664

Rover test track?

[cubinator]

Have cephalopods always been so intelligent? Squid and octopus-like creatures have been around for a long time, but have not built megastructures or colonized land or space. Is their relatively high intelligence a recent development, or have they simply never felt like taking over the world? Perhaps there was never an evolutionary necessity to advance beyond the point they are at now, and they don't have a reason to become intelligent enough to have such ideas.

[ARS]

3 hours ago, cubinator said:

have not built megastructures or colonized land or space

Because they never lived as a colony in the first place

[Xd the great]

8 hours ago, cubinator said:

Have cephalopods always been so intelligent? Squid and octopus-like creatures have been around for a long time, but have not built megastructures or colonized land or space. Is their relatively high intelligence a recent development, or have they simply never felt like taking over the world? Perhaps there was never an evolutionary necessity to advance beyond the point they are at now, and they don't have a reason to become intelligent enough to have such ideas.

They die too soon. TOO SOON.

[kerbiloid]

3 hours ago, Xd the great said:

They die too soon. TOO SOON.

Because they know too much. TOO much...

[magnemoe]

7 hours ago, ARS said:

Because they never lived as a colony in the first place

This, its not enough to be smart, you also need to form groups and cooperate, this is not only an requirement for an civilization but probably for high intelligence to.  
Note that while pretty smart they are far from smart enough, if you are in an group who cooperate and communicate we humans got an snowball effekt here. 
Other humans was the most complex thing early humans interacted with and higher intelligence helped here so it was an selection for higher intelligence. 

Now an underwater species will have other handicaps, metals is an obvious one but not really required for an civilization like ancient Egypt. but also other materials even wood, writing would be harder and food storage harder. 
Farming to, not many useful plants, all large animals outside of filter feeders are predators, you could farm shells and perhaps have crabs eating scraps like we hold pigs. 
You could manage an coral reef and drive of other predators but has problems seeing more than advanced hunter gatherers with some farming on the side. 
 

[kerbiloid]

27 minutes ago, magnemoe said:

Note that while pretty smart they are far from smart enough, if you are in an group who cooperate and communicate we humans got an snowball effekt here. 

Cats (big and small) hate each other, and don't cooperate a lot.
But they are as clever as dogs, do all canine tricks, though more selfish and do nothing just on demand, only if they wish themselves.

Cows, horses, sheep, deer are highly cooperative, but can hardly be compared with them.

[magnemoe]

11 minutes ago, kerbiloid said:

Cats (big and small) hate each other, and don't cooperate a lot.
But they are as clever as dogs, do all canine tricks, though more selfish and do nothing just on demand, only if they wish themselves.

Cows, horses, sheep, deer are highly cooperative, but can hardly be compared with them.

Its an huge step from cats and dogs up to primates and then another step to humans. 
Huge brains are expensive, you don't select for them unless they are an benefit. 
Herd animals don't really cooperate much, more about safety in numbers. 
Note that wolf packs or even chimpanzee groups don't require lots of intelligence as in its not much pressure for it. 
Among humanoids it was and it was not because their environment was so challenging, not was technology and planning advanced enough to require human levelintelligence. 

[K^2]

11 hours ago, magnemoe said:

Now an underwater species will have other handicaps, metals is an obvious one but not really required for an civilization like ancient Egypt.

Ancient Egypt was a Bronze Age civ, relying on writing and counting systems to maintain trade routes with their neighbors, on whom they relied for imports of tin that they needed to make bronze. And without bronze, they could not sustain agriculture on the scale that was necessary to maintain that level of civilization, hence the utter devastation of the Bronze Age collapse.

I think I can tell where you were going with this, but Ancient Egypt is an example of civilization that thrived due to its use of metal, and collapsed, partially, due to its shortage. There were plenty of nomadic groups, both before and after the Bronze Age, that managed to get by without metals. So it's not a requirement for a civilization, of course. Just not Ancient Egypt type civ.

[kerbiloid]

15 hours ago, magnemoe said:

Huge brains are expensive, you don't select for them unless they are an benefit. 

Huge muscles and poison glands are expensive, too.
Just brain is a device of indirect action. You need another effector to use it, rather than those direct muscles and fangs which are good enough themselves.

But I meant that communication and cooperation are probably overestimated in the intellect evolution.

Say, dogs. As clever as a cat when alone, but turning into a crowd of idiots when >2.
Like the intellect of a dog pack is limited from above with its most stupid member divided by the pack size.

While cats do everything what dogs do, but they do this alone, analizing, tracing, attacking on their own.
A pack of cats is a pack of individual cats keeping their own intellectual abilities.

Say, octopuses. They are the most clever between the boneless things, but they live alone and not gather into packs.

So, probably comm&coop play role only when your intellect is already high enough itself.
For stupid creatures comm&coop replaces the intellect, for clever ones it provides abilities of the information sharing
So, probably there is some threshold of intellect level. Below it the comm&coop curbs the intellect growth. Above it, it accelerates it. Probably. apes are this threshold.

15 hours ago, magnemoe said:

Its an huge step from cats and dogs up to primates and then another step to humans. 

I had an occasion to compare cats and growing children at once.

My impression is that a an adult cat is more clever than a 2-years old baby 
Its actions are more complex, focused, and competent. It looks at the baby like at a strange, dangerous, and big but a silly thing.
The cat doesn't ask it for something.

When the baby gets 4 years old, it's definitely more clever than this cat.
The baby's actions became more complex, focused, and competent, while the cat looks at it like at a incomprehensible monster.
And the cat is asking it for something.

So, probably cats and dogs are somewhere at 3-years old human level.

Edited July 31, 2018 by kerbiloid

[p1t1o]

On 7/29/2018 at 11:16 PM, Nightside said:

What's the deal with the crazy twisty roads NE of the shuttle landing strip at the KSC?

https://www.google.com/maps/d/viewer?hl=en&t=h&msa=0&z=14&ie=UTF8&mid=1VAskaWnNfx1r5UrYzvlRwq3vsfY&ll=28.610074555227815%2C-80.64845824555664

Sick dirtbike tracks with wicked jumps?

[Green Baron]

10 hours ago, K^2 said:

Ancient Egypt was a Bronze Age civ, ...

Sorry to correct, but @magnemoe is right, most of Egyptian history is neolithic. No metal, no wheels, even the potter's wheel came late. Actually, with the onset of the metal ages, the Egyptian civ started to decay and others entered the scene, like Hetites, Assyrians, Babylonians, and Greeks and Romans. At the time the Romans entered (iron age) there were merely city states left.

In a ridiculously small nutshell :-) But people are still working on correlating Egyptian chronology with absolute dates.

Edited July 31, 2018 by Green Baron

[Gargamel]

On 7/29/2018 at 6:16 PM, Nightside said:

What's the deal with the crazy twisty roads NE of the shuttle landing strip at the KSC?

https://www.google.com/maps/d/viewer?hl=en&t=h&msa=0&z=14&ie=UTF8&mid=1VAskaWnNfx1r5UrYzvlRwq3vsfY&ll=28.610074555227815%2C-80.64845824555664

Massive quantities of DDT were applied here for what was reported as mosquito control (probably dumped too) between 1946 and 1951, other insecticides were applied thereafter. A study/proposal was conducted in 2000 and these "roads" were constructed throughout the flatlands, wetlands, and marshes for drill rigs to move about to set shallow, intermediate, and deep groundwater monitoring wells.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20000116077.pdf

[magnemoe]

3 minutes ago, Green Baron said:

Sorry to correct, but @magnemoe is right, most of Egyptian history is neolithic. No metal, no wheels, even the potter's wheel came late. Actually, with the onset of the metal ages, the Egyptian civ started to decay and others entered the scene, like Hetites, Assyrians, Babylonians, and Greeks and Romans. At the time the Romans entered (iron age) there were merely city states left.

In a ridiculously small nutshell :-) But people are still working on relating Egyptian chronology with absolute dates.

Both are right in an way, stone tools was more common than bronze during the bronze age as bronze was expensive so bronze was not very important for everyday life. 
On the other hand you needed an civilization to utilize bronze well as its so rare you will need to import at least the tin, and bronze weapons was better. 
On the gripping hand Egypt location and need for irrigation was probably more important for creating an civilization. It lasted trough the bronze age but dynamic changed in the iron age. 
 

[K^2]

20 minutes ago, Green Baron said:

Sorry to correct, but @magnemoe is right, most of Egyptian history is neolithic.

Don't ever be sorry to correct.  But what you're saying isn't contradictory. General terminology distinguishes between Ancient Egypt and Prehistoric Egypt. Former starts a little before 3,000BC and roughly coincides with the beginning of the Bronze Age in Near East. The Prehistoric Egypt goes at least 3,000 years further back and is primarily neolithic as you've indicated. While majority of pre-Classical history of Egypt is, indeed, neolithic, that time period is not classified as Ancient Egypt. If we are talking specifically about Ancient Egypt, and not just "Egypt in the olden times," we are talking about a civilization characterized by its use of bronze tools, among other things.

P.S. Yes, I'm not talking about bronze being necessarily common in all aspects of life. Nonetheless, Ancient Egypt has grown dependent on use of bronze tools in agriculture, not just warfare, which was a contributing factor in the collapse.

Edited July 31, 2018 by K^2

[kerbiloid]

(Tries to imagine the Pyramids building with stone tools.)

[Xd the great]

(Tries to imagine the kerbals building Pyramids with stone tools.)

27 minutes ago, kerbiloid said:

(Tries to imagine the Pyramids building with stone tools.)

Anyway, there is still dispute over how pyramids are built.