DAL59

Serious Scientific Answers to Absurd Hypothetical questions

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4 hours ago, wumpus said:

Any country that consumes foreign illegal drugs will have plenty of professionals  fully capable of bypassing customs (I suspect even places with legal drugs will still have smugglers, just a lot less).  Of course, they are used to having a certain amount going missing, and customs expect to find a certain amount of missing drugs.  Finding smuggled plutonium should set off extreme alarms.

This is completely wrong idea of how it works, because those are completely different scenarios. Illegal drugs do no emit easily detectable amounts of radiation, and there are no customs officers looking for nuclides in body cavities. It's just sensitive detectors mounted at strategic places. Entry/exit gates at sea ports, airport gateways, highway toll passes… 

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43 minutes ago, Diche Bach said:

Sheeze, this thread got gruesome quickly.

Read some of the answers from the actual what if website...

https://what-if.xkcd.com/4/

If space was full of air, how far away could you hear a supernova?

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1 minute ago, sevenperforce said:

Yeah, I was thinking in terms of the old usage.

RDD is actually not that deadly, all things considered. Has more value as a weapon of mass chaos than actual mass destruction. Most more-available dangerous radionuclides are very short-lived. You need a reactor or a nuke to get the stuff that's both deadly and long-lived.

I agree, stuff exists but is hard to get. Add that downtown most are inside, simply kill the ventilation systems too limit exposure. then evacuate. Simple dust masks would also help a lot. 
Yes its generate a lot of fear and economic issues however terrorists prefer to simply kill lots of people. Terrorist operations also tend to become simpler, in part as it works well enough for their propaganda effort and the large attempt fails because of increased surveillance and reduced capabilities. An move away from bombs to guns and cars. 

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41 minutes ago, DAL59 said:

Read some of the answers from the actual what if website...

https://what-if.xkcd.com/4/

If space was full of air, how far away could you hear a supernova?

https://www.quora.com/If-you-could-hear-a-supernova-explosion-how-loud-would-it-be

A supernova at 1 AU would be about 314.4 decibels, based on energy output. The human hearing threshold is about 4 decibels.

314.4 decibels represents 1031.04 times more energy than 4 decibels. Because a sound wave loses power with the square of the distance, this means a supernova would need to be 5.57 AU away before it would drop to the human hearing threshold.

Edited by sevenperforce

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5.57?  Did you drop some zeros?  If it was 5.57 you'd be inside the supernova. :)

 

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2 hours ago, sevenperforce said:

However, upon review, it looks like "dirty bomb" is used interchangeably between RDDs and high-fallout thermonuclear devices.

The term you’re looking for is “salted bomb”.

2 hours ago, magnemoe said:

The arms dealer was an fool anyway, yes he might be told from the Russians that the plutonium would not work in an bomb, too unclean and wrong isotope, so he would just get an aircraft carrier after him not an nuclear strike, some stuff is just to dangerous to touch. 

And this is where red mercury showed up as a canard to lure out terrorists who choose to take up thermonuclear hobbies.

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1 hour ago, DAL59 said:

5.57?  Did you drop some zeros?  If it was 5.57 you'd be inside the supernova. :)

 

Well, just one more reason why you can't hear it ... :-)

Zeros do matter

36 minutes ago, DDE said:

The term you’re looking for is “salted bomb”.

I'd rather have mine with garlic, please ? :D

Edited by Green Baron

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2 hours ago, DAL59 said:

5.57?  Did you drop some zeros?  If it was 5.57 you'd be inside the supernova. :)

 

Well I fudged that up nicely. Took the square root of 31.04 rather than the square root of 1031.04.

The square root of 1031.04 is roughly 3x1015. And 3x1015 AU is 51% of the radius of the observable universe.

So the answer is: all of them. We would hear all the supernovas in the observable universe.

Pop.

Pop.

Pop.

BANG.

Pop.

Pop.

Whisper.

1 hour ago, DDE said:

The term you’re looking for is “salted bomb”.

A salted bomb is, as I understand it, a thermonuclear device in which the tamper is "salted" with isotopes specifically intended to maximize fallout, rather than yield. A dirty fusion bomb is a bomb where the tamper is made with isotopes intended to maximize yield.

A hydrogen bomb with a lead tamper is "clean", a hydrogen bomb with a uranium tamper is "dirty", and a hydrogen bomb with a cobalt-salted tamper is "salted".

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@sevenperforce: this may be a silly question and this is all a silly discussion but wouldn't we only hear those sn's that fled from us with subsonic speed ? Acoustic redshift sotosay ? Those closer would kill us anyway before we "hear" something.

:confused:

Edited by Green Baron

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2 hours ago, sevenperforce said:

So the answer is: all of them. We would hear all the supernovas in the observable universe.

Cool!  

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11 hours ago, sevenperforce said:

Well I fudged that up nicely. Took the square root of 31.04 rather than the square root of 1031.04.

The square root of 1031.04 is roughly 3x1015. And 3x1015 AU is 51% of the radius of the observable universe.

So the answer is: all of them. We would hear all the supernovas in the observable universe.

I don’t think it is quite that simple, assuming by space being made of air it is meant that it is air at Earths atmospheric pressure then the maximum volume possible is 194db after which the sound waves will distort.

Another issue is expansion, the audible universe will be a lot smaller than the observable universe as the speed of sound is so much slower than the speed of light it will be countered over a much shorter distance.

Of course star formation is what strips gas from space in the first place so somehow the star would have to drift into a dense gas cloud without dispersing it but I think that is beyond the scope of the question :wink:

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20 hours ago, radonek said:

This is completely wrong idea of how it works, because those are completely different scenarios. Illegal drugs do no emit easily detectable amounts of radiation, and there are no customs officers looking for nuclides in body cavities. It's just sensitive detectors mounted at strategic places. Entry/exit gates at sea ports, airport gateways, highway toll passes… 

They will need slightly different methods, but the point is that tons of cargo bypass customs everyday.  Shipping a nuke would typically involve forming the plutonium into lots of needles (possibly connected to magnets), inserting them into one hay bale each, burn the hay bales when delivered and then find the needles in the ashes.  Then take the needles and melt them into the forms needed and assemble your bomb.

Don't expect TSA yokels to be terribly concerned that the hay bales are emitting radiation somewhere between typical hay bales and a shipping container full of bananas.

20 hours ago, magnemoe said:

Breaking up the plutonium would be very stupid, first you have to be lucky in custom multiple times. If its found its an good chance it will continue but being replaced with an tracking device. This happens with drugs in containers, the detectors are sensitive and one major source of extra radioactivity is escaped dust. 
You would also need the bomb factory in the target country. Have fun with that. 

How many potential nuclear targets don't have a sufficiently advanced infrastructure where manufacturing all the (non radioactive) bits of an atomic bomb is particularly difficult?  Maybe Mecca, but that's about it.  Assembling the bomb in the target country is a feature.

And presumably you are willing to burn the agents who burn the hay bales.  But since they are melting down the plutonium, they don't have to worry about tracking/bug issues.  And passing that onto the less expendable agents is via dead drops (which is an old solution to this problem and presumably works).

Edited by wumpus

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7 hours ago, wumpus said:

They will need slightly different methods, but the point is that tons of cargo bypass customs everyday.  Shipping a nuke would typically involve forming the plutonium into lots of needles (possibly connected to magnets), inserting them into one hay bale each, burn the hay bales when delivered and then find the needles in the ashes.  Then take the needles and melt them into the forms needed and assemble your bomb.

Don't expect TSA yokels to be terribly concerned that the hay bales are emitting radiation somewhere between typical hay bales and a shipping container full of bananas.

How many potential nuclear targets don't have a sufficiently advanced infrastructure where manufacturing all the (non radioactive) bits of an atomic bomb is particularly difficult?  Maybe Mecca, but that's about it.  Assembling the bomb in the target country is a feature.

And presumably you are willing to burn the agents who burn the hay bales.  But since they are melting down the plutonium, they don't have to worry about tracking/bug issues.  And passing that onto the less expendable agents is via dead drops (which is an old solution to this problem and presumably works).

Your problem is not making an nuclear bomb, your problem is doing it without triggering something.
Who you want to employ? you have people loyal to your task but they might be flagged, you can not use criminals you just given them the ultimate get out of jail free card by exposing you. 
Its an reason why terrorist attacks at least in recent times tend to be idiotic simple, its because of increased complexity and number of people involved increases the risk of getting caught exponential.

9/11 worked as it exploited multiple holes in the system. 
Primarily how skyjacking was handled, it has been an couple skyjackings afterwards. Overall trying to pull of something as complex today will be extremely risky. 

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If you could orbit around a black hole with your eyes exactly at the event horizon (or better yet; one inside, the other outside), what would you see?

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17 minutes ago, Delay said:

If you could orbit around a black hole with your eyes exactly at the event horizon (or better yet; one inside, the other outside), what would you see?

The event horizon is an infinitesimal boundary, therefore it's physically impossible to be at the boundary, you can only be either inside or outside it.

The other scenario isn't much better, because you cannot transfer information across the boundary from inside -> outside.

Edited by Steel

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1 hour ago, Delay said:

If you could orbit around a black hole with your eyes exactly at the event horizon (or better yet; one inside, the other outside), what would you see?

Nothing in particular. The event horizon is just the point at which the escape velocity becomes greater than c, it's not a hard boundary and matter does not magically disappear when you cross it.

You'd still experience the relativistic and lensing effects of being near a black hole and orbiting it at a significant fraction of c, but it wouldn't be any different from being a bit closer or further from the black hole. In fact, due to general relativity causing time dilation you probably wouldn't be able to tell whether or not you are inside the horizon because you wouldn't be able to measure your speed or position relative to a "flat" space-time far away from the black hole.

 

Edit: actually you wouldn't be able to orbit the black hole at the horizon, because that would require you to travel at the speed of light, which is impossible if you aren't massless. "Standing" at the horizon would also be impossible since that would require an infinite force to avoid falling into the black hole. As soon as a part of you crosses the horizon, you can't escape it (not without leaving that part inside the horizon).

Edited by Gaarst

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44 minutes ago, Delay said:

If you could orbit around a black hole with your eyes exactly at the event horizon (or better yet; one inside, the other outside), what would you see?

Nothing; you'd be dead. The tidal forces approaching the event horizon would rip you apart like taffy.

 

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8 hours ago, wumpus said:

Don't expect TSA yokels to be terribly concerned that the hay bales are emitting radiation somewhere between typical hay bales and a shipping container full of bananas.

I think the dead giveaway would be someone shipping hay.

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37 minutes ago, GoSlash27 said:

Nothing; you'd be dead. The tidal forces approaching the event horizon would rip you apart like taffy.

 

It depends on the type of black hole. Stellar black holes have very strong tidal forces and you'd be ripped apart before entering the horizon, but super-massive black holes have small densities and tidal forces are very weak even at the horizon, so that you would enter the horizon before being ripped apart.

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Your right eye couldn't transmit the info to you brain.  

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Tidal forces are not a big problem for supermassive black holes.
But I still can't get a clear answer: what about the relativistic factor.

I have told my thoughts here 2-3 years ago, they said me that "this doesn't work this way" and "not a problem for rotating black holes, because metrics".
But I still have a very big doubt.

Say, whether the hole rotates or not, any body close to the event horizon is affected by the gravity-caused relativistic factor sqrt(1-Rg/R), where Rg is the gravitational radius, R is the body distance from the center.

If the body size is H, this means that the outer (relative to the black hole) end of the body lives in time compressed by sqrt(1-Rg/(R + H/2)), while the inner end of the body lives in time compressed by sqrt(1-Rg/(R - H/2)).
So this means that, say, while the head spends 1.1 seconds, the feet spend 0.9 second.

The closer the body gets to the Rg, the greater gets this relativistic factor difference.
This means that first the blood should stop circulating efficiently. Just because while 1 liter of blood runs through the legs, 10 liters should run throught the head (because head lives 10 times faster than legs due to the different time compression)
Then the chemical reactions should break apart.

At some distance the electrons on the opposite sides of the atoms would "live" in billion times different rate.

So, as I can understand, close to the event horizon any kind of interaction between the body particles should break into chaotic mess, and any object should scatter across the black hole as a chaotic spot of quark-gluon mess.

They say, it shouldn't. But I can't get why.

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On 11/9/2017 at 4:31 PM, radonek said:

But most damning is that you need smart people to handle stuff without blowing themselves up, pretty much opposite to idiots gravitating  to extremist groups.

By "idiots" you mean engineers? Because they're overrepresented in right-wing extremist groups. Perhaps luckily (unless you're trying to build a new nuclear power plant or something) nuclear engineers are rather uncommon amongst engineers to begin with, though.

 

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