Serious Scientific Answers to Absurd Hypothetical questions

[p1t1o]

18 minutes ago, Zeiss Ikon said:

<snipt>

Thanks! Learned a lot just then

 

10 minutes ago, kerbiloid said:

And if we take two non-charged metal slabs and put them enough close to each other, we'll get Casimir Effect.

And if we stack them just right we can build a shed!

Edited March 2, 2018 by p1t1o

[MinimalMinmus]

What if you linked the surface of the Earth and the surface of the Moon with an indestructible (and impossible to tear out) rope? I'm assuming the "linking" is made while the Moon is as close as possible from Earth, aligned to its equator, and that the rope is as short as possible.

[p1t1o]

1 hour ago, MinimalMinmus said:

What if you linked the surface of the Earth and the surface of the Moon with an indestructible (and impossible to tear out) rope? I'm assuming the "linking" is made while the Moon is as close as possible from Earth, aligned to its equator, and that the rope is as short as possible.

I think that this is a deceptively simple question. You are not only asking how a very long flexible strand (describing how long flexible strands act under various forces can actually get very complicated due to the sheer number of degrees of freedom - think of a chain with infinitely small links) will act whilst within the influence of two dissimilar gravity wells, but also how the attachment of both ends effects the dynamics.

And thats ignoring the complexity of having the Earth rotate very much faster than the Moon orbits and that you cant attach the rope to the geometric centre of either body.

 

Very simple, very quick top-of-my-head impression?

Well its hard to imagine that the rope would not be under tension, so there will be some extra attractive force between the bodies, meaning that the two bodies will adopt some other equilibrium than that which they are in now.

I assume that the Moon's orbital altitude would be reduced, taking up some of the tension with centri-fugal/petal force.

And that the rope will eventually adopt some stable/standing conformation other than a straight line, probably a smooth curve, possibly some kind of standing wave. Shortening the rope to decrease curvature will increase tension, which in turn will pull the Moon closer, producing more "slack". An equilibrium will be sought.

On the other hand, I cannot say for certain that it would be stable - that the equilibrium would ever reach a "steady state".

And even all of that assumes zero-point-zero friction at all points and some perfect way of having the Earthside attachment point run smoothly along the Earths surface (at no point will the circular "track" be perfectly circular due to the Earth's axis, equator and Moon orbit not being perfectly lined up.)

 

Its probably worth noting that the magnitude of the forces here (which will be on a similar order to that of the mass of the rope) will be very small compared to the masses of the two bodies, so the effects will be hard to see with the naked eye, so its not like the tides will start washing away continents, but there could be detectable effects.

Edited March 2, 2018 by p1t1o

[peadar1987]

Hmm... Interesting one...

The moon is tidally locked to the earth, so far so good.

However, the earth rotates a lot faster than the moon orbits.  The rope is going to want to speed up the moon. The energy required to do this has to come from the earth's rotation. The earth's rotational kinetic energy is 2.14*10²⁹J.

For the moon to complete 1 orbit every 24 hours, it would have to gain 2.66*1031J.  This is near enough to 100 times the rotational kinetic energy of the earth. So the moon's orbital velocity would increase by ~1%, and the earth's rotational period would increase to about a month. Depending on how stretchy your rope was, this would happen more or less instantaneously. So basically this would happen: https://image.gsfc.nasa.gov/poetry/ask/q1168.html

[MinimalMinmus]

On 02/03/2018 at 11:00 PM, peadar1987 said:

Hmm... Interesting one...

The moon is tidally locked to the earth, so far so good.

However, the earth rotates a lot faster than the moon orbits.  The rope is going to want to speed up the moon. The energy required to do this has to come from the earth's rotation. The earth's rotational kinetic energy is 2.14*10²⁹J.

For the moon to complete 1 orbit every 24 hours, it would have to gain 2.66*1031J.  This is near enough to 100 times the rotational kinetic energy of the earth. So the moon's orbital velocity would increase by ~1%, and the earth's rotational period would increase to about a month. Depending on how stretchy your rope was, this would happen more or less instantaneously. So basically this would happen: https://image.gsfc.nasa.gov/poetry/ask/q1168.html

Long before we'd see what happens in the link, let's keep something in mind: we just released a bit less than 0.1% of Earth's potential energy. That's ONE MILLION TIMES WORSE than the Chixculub impact!!!! Said otherwise, that's the explosion of tens of EXATONS of TNT, or the explosion of a trillion tsar bombas. Said otherwise again, the Earth is struck by an earthquake of magnitude 16,5. Said otherwise yet again, it's almost as bad as taking Pluto to the face.

It's safe to say that no one, not even the astronauts that would have been pulverized by the copious amount of matter sent to space, would be alive to see this.

Which makes me think: Okay, so the Earth is not torn asunder, even though it got quite a beating. But the Moon? At 1.2*10^29 J, its cohesive energy is comparable to the energy we just released. Because it's some ACME™-brand adamantium-reforced unobtainium rope, it wouldn't be torn out of the Moon. But what if the rope has nothing to be torn out anymore?

 

[DerekL1963]

1 hour ago, MinimalMinmus said:

Which makes me think: Okay, so the Earth is not torn asunder, even though it got quite a beating. But the Moon? At 1.2*10^29 J, its cohesive energy is comparable to the energy we just released. Because it's some ACME™-brand adamantium-reforced unobtainium rope, it wouldn't be torn out of the Moon. But what if the rope has nothing to be torn out anymore?

Reminds me of one of my favorite quotes from https://what-if.xkcd.com/ involving a human body being exposed to some massive amount electromagnetic energy.....  Something like "At this level of exposure, you'll die.  Not from anything in particular, you'll simply cease to exist as a collection of stable molecules".

[MinimalMinmus]

2 minutes ago, DerekL1963 said:

Reminds me of one of my favorite quotes from https://what-if.xkcd.com/ involving a human body being exposed to some massive amount electromagnetic energy.....  Something like "At this level of exposure, you'll die.  Not from anything in particular, you'll simply cease to exist as a collection of stable molecules".

Hehe, yeah.

Also in what if: "You stop being chemistry and you become physics"

[DerekL1963]

1 minute ago, MinimalMinmus said:

Also in what if: "You stop being chemistry and you become physics"

I was just logging in to say that I'd found the correct quote to find you seem to have known it by heart.     

https://what-if.xkcd.com/141/

[MinimalMinmus]

4 minutes ago, DerekL1963 said:

I was just logging in to say that I'd found the correct quote to find you seem to have known it by heart.     

https://what-if.xkcd.com/141/

" You wouldn't really die of anything, in the traditional sense. You would just stop being biology and start being physics."

Meh, close enough.

Also, something about a sunbeam that causes everyone to become physics should be highly ironical to a subnautica player

Spoiler

because trading ship sunbeam quite indeed becomes physics after being hit by ... well, a beam.

 

[Solarspot]

(I'm not sure if this is the right thread for this thought of mine.  Maybe it's hairbrained enough.)

Let's say we were building an electromagnetic catapult to lob payloads to Earth-orbit speeds.  Use a solid structure 100 km off the ground, and I've been guessing 100km length to accelerate on.  I've read that coil guns can't keep accelerating payloads above 2km/s, due to switching time on the coils taking too long compared to the payload's displacement during the switching time. (I've also read somebody say this is false.  I dunno.)  So, two alternatives, that are not-quite the same thing;

Since the speed of electric current in wire is not infinite, could one long coil of wires give current enough travel-distance that the electromagnetic field would only advance linearly-forward at some small pace?  Say, that same 2km/s that coilguns might or might not be capable of?  I remember calculating that a single-cable-thick coil of coaxial cable would advance linearly at... 70km/s or so.  I've thought that if the speed of the field can change merely via turns around a cylinder per linear-distance, then changing that could allow for a gradually accelerating singular field.  Could a payload ride the front of that to accelerate?

The second, and maybe more hairbrained version, would be to build up a static charge behind the (charged) payload, similarly have the charge advance at a small pace behind it, slowly accelerating as it accelerates the payload.  Would this one blow up?

[p1t1o]

 

1 hour ago, Solarspot said:

(I'm not sure if this is the right thread for this thought of mine.  Maybe it's hairbrained enough.)

Let's say we were building an electromagnetic catapult to lob payloads to Earth-orbit speeds.  Use a solid structure 100 km off the ground, and I've been guessing 100km length to accelerate on.  I've read that coil guns can't keep accelerating payloads above 2km/s, due to switching time on the coils taking too long compared to the payload's displacement during the switching time. (I've also read somebody say this is false.  I dunno.)  So, two alternatives, that are not-quite the same thing;

Since the speed of electric current in wire is not infinite, could one long coil of wires give current enough travel-distance that the electromagnetic field would only advance linearly-forward at some small pace?  Say, that same 2km/s that coilguns might or might not be capable of?  I remember calculating that a single-cable-thick coil of coaxial cable would advance linearly at... 70km/s or so.  I've thought that if the speed of the field can change merely via turns around a cylinder per linear-distance, then changing that could allow for a gradually accelerating singular field.  Could a payload ride the front of that to accelerate?

The second, and maybe more hairbrained version, would be to build up a static charge behind the (charged) payload, similarly have the charge advance at a small pace behind it, slowly accelerating as it accelerates the payload.  Would this one blow up?

 

2km/s sounds pretty slow for a limit on electronics, I've never heard of one like it for coilguns. I mean, there will be a limit to switching speed on particular types of hardware, but there are all sorts of things you can do to achieve faster speeds.

For one thing, after a minute or two of googling I found an example from 4 decades ago (1978) which used only a single coil, but accelerated a 2g projectile to 5km/s (within a space of 1cm!!)

https://journals.scholarsportal.info/details?uri=/00189464/v20i0002/239_mspia.xml

So yah, that 2km/s limit is 100% BS.

 

 

FunFact^TM: Super-fast switching hardware is often controlled under so-called "dual-use" regulations, as it is a key enabling technology that allows efficient nuclear weapon designs.

http://nuclearweaponarchive.org/Library/Pasley1.html

 

 

For your static charge idea, you neatly left out the part that explains how you accelerate the static charge that is propelling the projectile!

Anyway, it sounds pretty similar to a coilgun but swapping magnetic fields for electric ones. Seems workable in principle but I wonder if static fields can be manipulated with the same speed and power as magnetic ones?

 

Edited March 21, 2018 by p1t1o

[Diche Bach]

I have read a bit about the "island of stability" concept in chemistry/physics. But given my understanding of those physical sciences is probably below that of a Freshman, I'm still a bit unclear on what the possible significance of such isotopes might be?

Quote

Although predictions of the exact location differ somewhat, Klaus Blaum expects the island of stability to occur in the atomic mass region near the nuclide ³⁰⁰
₁₂₀Ubn
.^[1]

So "unbinillium"

Quote

 

Unbinilium, also known as eka-radium or simply element 120, is the hypothetical chemical element in the periodic table with symbol Ubn and atomic number 120. Unbinilium and Ubn are the temporary systematic IUPAC name and symbol, until a permanent name is decided upon. In the periodic table of the elements, it is expected to be an s-block element, an alkaline earth metal, and the second element in the eighth period. It has attracted attention because of some predictions that it may be in the island of stability, although newer calculations expect the island to actually occur at a slightly lower atomic number, closer to copernicium and flerovium.

Unbinilium has not yet been synthesized, despite multiple attempts from German and Russian teams. One 2011 attempt from the German team at the GSI Helmholtz Centre for Heavy Ion Research had a suggestive but not conclusive result suggesting the possible production of ²⁹⁹Ubn, but the data was incomplete and did not match theoretical expectations. Planned attempts from Russian, Japanese, and French teams are scheduled for 2017–2020. Experimental evidence from these attempts show that the period 8 elements will likely be far more difficult to synthesise than the previous known elements, and that unbinilium may even be the last element that can be synthesized with current technology. Its position as the seventh alkaline earth metal suggests that it would have similar properties to its lighter congeners, beryllium, magnesium, calcium, strontium, barium, and radium; however, relativistic effects may cause some of its properties to differ from those expected from a straight application of periodic trends. For example, unbinilium is expected to be less reactive than barium and radium and be closer in behavior to strontium, and while it should show the characteristic +2 oxidation state of the alkaline earth metals, it is also predicted to show the +4 oxidation state unknown in any other alkaline earth metal.

 

As a layman . . . well . . . a social/behavioral/biological scientist with minimal capacity in physical sciences . . . that is all very interesting, but I'm left to wonder: "So what?"

What are the possible implications of these "hypothetical" elements and why is it worthwhile to try to synthesize them?

Is it possible than in 150 years or something, we will be able to fashion some kind of "unobtainium" material that will revolutionize one or more technologies as a result of these experiments?

 

 

 

[sevenperforce]

On 3/21/2018 at 4:01 AM, Solarspot said:

Since the speed of electric current in wire is not infinite, could one long coil of wires give current enough travel-distance that the electromagnetic field would only advance linearly-forward at some small pace?  Say, that same 2km/s that coilguns might or might not be capable of?  I remember calculating that a single-cable-thick coil of coaxial cable would advance linearly at... 70km/s or so.  I've thought that if the speed of the field can change merely via turns around a cylinder per linear-distance, then changing that could allow for a gradually accelerating singular field.  Could a payload ride the front of that to accelerate?

Uh, the speed of electric current is 0.95c. So a little bit more than 70 km/s. More like 295,000 km/s.

4 hours ago, Diche Bach said:

I have read a bit about the "island of stability" concept in chemistry/physics. But given my understanding of those physical sciences is probably below that of a Freshman, I'm still a bit unclear on what the possible significance of such isotopes might be?

As a layman . . . well . . . a social/behavioral/biological scientist with minimal capacity in physical sciences . . . that is all very interesting, but I'm left to wonder: "So what?"

What are the possible implications of these "hypothetical" elements and why is it worthwhile to try to synthesize them?

Is it possible than in 150 years or something, we will be able to fashion some kind of "unobtainium" material that will revolutionize one or more technologies as a result of these experiments?

Yes.

If nothing else, the synthesis of superheavy stable elements would allow for advanced experimentation and testing. If you have big heavy stable atoms to play with, you can test all kinds of predictions of string theory and similar cutting-edge physics. What happens when you smash Element 120 into Element 122? String theory A predicts that you get particle X; string theory B predicts that you get particle Z; string theory C predicts that unicorns pop out and dance to Schoolhouse Rock. Let's see which one is right!

If we found a way to make them in quantity, superheavy elements could also be used in all kinds of novel tech as well.

[sh1pman]

34 minutes ago, sevenperforce said:

If we found a way to make them in quantity, superheavy elements could also be used in all kinds of novel tech as well.

I can see the military being interested in stable super heavy elements. Tank armor, anti-armor shells with immense kinetic energy, AP rounds, that sort of things. Maybe radiation protection as well?

[sevenperforce]

49 minutes ago, sh1pman said:

I can see the military being interested in stable super heavy elements. Tank armor, anti-armor shells with immense kinetic energy, AP rounds, that sort of things. Maybe radiation protection as well?

Kinetic penetrators and radiation shields, yeah.

[Diche Bach]

Interesting; thanks guys.

What about nuclear power generation, or fabrication of uber superconductors, which might then have implications for a wide range of tech: super powerful magnets, mass spectrometry, digital signal processors, magnetometers, etc., etc., etc.??

Quote

Promising future applications include high-performance smart grid, electric power transmission, transformers, power storage devices, electric motors (e.g. for vehicle propulsion, as in vactrains or maglev trains), magnetic levitation devices, fault current limiters, enhancing spintronic devices with superconducting materials,^[51] and superconducting magnetic refrigeration.

I get the impression that: it is difficult to speculate exactly what such hypothetical elements might or might not be useful for, but they MIGHT be useful for such a broad range of things that they could conceivable revolutionize civilization?

 

[p1t1o]

14 hours ago, sh1pman said:

I can see the military being interested in stable super heavy elements. Tank armor, anti-armor shells with immense kinetic energy, AP rounds, that sort of things. Maybe radiation protection as well?

Super-heavy elements are not always super-dense - eg: Osmium is the densest element, but not the heaviest atom.

Density is what makes good penetrators or armour.

For interest, the reason Osmium is not used in military applications is likely due to cost.

 

Edited May 22, 2018 by p1t1o

[kerbiloid]

7 minutes ago, p1t1o said:

the reason Osmium is not used in military applications is likely due to cost.

An osmium penetrator is even more stylish than a golden pistol.

[p1t1o]

1 hour ago, kerbiloid said:

An osmium penetrator is even more stylish than a golden pistol.

FunFact^TM: Some nuclear warheads have solid gold outer radiation casings which can be several centimetres thick (I think it maximises X-ray emissions for exo-atmospheric use...or something)

[kerbiloid]

10 minutes ago, p1t1o said:

FunFact^TM: Some nuclear warheads have solid gold outer radiation casings which can be several centimetres thick (I think it maximises X-ray emissions for exo-atmospheric use...or something)

Then it's better to keep as close as possible to GZ to pick up it first.

[DAL59]

Most anti-tank missiles are at least two feet long.  Is it possible with current tech to make a tiny missile like in Iron Man?

[mikegarrison]

2 hours ago, DAL59 said:

Most anti-tank missiles are at least two feet long.  Is it possible with current tech to make a tiny missile like in Iron Man?

No.

[Zeiss Ikon]

4 hours ago, DAL59 said:

Most anti-tank missiles are at least two feet long.  Is it possible with current tech to make a tiny missile like in Iron Man?

I agree -- no.  However, it's also not possible, with current tech, to make an arc reactor (of any size), or a powered suit even as capable as the Mk. 1 (the one he built in the cave).  And let's not forget the reactionless "repulsor" devices in hands and feet that let the suit fly, and the full-Turing AI (J.A.R.V.I.S. in the early suits, and F.R.I.D.A.Y. in the ones since Ultron).

Let's hypothesize that Tony Stark has access to a source of an appropriate Californium alloy -- those could be bullet-size nuclear warheads with a yield similar to a 500 lb bomb.  The suit uses multi-target laser designators and the tiny missiles fly toward their assigned code laser spot, explode on impact (presumably after passing a suitable "safe" time since launch, like making an artillery shell "bore safe").  Rumor has it that the Soviet Union actually fabricated some rounds of this type -- nuclear weapons delivered with a conventional rifle.  Nothing physically impossible, but the combination of technologies (propulsion, guidance, target designation, warhead fabrication, etc.) doesn't yet exist.  Ask again in twenty years...

[kerbiloid]

10 hours ago, DAL59 said:

Is it possible with current tech to make a tiny missile like in Iron Man?

If it were, then it would.

6 hours ago, Zeiss Ikon said:

Ask again in twenty years...

And they will look at the questioner like at a barbarian, because ecological hype will be growing exponentially.

(Just because to make somebody buy something useless, scare him with ecological safety.)

[sevenperforce]

20 hours ago, DAL59 said:

Most anti-tank missiles are at least two feet long.  Is it possible with current tech to make a tiny missile like in Iron Man?

So, I was under the impression that most antitank missiles are just penetrators; they punch through the armor and fill the inside of the tank with molten metal. There will be a chunk missing from the side of the tank and the insides will be shredded, but it's more or less intact.

Then I watched this:

Holy crap.

That missile doesn't even impact; it's designed to do that much damage simply by exploding directly over the target. It produced a shockwave so severe that it ripped the turret off the tank and sent it bouncing onto the ground in a ball of flames.

It's not entirely out of the question to imagine a miniaturized version, equipped with a depleted uranium or even osmium tip at the front to improve penetration. Even an explosion 1/10th as strong would absolutely obliterate a tank if it exploded partly inside.

(For reference, I was previously thinking of a HEAT missile, which would look more like this:)

A shaped charge missile could probably be made smaller than a TOW.