r/theydidthemath • u/Dear-Shelter-233 • 1d ago
[Request] Is it actually possible to pull a B-2 to the ground with a big magnet?
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u/nickeypants 1d ago
Yes. A magnetar is only 20km in diameter and produces a surface magnetic field at 100 billion Tesla. For reference, an MRI produces 3 Tesla and the strongest man-made magnet is 1,200 Tesla and is designed to operate for only an infinitesimal fraction of a second before it rips itself apart and explodes.
Neglecting all (considerable) gravitational effects and only considering magnetic effects, standing within a few thousand km of a magnetar's magnetic field would overcome the binding energy of your atom's electrons, cause you to undergo instant atomic dissolusion. It is theorised that the field is so strong it can crystalize the quantum vacuum of empty space. It would certainly be able to pull the plasma cloud of subatomic particles that used to be your B-2 to the ground at relativistic speed.
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u/DuckDodgersIV 1d ago
I’m still trying to figure out what exactly crystalizing the quantum vacuum of empty space means
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u/nickeypants 1d ago
Empty space isn't really empty, it's full of virtual particles that pop in and out of existence in a disordered unaligned mess. Under colossal magnetic environments, these fleeting ripples become aligned and polarize light in ways similar to when light passes through a solid crystal. But there's no solid, it's just passing through very magnitised nothing. So extreme magnitism can cause void to have similar optical properties to a solid.
It's an environment so far removed from the human experience that it just sounds made up. There are forces so extreme that they expose layers of reality we aren't properly equipped to comprehend or intuit. And it's not made up, it's floating around out there and we can see them... just sitting there... menacingly...
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u/Hotchumpkilla 21h ago
Thank you Professor Farnsworth
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u/nascent_aviator 17h ago edited 17h ago
It's sciency-sounding nonsense. (At a guess they're talking about vacuum birefringence, in very very pop sciencey terms). As is the "rip apart atoms" bit. Placing atoms into even an enormous magnetic field doesn't rip electrons off, it just distorts the shape.
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u/CuppaJoe11 1d ago
Ok... so why don't we find something somewhere between "MRI machine" and "Magnetar"
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u/nickeypants 1d ago
OP said possible, not feasible, and their diagram specifically said 'super big magnet'. More big, more fun.
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u/Yoinkitron5000 17h ago
A careful reading of official Major League Baseball Rule 6.08(b) suggests that in this situation, the batter would be considered "hit by pitch"
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u/Ok-Pomegranate858 1d ago
Hmmm, is there any other option that well doesn't mean the end of the planet? If it not too much to ask
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u/nascent_aviator 17h ago
This is nonsense. Magnetic fields don't rip apart atoms, regardless of their strength. Atoms and molecules exist on the surface of a magnetar just fine, albeit significantly distorted from their ordinary shape.
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u/Anomander2000 14h ago
Do you work for XKCD?
This sounds suspiciously like one of their answers: "Yes, and the result is EVERYONE DIES!"
(and I love xkcd! ❤️)
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u/GoldReplacement9546 1d ago
Considering it's flying at well above 50000 feet, nearly always, and its exterior is composites, although of course there's engines and bombs and other things that are Ferrous. And it's moving at 600 miles an hour, and it weighs 700000 pounds, and it's got 60000 pounds of thrust.
My guess is, it would be pretty difficult and you would need an incredible magnet. The likes of which has never been built.
Though you've also compounded the problem. Because you now need a radar that can tell you where the B2 is to even know where to point your magnet, very few radars in the world can do that basically 0 can do it with any accuracy.
And while I don't think magnets aimed, magnets can be designed that don't spread out through diffusion, I just think it's too high too fast.\n Too much left and you don't have any idea where to point your magnet. So I don't think it's going to happen. It's that last part actually, that might be the most difficult, although it may just be impossible to build a magnet of that capability.
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u/Snorkle25 1d ago
not to mention that the strength of a magnetic field falls off from its source at an inverse cubed rate so you would not be attracting only the B2. A field that strong would pull in almost everything with even a hint of ferrous materials within that same distance and closer. Might cause more collateral damage than it prevented.
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u/Technical-Cat-2017 1d ago
We can solve the problem with the inverse law by launching a much weaker magnet towards the B2 instead. Maybe with a cable to drag it back towards the surface. Like those magnetic fishing rod toys.
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u/Snorkle25 1d ago
If you know where the B2 is with enough accuracy that you can launch something at it, why would you choose to launch a magnet of all things and not a missile? The whole point with stealth aircraft is that they defeat modern detection and targeting networks to avoid being targeted in the first place.
And how are you going to get the magnet you launch to be more attracted to the far away plane than any other ferrous metal object that would be closer to it, like say the launching device or the large spool of metal cable you want to attach to it?
The problem with the inverse square law is that it works both ways, and works on all objects that are attracted by magnets simultaneously at the same time. So right from the moment you want to launch the magnet it would need the thing you want it to be attracted to (the far away plane) to be the most attractive thing to the magnet and not anything else which is a pretty hard problem to solve since a lot of other things will be closer and therefore have a stronger attractive force.
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u/nascent_aviator 17h ago edited 17h ago
The strength falls off as 1/r3, so the gradient is 1/r4. The induced polarization in is proportional to the field strength, so that's also 1/r3. Put that together and the attractive force falls off as distance to the seventh power.
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u/Baron_Ultimax 1d ago
Lets for funsies assume you had a space magic monopole magnet.
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u/GoldReplacement9546 1d ago
Of infinite strength and you have the ability to detect the B2 then sure if we’re gonna go to magic once you invoke magic everything is possible
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u/Double_Distribution8 1d ago
what if the B2 is traveling at the speed of light though?
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u/GoldReplacement9546 1d ago
What if the B2 was a tachyon
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u/Snorkle25 1d ago
“Is it actually possible” does not include magically nonexistent monopole magnets.
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u/Friendly-Gur-6736 1d ago
B2s don't fly any higher than your typical commercial airliner.
Only practical reasons to fly higher is fuel consumption and weather. Surface to air missiles have ceilings in excess of 60,000', so you're not going to be up there to avoid those.
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u/GoldReplacement9546 17h ago edited 17h ago
They do fly higher than commercial airliners for several reasons one you don’t want a commercial airliner to visually notice you negating all the selfie and effort you put in
Two fuel efficiency is super important when you wanna do a super long range mission
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Even though there are servers that can hit that high may become less likely to hit the higher you are
Radar capability, especially the kind that does have a chance of detecting it goes down with overall distance of being higher is beneficial
Another one is infrared, but he has more chance to dissipate in the colder atmosphere although you do stand out more so that one’s a bit of a wash
B2 missions officially fly at 50,000+ fee. The reality is their ply probably flying closer to 60,000 feet when they’re in combat.
Another huge factor is the higher you are the further you can have the bomb glide so you don’t have to fly as close to the target as you would otherwise
Also above 60,000 feet is uncontrolled airspace so they don’t have to notify anybody where they are to avoid a collision though in reality, anything above about 52,000 there’s not really gonna be anything else flying up there except for a few fighter jets
But I guarantee you they’re not flying around at 40,000 feet. They have the flying wing shape which is just about the best there is for Lyft to drag.
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u/Friendly-Gur-6736 16h ago
I'm a controller. I've talked to a fair number of them over the past 17 years. They don't fly that high.
30-40k is more typical, though their ceiling is estimated at 50k but that's probably without a bomb load under test flight conditions. Performance margin on many aircraft gets to be quite small at that altitude. Not much operates over FL600 save U2s and WB-57s.
Highest I've personally worked at B2 at was at FL410.
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u/GoldReplacement9546 16h ago
And you’re over the United States, right?
F-22 can go above the Armstrong limit at 62,000 feet and do sometimes even though that’s really dumb because if I have a leak they die
Air Force One when it’s light on passengers and fuel like doing a training mission can go to 49,000 feet
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u/HAL9001-96 1d ago
nah
to apply one extra G of force over that distance you'd need an insanely strong magnet their actual attracitve force goes down rapidly with distance relative to size
so you'd be looking at am ountain sized magnet or terawatts of electromagent power
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u/frogturtle14 1d ago
At 50000 feet in the air the magnet would have to be so powerful it would pull all ferrous metals to it from about 9+ miles around. I’m thinking that would be more hazardous to the people on the ground, than the payload of the B2.
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u/Yoinkitron5000 17h ago
And from 9 miles below also. You'd be yanking on the Earths mantle with that kind of magnetism.
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u/MightyMackie 22h ago
Most aircraft are made of aluminum. Not nickel or steel. So the size of your magnet to even have an effect on the small amount of steel in the aircraft, let alone pull it off course, would not be practical
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u/C00kie_Monsters 21h ago
Since it’s airframe is mostly made from non-magnetic materials, I would guess that a magnet strong enough to generate enough force upon the few magnetic components to theoretically bring it down would probably rip them out
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u/GabrielReichler 1d ago
I assume there are other ways pacifists could use those kinds of exceptionally large magnets that would be more effective at undermining militarism. Lots of ways to go after firearms and munitions for usage by forces on land or go after military, law enforcement, or intelligence agency drones that are typically smaller than crewed aircraft
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u/Ok_Law219 1d ago
You mean ways that won't kill everything in miles distance?
Probably true.
Missiles would kill fewer people than this magnet.
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u/MAXQDee-314 21h ago
Would someone be so kind as to direct me to an explanation of how such a object as a Magnetar, would exist without consuming it's self? I have developed a general understanding of the base of the kelvin scale, does magnatism have a similiar scale by opposites. Obviously zero magnetic field would be one end...
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u/nascent_aviator 15h ago
A magnetar, like all neutron stars, is kept from collapsing by neutrons being packed very very very close together, basically so close that they're touching, which gives them an enormous repulsive force that counteracts gravity.
It's kept by tearing itself apart by the enormous force of gravity. It's the mass of a large star compacted into the size of a city- the density and the resulting force of gravity is beyond anything a human can truly imagine.
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u/Peejay22 18h ago
I remember that one of the conspiracy theories regarding the Smolensk air disaster (polish president and many of his cabinet died there) was that Russia used super powerful magnet to bring it down lol
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u/nascent_aviator 16h ago
Yes, if you had a magnetar (a neutron star with exceptionally high magnetic fields). Which would destroy the earth, so actually no.
Suppose your "really big magnet" is a magnetar, 10 km in radius and with a surface field strength of 1010 T. At 20 km out, the field would be 3.7x108 T, with a magnetic field gradient of 37 kT/m.
With ridiculous field strengths like 370 million tesla, ferromagnetic materials are all well past their saturation fields, and everything essentially acts like a paramagnetic material at that point. Assuming a typical magnetic suspectibility of 10-5, this gives a magnetization of about 3x109 A/m. For a block of iron, this gives a magnetic dipole moment per unit mass of 3.8x105 A-m2/kg.
Combining this gives you on order 109 g of acceleration. Which is a lot, plenty to down a B2! But considering it requires a star, it's not that much. For perspective, say we reduced the size of the magnetar to 1km in radius while keeping its magnetization the same. We need space to put our bunker, after all! Its surface field is still quite large at 107 T. But the field strength at altitude is a measly 1.1kT and the gradient is mere 0.15 T/m. That brings the acceleration we can apply down to 0.01g, using the same magnetic suspceptibility as before. (Ferromagnetic materials would feel somewhat more than this- we're still well past saturation but not so far past that the ferromagnetic amplification is negligible like before. But a B2 largely isn't ferromagnetic anyway).
0.01g of acceleration wouldn't even be noticeable, much less bring that plane down. The magnetic fields themselves would probably destroy the avionics, at least. Any bombs they drop would at least be pulled in.
And a 1 km neutron star is still well out of the range of possibility. Anything actually remotely buildable won't do anything to a B2.
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u/factorion-bot 16h ago
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