The Question thread

Blackwing
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Re: The Question thread

Post by Blackwing »

Well, you can mask heat signatures by using heavy insulation on the outside of the pod, which you'll end up doing any way since the thing is going to be making an atmospheric entry, but other than that there's indeed no reason for the characteristics of the pods to be the same.

The main problem I can see with orbital bombardment of any kind is not practicality, but cost effectiveness. Space-to-surface weaponry needs to be heat shielded and either simple enough to no be prohibitively expensive (which would mean dumb bombs dropped from a point to compensate for wind and such throwing them off course), but easy to counter or capable of defeating counters and other impeding factors, but relatively expensive.

People on the surface really only need to get into a bunker (and make sure their anti-invasion defences are similarly protected) in order to turn the whole idea of 'softening up the defences before landing an invasion' around 180 degrees and necessitating a ground invasion to deal with anti-bombardment defences before bombardment is viable.

If you have the technology needed to make space-to-surface weapons capable of defeating all countermeasures then a much more cost effective method would be to use that technology to make your invading landing craft able to do the same.

Especially since the defending planet, if they're smart, will put their anti-invasion and surface-to-space weapons in the middle of industrial production centres and other locations that an invading enemy would want to capture as intact as possible.

The only way to defeat possible countermeasures without really expensive and delicate tech would be overwhelming force: something so hard and/or dangerous to destroy and destructive that it will render defences completely useless, but also make the entire invasion moot. Something like a swarm of nukes, a gigantic meteor or a wide area mass volley of lasers.

So most likely orbital bombardment would take a role in warfare rather similar to nukes in modern times: Used as a threat more so than an actual weapon or used when the target absolute, positively needs to be destroyed.

Also:

Destructionator. I'll admit that I made a mistake and was blatantly wrong, but here comes the kicker:

In addition having been wrong, I'm also sorta more right than I even thought and you're wrong on at least one point: it's very possible to have a recoilless magnetic weapon.

Why was I wrong?

Three year ago, I was majoring in applied sciences. For out physics projects, we used a rig fitted with an eletro-magnetic device to propel a projectile at faster than most people can run. We were given a failing grade.
I eventually switched majors, because in addition to physics we also had to do chemistry and molecular biology, both of which required us to use volumetric pipettes, for which I lacked the manual motor control (I am physically incapable of getting the right amount of liquid into those fuckers using a pipette bulb, except by chance and that meant I had repeat our practicals four or five times more than my classmates, it was too stressful).

For two years after that though, I kept referring to the rig we'd constructed as a 'rail gun' until someone pointed out we didn't use a rail. So I figured it was a coil gun instead and kept thinking of that rig as what a coil gun is.

But about that I was wrong, because it wasn't a coil gun and the projectile we used wasn't just a regular piece of ferric metal.

So why am I right after all?

Because the project we were doing was a demonstration of the Magnetic Levitation principle used in Maglev trains.
The electro-magnetic devise we used was a linear motor.
And we got a bad grade because one of us (not me, I was in charge of building the rig, because I needed credits in the area of 'setting up and performing a practical experiment' because I was falling behind in that area due to my pipette problem) miscalculated the power requirements for getting the thing moving and instead of ~10 m/s the little bastard should've 'cruised' along at about ~1 m/s.
The 'projectile' we fired was a pretty basic dipole magnet.

I go bit confused when I read that coil guns fired non-magnetic bullets. Since I was still under the assumption that what we built was a coil gun, I figured that was what went wrong. I thought we got the speed wrong because we shouldn't have used a magnet.

The kind of 'coil gun' I've been proposing:
A truly well designed Coilgun has a barrel a few mili-meters larger than the bullet and uses the magnetic field to suspend the bullet in the middle of the barrel.
I admit my mistake, but I find it a bit disappointing that no one noticed the words 'suspend the bullet' and pointed out to me 'I think you're referring to a Linear motor, not a coil gun'.

At any rate, since a Linear motor uses Lorentz Force to propel the 'projectile', it's one of those things that can impart momentum onto a body without being subject to the Third Law of Motion, because it is a forcefield that possesses it's own moment.
You can look that up, it's 100% correct.

I'm still inclined to say that a real Coil Gun probably isn't subject to the Third Law of Motion the way a gunpowder weapon is, since it also uses Lorentz force, but since the bullet touches the barrel, it still imparts kinetic energy onto the weapon through friction. So yes, Recoil (though somewhat less than a gunpowder weapon).

But for a Linear Motor, I can at least prove it, having done both the math and the experiment.

All that really needs to change is the name (Linear Motion Gun?) and the ammunition.

Now I noticed that I'd been wrong all along when, in an attempt to give practical example why I was wrong, I looked up 'maglev' on Wikipedia.
However, thanks to that, I do at least have an good material suggestion for the ammunition: high purity pyrolitic carbon, tipped with either an armour piercing (Depleted Uranium?) or traditional bullet (lead) material.
It should be easy enough to make for space-faring people since one method of making it involves synthetic materials in a vacuum, of which space has plenty.

Any way, I'm sorry for kicking up such a fuss when I turned out to be mistaken, but I am happy that I now at least understand what my mistake was.
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Re: The Question thread

Post by Destructionator »

I've gotta get to bed again, so I must once more be very brief.

Blackwing, a coilgun is a linear motor, like a square is a rectangle.

All projectile weapons will have the reaction force, including magnetic ones - it is impossible to apply a force to a field; it is always applied to the object generating that field. Momentum is always conserved. This is fundamental first year physics.

--------

On using bunkers to hide from orbital bombardment: if everyone are hiding in their bunkers, aren't they harmless? If they come out to shoot you, can can deal with that when it comes. Unless their industry is also hiding underground, they won't be very productive. You can wait them out (siege!), or burn their factories and such so when they come out of hiding, they have nothing left.
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Re: The Question thread

Post by Heretic »

Ugh, coilguns are just making my head screwed. And finally one of my first questions starting this thread was answered concerning orbital strikes.

Another topic, as we know, graveddies orbit and switch locations. Is there a way to map the galaxy, and maybe some patterns graveddies make when switching, so that if a ship wants to go from point A to point B, but ends up at point M, is there a way to access a map on their computer or something and find out the latest graveddie change so that they can try to go there? Or, as it seems with the Colony of Elol, screwed over? Heck, maybe a map like that would be a holy grail, and is some ancient device polities are fighting over like crazy.

Edit: Or maybe instead of patterns of graveddies, said maps might have methods to get information about certain graveddies, and have equations to find out its future route. Maybe.
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Re: The Question thread

Post by Artemis »

You could pretty easily find your location by calculating your distance from various points in the galaxy, such as the galactic core, particularly large local stars, things like that. Constellation mapping, as in what the stars look like from one part of the galaxy as opposed to another, might also have possibilities.
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Re: The Question thread

Post by Blackwing »

Destructionator wrote: This is fundamental first year physics.
And like most fundamental first year physics, it is a simplification of the truth that's ultimately not 100% correct.

Like I said, get acquainted with General Relativity and how Lorentz Forces operate and read up on why Einstein formulated General Relativity in the first place. Newtonian physics holds that fields of force (force fields) cannot hold their own momentum, General Relativity and a little thing called reality disagree.
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Re: The Question thread

Post by Destructionator »

Blackwing wrote:Newtonian physics holds that fields of force (force fields) cannot hold their own momentum, General Relativity and a little thing called reality disagree.
Relativity doesn't throw out classical physics, it instead refines it around edge cases. For everyday situations, the relativistic result and the Newtonian result are, for all practical purposes, the same thing.

If you crunch the math from general relativity, you'll find that relativistic momentum is the same as classical momentum for non zero masses with speed far less than the speed of light - both of which are true for our gun.

Momentum for things with zero mass is different than the classical result in that it is non-zero, but for practical purposes, we can ignore this - the result is so very close to zero that it doesn't matter for most cases. (If you are building a solar sail you might care, but for a gun? This effect is not remotely big enough to worry about.)


This gun isn't an edge case. The everyday applicability of classical mechanics works very well here. If you want to argue otherwise, prove it. Show me your calculations that demonstrate this result - show that momentum is still conserved in your model, or give me an experiment that I can repeat and verify showing that conservation of momentum itself is flawed (then let me be the first to congratulate you on your Nobel Prize).

While you're at it, explain why your calculations apply to the magnetic gun while my calculations accurately describe the refrigerator magnet and fork you can hold in your hand to feel the reaction force. Why does the momentum get carried away in the magnetic gun but not in the magnetic fork? Before you say "electomagnets are different", try that at home too. An easy way to do that is to pick up a cheap electric motor. Hold the body and feel the reaction force - the shaft spins one way, the body wants to spin the other way.


If you can't provide these calculations, concede the point. This will be my final post on this subject.
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Re: The Question thread

Post by Destructionator »

Heretic wrote:Edit: Or maybe instead of patterns of graveddies, said maps might have methods to get information about certain graveddies, and have equations to find out its future route. Maybe.
Yeah. Such a map seems like it would be possible to make, but story wise, I like the idea of it being really rare. Maybe it takes ten thousand years to get enough observational data to make accurate predictions.

A new polity to the scene would try to predict it, but simply don't have enough data, so they are wrong a large percentage of the time. An ancient race would have been around long enough, see enough graveddy swaps and such, that they have enough data to be right most the time.


This is something the coalitions may have the advantage in. No one member nation has enough data to guess graveddy actions on their own, but if they pool their data with every one else in the alliance, they can make a more accurate model.
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Re: The Question thread

Post by Blackwing »

Destructionator wrote:If you can't provide these calculations, concede the point. This will be my final post on this subject.
Image

There's your formula.

P is momentum.
m is the object (in this case bullet)'s mass
v is the velocity of the object.
q is the object's charge.
A is the vector potential.

Then we have the Lorentz Force of the Linear Motor, which acts upon the object through a magnetic field.

Image

Newton's First and Second Laws of Motion define F (force in Newtons) as:

Image

Where the p with the little arrow over it is momentum and t is time (so F is momentum over time as a differential)

As soon as the P (over time) of the magnetic field increases above the P (over time) of the bullet, the bullet must equalize the difference BECAUSE of Conservation of Momentum, because the electromagnetic field and (invariable magnetic field of) the bullet are interacting.

Since the q of the bullet is finite (and relatively stable) and the A is equal to the vector of the Lorentz force nearly instantly (in a linear motor fitted on a gun, the vector is 'along the course of the barrel'), this means that in order to equalize P it must increase it's v.

As a result the bullet is launched.

Conservation of Momentum is maintained. The Third Law of Motion does not apply to cases where a force field holds it's own motion (350 years of post-Newtonian science and practical experiments both say this, so I am not going to argue with them, or with you, on this point).

Your example of the 'cheap electric motor' is indeed a good example of the Third Law of Motion. But it's the result of the friction between the shaft and part of the motor that holds it in place (duh)... A Linear (Induction) Motor uses Magnetic Levitation in order to reduce friction to 'negligible' (which is physics language for 'so ridiculously close to zero that we won't ever notice it in macroscopic objects, but it's still there, sorta, on a quantum level and all, so yeah').

Destructionator, your issue here is that you need to realize that Conservation of Momentum is NOT the same thing as Newton's Third Law of Motion.
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Re: The Question thread

Post by Siege »

Blackwing wrote:The main problem I can see with orbital bombardment of any kind is not practicality, but cost effectiveness. Space-to-surface weaponry needs to be heat shielded and either simple enough to no be prohibitively expensive (which would mean dumb bombs dropped from a point to compensate for wind and such throwing them off course), but easy to counter or capable of defeating counters and other impeding factors, but relatively expensive.
Heat shielding shouldn't be a problem for polities that throw around high-energy lasers, build torchships and have plentiful access to SSTO transatmospheric interface craft. And cheap bombs don't need to be dumb by necessity; look at the current day JDAM guidance kit which converts existing unguided gravity bombs into all-weather smart munitions on the cheap.

People on the surface really only need to get into a bunker (and make sure their anti-invasion defences are similarly protected) in order to turn the whole idea of 'softening up the defences before landing an invasion' around 180 degrees and necessitating a ground invasion to deal with anti-bombardment defences before bombardment is viable.
If the enemy is sitting in bunkers, you've just neutralized him and can land your forces entirely unopposed. If the bunkers have active defenses, they'll need sensors. Sensors can't be armored, and thus will always be a weak spot-- unleash the orbital equivalent of Wild Weasel assets equipped with HARM bunker busters on them. Finally, the bunkers themselves are hardly impenetrable, especially if you've got gravity on your side, unless they're buried real deep, in which case whoever's inside is in no position to fight the landers as they're coming down.

If you have the technology needed to make space-to-surface weapons capable of defeating all countermeasures then a much more cost effective method would be to use that technology to make your invading landing craft able to do the same.
What countermeasures?

Also: technology applicable to weapons will not always be applicable to landers. What if my way of dealing with your elaborate countermeasures is to drop a multi-ton tungsten KKV on your bunker? Or zap your exposed sensors with a high-powered laser?

Especially since the defending planet, if they're smart, will put their anti-invasion and surface-to-space weapons in the middle of industrial production centres and other locations that an invading enemy would want to capture as intact as possible.
In a total war situation those industrial production centers are a key strategic target, and the enemy will most likely have no qualms about destroying them utterly. Furthermore, if I'm an alien and I'm attacking a human planet, I'm probably planning on removing most human infrastructure anyway because it's not suited to my alien physiology, so what's preventing me from nuking the site from orbit? Finally, even if I preferred to capture those industries intact, if the choice is between the safety of my crack planetary invasion teams vs. the safety of the enemy industries, the enemy industries will be the ones to go.

The only way to defeat possible countermeasures without really expensive and delicate tech would be overwhelming force: something so hard and/or dangerous to destroy and destructive that it will render defences completely useless, but also make the entire invasion moot. Something like a swarm of nukes, a gigantic meteor or a wide area mass volley of lasers.
Again: What countermeasures?
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Re: The Question thread

Post by Destructionator »

I guess that wasn't my final post.
Blackwing wrote:There's your formula.
Where are your calculations?

Tip: Those equations don't even imply that the magnetic field can hold any momentum at all.
But it's the result of the friction between the shaft and part of the motor that holds it in place (duh)
Wow.

Do you know what happens with significant friction between the shaft and the body? It jams the motor - both parts are connected and thus try to spin in the same direction, but that's impossible since it would be creating angular momentum, so instead it doesn't spin at all. (And the electrical energy that would have caused it to spin is now turned to heat, causing it to get hot.)

Speaking of friction, do you know what force actually causes it on the microscopic level?

I'll give you a hint - the atom's electron shells never actually touch, but they have like charges....

That's right kids, it's the electromagnetic force!
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Re: The Question thread

Post by Blackwing »

Destructionator wrote:I guess that wasn't my final post.

Where are your calculations?

Tip: Those equations don't even imply that the magnetic field can hold any momentum at all.
Erhm... 'Magnetic fields can hold momentum' is a scientifically accepted fact, I don't need to prove, imply or otherwise do anything with it, because it's still fact. Unless you want to argue with Hendrik Lorentz and tell him that all his work on Electrodynamics is wrong...

As for the Lorentz Force not implying that a magnetic field can hold momentum: You're right, it doesn't imply, it outright states it, since Lorentz Force is the equation used to CALCULATE the Momentum (over time) of a magnetic field.
Speaking of friction, do you know what force actually causes it on the microscopic level?

I'll give you a hint - the atom's electron shells never actually touch, but they have like charges....

That's right kids, it's the electromagnetic force!


... Shall we both agree not to drag Quantum Mechanics into this?
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Re: The Question thread

Post by Booted Vulture »

As for the Lorentz Force not implying that a magnetic field can hold momentum: You're right, it doesn't imply, it outright states it, since Lorentz Force is the equation used to CALCULATE the Momentum (over time) of a magnetic field.
Not really. It's used to calculated the Lorentz Force acting upon an object in the field. Force is the change in momentum, over the change in time. (hence all those 'd's) and doesn't apply to the field, it applies to an object being acted on by the field.
As soon as the P (over time) of the magnetic field increases above the P (over time) of the bullet, the bullet must equalize the difference BECAUSE of Conservation of Momentum, because the electromagnetic field and (invariable magnetic field of) the bullet are interacting.

Since the q of the bullet is finite (and relatively stable) and the A is equal to the vector of the Lorentz force nearly instantly (in a linear motor fitted on a gun, the vector is 'along the course of the barrel'), this means that in order to equalize P it must increase it's v.

As a result the bullet is launched.
As far as I can tell; you seem to be saying that as soon as the electro magnetic activates and creates an electric field with a momentum that by conservation of momentum then the bullet must accelerate so it has equal momentum to the field?
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Re: The Question thread

Post by Destructionator »

Blackwing wrote:As for the Lorentz Force not implying that a magnetic field can hold momentum: You're right, it doesn't imply, it outright states it, since Lorentz Force is the equation used to CALCULATE the Momentum (over time) of a magnetic field.
No, it is used to calculate the force on a charge in that field (see, that's what the q and the v are about - the attributes of the charged particle the force is acting upon).

The page you grabbed those equations from put this in plain English, in the very first sentence, no less:
Wikipedia wrote:In physics, the Lorentz force is the force on a point charge due to electromagnetic fields.
Thus, the momentum is gained by the item holding that charge, such as the bullet or weapon's magnetic launch apparatus, not the field.
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Re: The Question thread

Post by Blackwing »

Actually...
The Lorentz equation IS used to calculate the momentum of the field is that the momentum of the field cannot be determined except through observing it's effect on charges within that field. Since momentum cannot be spontaneously created, as per Conservation of Momentum, the momentum of the field must be equal to the (sum of) the momentum it imparts on the charge(s) within that field.
As far as I can tell; you seem to be saying that as soon as the electro magnetic activates and creates an electric field with a momentum that by conservation of momentum then the bullet must accelerate so it has equal momentum to the field?
Right on the mark, in a practical experiment the reasoning is reversed in the sense that when the electro magnetic field is generated, the object (a magnet) within the field is observed to increase it's velocity along the vector of the field (as a result of increased momentum) and because of this we can deduct that this means the field has it's own momentum.

As for Destuctionator's previous point about friction ('the shaft and the body want to move in the same direction') that conflicts with both observed reality and the Third Law of Motion (which, since the shaft and the connector between the motor and the shaft are both bodies, applies). The shaft and the connector do not want to move in the same direction, they want to move in opposite directions. If they are not able to, then the parts will impart their momentum and vector onto a object with which it is interacting which IS able to move along that vector.
Which means that if the shaft is 'immobile', the connector will impart it's momentum onto the rest of the motor. Ergo the motor will spin in the opposite direction of the vector of it's Lorentz Field.
It may look like this is and equal but opposite reaction between the Lorentz Field and the object it's acting on, but it's not.
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Re: The Question thread

Post by Destructionator »

Blackwing wrote: Since momentum cannot be spontaneously created, as per Conservation of Momentum, the momentum of the field must be equal to the (sum of) the momentum it imparts on the charge(s) within that field.
Unless the force also acts upon the magnet, which, of course, it does.
Right on the mark, in a practical experiment the reasoning is reversed in the sense that when the electro magnetic field is generated, the object (a magnet) within the field is observed to increase it's velocity along the vector of the field (as a result of increased momentum) and because of this we can deduct that this means the field has it's own momentum.
Pretending you were right, what happens here when you turn the electromagnet off (cease firing the gun), destroying the field? That momentum it is allegedly holding can't disappear, so where does it go?
As for Destuctionator's previous point about friction ('the shaft and the body want to move in the same direction') that conflicts with both observed reality
Try it yourself. Connect the shaft of a motor to the body of that motor with some friction. The motor jams - this is why they try to minimize the friction by either keeping it from touching or using something like lubrication.
The shaft and the connector do not want to move in the same direction, they want to move in opposite directions.
Yes, exactly, that's my point - the reaction force exists naturally. But if you connected the shaft to the body with friction, like you erronously claim is the mechanism of the reaction force (I remind you that you claimed: "[the reaction force is] the result of the friction between the shaft and part of the motor that holds it in place (duh)"), you jam the motor, not allow it to operate.
If they are not able to, then the parts will impart their momentum and vector onto a object with which it is interacting which IS able to move along that vector.
Which means that if the shaft is 'immobile', the connector will impart it's momentum onto the rest of the motor. Ergo the motor will spin in the opposite direction of the vector of it's Lorentz Field.
If the shaft is immobile connected to something so big that you won't notice its slight movement (like your hand or the Earth) and not connected to the body of the motor, yeah, it will spin in the opposite direction. Congrats, you just discovered the principle behind the wheel.

But if the shaft is connected to the body of the motor such that it can't move (real life example: slam on your brakes in a wheeled vehicle PROTIP: wear a seatbelt and always follow traffic safety laws), it will jam and potentially overheat, not produce a net reaction force on the axle.
It may look like this is and equal but opposite reaction between the Lorentz Field and the object it's acting on, but it's not.
It might not, but only because the magnetic field has practically nothing to do with it.

What it is: an equal and opposite reaction between the shaft and the body. Take the electric motor and hang it from a couple of strings so it can move freely in the air. Turn it on - note the shaft spins one direction and the body spins in the other direction (until it twists its wires and breaks them off, or twists the string holding it up and gets stuck, so use caution if you try this at home).

The electric motor is the same thing as in our magnetic weapon, just instead of spinning, it accelerates something in a line. Just like the motor spins in both directions, the linear motor will push backward as it pushes the bullet forward.
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Re: The Question thread

Post by Blackwing »

Destructionator wrote: Pretending you were right, what happens here when you turn the electromagnet off (cease firing the gun), destroying the field? That momentum it is allegedly holding can't disappear, so where does it go?
You seem to be a bit at a loss regarding the workings of an electro-magnet.

Where does the momentum go? Nowhere, it stays exactly where was, in the magnetic field which dissipates naturally as always, however when the electric stream stops, the previously moving electrons in the electro-magnet come to a rest.

Normally these moving electrons are what cause the magnetic waves (I presume by imparting their own momentum on them). Since the electrons stop moving, no new magnetic waves (beyond what an uncharged copper wire, or whatever we're theoretically using here, generates normally) are generated, the magnetic waves continue along their vectors until the field dissipates (which, considering they move at the speed of light is near instant).

That's actually more proof that the waves that make up the field do have momentum: if they didn't, shutting an electromagnet off would cause the magnetic field to dissipate relatively slowly (the way it does in magnetized iron) since the waves would then 'stick around' for a while.

This isn't exactly rocket science... Heh.
I say that because in 'rocket science' the Newtonian Laws of Motion are very near to 100% accurate for all purposes, hence a rocket scientist would rely on them so much he'd be tempted to forget that they don't all apply to every possible situation.
<all the blah blah about the electric motor, still>
Lubrication? I think we're talking about different frictions here, I'm talking about the phenomenon of friction in physics, you're talking about a rusty car... No matter how much you lubricate (with conventional lubricant, if you use some king of theoretical zero-friction superlubricant, not so much) the connection between any motor of any kind and whatever it's supposed to impart motion onto there will always be friction, because that's what a motor relies on to work.
Perhaps I should have said torque, but it's still friction.
Jamming? Mate that happens when both the motor and the body it's connected to are immobile, you were talking about holding the motor in your hands...

And the actual 'principle' behind the wheel is that the closer a shape gets to a perfect circle the smaller the contact area between the shape and a contact surface, thus reducing traction, which has nothing to do with any of this...

I think what we have here is a difference in understanding of terms. I'm thinking of a theoretical electric motor, you're thinking of hooking something up to your car.

So let's step away from the car terms and use substitutes, let's call the two parts of the motor I was talking about the 'touchy bit' and the 'move-y bit'. The 'touchy bit' is part of the motor that physically spins. It's task is to connect to the 'move-y bit'. The 'move-y bit' is whatever object the motor is used to impart motion on through the 'touchy bit'...

In my previous explanation, the 'connector' is the touchy bit, the 'shaft' is the move-y bit. If the motor is imparting motion on the touchy bit in order to try and get the move-y bit to move, but the move-y bit is somehow immobile (let's, for a second here, say that it is a theoretical immovable object), then the touchy bit's will try to spin in the opposite direction from the way the move-y bit is supposed to move, which it then also can't do because it's attached to the immovable move-y bit. So instead the rest of the motor, which is physically connected to the... wait, let me test this...

Actually dude, with an electro-motor, it doesn't move. I've just tried it, you were wrong. The rotating electro-magnetic field is (probably) trying to get everything moving, but it's not managing. The motor isn't turning either.

What DOES happen, though is that if it is moving already and I grab the bit that's moving (with safety gloves) then the motor bucks a bit since the momentum of the moving bit is then transferred back onto the motor, but that's kinetic energy.

At any rate, if what you said about the equal and opposite reaction on the magnet was true, the motor should be spinning when I hold the part that is supposed to move, but it isn't (and it's not heavy enough that the momentum's not defeating gravity or something). All that's happening is that the coil's heating up a bit.
I'm using a (nearly) completely round motor here, according to you it should roll when I hold the bit that should be moving, but it's not.
Does this make a me a Mythbuster or do I have to blow up the engine with explosives first?
So Einstein was wrong when he said "God does not play dice". Consideration of black holes suggests, not only that God does play dice, but that He sometimes confuses us by throwing them where they can't be seen. ~ Stephen Hawking
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Re: The Question thread

Post by Destructionator »

Blackwing wrote:You seem to be a bit at a loss regarding the workings of an electro-magnet.
lawl
That's actually more proof that the waves that make up the field do have momentum: if they didn't, shutting an electromagnet off would cause the magnetic field to dissipate relatively slowly (the way it does in magnetized iron) since the waves would then 'stick around'
Blue light has more momentum than red light. Does that mean it travels faster? No, it doesn't - momentum has nothing to do with the propagation speed of waves.

And waves have very little to do with force fields anyway, unless you want to get into some irrelevant quantum stuff.
Lubrication? I think we're talking about different frictions here, I'm talking about the phenomenon of friction in physics, you're talking about a rusty car
:roll:
it's supposed to impart motion onto there will always be friction, because that's what a motor relies on to work.
No, it doesn't. The motor is designed to minimize internal friction - it is a liability, not an asset.

If you are talking about friction holding the payload to the shaft, which is useful, but also completely irrelevant to the motor's operation.
I think what we have here is a difference in understanding of terms.
Yeah: I understand them. You don't.
In my previous explanation, the 'connector' is the touchy bit, the 'shaft' is the move-y bit.
Do you utterly fail to understand the basic operation of a motor or you are purposefully trying to confuse everyone with bizarre terms?

On a motor, the thing sticking out that is meant to spin is the shaft. Everything else is the body. I thought that was obvious.
Actually dude, with an electro-motor, it doesn't move. I've just tried it, you were wrong.
No, this is exactly what I said. Connect the shaft to the body and the motor jams.

Is your bizarre terminology confusing you too or do you not know how to read?
All that's happening is that the coil's heating up a bit.
Yup. Jam the motor but keep power going to it and it will eventually overheat, just like I said.
I'm using a (nearly) completely round motor here, according to you it should roll when I hold the bit that should be moving, but it's not.
You're either holding it in place or simply lying. Suspend it freely, like I god damn said.
Does this make a me a Mythbuster or do I have to blow up the engine with explosives first?
It makes you an illiterate idiot.


I have to ask: are you just too proud to concede? You shouldn't be: there's no dishonor in simply being wrong, no shame in not knowing something. But, carrying on like this just makes you look like a run of the mill Internet bullshiter, and there's nothing good that can come from that.
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Re: The Question thread

Post by Blackwing »

I feel I should say 'it's on now', but frankly, I'm tired of getting you to understand and stop making an ass of yourself:

Magnetic fields can hold momentum, otherwise the bullet in a coil gun wouldn't move, a mag-lev train wouldn't move and an electric motor wouldn't move.

Because Momentum is conserved, it does not spontaneously come into existence.
A bullet in a coil gun moves. It gains velocity. Since it does not decrease in mass, this means that it gains momentum.
If there is recoil in a linear motor as you claim there is, the magnet also gains momentum.

Where the fuck is this momentum coming from then, eh? Does God wiggle his fingers every time the Toei Ōedo Line tram moves to the next station? Do the invisible eco-conservation fairies start pushing every time someone drives their electric car?

No.

Magnetic fields have momentum, they can impart it on objects with the right properties.

You sir, fail physics forever and you're acting like a little kid about it too.
So Einstein was wrong when he said "God does not play dice". Consideration of black holes suggests, not only that God does play dice, but that He sometimes confuses us by throwing them where they can't be seen. ~ Stephen Hawking
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Re: The Question thread

Post by Destructionator »

Blackwing wrote:Magnetic fields can hold momentum, otherwise the bullet in a coil gun wouldn't move, a mag-lev train wouldn't move and an electric motor wouldn't move.
Unless there is a reaction force balancing it out. You know, like in the real world.
Because Momentum is conserved, it does not spontaneously come into existence.
Which is why there is necessarily a reaction force. You know, like in the real world.
Where the fuck is this momentum coming from then, eh?
The reaction force. You know, like in the real world.

I'm sure you haven't gotten to vector addition yet in your Jr. High classes, but when you grow up, you'll learn that a forward vector plus a backward vector of the same magnitude (there's a vocab word for you to frantically google) adds up to zero, meaning no momentum is actually created when there is the equal and opposite reaction force.
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Re: The Question thread

Post by Blackwing »

Erhm... what?

Reaction Force doesn't actually exist as an actual force. Reaction Force is simply a term for the force that is applied to another object as a reaction to 'Action Force' force acting upon an object.
And 'Action Force' is simply a force acting upon an object to which there must be a reaction.

There is no such thing as 'the' Reaction Force.

If the action force acting upon the bullet is the magnetic force then the reaction force acting upon the magnet must be a magnetic force as well.

But this is circular reasoning, because in order for a Reaction Force to be in effect there must first be an action-reaction interaction between two objects. In this case, however there is an interaction between an object and a non-object wave.

Any way, to once again quote wikipedia:
Newton used the third law to derive the law of conservation of momentum;[19] however from a deeper perspective, conservation of momentum is the more fundamental idea (derived via Noether's theorem from Galilean invariance), and holds in cases where Newton's third law appears to fail, for instance when force fields as well as particles carry momentum, and in quantum mechanics.
Apparently Wikipedia seems to think force fields can carry momentum. I know Wikipedia isn't always reliable, but in this case the claim is from a peer reviewed source.

Some more examples from the talk page for the page that the quote is from:
The third law is not always true. It fails to hold for electromagnetic forces, for example, when the interacting bodies are far apart or rapidly accelerated and, in fact, it fails for any force which propagate from one body to another with finite velocities.
Source: Mechanics, by Keith R. Symon, University of Wisconsin, Addison-Wesley Publishing Company, Inc., chap. 1-4
We need to include something about the limitations of the 3rd law. An example of it not holding is two magnetic dipoles pointing in the same direction. If you release them they will begin to rotate in the same direction, i.e. the torques they exert on eachother are not opposite. (Conservation of angular momentum is counter-intuitive to the 3rd law here, it is held because of the angular momentum of the field being opposite that of the dipoles)
Or in summary: You no understandy Electro-dynamics. Newton's Third Law of Motion no worky-worky on magnetic fields. I swear if you keep this up I'll arrange for Einstein's and Lorentz' Ghosts and Stephen Hawking to team-tag bitch slap you until you promise to learn wtf Electrodynamics is all about.
So Einstein was wrong when he said "God does not play dice". Consideration of black holes suggests, not only that God does play dice, but that He sometimes confuses us by throwing them where they can't be seen. ~ Stephen Hawking
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Re: The Question thread

Post by Destructionator »

Blackwing wrote:But this is circular reasoning, because in order for a Reaction Force to be in effect there must first be an action-reaction interaction between two objects. In this case, however there is an interaction between an object and a non-object wave.
My easy try-it-at-home experiments support the theory of a reaction force. You can feel the damn thing yourself. Hold two magnets in your hand - they pull each other or push each other (depending on their orientation). You can feel the force on both magnets. The same thing happens if you replace one of the magnets with a piece of steel. The same thing happens in the electric motor. You can experience all these effects at home. With a little care, you can measure them and see how Newton's theory adequately explains them.

But, you are rejecting Newton's theory. So how do you explain this?

For all the massive amounts of stupidity you are polluting this thread with, that's the core question. Everything else are red herrings.


(As a side note, readers might find something interesting: assuming Blackwing's nonsense was true, the counter-momentum for the bullet would be carried away as electromagnetic radiation - light. Relativity does indeed tell us that light carries momentum, not much of it, but a little bit - a fact we can exploit with the solar sail.

Anyway, if you do the math, to satisfy conservation of momentum, the M16 would need to put out about 1 GJ of light shooting backward - a ravening death beam with about a million times more energy than the bullet has!

This would be recoilless and would violate no physical laws (assuming the gun's battery can provide all that energy), but is obviously quite an absurd weapon design. Since coilguns have been built before and don't have this death beam shooting out their backs, we know this theory must be flawed.)
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Re: The Question thread

Post by Heretic »

Rofl, what are you children fighting over? From what my feeble mind can summarize, coilguns are possible, though heavier. So, like a futuristic WWII rifle, right?
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Re: The Question thread

Post by Malchus »

It's not whether coilguns are possible or not, Heretic. The main point of contention in their discussion is whether coilguns have any significant recoil and, on a related note, whether or not magnetic fields have and can impart momentum.
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Re: The Question thread

Post by Blackwing »

Destructionator wrote: But, you are rejecting Newton's theory. So how do you explain this?
I'm done talking to you, you're never going to understand the simple fact that even a 'Law' in science can over time proven to be wrong and for that matter Newton's laws aren't even wrong, they're just not universally applicable to all extant forces in the universe.
And that nothing I've said is rejecting Newton's Laws of anything.

It helps to realize that Newton formulated the working version of his laws in 1687, nearly exactly twenty years before Benjamin Franklin was born and half a century before Franklin popularized the concept of electricity in scientific circles (and devised Conservation of Charge).

Newton's work failed to take into account electro-magnetism, because it wasn't recognised as something that actually exists until about a century after Newton started publicly demonstrating his First Law by means of his lifeless body, a wooden box and about 12 cubic feet of grave dirt (aka after he died).

At any rate, Electro-magnetic radiation encompasses more than light and you still fail to realize that there wouldn't be a wave of it in the opposite direction because action-reaction DOES NOT FUCKING APPLY IN THIS CASE.
So Einstein was wrong when he said "God does not play dice". Consideration of black holes suggests, not only that God does play dice, but that He sometimes confuses us by throwing them where they can't be seen. ~ Stephen Hawking
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Re: The Question thread

Post by Destructionator »

Heretic wrote:Rofl, what are you children fighting over?
If you have two magnets, they pull on each other - both experience the pull, not just one. They try to get closer together of farther apart.

In a coilgun or other magnetic weapon, this effect gives you recoil. The gun pushes the bullet forward, and just like with the fridge magnets, the bullet pushes the gun backward.

For some reason, Blackwing refuses to admit this.
From what my feeble mind can summarize, coilguns are possible, though heavier. So, like a futuristic WWII rifle, right?
Yes, that's exactly what I'd expect. The weight could potentially be brought back down with future technology too; I'm merely being conservative.
Blackwing wrote:*snip*
Hold a magnet in each hand. Feel the forces. QED.
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