Ask a Physicist!

[retsupurae yahtsee]

I wonder about something: If twin electrons could be accelerated to thousands of times the speed of light, could you create a lightbulb that produced light filled with such particles, or glasses that split and accelerated the electrons coming towards him? I wonder if someone exposed to particles accelerated that fast would experience changes in the perception or flow of his time.

 

[Slenn]

As someone who works with a camera a lot, I was wondering if you could tell me how a lens element in an adapter in between a lens and a camera body can somehow bring in more light. The science of that confuses me and I haven't found a satisfactory answer yet.

Light -> Lens body -> Adapter -> A 'stop' more light on sensor?

I don't get the science one bit but over the course of testing it with lighting conditions, it does work.

I had to get some help from my photography friends to explain it to me, and one of them redirected me to this video.

Spoiler: Skip to 8:45. It should explain what you're asking about.

One question I've always wondered about, and never had a particularly satisfactory answer on, is how reliant are the scientific consensus on dark energy/dark matter (and other big weighty topics) on relatively old pieces of unchallenged wisdom? e.g: Standard candles, Hubble's constant, the main sequence of stars. If we turn out to actually be mistaken in some major way for one of those things, how much impact could it have?

The reason I ask this comes from me originally receiving a bad explanation of the doppler red-shift as "The further away it is the faster it's moving away" which sounded too trite to me for explaining the reality of a chaotic universe! And then I read that many of our distance calculations are based on the red-shift, and our views of how much matter there is depend on the distances involved which depends on the previous answer, and so on and so forth! I've since had much better explanations of how distance is calculated, but the nagging doubt has remained - what if we're wrong about the basic stuff that form the assumptions that everything else is built on? p

We're pretty dang solid on these topics. The problem that any contradictory evidence would have is that it would have to challenge a lot of evidence that says otherwise.

But what if we're wrong? Life goes on. No one gets sacked, beaten, or stoned. No nation is going to go to war over it. And it may be profound for lots of scientists around the globe if it does happen. But it doesn't get treated negatively. If the data is solid and it lines up with no mistakes, then it's considered an amazing discovery. It happens all the time in science.

 

[retsupurae yahtsee]

Are those "scientifically accurate" sketches on Animation Domination actually accurate?

 

[Saulkar]

What does its charge need to be relative to the positive or negative charge of plasma?

I'm not understanding the question. What's the first charge that we're talking about?

If the plasma has a negative charge does the electromagnetic field sustaining it have to be the negative or opposite?

 

[Saulkar]

The reasons I ask is because I envisioned a projectile based plasma weapon that fires a three layer slug (a 0.5KG magnetic plastic outer layer with two 1KG layers of metal). An Eletro-induction field is used to superheat the plastic outer layer into a cloud of plasma around 6000K while one or both of the two inner layers are made to spin/counter spin with each-other to produce an electromagnetic field to sustain the cloud of plasma around it. The slug does kinetic external/armor penetrating damage while the plasma does heat/electromagnetic internal damage like expanding in a crew cabin.

Now, what material would be best for the two metal layers of the slugs in order to produce an appreciable electromagnetic field?
Would both slugs need to spin and how fast, even if it was impossibly fast, in order to maintain a meter wide cloud of plasma while traveling at Mach 5 though the atmosphere at sea-level?
Would a Gauss cannon or Railgun be best as a firing mechanism or would their electromagnetic fields be so similar as to negate any differences they have in disrupting the projectile?

Any other issues with this weapon you can see off the top of your head beside the incredible energy requirements and recoil?

Slow down a bit. Before we get to anything else besides the firing mechanism, we need to postulate about a few things.



Is there any reason why you're picking plastic? I suppose it does become a gas at 6000 K. But a gas at 6000 K will not necessarily be a dense plasma. Or is there some gas trapped between the plastic and the metal?

That is an interesting point. I chose plastic because I have read in many sci-fi media that the matter used in plasma weapons is normally some sort of doped plastic. I assumed that this was a common theory for an ammunition for plasma weaponry.

In order for the metal to survive such a temperature it would have to be tungsten.

I thought that was best but was not entirely sure.

I'm not understanding the need for the shells to spin. You say it's for creating an electromagnetic field. But you don't need spinning metal to create an electromagnetic field to hold in charged particles.

How would you recommend creating the EM field? I was basing it on my knowledge of how the earths magnetic field is created by its own molten metal core and how a spinning dynamo works.

 

[retsupurae yahtsee]

That plasma weapon seems overcomplicated: It would probably be cheaper and more powerful to fly a plane into the upper atmosphere and drop the tungsten rod from there. You would not need a fancy firing mechanism: Just use a tube with a big spring, and let momentum and inertia do the work from there.

 

[Lightknight]

That plasma weapon seems overcomplicated: It would probably be cheaper and more powerful to fly a plane into the upper atmosphere and drop the tungsten rod from there. You would not need a fancy firing mechanism: Just use a tube with a big spring, and let momentum and inertia do the work from there.

Exactly. Though if it were just a tube with a big spring then you'd run into the biggest downside of this mechanism. You have to have fins and a guidance system like I'll mention below.

Wouldn't be terribly surprised if a few countries already had a few satellites with a few of those suckers already on board. Since the outer space treaty and the Anti-Ballistic Missile Treaty both failed to account for kinetic bombardment it is also entirely legal for countries to have these up there since they aren't technically weapons of mass destruction.

I mean, heck, we have documentation of the idea of this dating back to the 50s with Project Thor by Boeing and the airforce recently described the idea of large tungsten poles in space that have fins and a guidance system and deliver somewhere between the kinetic force equivalent of 11.5 Tons of TNT to 120 tons depending on velocity. I mean, that is a lot. That's the equivalent of a conventional missile to start with and then goes to ten times that in one location. They also take half the time to arrive at a target (less than 20 minutes) and are very hard to detect/defend against.

This sounds like it would more than do the task the poster was asking about and with significantly less complexity.

The Wiki also talks about us doing a similar thing in Vietnam with something called a Lazy Dog bomb that functioned like machine gun fired vertically. That was pretty effective and within the atmosphere.

 

[Slenn]

If the plasma has a negative charge does the electromagnetic field sustaining it have to be the negative or opposite?

It won't matter. For the record, there's no such thing as a "positive" or "negative" field. This is because the field is composed of vectors, and where they point is dependent on your frame of reference.

That is an interesting point. I chose plastic because I have read in many sci-fi media that the matter used in plasma weapons is normally some sort of doped plastic. I assumed that this was a common theory for an ammunition for plasma weaponry.

That being said, I'm also not understanding the use of induction to heat the plastic. Plastic does not conduct electricity, so it won't heat up like a metal pot on an induction stove top. Unless you're thinking of the metal shells heating up to heat the plastic.

How would you recommend creating the EM field? I was basing it on my knowledge of how the earths magnetic field is created by its own molten metal core and how a spinning dynamo works.

Just use copper coiling and make a toroid to store the plasma. Moving electric charge is what creates magnetic fields.

But like two other people have pointed out, the system for creating a shell based plasma gun is becoming more complicated than expected.

Are those "scientifically accurate" sketches on Animation Domination actually accurate?

Could you point to me what you're talking about?

 

[Lightknight]

@LightKnight Fins and a guidance system have to be deployed AFTER re-entry. You actually need a launch mechanism of some kind, and in space a spring or rail gun would launch the "gun" in the opposite direction, firing such a massive object. You'd need some kind of rocket motor on the rod, the "Launch" vehicle would just kick the rod out, then the rod itself would engage a rocket motor to break orbit. It would have to undergo reentry nose-first (the nose would be moderately shielded), and then after the plasma envelope from reentry dissipated you'd have fins and terminal guidance.

I thought the guidance system was for positioning while in space with gravity doing the rest of the work.

 

[Myrios]

I admit, this took some research to do, because I wasn't familiar with the theory. I'll try to condense what I've found out.

The idea behind the hidden variable stuff that Bell addresses is that quantum mechanics does not have a deterministic nature. This means that answers to questions like "where is the particle?" are going to be given as probabilities rather than absolutes. Classical mechanics on the other hand, if you did your math right, you can figure out the position and momentum simultaneously and accurately without any repercussions.

Hidden variable theories think that there might be variables that are unknown at this point that allow for quantum mechanics to be deterministic. Bell's theorem states that if there are hidden variables for smaller cases, they will not account for all of quantum mechanics' predictability.

The short answer is "Even if there was a deterministic value to be found from quantum mech', it won't account for everything within quantum mechanics' power."

I probably should have been more specific.
I was hoping you could explain how Bell came to that conclusion.

You already answered one of my questions, though, so you don't feel like you have to answer.

 

[Saulkar]

Just use copper coiling and make a toroid to store the plasma. Moving electric charge is what creates magnetic fields.

Do you know of where I can find any images of such a device.?

 

[Saulkar]

Just use copper coiling and make a toroid to store the plasma. Moving electric charge is what creates magnetic fields.

Do you know of where I can find any images of such a device.?

Don't actually try to confine plasma. You will probably either electrocute yourself, or set yourself and your surroundings on fire.

That is sort of the point, no destruction is better than plasma destruction; Unleash the plasma cannons!

 

[Saulkar]

Plasma isn't as special as you seem to think it is.

It is the novelty of it in a science fiction environment. It is fun to think about its many application outside of a lamp lighting, star, neon sign, or display screen no matter how impractical or ridiculous. If only to give yourself a (flimsy) justification for a Rube Goldberg solution to weaponise it over range in an atmosphere (where it quickly dissipates).

 

[Saulkar]

Plasma isn't as special as you seem to think it is.

It is the novelty of it in a science fiction environment. It is fun to think about its many application outside of a lamp lighting, star, neon sign, or display screen no matter how impractical or ridiculous. If only to give yourself a (flimsy) justification for a Rube Goldberg solution to weaponise it over range in an atmosphere (where it quickly dissipates).

X-Ray LASER's,

Why is it never gamma-ray lasers? Is there something with their wavelength or energy levels that makes weaponising them impractical, even in a sci-fi environment?

P.S. The main reasons I am set on the Plasma cannon is because I am trying to design a working mechanism for one in an old videogame that I love.

 

[Saulkar]

Back to your original point though, this plasma weapon. I think the best plan would have to be some kind of projectile that didn't contain plasma, but produced it upon impact. You would essentially be firing a complex device rather than just a simple explosive shell (Nukes are like this actually) which contain the means to produce a complex effect. The "Physics Package" of your shell would have to have some rapid means to generate energy, and either a means to convert that into usable electrical energy, or have it directly convert a solid mass to plasma.

Nukes do this, but their other effects overshadow it. You need something similarly energetic, but it needs to be on a small scale. Something like a very small matter-antimatter annihilation, with most of your shell being some kind of material that would rapidly absorb all of that energy and be converted to expanding (explosive) hot plasma. At the point of impact, you'd either get a flash (depending on how incredible the mass which flashes to plasma is at its job) or just a giant explosion of expanding plasma. A plasma fireball basically.

It wouldn't be efficient, but I think in Sci-Fi terms it's workable. In real life? Maybe there is some way to use a new supercapacitor to provide the initial "flash", and then use a huge mass of polystyrene foam to absorb the flash and convert to plasma.

I just had an idea! What if the bullet was a superconducting meta-material laminated on the surface of a tungsten projectile with a substance embedded in the lattice. Electro Induction is used to both melt the material in the lattice into a plasma while giving an electromagnetic charge to the meta-material to prevent all of the plasma from venting before it impacts?

 

[Saulkar]

Back to your original point though, this plasma weapon. I think the best plan would have to be some kind of projectile that didn't contain plasma, but produced it upon impact. You would essentially be firing a complex device rather than just a simple explosive shell (Nukes are like this actually) which contain the means to produce a complex effect. The "Physics Package" of your shell would have to have some rapid means to generate energy, and either a means to convert that into usable electrical energy, or have it directly convert a solid mass to plasma.

Nukes do this, but their other effects overshadow it. You need something similarly energetic, but it needs to be on a small scale. Something like a very small matter-antimatter annihilation, with most of your shell being some kind of material that would rapidly absorb all of that energy and be converted to expanding (explosive) hot plasma. At the point of impact, you'd either get a flash (depending on how incredible the mass which flashes to plasma is at its job) or just a giant explosion of expanding plasma. A plasma fireball basically.

It wouldn't be efficient, but I think in Sci-Fi terms it's workable. In real life? Maybe there is some way to use a new supercapacitor to provide the initial "flash", and then use a huge mass of polystyrene foam to absorb the flash and convert to plasma.

I just had an idea! What if the bullet was a superconducting meta-material laminated on the surface of a tungsten projectile with a substance embedded in the lattice. Electro Induction is used to both melt the material in the lattice into a plasma while giving an electromagnetic charge to the meta-material to prevent all of the plasma from venting before it impacts?

Sure, as long as you're producing the plasma on impact, and not trying to contain in it bullets for a long time I don't see a problem with it. It's science fiction, so you get things like room temp superconductors I think. You could even make some sense of it too.

Now about, this is a shell meant to penetrate heavy armor. Instead of a giant RPG with chemical propellants and explosives, creating a jet of molten metal, you have this small bullet which uses exotic effects to create a cutting jet of plasma. If you're inside an armored vehicle, you'd literally be cooked. It would probably kill unshielded electronic too. All of the power would come from the effect of the shell on the target, so you wouldn't have outlandish recoil either.

That is what I am thinking my fine paesano! Small shell penetrates armour, blast cloud of plasma cooks everyone inside and unleashes electrical goodness!