Force fields

[Redshirt]

I have a question for the physics buffs present. We all know that it's frequently the case that science fiction becomes science fact. What about force fields? Is this a technology within the realm of possibility? Will saying "shields up" someday become a reality?

[nygreenguy]

Absolutely. There can be magnetic force fields, ive also heard of some sort of field that could reflect lasers. After all, phasers are rally lasers IIRC.

[Berthold]

The term "force fields" has a well established meaning in classical physics, too. :)

[ofro]

Absolutely. There can be magnetic force fields, ive also heard of some sort of field that could reflect lasers. After all, phasers are rally lasers IIRC.

In a sense you find that on the surface of just about all metals and a lot of nonconductors. The whole assembly is also referred to as mirror. Also works with regular, not just laser light :)

[nygreenguy]

Absolutely. There can be magnetic force fields, ive also heard of some sort of field that could reflect lasers. After all, phasers are rally lasers IIRC.

In a sense you find that on the surface of just about all metals and a lot of nonconductors. The whole assembly is also referred to as mirror. Also works with regular, not just laser light :)

but clearly lasers are the weapons of the future..... :D

[Spherical Time]

The other question is, who knows what's available with advances in technology? If it is possible though, it'll be a long time before we see any of them.

[VoxRat]

Absolutely. There can be magnetic force fields, ive also heard of some sort of field that could reflect lasers. After all, phasers are rally lasers IIRC.
I thought "phasers" were fictional devices whose name was meant to connote super futuristic technology, somehow analogous to lasers (which were pretty exotic cutting edge technology back in the 1960's when Star Trek first appeared), but using some form of energy that won't be discovered for perhaps hundreds of years.

Then again, I haven't read Lawrence Krauss's "The Physics of Star Trek", where these things are probably all clarified.

[Jobar]

Speaking as a lifelong sf fan, and also a graduate of the Ga. Tech physics school- probably not.
:(
One day there may be spacecraft with fusion engines that use a 'magnetic shield' to either shunt charged particles away from the craft, or funnel them in to use as fuel. (See Larry Niven's A Gift From Earth, and a number of his other early stories.) But as far as neutral particles, and masses greater than perhaps a few grams, there's no way to deflect or stop such things without material armor, especially when velocities get into the kilometers/second range.

Powerful lasers precisely aimed by very fast computers may enable us to shoot down missiles, or deflect kinetic projectiles somewhat. But there's no way to spread the astonishing energies you need to do that, out into a 'field' which would cover an area, instead of being focused along a line. The energy demands to stop even something small and (relatively) slow, like a .22 bullet, would be prohibitive. Physical armor will always be necessary.

As a science fiction fan, I think this really, really sucks. But unless something totally unexpected comes out of left field, them's the facts.

[DMB]

I thought this was going to be a question about field theory, perhaps something like this (http://www.physicsforums.com/archive/index.php/t-30057.html).

[lpetrich]

The big problem with science-fictional force fields is that are sort-of slab-shaped, which is very difficult to produce with real-life fields unless one cheats in certain ways.

That's because the fields tend to have the same length scale of variation in all directions at each point. This is something that has been abundantly tested, and something that is a consequence of the very successful theories of them. I'm trying to avoid detailed mathematics here, but if anyone wants it, I will describe it.

Here is how to cheat.

For an approximately-planar wave, one can let it through an opening much larger than that wave. It will then continue onward mostly unaffected, but its edges will get fuzzed out (diffraction), and if it continues far enough, the fuzzing out will extend over the whole wave. That will happen at a distance traveled of

(distance traveled) ~ (opening size)2 / (wavelength)

That is why a laser can produce such precisely-collimated light; its aperture is much larger than the wavelength of light that it emits, about (4 - 7) * 10-7m. But even laser light cannot escape its wave nature; it also will diffract.

Alternately, one can produce field configurations with very small, localized variation. But that already happens in ordinary matter. Valence electrons, those in atoms that interact with other atoms, have atom-sized field distributions, about 10-10 m. In fact, those distributions are what give atoms their sizes. Inner-shell electrons have smaller distribution sizes, sometimes much smaller.

[Schneibster]

The basic problem with trying to make what most people think of when they hear "force field" is that it contradicts the basic natures of matter and energy.

I also will avoid complicated math, but the general idea is this:

There are two types of particles: half-integer spin, and integer spin. They are different, in some ways opposite. The biggest difference between them is something called the exclusion principle. The half-integer spin particles obey it; the integer spin particles not only do not, they obey something almost diametrically opposite to it.

The exclusion principle states that two half-integer spin particles with the same quantum numbers cannot occupy the same space at the same time. It's for kind of an odd reason; it's because their probability of existing would be canceled if they could, and if it was, it would violate mass-energy conservation.

For integer spin particles, it's just the opposite: they are more likely to have the same quantum numbers and occupy the same space at the same time.

This means that half-integer spin particles collect into lumps; they can't all occupy the same space, so they have to be at closest next to each other; they can't get closer than that. And this in turn means that we identify half-integer spin particles with matter, and integer spin particles with energy.

Fields, at least as used in the concept "force field," are energy, not matter. That means they are integer spin particles. They can't exclude things; it's their very nature not to exclude things. And that's why "force fields," at least as commonly conceived, are impossible.

And since I'm popping bubbles, neither are light sabers, and for the same reason.

[lpetrich]

That's VERY simplistic. This inclusion/exclusion applies only to otherwise-identical particles, and it ignores interactions between them.

It's possible to make a Bose-Einstein condensate from gases of various metals, like rubidium and sodium, but one has to chill them to VERY low temperatures before that can happen, a few hundred nanokelvin or thereabouts. This is because if the gases get any hotter, their atoms will move faster, driving down their wavelengths and keeping their wavefunctions from overlapping.

[BWE]

Absolutely. There can be magnetic force fields, ive also heard of some sort of field that could reflect lasers. After all, phasers are rally lasers IIRC.

In a sense you find that on the surface of just about all metals and a lot of nonconductors. The whole assembly is also referred to as mirror. Also works with regular, not just laser light :)

you can't see the wavelength of a laser. It cuts metal pretty handily. Molybdenum mirrors and other highly polished metals used in laser optics fry when a speck of dust gets on them.

just saying.

[Berthold]

you can't see the wavelength of a laser.
Huh?

It cuts metal pretty handily. Molybdenum mirrors and other highly polished metals used in laser optics fry when a speck of dust gets on them.

just saying.
Bar codes don't (with or without dust ;)).

[BWE]

you can't see the wavelength of a laser.
Huh?

It cuts metal pretty handily. Molybdenum mirrors and other highly polished metals used in laser optics fry when a speck of dust gets on them.

just saying.
Bar codes don't (with or without dust ;)).

grrr. I have to assume you know what I meant. Bar code readers are typically not things you would need a force field to defend against. A small screwdriver would suffice.

[Schneibster]

That's VERY simplistic. This inclusion/exclusion applies only to otherwise-identical particles, and it ignores interactions between them.

It's possible to make a Bose-Einstein condensate from gases of various metals, like rubidium and sodium, but one has to chill them to VERY low temperatures before that can happen, a few hundred nanokelvin or thereabouts. This is because if the gases get any hotter, their atoms will move faster, driving down their wavelengths and keeping their wavefunctions from overlapping.You apparently neglected to read the first sentence of the article you linked:

A Bose–Einstein condensate (BEC) is a state of matter of bosons

I'll also point out that the entire point of this is how they interact; that would be explicitly not ignoring interactions between them.

It's simply a matter of probability, and it explains why laser light is coherent, and why matter can't be. Simplistic it may be, but correct it also is.

[lpetrich]

It's possible to make a Bose-Einstein condensate from gases of various metals, like rubidium and sodium, but one has to chill them to VERY low temperatures before that can happen, a few hundred nanokelvin or thereabouts. This is because if the gases get any hotter, their atoms will move faster, driving down their wavelengths and keeping their wavefunctions from overlapping.You apparently neglected to read the first sentence of the article you linked:

A Bose–Einstein condensate (BEC) is a state of matter of bosons

I'll also point out that the entire point of this is how they interact; that would be explicitly not ignoring interactions between them.
And how are you taking interactions into account? Have you worked out any of the mathematics?

I had been trying to avoid mathematics, but it looks like I'll have to start doing some of that here.

It's simply a matter of probability, and it explains why laser light is coherent, and why matter can't be. Simplistic it may be, but correct it also is.
Your "reasons" are just plain wrong.

[Linus]

I have a question for the physics buffs present. We all know that it's frequently the case that science fiction becomes science fact. What about force fields? Is this a technology within the realm of possibility? Will saying "shields up" someday become a reality?
I don't know, but probably not. Here's some hope for another futuristic technology though:

http://berkeley.edu/news/media/releases/2008/08/11_light.shtml

[Linus]

The basic problem with trying to make what most people think of when they hear "force field" is that it contradicts the basic natures of matter and energy.

I also will avoid complicated math, but the general idea is this:

There are two types of particles: half-integer spin, and integer spin. They are different, in some ways opposite. The biggest difference between them is something called the exclusion principle. The half-integer spin particles obey it; the integer spin particles not only do not, they obey something almost diametrically opposite to it.

The exclusion principle states that two half-integer spin particles with the same quantum numbers cannot occupy the same space at the same time. It's for kind of an odd reason; it's because their probability of existing would be canceled if they could, and if it was, it would violate mass-energy conservation.

For integer spin particles, it's just the opposite: they are more likely to have the same quantum numbers and occupy the same space at the same time.

This means that half-integer spin particles collect into lumps; they can't all occupy the same space, so they have to be at closest next to each other; they can't get closer than that. And this in turn means that we identify half-integer spin particles with matter, and integer spin particles with energy.

Fields, at least as used in the concept "force field," are energy, not matter. That means they are integer spin particles. They can't exclude things; it's their very nature not to exclude things. And that's why "force fields," at least as commonly conceived, are impossible.
I agree up to this point. Bosons, however, can also have mass and do count as matter. I also don't understand why you think that bosons can't be used as a "force field" simply because of their being bosons.

[Norrin Radd]

Absolutely. There can be magnetic force fields, ive also heard of some sort of field that could reflect lasers. After all, phasers are rally lasers IIRC.
I thought "phasers" were fictional devices whose name was meant to connote super futuristic technology, somehow analogous to lasers (which were pretty exotic cutting edge technology back in the 1960's when Star Trek first appeared), but using some form of energy that won't be discovered for perhaps hundreds of years.

Then again, I haven't read Lawrence Krauss's "The Physics of Star Trek", where these things are probably all clarified.

Originally, when Chris Pike captained the Enterprise, LASERs were the only named energy weapons. By the time Jim Kirk took over a decade or so later, phasers were standard. This has probably been retconned into oblivion by the odious series with Jonathan Archer in the captain's chair, since that warp-5 class Enterprise was already equipped with "phase cannons" nearly a century before Pike.

[Norrin Radd]

FWIW, you might want to check out Memory Alpha (http://memory-alpha.org/en/wiki/Portal:Main) for some of the in-universe explanations of the technology of Trek.