you would need a dyson sphere sized construction in order to generate the power required to build a dyson sphere (assuming you've got some way to convert energy to matter, which would be as required)
Ringworld's "ring" is built out of a material dense enough to block 40% of neutrinos; a ♥♥♥♥ IMPOSSIBLE amount. it's a purely fictional material, and utterly impossible to current understanding of nuclear physics. something one AU wide would require constant outward force (basically, being made of a solar sail) to maintain the "spherical" shape, and the tensile forces applied would be literally ridiculous.
apes and angels comes to mind in regards to CC's universe
in summary: any alien civilization we encounter will be astronomically ahead or behind of us; the possibility of two civilizations encountering each other at a "similar" stage of cultural progression is minuscule.
along with that, Clarke's Third Law: any sufficiently advanced technology is indistinguishable from magic.
being unable to fathom the energy requirements of a future civilization doesn't mean that they don't exist
what if a society invents faster-than-light travel/communication, but it requires investing
so much energy that it'd be more efficient to just launch something there at exactly c? the advantage would be worth the power required, and Dyson is perhaps conservative: who's to say power generation stops at fusion? exploiting the fabric of spacetime could have just as many ramifications. again, there are very likely civilizations among the trillions of galaxies that are
millions, if not billions of years old. in the last ten thousand years human civilization has changed so radically that the next ten thousand are an utter crapshoot to predict. now, talk about timespans THOUSAND OF TIMES longer than that
energy requirements are a universal constant, because think about this: banging sticks together > lashing horses together > using dead, compressed plant matter as fuel > pure electrical input?
we just don't know, and there's no reason to say that energy requirements will not spike suddenly for some unforeseen technological advancement.
on lasers: ten kilowatts of energy with minimal dispersion would probably be enough to impart a few thousand watts directly into the target surface. a maser at that scale would probably fry someone's brain; who knows about other forms of lasers, but it's not going to be pretty in any event.
http://www.af.mil/news/story.asp?id=123154924100kW laser, tested from an airborne platform
there's video (somewhere, I remember seeing it) of this thing frying a truck engine within three inches, while flying regularly
flechette railguns would be an interesting technical experiment, but I can't see them being useful for bombardment or direct attack unless A: it was a large-scale projectile that only "seperated" on the downward trajectory or B: railguns somehow become low-level portability weapons.
however, flechettes in an orbital, mass-based weapon platform have a whole new meaning. I believe something the size of a crowbar (out of tungsten) explodes with about 5 kT of energy (with the 9 km/s reentry velocity)
railguns are a decent technical experiment, but modern materials have serious issues with the barrels getting worn, specifically, they're a one-shot basis, and that's gonna be their biggest issue. ramping up power is secondary. naval bombardment is the most likely candidate, but won't be used too much until accuracy is better than "smart" munitions
antimatter is a ♥♥♥♥ waiting to happen
any logistic distribution requires some kind of storage facility
storing more than a few atoms of antimatter anywhere at once is going to cause a disaster at some point
distributing it to individual soldiers is a terrible idea (tactical nukes never worked out, imagine tactical antimatter), and even an artillery-scale system wouldn't work well. the investment of time and energy required would only make it worth using as a massive-scale utter annihilation weapon
rditto, you seem to not understand the energy scales involved here
modern armor-piercing systems do not use "explosives" per se to penetrate anything; they use explosives to force copper at massive speeds into a target
a railgun can completely forgo the explosives because
the actual round will have more than enough energy to penetrate ANY target that isn't meters thick. a few inches of steel against a moderately sized railgun (at current, relatively low power levels) is a comical sight. the projectile will actually ignite the steel with the sheer amount of energy imparted. killing a tank with a railgun is a simple matter of hitting it
killing a person with a railgun is a simple matter of proximity
I can almost guarantee you that more energy would be released inside a tank when a railgun projectile hits it then if you threw a hand grenade inside it
on modern AA systems:
things like the Patriot are really given a bad rap in popular culture
picture taking a .22 revolver, and then hitting a .50 caliber slug in mid-flight without knowing where it's going to come from
now multiply the speed by three times and make it so you have to hit a particular PART of the .50 round
AA "guns" (or CIWS, technically) are typically massive bullet spammers designed to put a literal wall of lead between the point defended and the projectile entering. be that a plane, missile, or even
mortar rounds, the technology is there to do point defense using nothing more than large, fast, bullets
also, railguns have no use for AA
the setup time involved is less than economical, even with "scattering" rounds
how many times do you see planes attacking in a close enough formation to be hit by the spread that would have to be tight enough to ensure hitting the actual target
hell, in the '50s they tried to make nuclear AA missiles
again, just because we have a "gamechanging" technology doesn't mean that we have to use it for
everythingmissiles revolutionized AA, but railguns are a step backward; they're just higher velocity guns
oh man rawtoast
"Look up the numbers on the surface area required for 100% solar energy and tell me it's more efficient."
look up the numbers on the efficiency of current photovoltaic panels that convert only visible light and a smidgen of infrared
then compare that to the per-second energy production of the sun across the entire EM spectrum (I am pretty sure it's something like enough to power the entire US for a couple thousand years)
rawtoast, would you be happy in a simulated world with "graphics" no better than crysis? what if our hypothetical future cousins decide to model
an entire universe, in realtime. the energy requirements would be tremendous, but every person in the world could have access to the ultimate escapism.
what if computer modelling entirely surpasses real world experimentation? what happens when we hit the technological singularity (look it up)? power requirements will spike, guaranteed