Widdekind

http://www.sciencedaily.com/releases/2013/07/130705101626.htm http://www.sciencedaily.com/releases/2013/07/130705102031.htm are those authors saying, that "radio bursters" are somehow similar to (long) "gamma-ray bursters" ? i.e. that the two are somehow part of the same spectrum of space phenomena ?

event A = (0 AU, 0 min.) = emission of photon from sun event B = (1 AU, 0 min.) = earth experience of "simultaneous" to emission at sun, but back on earth event C = (1 AU, 8 min.) = earth receipt of solar photon from B ----> C = 8 minutes of space-time interval = 8 minutes of "proper" time to earthlings... from A ----> C = 0 minutes of space-time interval = 0 "proper" time to photon... So, seemingly, photons in flight do not age, hence do not change, etc.... photons "emerge" into reality when generated... photons then "are"... until they are absorbed, when their quantum wave-functions "collapse", depositing their energy & momentum into some other quantum object... when the photons "are not"... but whilst they "are", they are timeless, changeless, "frozen koosh-balls of EM field vectors", whizzing at light-speed thru space-and-time... never-the-less, a "photon reference frame" is not well-defined -- even though the space-time interval = 0 all along their photonic flight path is well definedly 0, so that their "proper time" elapsed "must" be well definedly zero

[math] \kappa \propto k_B T \sigma = k_B T \frac{J}{E}[/math] [math] = k_B T \frac{q_e^2 n_e v_e}{q_e E}[/math] [math] = q_e^2 \times k_B T \frac{n_e v_e}{\left( \frac{m_e v_e}{\tau} \right)}[/math] [math] = q_e^2 \times \left( k_B T \right) \frac{n_e}{m_e} \times \tau[/math] so, according to the Wikipedia page provided per PP, the mean-free-collision-time is invariant, for a given metallic material... as more electric field is applied, the electrons are accelerated to higher drift velocities... but they collide, with lattice ions (?), at the same (average) rate, of (on average) once per [math]\tau[/math] seconds... so, i guess, that when you consider converting the calculation, over to thermal energy conduction... then you have to re-insert an electron velocity, which would be the "Fermi velocity", of conduction electrons, at the "top" of the "Fermi sea": [math]\phi_Q = \kappa \nabla T \propto \left( k_B T \right) \frac{n_e}{m_e} \times \tau \times \nabla \left( k_B T \right) [/math] [math] = \left( k_B T \right) \frac{n_e v_F}{m_e v_F^2} \times \delta \times \nabla \left( k_B T \right) [/math] [math] \approx \frac{k_B T}{E_F} \times n_e v_F \times \Delta E [/math] which states, that the heat flux (Watts per square meter) is proportional to the flux of conduction electrons (# per area per time), multiplied by the extra thermal energy those electrons acquire from one mean-free-collision-distance up the thermal gradient, multiplied by a "Fermi fraction" [math]\left( \frac{k_B T}{E_F} \right) [/math], which represents the fraction of electrons, residing in the thermal "froth" on the "top" of the "Fermi sea", according to Fermi-Dirac statistics, which demand, that the width, in energy, of the transition region, from fully occupied states near zero momentum, to fully unoccupied states at infinite momentum, has an energy width proportional to the thermal energy. Low energy electrons are "locked in" to their states, by the Pauli exclusion principle, and the completely-filled nature of nearby momentum states, into which they would "want" to scatter... only electrons with energy near the Fermi energy, in the "froth" on the "Fermi sea", have available states (of comparable energy) to scatter into... only those electrons in the "Fermi froth" can scatter, off from higher energy ions in the hot zone, to lower energy ions in the cold zone... only they can contribute to the (electronic) thermal conductivity... so, of all available conduction electrons per unit volume [math]\left( n_e \right)[/math], only a fraction can contribute [math]\left( n_e \times \frac{k_B T}{E_F} \right)[/math]... is that the correct interpretation, of the Wikipedia page provided per PP ? http://hyperphysics.phy-astr.gsu.edu/hbase/solids/fermi.html

[math] \kappa \propto k_B T \sigma = k_B T \frac{J}{E}[/math] [math] = k_B T \frac{q_e^2 n_e v_e}{q_e E}[/math] [math] = q_e^2 \times k_B T \frac{n_e v_e}{\frac{m_e v_e}{\tau}}[/math] [math] = q_e^2 \times k_B T \frac{n_e v_e}{m_e v_e^2} \times \delta[/math] relating the mean-free-collision-time [math]\left( \tau \right)[/math] to the mean-free-collision-distance [math]\left( \delta \right)[/math]. Now, the actual measured heat flow flux (Watts per square meter) is the product of the thermal conductivity, multiplied by the actual temperature gradient: [math] \vec{\phi_Q} = \kappa \nabla T \propto q_e^2 \times k_B T \frac{n_e v_e}{m_e v_e^2} \times \delta \nabla \left( k_B T \right)[/math] [math] = q_e^2 \frac{k_B T}{m_e v_e^2} n_e v_e \Delta E[/math] where [math]\Delta E \equiv \delta \nabla \left( k_B T \right)[/math] is the extra energy (Joules) electrons acquire, from one mean-free-collision-distance up the temperature gradient, i.e. from the hotter region, which energy the electrons then transport, one mean-free-collision-distance down the temperature gradient, i.e. to the colder region. Then, [math]n_e v_e \Delta E[/math] is a heat flux (Watts per square meter), transported by the conduction electrons. But, that electron velocity [math]\left( v_e \right)[/math] is the drift velocity, of electrons, through the lattice of nuclei, under the influence, of an applied electric field; the former is proportional to the latter; w/ no applied electric field, no drift velocity occurs. Yet, if [math]v_e \longrightarrow 0[/math] in the above equation, then the equation breaks down. What weirdness has happened here ? i have made no mathematical mistakes, doing the derivation, yes ?

what tokamak has broken even ? so, D-T reactions do not emit gamma rays, all the energy is released, as KE, of the He-4 and of the free space neutron ? i guess only astrophysical "natural" fusion often generates gamma-rays how do you capture that kinetic energy ?

there is zero space-time interval, between any two events, on a photon's trajectory e.g. "source to destination" as one of many examples for the photon, that space-time interval (invariant for everybody, invariantly zero) IS the proper time experienced by the photon, whose world-line threads through those events i.e. photons experience zero proper time, they are "frozen globs of EM field" everybody else perceives change, b/c the photon is not there... then its "front" is there... then its "back" is there... then it is not there... so everybody else perceives EM field oscillating to-and-fro', forth-and-back, and says the photons are "changing"... no, the photons are "frozen"... what is changing, is their position RELATIVE to the observer... that change of relative position, gives the observer a changing vantage point of observation, giving the impression of change... somewhat similar to feeling your way along a car, first you feel the bumper, then the hood, then the windshield, etc. you perceive change, as the car rolls past your outstretched hand... but the car is "frozen" in a fixed shape

for electrically conductive metals, the thermal conductivity ( Watts per area per temperature gradient ) seems to be two orders of magnitude more, than one would expect, from heat capacity, propagating at the sound speed: [math] thermal conductivity \gg C_m \rho L^3 L L^{-2} \frac{C_S}{L}[/math] where L = lattice length, typically several hundred picometers. So, i conclude, that heat flows far faster, than the nuclei are jostling back and forth, fro' and to. Q: do conduction-band electrons play an important part in thermal conductivity (in electrically conductive metals) ? do nuclei, in the hotter zones, impart energy to conduction electrons, which then zip thru the lattice, until they collide with another nucleus, far far away, in the colder zones ? i.e. is thermal conductivity, the transfer of thermal heat energy, from hotter nuclei, to colder nuclei, via mediating conduction electrons: hot nucleus ----> electron ----> cold nucleus ? If so, then are conduction electrons propagating hundreds of times more quickly, than the sound speed, of most metals, i.e. hundreds of km / sec <-----> eV scale energies ? eV scale energies seems plausible, for conduction electrons, near the Fermi energy, of their "host" lattice material.

imagine a double-slit experiment w/o the slit... i.e. a blob-like electron wave-function is projected towards a detector... imagine that the detector absorbs 90% of incident electrons, and reflects 10%... you mathematically model the physics on a computer, with a fully 3D computer simulation... the blob-like electron wave-function is some 3D lego-like blocky cellularized shape, occupying some swath of the 3D grid "voxel" cells... the discretized wave-function propagates towards the detector, time-step by time-step... eventually, the "front" of the wave-function reaches the detector... the first such grid "voxel" cell, at the detector, to be (partially) filled with (some) wave-function, has some percent of the particle present, [math]P \equiv \Psi^{*} \Psi dV \ll 1[/math] embodying some amount of momentum, [math]\vec{p} \equiv \Psi^{*} \hat{p} \Psi dV[/math] Q: is the following the appropriate procedure ?? probability the particle is absorbed = P x 90% << 1 => wave-function collapse, into classical particle-like state, absorbed into that spot on detector, which absorbs momentum [math]\vec{p}[/math] probability the particle is reflected = P x 10% << 1 => wave-function collapse, into classical particle-like state, reflected from that spot on detector, which reflects momentum [math]\vec{p}[/math] else, with probability 1-P = 1 - 0.9P - 0.1P, no collapse occurs, no classicality occurs, that piece of the blob of the wave-function merely reflects from that spot, still as a quantum wave, as if that spot of the detector was simply some infinite potential barrier ? then, time-step by time-step, as more and more of the discretized wave-function impacts the detector, you repeat this procedure (??), each "voxel" grid cell's worth of wave-function, gets its chance, to usher in the absorption of the whole particle (90% Pi), to usher in the reflection of the whole particle (10% Pi), or to merely remain as wave-function, reflecting from the spot, as a quantum wave (1-Pi) ? hypothetically, the whole discretized wave-function could fail to absorb classically, and fail also to reflect classically, and so merely reflect as a quantum wave... in which scenario, the blob-like blocky discretized wave-function would wind up evolving / propagating away from the detector, back towards where it originated... ??

the space-time interval, between all events, on a photon's trajectory, dx2 - dt2 = 0 for an observer moving between those events, i.e. a photon, that space-time interval = proper time elapsed (to the photon) = 0 sloppily stated, photons are "frozen bundles of EM field vectors", in a strained analogy, "frozen koosh-balls" (for want of worthier words) as they propagate past you, their crests-and-troughs propagate past you, so you perceive a changing fluctuating oscillating EM field. Said fluctuating field is interpreted, as the "frequency" of the photon. However, if you could "surf the crest or trough" of some photon, i.e. "hop on it at the speed of light", then the wave-train wouldn't be whizzing & propagating past you, and so you'd notice no frequency at all... in terms of Relativity, if you accelerate parallel to the path of propagation of some photon, that photon red-shifts to you (photons flying the opposite direction, towards you, would be blue-shifted). So, if you could accelerate all the way to light-speed, then parallel-propagating photons would red-shift all the way to zero frequency, and so you'd indeed notice no changing EM fields fluctuating, no frequency, no elapsed proper time, you'd perceive the photons as "frozen koosh-balls of EM field". photons, propagating along light-like trajectories, all along which the space-time interval is zero, experience zero proper time, yes ?? Is that not basic Relativity ? If so, then photons perceive every event they ever encounter, all along their entire path of propagation, as instantaneously co-occurring, at the same place (the photon's location), at the same proper time (one instant). yes ?

so, then, they experience exactly zero proper time, all along their trajectories ? photons are... and then are not... but they never experience any passage of proper time ?

photons don't dis-obey the Minkowski metric, yes ? so, there is still no s-t interval, between any light-like-separated events, on a photon's trajectory... and so the photon "must" experience no proper time ?? so, you're saying, that the "v=C" frame would be a preferred reference frame ? hypothetically, photons could carry some minuscule amount of mass << neutrinos

i follow your first sentence... why would a photon frame = "absolute preferred frame" ? is there a possibility, that photons propagate at some smidgeon less than light-speed, i.e. there is an actual ontological "C = 3.01e8 m/s", and photons fly at "c = 3.00e8 m/s", or some such ??

if photons experience no proper time, then from a photon's perspective, every event on their flight path = simultaneous at the same moment of time, and also co-occurring at the same place (= location of photon) so, from the photon's POV, every possible interaction, w/ space plasma, space dust, or some human HST; near or far, from its location of origination; are all perceived as simultaneous in space & time, a little like a "lifetime passing before one's eyes" sort of experience. so, the from the photon's POV, it emerges into existence; is immediately presented with a panoply of options for interaction, similar to a multi-slit experiment ("which door to take"); and immediately "chooses" some selected option to interact with; and immediately its wave-function "collapses" into that interaction, with the "ignoring" of all the others. meanwhile, that "instantaneous selection" of the photon, appears to play out, over millions to billions of years, of cosmic eons of time, from "everybody else's POV" (i.e. observers moving slowly w.r.t. the cosmic background radiation "rest" reference lab frame) so, from some strange apparently paradoxical perspective, the photon is "fore-ordained" to some selected interaction, which it perceived as simultaneous w/ all others, and simply propagates thru space, to that interaction option ("exciting an electron in some piece of space dust, or some other space plasma ion"), where its wave-function dutifully "collapses". The photon "knew the entire time" what potential option for interaction its wave-function "would" eventually collapse into... that "instantaneous choosing" appears to play out, over vast cosmic distances, and times, from "everybody else's" POV if you drew to space-time diagrams, the first for the photon; and the second for "everybody else"... and if you drew a "string of pearls" along the trajectory of the photon, in the second s-t diagram, each "pearl" representing an event along the path of the photon (representing interactions with space plasma, space dust, human telescopes, etc.)... then that entire "string of pearls" would map to the origin, in the photon's re-ference-frame... so that all of those potential interactions, would be perceived, as simultaneous & overlapping in time & space thus, the photon "poofs into existence", is immediately presented with a smorgasbord of potential options for interaction, picks one, and "poofs out of existence", in its own frame... but that appears to play out over vast cosmic space distances & eons of time, in others' frames... the photon "sees" all potential possible places-and-times of eventful interaction, to co-exist (spatially) and co-occur (temporally), as a single "multi-slit experiment"; the photon "selects some slit", and "goes thru that door"... but everybody else's perception of space-time, is so warped w.r.t. the photon, that what "seems" to the photon to be a simultaneous multi-slit experiment, appears to play out over enormous spans of space and eons of time

[math]\Delta x \; \Delta p \ge \hbar[/math] [math]\Delta t \; \Delta E \ge \hbar[/math] what about [math]\Delta \theta_{\perp} \; \Delta L \ge \hbar[/math] ? i.e. a wave-function confined in angle (about some axis), would be required to possess a statistical spread, in its angular momentum, about said same axis ?

1) has any tokamak worked ? 2) fusion is reversible... if protons fuse into helium, emitting gamma-rays... then those gamma-rays could split apart helium, into constituent proton pieces parts... yes ?

very vaguely, about a billionth of an earth-mass of AM => "Aldebaran" such seemed readily rememberable, "mass ratio (AM:M) ~ radius ratio (RS:R)", and seemingly works well(-est) for "classical" or "sub-relativistic" ball-shaped bodies

so, bigger galaxies (tend to) generate bigger (& brighter) stars, so increasing their ratio of Light-per-Mass, et vice versa (?)

no -- the amount of anti-matter required to obliterate a gravity-bound ball-shaped world/planet

not w/o gravity the Strong interaction fuses He in stars... not w/o gravity (ultimately) providing the pressure / temperature ------------------- how would a fusion furnace "catch" the energy released? Our's sun's central temperature ~1KeV; the gamma-ray photons released are ~MeV, x1000 greater. The ratio of protons to helium-nuclei in the sun's center is (a little less than) 14:1. So, after a gamma-ray photon is generated, probabilities imply, that the photon will "rattle around through, amongst, off" of numerous other protons, dispersing its energy amongst them, until they all equilibrate to ~1KeV. Of course, if the first thing the gamma-ray photon collided into, was another helium-nucleus, then the latter would be un-fused by the former, absorbing the gamma-ray and splitting back into pieces / parts. Since, however, the sun's center is only "tainted / doped" with helium, such inverse-fusions are surely rather rare. In an artificial energy-by-fusion-generator, what would diffuse & disperse the gamma-ray photons, from fusions, into lower frequencies / longer wavelengths? All the sun's plasma, surrounding its center, acts as a natural frequency converter, reducing photon energies, down to more manageable levels. In a lab version, what would absorb the energy? Would some sort of lead-like lining have nuclei, with tightly-bound electrons, with ~MeV binding energies / resonances ? The binding-energy, of the lowest-lying 1S orbitals, scales as Z squared; so for elements near A=100 (e.g. Pb, U), that would be about 1MeV.

L = luminosity = energy per time P = "luminosity density" = energy per time per volume standardized definitions would be better; if "P" = "power" (J / s), then "P" = "L" = energy per time... for want of worthier symbols, i stuck w/ the "P" from the link, and tossed in "L" from astronomy conceptually, the former is the spatial density of the latter (Power per volume vs. Power total) -------------------------------------------------------------------------- Hypothetically, if fusion could occur, in diffuse space plasmas; then those plasmas would accumulate the products of fusion, such as D,T. So, those plasmas would not necessarily be "pristine" / "primordial", but would have undergone some fusion phenomena. In some sense, the whole of the universe, is like the inside, of a vast cosmic-scale star, some super-diffuse super-O/B/A super-blue giant. D/T/He3/He4 could have been accumulating therein, for the lifetime of the universe. Observed abundances of such intermediate fusion nuclei need not indicate pristine/primordial/unprocessed abundances, from the Big Bang.

?? Gravity compacts matter, to nuclear densities, in NS; and to some next-more-exotic state, in BH. Thus, the "cumulative" nature of gravity => that enough mass can exert forces, comparable to forces exerted in Strong (& Weak) nuclear interactions. That's all i was saying. (Yes, i understand, the Weak force converts electrons into neutrinos, and protons into neutrons (u quark -> d quark), during "neutronization" of matter. That is correct. And, "neutronization" only naturally occurs, in compact objects, because gravity supplies the forces / energies to "incentivize" the reaction. Gravity is cumulative; given enough matter, gravity can in principle be the strongest force of all.) EM forces decrease with distance, away from what-so-ever generates those forces. So, even if you generate a "strong" EM field, from some apparatus "here"; then that field will be weak "there". So, trying to generate magnetic fields, from the walls of a tokamak, to squeeze plasma well away from those walls, seems impossible in principle. Even if you could generate some EM field, which was strong enough, within the generating apparatus, to overcome ion-ion repulsion, and induce fusion within the material of the apparatus itself; the field would be too weak to do so, outside of & far from the same. But, the "fusor" could perhaps benefit, from what i'm (trying to) say. Why couldn't you not only charge the central grid, to -80KV (say); but also run current thru the wires, to generate magnetic fields, which would repel the plasma, keeping the plasma away from the grid material? If magnetic fields can serve as shielding, for space stations / space craft vs. plasma in solar wind / CRs / ISM / IGM, then they could do so, for the fusor's central grid, which is immersed in plasma. in my swift scanning of the wikipedia article, the same seemed to differentiate the "fusor" from magnetic-confinement methods, implying magnetic fields are not used, although not explicitly saying so. You could create a spherical grid, composed of (say) triangular sections of wire -- 'twould look like a geodesic dome -- each section of which was a current loop, producing a solenoidal field, funneling plasma thru the middle, away from the wires. By alternating the sense of circulation of current, in adjacent loops -- like a checkerboard in pattern -- you could create a geodesic-dome-ish grid, of a checkerboard-like patchwork of "left-handed" & "right-handed" current loops, producing magnetic fields alternately going "in" & "out" of the sphere, such that all the currents w/in the wires would add, and none would wind up canceling out the currents of adjacent sections.

fusor's seem potentially amazing. Perhaps you could inject a certain quantity of fuel, quickly, and then ramp up the voltage, on the outer grid, to "wall off" the positively-charged plasma within the "fusion kettle" of the fusor? And, perhaps the inner grid could be built, intended to absorb all of that fuel. So, you'd inject a known quantity of fuel, which would translate into a known energy, which would be absorbed into the inner grid. After several minutes, when the fusions finished, the inner grid could be removed, and similar to a hot "cooking rock" plunged into some water to make steam. Or, perhaps the inner grid could be made of hollow fibers, carrying water through them, to whisk away the heat absorbed by bombarding ions. otherwise, i only meant, that gravity can ultimately become stronger (in magnitude) than even the strong force, in BHs & NSs. Even in NSs, gravity crunches matter down into nuclear densities, showing that the magnitude of the force of gravity is comparable to the SF, in such objects.

If hot gaseous galactic halo coronae contain multi-million-Kelvin plasma, then why wouldn't such gas undergo fusion, and thereby generate gamma-rays ? Prof. Lawson claims: [math]P \approx 1.4 \times 10^{-34} n^2 T^{1/2} \frac{watts}{cm^3}[/math] [math]L = P V \approx \frac{P V^2 m_H^2}{V m_H^2} watts \approx \frac{ 1.4 \times 10^{-34} M^2 T^{1/2} }{ \frac{4 \pi}{3} R^3 m_H^2 } watts [/math] For galaxy clusters, the estimated fusion luminosity, of the cluster halo gas, could be considerable: [math]\approx 4 \times 10^{11} \left( \frac{ \left( \frac{M}{100 T M_{\odot}} \right)^2 \left( \frac{T}{100 MK}\right)^{1/2} }{ \left( \frac{R}{Mpc} \right)^3 }\right) L_{\odot} [/math] [math]\approx 40 \left( \frac{ \left( \frac{M}{100 T M_{\odot}} \right)^2 \left( \frac{T}{100 MK}\right)^{1/2} }{ \left( \frac{R}{Mpc} \right)^3 }\right) L_{*} [/math] where [math]L_{*} \equiv 10^{11} L_{\odot}[/math] is a characteristic (big, spiral) galaxy luminosity. Prof. Sarazin seems to say, that the total x-ray luminosity, of galaxy cluster halo gas [math]\approx 10^{44.5} \frac{erg}{s} \approx L_{*}[/math]. So, this estimate, for fusion-generated luminosity, could account, for observed luminosities, or even exceed the same. Against this, because collisions in the IGM would be rare, perhaps inter-mediate fusion products (D,T,He-3) would decay back into H, before they re-collided, and fused into He-4 ? Were the fusion to occur, then the mass production rate, of He-4, in galaxy cluster coronae, would be: [math]L \times \frac{m_{He}}{4.23 \times 10^{-12} J} \approx \frac{4 GM_{\odot}}{Gyr}[/math] times all the factors in the parentheses. In the age of the universe (10 Gyr), that translates to [math]\approx 40 G M_{\odot}[/math], implying a metallicity of [math]\frac{4e10}{e14} = 4e-4[/math], which is negligible, and probably allot less than the errors in estimates of cluster halo gas metallicity. Q: does fusion occur, in gaseous galaxy (cluster) coronae ? more simply, our sun converts 10% of its mass to He-4, in 10Gyr. So, 4e11 L_sun ----> 10% x 4e11 M_sun / 10 Gyr = 4e9 M_sun / Gyr oops: L* = 1e10 L_sun

Positively-charged nucleons resist fusion, according to the EM force. Logically, to compress plasma, with EM force-fields, seems impossible -- the charged particles repel each other, at nanoscopic range; but they would be compressed, with EM force-field-generating equipment, at macroscopic distances away. Since EM force-fields decay with distance, a fusion reactor would have to generate enormous fields, macroscopically, to over-come the particles' repulsion, at "point-blank" nanoscopic ranges. Gravity in stars can over-come EM, b/c gravity is cumulative -- w/ enough mass, even the Strong Nuclear Force can be over-come, in relativistically compact objects. But, fighting EM (at nanoscopic range), with EM (at macroscopic distances away, w/ some experimental apparatus), seems futile. Perhaps EM-controlled "tokamak" fusion reactors, are intrinsically impossible (and tax-payers will never see return, on any investment) ?

please ponder & picture a checker-board pattern, and assign clockwise currents to white squares, and counter-clockwise currents to black squares. If all currents are individually each equal to I, then each square is enclosed, by a (squarely) circular current, of magnitude 2I. So, each square would be protected, by a solenoidal field; and the whole mesh-frame-work would also be protected, by solenoidal fields that "tesselate" (for want of worthier words). So, a honey-comb mesh-frame-work, resembling a radio-dish, could be hurled through space, and the whole frame-work would be protected from space plasma, which would be funneled & shunted through the mesh, around and away from the frame. Such a honeycomb could then cruise thru the cosmos, whilst also transmitting space-radio-signals. If they dish was accelerated to transluminal speeds, then perhaps relativistic beaming head-light effects, would amplify the angular gain of the beam ? Perhaps considerable energy would be stored, in the currents & EM field. If all of that energy were released, into an energy beam, a space-laser blast might result. If earth was the target, and the blast originated from ~90 AU (within our sun's heliopause), then the "spent" mesh craft would begin to burn up, plowing through the inter-planetary-medium, for ~12hours. The half-blasted earth would spin around, bringing the other hemisphere around to face an inbound burning meshy-wall of plasma, which would slam into the other half of earth. One such weapon system could perhaps dole out two hemispheres of damage. If equipped with an AI, and fired across inter-galactic distances, then such a speculative (Super-)smart (space-)bullet could cruise thru the IGM in cryogenic torpor, until on-board accelerometers detected descent, down into the other guy's galaxy's gravity-well. Then, within the other guy's galaxy, the (Super-)smart (space-)bullet would whir to life, and begin low-power transceiving against the target, perhaps ultimately increasing transmission energies, at closer cosmic range. In the end, at least according to the most realistic space war-games i know of, actual laser-fire would have to occur, at near-space-point-blank range, i.e. within the target's star system / astrosphere / astropause (so as also to minimize EM diffraction & reflection, at that plasma-y boundary).