Lasers are probably the most misunderstood technological innovation in the modern world. Laser is an acronym standing for Light Amplification by the Stimulated Emission of Radiation. A firing chamber, filled with a particular substance, is exposed to energy. This energy excites the molecules of the substance in question. Without getting into too much chemical detail, the electrons bound to the nuclear cores by strong nuclear force are agitated by said energy and leap free. Channeled as they are by the shape of the emission chamber, these unusually intense beams of light shoot forth.

1. Lasers produce a sound on firing; a crackling popping sound, but it only lasts a few seconds. If the beam is perpetuated beyond that, it is silent. This is caused by the ionization of air molecules along the beam's path, and once the beam is established the air is no longer in its way, and no longer being ionized. Also note that this sound is only produced by extremely large and powerful lasers, such as those used experimentally by the U.S. weapons research people (which is, one wishes to note, roughly the size of a small car).
2. Lasers sometimes produce visible light and sometimes they don't. Many lasers, usually including the more powerful ones with noticeable damage dealing potential, are tuned to produce IR light and thus cannot be seen by the unaided eye. Again, for a brief fraction of a second as the beam is activated, any powerful laser will make itself known by a sparkling line along its path of flight (caused by photons emitted as electrons on the ionized air molecuels are released along its path of firing. It is really quite pretty, I have a picture of a large laser producing them).
3. The light and heat of a laser's firing are secondary. Contrary to popular perception, lasers don't burn, scald or fry their targets. Damage is inflicted by the wave of submolecular particles pushed ahead of the beam. (BTW, if you don't think that effect is enough to burn a hole through three inches of steel, go talk to a Hiroshima survivor about ionizing radiation.) Since it is these particles which produce the damage, mirrored or highly reflective surfaces (like our friend GB) don't do squat. You can hold a mirror up to a highly powered laser; the light beam bounces off, and then the laser sears a nice hole in the mirror.
4. Due to the source of the damage, lasers don't burn nice neat holes, like they do on Andromeda Strain. They produce large holes, ionizing great chunks of their targets and inflicting massive cellular damage on living targets due to a) secondary production of radiation and b)scattered radiation from the primary source. If a powerful laser hit you in the thigh, it would burn a deep hole, and your entire leg would go numb as most of the nerve cells died.
5. As I have said before, Lasers will most likely not ever be a practical military weapon anyway; they are too delicate, expensive, and power-hungry. To head off argument, this statement does not deal simply with current lasers, but with any laser weapon in the foreseeable future. With enough time and technological effort, lasers could possibly be made economical, but they never will be because other weapons are more effective with less hassle.

1. Plasma maintains a temperature of 15 million degrees celcius or so. Imagine a blob of matter at that temperature hitting something like the U.S.S. Iowa. At that energy level, armour plate explosively vaporizes in a fraction of a second. Ergo, unless you can produce a forcefield defense, you're dead.
2. Plasma is managed, contained and fired magnetically. This allows much greater accuracy than lasers.
3. The Plasma never actually touches the weapon's components. The U.S. M-1A2 Abrams has a very expensive computer to keep track of barrel droop, a phenomenon produced by the fact that you are detonating explosives inside of it and that causes barrel wear and heat deformation. Plasma is magnetically constricted, and never touches the working parts. This means dramatically reduced maintentance, repair costs, and much higher ability to survive in the field. If you don't recognize the value of this, you don't know much about the military.
4. Plasma is multi environmental. Lasers don't work well underwater, due to diffraction, and they have problems with particulate atmospheres (sandstorm, snow, rain, smoke, etc). If you install a laser in a tank, and then tell the tank crew that they can only shoot back if the weather is nice, you'll have a revolt on your hands. (Yes, I know, with enough power supplied to the laser, this can be overcome. I offer it up as a further point of its limitations, that you would indeed have to enhance the power requirements to make up for this.) Plasma can be used with equal efficiency in space, in a snowstorm, underwater, anywhere.
5. Plasma can be made from anything. You can have a big tank filled with hydrogen, which would be completely nonreactive if it is hit by enemy fire. Modern weapons have to worry about their ammunition touching off, but Plasma weapons don't.

Solid Projectile Weapons, which we all know and love, will most likely survive relatively unchanged, with the addition of magnetic firing. Rail guns, the perrennial favourite of the Rifts Borg, are a viable weapon system and again have been experimented with by the U.S. military. Magnetically accellerating a solid projectile is just as good as firing them conventionally save for point number 3 under Plasma (no explosion means no barrel wear), and that they no longer need shell casings. The big bronze shell casings you see on tank rounds contains the firing propellant. These things are a pain in the neck because all the propellant takes up room inside the tank that could be used for more projectiles (and in any tank, space is at a premium), and because you need to get rid of the spent casings, which is not easy in an NBC warfare environment. (NBC: Nuclear, Biological, and Chemical. The tank would have to maintain an environmental seal against the external environment.) This also pertains to personal arms; a weapon which does not have to eject shell casings, and does not have to store solid propellant, can fit more rounds per magazine and has one less external opening to clog with mud, grime and filth through which soldiers have waded since time immemmorial.

Further, the sections in Triax & the N.G.R. concerning Depleted Uranium rounds are interesting. Uranium is a large and chemically unstable element which moves toward a stable atomic configuration by atomic decay, producing radiation. Depleted Uranium is a stable isotope used by military forces the world over. Depleted Uranium is not even slightly radioactive, as Mr. Siembieda quite correctly describes, but is used quite frequently (in the GAU-8A cannon of the A-10A Thunderbolt II, for example) due to the fact that it is composed of extremely large molecules and is harder than diamond. The use of Depleted Uranium rounds have been long familiar in the modern world's armies, and as the production of synthetic materials advances, one can only conclude that similar materials will be used in the future.


STEALTH TECHNOLOGY

Time to get something off my chest. This falls into the general category of flagrant violation of the laws of physics, and while it is in a game and so really not very important, I wanted to point it out. Rifts Undersea, Pg. 124, bottom left hand corner. The Stealth version of the S-16 is different in that it is painted black, and therefore is radar evasive.

Stealth technology works because of its construction. The reason the F-117 looks so bizarre is because it has to look that way to be Stealth. No aircraft shaped like the S-16 so beautifully illustrated by Kevin Long could ever be radar evasive.

Radar is another acronym: Radio Assisted Detection And Ranging. It operates by releasing radio waves, a high frequency radiation, and waiting for them to return. Based on the returning wave's direction and frequency, the radar can determine the object's altitude and heading. Stealth aircraft avoid this by their shape, and their materials.

Shape: Radar returns are most obvious when reflecting from a perpendicular structure. F-117's don't have any. Every place where it would otherwise have a 90 degree angle, it instead has a slope or a smooth surface. From almost any angle, the radar wave will deflect off.

Materials: the F-117 is built of radar absorbent materials. On a microscopic level, its surfacing looks like a honeycomb; radio waves which do impact cleanly bounce around in them to the point that, upon reflection, they are dramatically weakened.

No system can produce a truly radar invisible vehicle; the goal is to be radar evasive, to trick the radar and its operator to think you're a shadow, a quirk of software, anything but a fighter. In the final analysis, true Stealth is almost too difficult to be useful; the F-117 has a pathetic ordnance load, extremely short radius of operation, and poor maneuverability. The new F-22 is a much more capable aircraft, because it is less dedicated to the Stealth approach; whileas the F-117 is all but invisible, the F-22 is only sneaky.

I just wanted to point this out, since I have seen so many movies, TV shows, games, etc etc etc where a pilot flips a switch and activates stealth, or turns on the Stealth mode. A Stealth craft is just as stealthy parked on the tarmac as it is sneaking through enemy airspace, and it is all entirely due to its shape and construction.