When can we apply FTL technology

Question

NASA is currently speculating about faster than light technology. When will we be able to apply said technology to our vessels?

"Warp Drives", "Hyperspace Drives", or any other term for Faster-than-light travel is at the level of speculation, with some facets edging into the realm of science. We are at the point where we know what we do know and know what we don’t, but do not know for sure if faster than light travel is possible.

The bad news is that the bulk of scientific knowledge that we have accumulated to date concludes that faster than light travel is impossible. This is an artifact of Einstein’s Special Theory of Relativity. Yes, there are some other perspectives; tachyons, wormholes, inflationary universe, spacetime warping, quantum paradoxes...ideas that are in credible scientific literature, but it is still too soon to know if such ideas are viable.

Ever since the sound barrier was broken, people have been asking: "Why can’t we break the light speed barrier too, what’s the big difference?" It is too soon to tell if the light barrier can be broken, but one thing is certain -- it’s a wholly different problem than breaking the sound barrier. The sound barrier was broken by an object that was made of matter, not sound. The atoms and molecules that make up matter are connected by electromagnetic fields, the same stuff that light is made of. In the case of the light speed barrier, the thing that’s trying to break the barrier is made up of the same stuff as the barrier itself. How can an object travel faster than that which links its atoms? Like we said, it’s a wholly different problem than breaking the sound barrier.

Source: http://www.nasa.gov/centers/glenn/technology/warp/warpstat_prt.htm

Please note: The form of FTL doesn't matter, aslong as it artificial, so no warpholes

Answer 1

Ok, there are so many problems with true FTL (as opposed to effective FTL, which is perfectly possible) that it's hard to think of a good starting point.

Perhaps the most logical point to start is the corrected speed~acceleration formula:

$v = \frac{at}{\sqrt{1+a^2t^2/c^2}}$

If math is not your forte, I'll spell it out for you. $v$ is velocity (I'll be a ++not-good person and also use the word 'speed' here - gasp), $a$ is your acceleration, $t$ is time and $c$ is the speed of light in a vacuum (~300,000,000 m/s).

At low speeds $<<c$ the formula approximates the classical $v=at$ that you may or may not have learnt in high school. At the other end, as either a or t tend towards infinity, v tends toward c. In English, it means that if you want to reach c (never mind exceed it), you have to have either infinite time or infinite acceleration.

So, if you literally want to take a rocket or something and push really, really hard, you'll only get arbitrarily close to c, the speed of light.

If math is not a problem, look up the Minkowski space-time tensor equations. Explained simply, it states that an object 'at rest' moves at lightspeed through time. The squares of the four 'coordinates' of the vector of speed add up to $c^2$. The faster your move, the more you move through the 3 spacelike dimensions (xyz) and the less through the timelke component (t). If you want to move faster than c (somehow) you would have to have a negative value for t (i.e go back through time). If you leave on Wednesday, people will see your ship whooshing towards its start location on Tuesday, so to speak. Weird stuff.

Now, before you pour ashes over your head, there are tricks and ways, if your civilization is cunning and powerful enough. Nature herself (or perhaps some powerful aliens caused this?) seems to have undergone something called cosmic inflation during which space expanded exponentially. Locally (as in, in our observable universe), this period lasted about $10^{-32}$ seconds, so it was pretty brief, but the space metric of our observable universe looks like it expanded much, much faster than light during this time. Keep in mind, this is a pretty strong theory, but there are alternatives, like various modified theories of gravity and such, sot it's not 100% set in stone. After all, we're talking about something in that happened in a fraction of the first femtosecond of our universe.

Regardless, if we assume that we'll be able to use some sort of space-metric distortion generator (look up Alcubierre Drives and their successors), we still have a bunch of issues. For instance, it looks like we need a giant amount (as in galaxies-worth, if not universes-worth) of negative mass. We don't know of any negative-mass objects, never mind such mind-boggling amounts of it. Refinements might bring the amount down drastically, but you'll still need exotic materials that might literally not exist/be possible in our universe.

Here I get outside of any claim to expertise, so take this with a dollop of salt. Perhaps you can use quantum-entanglement, which seems to be strongly non-local, to transfer all the quantum states of a massive object (say, your big goddamn heroes) across an arbitrarily large distance in spacetime. Each of their subatomic particles would have to interact with an entangled pair, collapsing the distant link in the entangled pair into a state that allows a complicated system at the distant receptor to recreate the interacting object (your BGDHs). Obviously, the infrastructure would have to already be in place at the distant location, and someone will have had to send the quantum information at normal (c-bounded) speed before any teleportation can take place. So, in English, it'd be like having portals, minus having to build your portals and send 'teleportation fuel' packets otherwise the teleports cannot work.

---

So, the ugly reality out of the way, when would something like this realistically be on humankind's to-do list? Well, if you want to accelerate clasically, our entire civilization's current power output could barely accelerate a 100 ton ship to 20% of the speed of light. We have no way of building and storing fuel for such a ship, no way of building and storing exotic matter (antimatter or the theoretical negative mass matter). Putting a time estimate on these factors is impossible with our current knowledge.

However, we can say that the ease of such travel or gargantuan engineering projects estimate humanity's power output under various scenarios.
Scenario 1: 3% growth -- This has been the upper end of growth for industrial civilizations at the technological frontier. At this rate, simply building the infrastructure to harness the levels of energy we need would take thousands of years.
Scenario 2: Hard limits to growth (we run out of coal and can't figure a good replacement) -- never.
Scenario 3: AI goes FOOM! Technological singularity makes future growth rates unpredictable. Comparing past growth phase transitions, a ten to hundredfold acceleration in growth rates appears possible. So it could take as little as a century, but no guarantee we'll have flesh humans around to see it.

A longer discussion of humanity's energy output is here.