Mankind has always been obsessed with space exploration. Just look at the immense popularity of science fiction novels as evidence. But with the exception of the Moon missions several decades ago the reality has not met the dream. It would still be decades away, but could current breakthroughs in technology one day allow us to explore worlds outside our solar system? Maybe, but there are still obstacles that stand in the way.
Warp Speed and the Alcubierre Drive -- Traveling Faster Than the Speed of Light
If it sounds like something out of a science fiction novel, that's because it is. Made famous by the Star Trek franchise, faster than light speed -- or warp speed as it is sometimes referred -- is nearly synonymous with interstellar travel.
The problem, of course, is that warp speeds are strictly prohibited by actual science, specifically by Einstein's laws of relativity. Or is it? In an effort to come to a singular theory that describes all of physics some have proposed that the speed of light may be variable. While these theories are not widely held (being dismissed for popular string theory models), they have been gaining some momentum as of late.
While the details of faster-than-light theories vary depending on whom you talk to and/or what specific theory you are dealing with, the basic principle is that the speed of light -- under the right conditions, or right moment in time -- may change. This has given some the idea that there might be a way to manipulate space in such a way as to allow someone (or something) to exceed the speed of light.
One example of such a theory, that will not violate relativity, involves actually allowing space to carry a craft at faster than light speeds. Imagine going surfing. The wave carries the surfer through the water. The surfer only has to maintain his balance and allow the wave to do the rest. Using this type of transport, known as the Alcubierre drive (named for the Mexican physicist Miguel Alcubierre who derived the physics that make this theory possible), the traveler would actually not be traveling at or even near the speed of light locally. Instead, the ship would be contained in a "warp bubble" as space itself space carries the bubble at light speed.
Even though the Alcubierre drive does not directly violate the laws of physics, it does have difficulties that may be impossible to overcome. There have been solutions suggested to some of these difficulties, such as certain energy violations (some models require more energy than is present in the entire Universe) being explained if various quantum physics principles are applied, but others lack any viable solution.
One such problem states that the only way such a transport system is possible if, like a train, it followed a pre-set path that had been laid ahead of time. To complicate matters, this "track" must also be laid at the speed of light. Essentially requiring that an Alcubierre drive would have to exist in order to create an Alcubierre drive. Since none currently exist, it does not seem possible that one could be created.
Another point of interest, the work of physicist Jose Natoro has conclusively shown that a consequence of this transport system is that light signals would not be able to be transmitted within the bubble. As a consequence astronauts would not be able to control the ship at all. So, even if such a drive could even be created, there would be nothing stopping it from crashing into a star, planet or nebula once it got going.
It appears that there is no viable solution for traveling at light speeds. So how could we get to distant stars? What if we just bring the stars closer to us? Sound like fiction? Well, the physics is very real.
Since it appears that any attempt to allow matter to travel at near light speeds is thwarted by pesky physics violations, what about simply bringing the destination to us? One consequence of general relativity is the theoretical existence of wormholes. Simply, a wormhole is a tunnel through space-time that connects two distant points in space.
There is no observational evidence that they exist, though this is not an empirical proof that they aren't out there. But, while wormholes do not readily violate any specific laws of physics, their existence is still very unlikely.
In order for a stable wormhole to exist it must be supported by some sort of exotic material with negative mass -- again, something we have never seen. Now, it is possible for wormholes to spontaneously pop into existence, but because there would be nothing to support them they would instantaneously collapse back in on themselves. So using conventional physics it does not appear that wormholes could be utilized.
But there is another type of wormhole that could arise in nature. A phenomenon known as an Einstein-Rosen bridge is essentially a wormhole that is created due to the immense warping of space time resulting from the effects of a black hole. Essentially as light falls into a black hole, specifically a Schwarzschild black hole, it would pass through a wormhole and escape out the other side from an object known as a white hole. A white hole is an object similar to that of a black hole but instead of sucking material in, it repels the material from the object. Light would be accelerated away from a white hole at, well, the speed of light at the light cylinder.
However, the same problems arise in Einstein-Rosen bridges as well. Due to the lack of negative mass particles the wormhole would collapse before light would ever be able to pass through it. Of course it would be impractical to even attempt to pass through the wormhole to begin with, as it would require falling into a black hole. And there is no way to survive such a trip.
It appears that there is no way, given our current understanding of physics that interstellar travel will be possible. But our understanding and grasp of technology is always changing. It wasn't so long ago that the thought of landing on the Moon was only a dream. Who knows what the future may hold?