At the start of 2013, a research paper was submitted to the Astrophysical Journal and made public on arxiv.org about the discovery of 15 new planets, which add to the dozens of potentially habitable candidates out there. To travel to these planets in any meaningful time requires science to overcome the problem of the vast distances in the universe. Even the closest exoplanet found so far is four light years or 24 trillion miles away. Recent developments have NASA starting a laboratory called Eagleworks to develop interstellar warp drive technology. One idea they have is to create warp engine that enables faster-than-light travel. If this sounds all too Star Trek, it's because the proposed warp drives are directly influenced by the cult sci-fi series.
In December 2012, researchers submitted a paper on HAL, an open-access archive for published and un-published scientific papers, that describes a Natario warp drive that could reach Gliese 581 c, the first Earth-like planet found in a habitable zone (just over 20 light years, or over a hundred trillion miles away) in just a few months traveling at 200 times the speed of light. But, there're many impracticalities with theoretical warp drives. Take the precursor to the Natario drive, known as the Alcubierre warp drive. Astrophysics researchers from the University of Sydney, Australia, published a paper in Physical Review D in March 2012 about its catastrophic side effects.
The researchers conclude that not only would a spaceship require shields to protect its crew from dangerous particles moving towards them, but light particles or anything else that's picked up during the ship's journey would be deposited at its destination as high-energy particles. "Any people at the destination would be gamma-ray and high-energy-particle blasted into oblivion," say the researchers. Now, they plan to analyze this problem in more detail, which may involve parallel computing to simulate the warp physics in various space-time dimensions.
Like ants on rubber
The Alcubierre warp drive concept is capable of moving a spaceship, within an enclosed bubble of space-time - also known as a warp bubble - at any speed by expanding space-time behind and compressing space-time in front of the ship.
For those still contemplating how this idea could exist outside of sci-fi fantasy, Brendan McMonigal, a researcher from the gravitational astrophysics group at the University of Sydney, who is a co-author on the Physical Review D paper, gives a terrestrial analogy. "Think of ants walking on a sheet of rubber," says McMonigal. "The ants can only walk so fast but the underlying structure they exist on (the rubber) is stretchy, so we can drag a small piece of the rubber surface around much faster than the ants can walk."
From an observer's point of view an ant on this rubber surface will appear to be moving faster than normal, but from the ant's perspective it is still walking on the rubber at normal speed. This is where the analogy breaks down.
"This makes it seem that the universe should want to snap back after a warp drive has traveled somewhere, but this is not the case," says McMonigal.
Even if the Alcubierre warp drive were possible, there's still the matter of that explosion once you reach your destination.
Which journey has the biggest boom!
The Sydney-based researchers looked at three different scenarios: a warp bubble at a constant velocity, a warp bubble on a one-way trip, and a warp bubble on a round trip. From their calculations, a ship traveling at a constant faster-than-light - superluminal - velocity would have the largest destructive result on a destination, also destroying the ship in the process. "Realistically, the large build-up of energy in front of the ship would disrupt the warp bubble before it became too ridiculous," says McMonigal.
The most devastating journey when comparing a one-way trip with a round trip would be the round trip, with the ship's origin point receiving the most destructive blast of high-energy particles, picked up as a ship makes its way back from the destination to its origin.
These damaging particles are in a region in front of the warp bubble called P+. Space-time is compressed at such a high-rate that more space-time is compressed than light particles can travel through in the same time period, meaning that any particles caught here are trapped, while increasing in energy.
The burst or beam of explosive energy is a result of the ship decelerating from faster-than-light to sub-light speed, depositing a large number of high-energy particles in a very short space of time. This is similar to high-energy particles impacting our atmosphere, higher than anything created in the Large Hadron Collider at CERN, near Geneva, Switzerland.
The creator of the Alcubierre warp drive concept is Miguel Alcubierre, a theoretical physicist and director of the Nuclear Sciences Institute at the National Autonomous University of Mexico, who emailed William Shatner, aka Captain Kirk, telling him of Star Trek's inspiration on his warp drive idea. While Alcubierre no longer works on the warp drive problem, he does say the University of Sydney researchers have an interesting approach. "However it is based on a one-dimensional calculation. I think that in all probability when one considers three-dimensional space-time the effect will be much less severe," says Alcubierre.
Distributing the warp problem
"The next big question is what happens in three dimensions of space? What happens if the warp bubble turns? Doing a four-dimensional [4D] analysis - one of time and three of space - would allow us to answer these questions and how focused the energy released in front of the warp bubble is," says McMonigal. With computer clusters, McMonigal says they will be able to conduct a 4D analysis. If supercomputing or grid computing were used then calculation time would be saved as a large number of numerical integrations could be spread out.
However, Alcubierre does say that the warp drive concept he proposed in 1994 requires matter with negative energy - antigravity - which has currently not been seen in nature. Newer research in arXiv states that the Alcubierre drive becomes unstable when quantum effects are introduced, which the University of Sydney researchers chose to exclude from their calculations.
Fernando Loup, a physicist from Residencia de Estudantes Universitas, in Lisbon, Portugal, who wasn't involved in this research and has a personal email signature that's a tribute to Star Trek, says the Alcubierre warp drive is impossible. "Negative energy that distorts space-time is above and below the ship... there is nothing to protect the crew against particles of interstellar dust that would impact the ship in a real spaceflight," says Loup.
But, the warp drive dream is not dead. Loup says the Natario warp drive is a valid candidate for interstellar travel, providing a better theory for quantum gravity arises. "In this drive, the negative energy is in front of the ship, deflecting photons or particles of interstellar dust and protecting the crew, while keeping the negative energy density at low and affordable levels," says Loup.