There are several very real challenges that must be overcome when attempting to travel to another star, let alone another galaxy. However, with today’s technology and understanding of physics, we can envision potential ways to make interstellar travel, and even time travel, a reality, giving rise to the question of why other potential civilizations have not invented and made use of it yet. This is especially suspicious because considering the immensity of the universe, there are bound to be other intelligent civilizations, begging the famous question of the Fermi Paradox, “So where is everybody?” It’s answer would enable us to evolve into an interstellar or intergalactic species, while failing to do so could spell our demise.
Einstein’s theory of special relativity is where the cosmic speed limit (the speed of light) was first introduced. His theory also gives rise to the concept of time dilation, which states that time runs slower for those traveling extremely fast than it does for those on Earth, and that distances shrink when travelling at high speeds.1 So, when a spaceship is travelling close to the speed of light, time measured aboard runs slower than it would on clocks at rest. This can play an important role in interstellar travel, because it can allow travelers moving close to the cosmic speed limit to age slower than those on Earth. For example, if a spaceship left Earth in the year 2100 and made a roundtrip to the star Vega at 90% the speed of light, it would return in Earth year 2156, but only 24 years would have passed for the crew of the ship.2 Because of time dilation, journeys could be made to very distant places, and the crew would age very little. Due to this amazing effect, one could theoretically travel to the black hole at the center of the Milky Way Galaxy, 28,000 light years away, and only age 21 years, if travelling fast enough.2 At a high enough percentage of the speed of light, you would be able to reach Andromeda (2.5 million light years away), and return to Earth only 60 years older while 5 million years have passed on Earth.2 Clearly, time dilation is a real form of time travel to the future, assuming relativistic speeds are achievable. Therefore, it follows that the main obstacle for this method is reaching a percentage of the speed of light where time dilation becomes significant, requiring enormous amounts of energy.
Though obtaining the energy required for interstellar travel may seem like a far off goal, it will definitely be possible to travel great distances at great speeds in the near future with the science and technology that we have today. The first of these technologies are rockets that use nuclear energy as power. According to Albert Einstein’s equation, E=mc2, any small amount of mass can release a very large amount of energy. In fact, through the use of nuclear fission, only 0.6 grams of Uranium (less than the weight of an M&M) was sufficient to level Hiroshima during World War II.3 Nuclear fission makes use of the lost mass when an atomic nucleus splits into two. Nuclear fusion, on the other hand, involves two atomic nuclei fusing into one, releasing ten times the energy of fission. This process is the source of energy for the sun, occurring at its core. Nuclear fusion, if controlled, is a viable source of energy in the future. Just using the hydrogen present in the water coming out of one faucet could provide enough energy for the United States’ current needs, a staggering 2,850,000,000,000 joules/second.2
In order to conduct nuclear fusion, an environment similar to the center of the sun must be created, with the same temperatures and pressures. Gas must be converted into an highly ionized state known as plasma. Recently, MIT was able to use their Alcator C-Mod tokamak reactor’s extreme magnetic fields to create highest plasma pressures ever recorded4 In addition, a 7-story reactor in southern France, 800 times larger than MIT’s reactor, is set to be completed in 2025 and will have magnets that are each as heavy as a Boeing 747.5 Nuclear fusion could one day provide limitless energy for a spacecraft, accelerating it to relativistic speeds. Enormous scoops could be attached to the spacecraft to collect interstellar hydrogen gas throughout the journey, allowing travel to the distant corners of the galaxy.
Another technological development to facilitate interstellar travel is the EM drive, which is purported to be an electromagnetic thruster. This form of propulsion is highly controversial because it seemingly violates Newton’s 3rd law and thus the Law of Conservation of Momentum, which together say that for something to move in one direction, an equal and opposite force must be exerted in the opposite direction. The EM drive is thought to use electromagnetic waves as fuel and create thrust through microwaves within the engine cavity that push on the inside and cause the thruster to accelerate in the opposite direction.6 Simply put, the EM drive is able to go in one direction without a propellant or an opposite force pushing it. It has been tested multiple times, most notably by NASA’s Eagleworks Lab. The EM drive has repeatedly been measured to produce a small amount of thrust, making it difficult for scientists to dismiss the possibility that it works.7 The thrust seemingly cannot be explained by our current understanding of physics, but the Eagleworks Lab has nevertheless submitted its results to be published soon in the American Institute of Aeronautics and Astronautics’ Journal of Propulsion and Power. This Eagleworks experiment, if shown to be reproducible, would open up opportunities for researchers around the world to conduct further experimentation. In August, plans were announced to test the EM drive in space, which would be the most robust test of its efficacy to date. The EM drive could one day provide an essentially limitless supply of thrust on a spacecraft without the need for propellant, allowing it to constantly accelerate until it reached relativistic speeds.
These are only two examples of technologies that could make interstellar travel possible. In the next few decades, we can look forward to more innovative research that will push the boundaries of science and redefine interplanetary, interstellar, and intergalactic travel. If relativistic speeds are achieved, humans could travel thousands, if not millions of years into the future by aging much slower than the rate at which time would actually pass on Earth. So who says we can’t time travel? Certainly not science!
References
- Bennet, J. The Cosmic Perspective; Pearson: Boston, 2014.
- Bennett, J. Life In the Universe; Pearson: San Francisco, 2012.
- Glasstone, S. Dolan, P. The Effects of Nuclear Weapons, 3rd; United States Department of Defense and United States Department of Energy: 1977.
- Plasma Science and Fusion Center. https://www.psfc.mit.edu/research/magnetic-fusion-energy (accessed Nov. 11, 2016).
- ITER. https://www.iter.org/mach (accessed Nov. 05, 2016).
- Shawyer, R. New Scientist [Online] 2006, https://www.newscientist.com/data/images/ns/av/shawyertheory.pdf (accessed Nov. 10, 2016).
- Wang, B. NASA Emdrive experiments have force measurements while the device is in a hard vacuum. NextBigFuture, Feb. 07, 2015. http://www.nextbigfuture.com/2015/02/more-emdrive-experiment-information.html (accessed Nov 7, 2016).