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# How Long Would It Take to Get to the Nearest Exoplanet?

What are the prospects of actually traveling to a planet outside our solar system? Currently, the nearest exoplanet to Earth (alpha Centauri B b) is 4.24 light years away. Given the physical limit of the speed of light that means that the absolute minimum travel time (in the reference frame of the traveler) is 4.24 years, but achieving velocities close to that of light is way beyond our means. Velocities that are currently achievable are more like 20,000 miles per hour (or about 32,000 kilometers per hour) and at that speed it would take about 142,000 years to cover a distance of 4.24 light years. A velocity of 20,000 miles per hour is less than 0.003% of the speed of light.

Of course we can expect continued improvements in our capabilities to achieve higher speeds but an exponentially increasing amount of energy is required to approach the speed of light. At this time it is difficult to envisage how velocities of 99% of the speed of light or more will be achievable. If it is ever possible, the so-called “time dilation” effect of relativity comes into play, which leads to some interesting consequences. At 99% of the speed of light the frame of reference that the traveler left behind (home) and the parts of the rest of the Universe that had velocities relative to home that were much less than that of light, age approximately seven times slower than the traveler. Thus, if the traveler made a round trip that took 30 years (not stopping at the destination but just turning around), upon return, the traveler's home planet and everything on it will have aged by about 210 years. So although the time dilation is beneficial for the traveler, it is bad news for anyone back home who wants to know what happened. For exoplanets that are further away, millennia could pass before the home planet witnesses the return of the traveler, or receives signals from the traveler upon landing on the alien planet. Such experiments and programs would have to be planned for durations of hundreds to thousands of years across multiple human generations. This is truly mindboggling. Are we up to this task?

File under: Travel time to exoplanets; How long would it take to travel to the nearest planet to Earth and the solar system?