Three Fathoms Observatory
Stewart Yeung








                                                                                                                                                                                               Studies of Physics







The Earth-size exoplanet just found in Alpha Centauri B is only 4.3 light-years away!
Being too close to the sun-like star, it is too hot to be within a human habitable zone. But what if this exoplanet has a friendlier companion, eligible to become the twin Earth?

Hitherto we have achieved the fastest speed of 1/18000 c for the spacecraft Voyager I, so it takes about 72,000 years to travel there. At this rate, astronauts departing Earth would have their children born in space on the way, for some 2000 generations, before the last families reach the destination to set up new settlements in the brave new world.

As technology advances further, the traveling time constraint will become less stringent. A spacecraft by nuclear pulse propulsion (using nuclear explosion, already within our technological grasp, for thrust) could reach a velocity comparable to c, and relativistic time dilation would make the voyage much shorter for the astronauts, who could then reach there within 100 years (while the people remaining on Earth experience more elapsed time). Instantaneous communication could be made with Earth using quantum teleportation (by bringing aboard a prepared quantum entanglement system with its counterpart remaining on Earth).

Home sapiens will then extend their choice of living not just among different countries or continents, but also between two different Earths.

Unfortunately, the required energy output for the nuclear pulse propulsion engine amounts to 100 times the total energy output of the entire world today. Hopefully, other more economic possibilities, such as antimatter rockets or laser-beamed propulsion, will eventually become within our grasp, too. But there are yet other uncertainties, including inter alia the risk of spacecraft erosion due to cumulative impacts of interstellar gas/dust/micrometeroids, health hazards of extensive radiation exposure, and unknown effects of prolonged near light speed travel on human life span. We could not even exclude the remote possibility of fatal encounter with hostile aliens, so vividly depicted in recent movies, such as Prometheus.

So the choice to live in a brave new world is surely unavailable within our lifetime. Our consolation just lies in the realm of our imagining the infinite possibility of being.