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On the 6th of October, 1995, the world learned that we were not alone. No, the aliens hadn't shown up, but the first confirmed planet orbiting another star was found. 51 Pegasi b, orbiting a star roughly 50 light years away, changed how we saw the universe.
Because astronomers had been saying for centuries that there was no reason for other stars not to have their own family of planets. But until we found evidence, it was still just a hypothesis. But once we found that first planet, the flood gates opened. Observatories began confirming dozens, then hundreds of "exoplanets" orbiting other stars. Orbital observatories like TESS (Transiting Exoplanet Survey Satellite) are finding more every day. To date, we've confirmed nearly 4,000 planets orbiting other suns.
But there are a few problems for the science-fiction fan dreaming of colonies on strange new worlds. Of these 4,000 worlds, only a tiny fraction might be habitable. Many are super-Earth, much larger and more massive, which would indicate much higher gravity than Earth's 1g. Imagine living on a world where the force of gravity is three times stronger. You weight three times as much, and falls would be bone-shattering. You'd also be breathing air that was thick as soup assuming there was any free oxygen there to begin with. Other worlds have similar issues. So close to their stars that their year lasts less than a week and the sunward face would be molten, or so far out that they are ice-encased balls of dead rock. Not very inviting.
Add in that getting anywhere is a daunting prospect. Our closest neighbor, Proxima Centauri, is 4.244 light years away. That's 2.49489x10^13 miles. Unless we turn everything we know about physics on its head and find a way to cheat lightspeed, getting anywhere is going to be a slog. There is an "effective" speed limit of about 40% of the speed of light with the technology we have now. Any faster, and you start to have real problems with both relativistic effects (your ship gets more massive as it approaches the speed of light) and the random bits of dust and hydrogen you hit start having the impact energy of atomic bombs.
That makes the trip to Proxima Centauri b take about 17 years (ship time, the trip feels a little quicker for those on board due to relativity) which means that that ship needs to be able to support both crew and colonists for a long time. These are known in science-fiction as generation ships, Huge vessels built to carry thousands and support them with a functioning ecosystem. These ships have to be built to last because as the name implies, generations will live and die before the ship reaches its destination. For example, the closest candidate for a twin to Earth is Kepler-186f, which is 500 light years away. With our .4c speed limit, getting there is going to take 2,271 years, ship time. For reference, 2,271 years ago, Ptolemy II Philadelphus was king of Ptolemaic Egypt.
Which raises the question, after untold generations in space, living in an enclosed world, would the settlers choose to leave the home of their families for untold generations to settle a new world? What kinds of cultures would evolve on these ships? Given centuries, it's quite possible that any given generation ship could experience the same cycle of rising and falling, with new religions, new languages, even the possibility that over time the population forgets they are on a ship at all and see the ship as their entire universe.
Even on shorter hauls, even if we figure out how to beat the problems of relativity, the journies are going to take a long time. Tau Ceti, long a favorite of science fiction writers because the star is a close twin to our sun, lies a mere 11.9 light years away. If our transport can boost at 1G acceleration (adding roughly 10m^2 velocity every second) and can make it to .99c, the onboard trip will take a bit over five years for those on the ship. But here's where things get fun. Relativity means that those 5.14 years on the ship happened while 13.7 years passed outside the ship. If you take the same ship from Earth to Kepler-186f, it gets much worse. You have 12 years onboard to practice saying "Hello, my name is" in Keplerian, but 501 years have passed in the non-relativistic universe, and the language has changed beyond recognition.
In this case, I think you would develop a caste of spacers who live their entire lives on their ships and pass through the centuries as ghosts, visiting colonized worlds for trade and passing information. British author Alastair Reynolds has written an entire series, called Revelation Space, around this idea.
Science fiction loves to break the rules. Faster than light travel, magic energy sources that can provide endless power with no input, and fantastic but plausible technologies. Larry Niven also played with the concept with his Léshy Circuit stories, where vast slower than light starships used magnetic scoops to feed their fusion drives with interstellar hydrogen. Sometimes, the story is more interesting with you don't break physics. I should try that.
All travel times were generated at the Relativistic Star Ship Calculator http://convertalot.com/relativistic_star_ship_calculator.html
Because astronomers had been saying for centuries that there was no reason for other stars not to have their own family of planets. But until we found evidence, it was still just a hypothesis. But once we found that first planet, the flood gates opened. Observatories began confirming dozens, then hundreds of "exoplanets" orbiting other stars. Orbital observatories like TESS (Transiting Exoplanet Survey Satellite) are finding more every day. To date, we've confirmed nearly 4,000 planets orbiting other suns.
But there are a few problems for the science-fiction fan dreaming of colonies on strange new worlds. Of these 4,000 worlds, only a tiny fraction might be habitable. Many are super-Earth, much larger and more massive, which would indicate much higher gravity than Earth's 1g. Imagine living on a world where the force of gravity is three times stronger. You weight three times as much, and falls would be bone-shattering. You'd also be breathing air that was thick as soup assuming there was any free oxygen there to begin with. Other worlds have similar issues. So close to their stars that their year lasts less than a week and the sunward face would be molten, or so far out that they are ice-encased balls of dead rock. Not very inviting.
Add in that getting anywhere is a daunting prospect. Our closest neighbor, Proxima Centauri, is 4.244 light years away. That's 2.49489x10^13 miles. Unless we turn everything we know about physics on its head and find a way to cheat lightspeed, getting anywhere is going to be a slog. There is an "effective" speed limit of about 40% of the speed of light with the technology we have now. Any faster, and you start to have real problems with both relativistic effects (your ship gets more massive as it approaches the speed of light) and the random bits of dust and hydrogen you hit start having the impact energy of atomic bombs.
That makes the trip to Proxima Centauri b take about 17 years (ship time, the trip feels a little quicker for those on board due to relativity) which means that that ship needs to be able to support both crew and colonists for a long time. These are known in science-fiction as generation ships, Huge vessels built to carry thousands and support them with a functioning ecosystem. These ships have to be built to last because as the name implies, generations will live and die before the ship reaches its destination. For example, the closest candidate for a twin to Earth is Kepler-186f, which is 500 light years away. With our .4c speed limit, getting there is going to take 2,271 years, ship time. For reference, 2,271 years ago, Ptolemy II Philadelphus was king of Ptolemaic Egypt.
Which raises the question, after untold generations in space, living in an enclosed world, would the settlers choose to leave the home of their families for untold generations to settle a new world? What kinds of cultures would evolve on these ships? Given centuries, it's quite possible that any given generation ship could experience the same cycle of rising and falling, with new religions, new languages, even the possibility that over time the population forgets they are on a ship at all and see the ship as their entire universe.
Even on shorter hauls, even if we figure out how to beat the problems of relativity, the journies are going to take a long time. Tau Ceti, long a favorite of science fiction writers because the star is a close twin to our sun, lies a mere 11.9 light years away. If our transport can boost at 1G acceleration (adding roughly 10m^2 velocity every second) and can make it to .99c, the onboard trip will take a bit over five years for those on the ship. But here's where things get fun. Relativity means that those 5.14 years on the ship happened while 13.7 years passed outside the ship. If you take the same ship from Earth to Kepler-186f, it gets much worse. You have 12 years onboard to practice saying "Hello, my name is" in Keplerian, but 501 years have passed in the non-relativistic universe, and the language has changed beyond recognition.
In this case, I think you would develop a caste of spacers who live their entire lives on their ships and pass through the centuries as ghosts, visiting colonized worlds for trade and passing information. British author Alastair Reynolds has written an entire series, called Revelation Space, around this idea.
Science fiction loves to break the rules. Faster than light travel, magic energy sources that can provide endless power with no input, and fantastic but plausible technologies. Larry Niven also played with the concept with his Léshy Circuit stories, where vast slower than light starships used magnetic scoops to feed their fusion drives with interstellar hydrogen. Sometimes, the story is more interesting with you don't break physics. I should try that.
All travel times were generated at the Relativistic Star Ship Calculator http://convertalot.com/relativistic_star_ship_calculator.html
