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Following the answer from this link and assuming this is the best choice from the lot, if we had leave Earth right now and inhabit another world in a different planetary system, how would we humans go about migrating from one planet to another?

Even though I cite the same source, this question is about mass migration of the human population. I don't know how this post (asking about parameters used to rank similarity of planets to Earth) is similar to this question about transportation possibilities.

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    $\begingroup$ With commonly available technology, the answer would be "We don't". At this point, we simply don't have the resources for something like that. $\endgroup$ – Erik Jun 12 '15 at 11:18
  • $\begingroup$ possible duplicate of Most earth-like planet in real life $\endgroup$ – Magic-Mouse Jun 12 '15 at 11:19
  • $\begingroup$ At the time i flagged the post it was 2/3 the same text copy paste, you have since been editing them. I still think you should sit and take time thinking about your quesion throughly before asking 5 questions within 50 minutes about the same subject with the main body of the question as a copy and paste. Though that is my subjective opinion that not everyone may share. $\endgroup$ – Magic-Mouse Jun 12 '15 at 11:28
  • $\begingroup$ I originally asked all 5 questions in a single post. Since they said it was too broad, I expanded the number of questions. I copied the reference links with the main body of the question in the last lines. I hope the present question is not flagged off as a duplicate. $\endgroup$ – Arpith Jun 12 '15 at 11:31
  • $\begingroup$ My preferred mode of travel from this world to the next is passing, I'll admit I failed umpteen times already sometimes I get as far as seeing a star shining brightly at the end of a tunnel and all of a sudden I'm awake and find myself just passing motion... $\endgroup$ – user6760 Jun 12 '15 at 12:13
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Assuming the civilization is willing to spend the resources necessary to evacuate Earth, the best way to do this using current technology is to build a laser or microwave launcher.

This system (first proposed by Arthur Kantrowitz and Wolfgang Moekel in the 1970's) uses the energy of an off board generator to energize the reaction mass and can provide extremely efficient rocket propulsion (Lyek Myrabo's "Lightship" proposals using atmospheric gasses for the first part of the flight have an effective ISP of infinity, once past the sensible atmosphere and using laser light to heat H2 reaction mass the ISP drops to a "mere" 1000 seconds). Since the rocket does not have to carry fuel and oxidizer, and the rocket motor can consist essentially of a parabolic reflector, the rocket is much smaller and lighter than what we are used to (the Space Shuttle launch stack of 2000 tons was mostly propellant and liquid oxygen; the shuttle itself weighed @ 120 tons fully loaded).

Laser launchers could potentially operate on an assembly line basis for evacuation, being build, loaded and rolled straight to the launch site and launched with minimum preparation. Since the preparation and handling of spacecraft is the primary driver of costs, (fuel and liquid oxygen are pennies to a few dollars a kilogram, and the hardware is about as expensive as a jumbo jet per kilogram as a rough estimate) minimizing this makes launching much cheaper.

Microwave beams for rocket launching work on similar principles. The microwave generator is potentially much cheaper and more efficient than lasers of equal power, but the means of coupling the microwave energy to the reaction mass of the spacecraft is different and the spacecraft itself might be much larger to carry the microwave receiver; the tradeoff in this case might not be worth while.

Once everyone is in orbit, the laser beam from Earth could be redirected by a series of orbiting mirrors to power the spacecraft around in the Earth Moon system, but if we are going that far, the first wave of people into orbit should have been building proper infrastructure to live and move in deep space.

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  • $\begingroup$ Very very interesting. Thank you for taking the time to answer this in detail Thucydides. $\endgroup$ – Arpith Jun 17 '15 at 2:04
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Mass migration (in the meaning that it includes most of humanity) would probably be very difficult and drain the resources of earth. This is explained in detail in the what-if Everybody out. To give a simple summary: bringing every person on earth into the space needs incredible amounts of energy. That would be the biggest problem. Traveling between the stars is the smaller problem in comparison (if we have enough time, so that the ship can travel in centuries or even thousands of years) and building space ships big enough is clearly difficult, but pales in comparison to bring the humans into space in the first place.

Now, these issues can be alleviated in two cases. First: we don't need mass migration of all humans, but send some colonists, that build a new civilization at the target. Second: the mass migration is needed after some apocalyptic event. If we could assume this event reduced the number of humans, it would naturally reduce the need for energy.

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