Likewise if you live on the surface of Mars in the throes of terraforming； or Venus； or Titan。 This strategy—breaking up into many smaller self…propagating groups； each with somewhat different strengths and concerns； but all marked by local pride—has been widely employed in the evolution of life on Earth； and by our own ancestors in particular。 It may； in fact； be key to understanding why we humans are the way we are。* This is the second of the missing justifications for a permanent human presence in space： to improve our chances of surviving； not just the catastrophes we can foresee； but also the ones we cannot。 Gott also argues that establishing human munities on other worlds may offer us our best chance of beating the odds。
* Cf。 Shadows of Forgotten Ancestors： A Search for Who We Are； by Carl Sagan and Ann Druyan （New York： Random House； 1992）。
To take out this insurance policy is not very expensive； not on the scale on which we do things on Earth。 It would not even require doubling the space budgets of the present spacefaring nations （which； in all cases； are only a small fraction of the military budgets and many other voluntary expenditures that might be considered marginal or even frivolous）。 We could soon be setting humans down on near…Earth asteroids and establishing bases on Mars。 We know how to do it； even with present technology； in less than a human lifetime。 And the technologies will quickly improve。 We will get better at going into space。
A serious effort to send humans to other worlds is relatively so inexpensive on a per annum basis that it cannot seriously pete with urgent social agendas on Earth。 If we take this path； streams of images from other worlds will be pouring down on Earth at the speed of light。 Virtual reality will make the adventure accessible to millions of stay…on…Earths。 Vicarious participation will be much more real than at any earlier age of exploration and discovery。 And the more cultures and people it inspires and excites； the more likely it will happen。
But by what right； we might ask ourselves； do we inhabit； alter； and conquer other worlds？ If anyone else were living in the Solar System； this would be an important question。 If； though； there's no one else in this system but us； don't we have a right to settle it？
Of course； our exploration and homesteading should be enlightened by a respect for planetary environments and the scientific knowledge they hold。 This is simple prudence。 Of course； exploration and settlement ought to be done equitably and transnationally； by representatives of the entire human species。 Our past colonial history is not encouraging in these regards； but this time we are not motivated by gold or spices or slaves or a zeal to convert the heathen to the One True Faith； as were the European explorers of the fifteenth and sixteenth centuries。 Indeed； this is one of the chief reasons we're experiencing such intermittent progress； so many fits and starts in the manned space programs of all nations。
Despite all the provincialisms I plained about early in this book； here I find myself an unapologetic human chauvinist。 If there were other life in this solar system； it would be in imminent danger because the humans are ing。 In such a case； I might even be persuaded that safeguarding our species by settling certain other worlds is offset； in part at least； by the danger we would pose to everybody else。 But as nearly as we can tell； so far at least； there is no other life in this system； not one microbe。 There's only Earthlife。
In that case； on behalf of Earthlife； I urge that； with full knowledge of our limitations； we vastly increase our knowledge of the Solar System and then begin to settle other worlds。
These are the missing practical arguments： safeguarding 'the Earth from otherwise inevitable catastrophic impacts and hedging our bets on the many other threats； known and unknown； to the environment that sustains us。 Without these arguments； a pelling case for sending humans to Mars and elsewhere might be lacking。 But with them—and the buttressing arguments involving science； education； perspective； and hope—I think a strong case can be made。 If our long…term survival is at stake； we have a basic responsibility to our species venture to other worlds。
Sailors on a becalmed sea； we sense the stirring of a breeze。
CHAPTER 22 TIPTOEING THROUGH THE MILKY WAY
I swear by the shelters of the stars （a mighty oath； if you but knew it） 。 。 。
—THE QUR'AN； SURA 56 （7TH CENTURY）
The prospect of scaling heaven； of ascending to the sky； of altering other worlds to suit our purposes—no matter how well intentioned we may be—sets the warning flags flying： We remember the human inclination toward overweening pride； we recall our fallibility and misjudgments when presented with powerful new technologies。 We recollect the story of the Tower of Babel； a building 〃whose top may reach unto heaven；〃 and God's fear 。shout our species； that now 〃nothing will be restrained from them which they have imagined to do。〃
We e upon Psalm 15； which stakes a divine claim to other worlds： 〃＇T＇he heavens are the Lord's； but the Earth lath he given to the children of men。〃 Or Plato's retelling of the Greek analogue of Babel—the tale of Otys and Ephialtes。 They were mortals who 〃dared to scale heaven。〃 The gods were faced with a choice。 Should they kill the upstart humans 〃and annihilate ＇their＇ race with thunderbolts〃？ On the one Band； 〃this would be the end of the sacrifices and worship which mien offered〃 the gods and which gods craved。 〃But； on the other hand； the gods could not suffer ＇such＇ insolence to be unrestrained。''
If； in the long term； though； we have no alternative； if our choice really is many worlds or none； we are in need of other sorts of myths of encouragement。 They exist。 Many religions； from Hinduism to Gnostic Christianity to Mormon doctrine； teach that—as impious as it may sound—it is the goal of humans to bee gods。 Or consider a story in the Jewish Talmud left out of the Book of Genesis。 （It is in doubtful accord with the account of the apple； the Tree of Knowledge； the Fall； and the expulsion from Eden。） In the Garden； God tells Eve and Adam that He has intentionally left the Universe unfinished。 It is the responsibility of humans； over countless generations； to participate with God in a 〃glorious〃 experiment—〃 pleting the Creation。〃
The burden of such a responsibility is heavy； especially on so weak and imperfect a species as ours； one with so unhappy a history。 Nothing remotely like 〃pletion〃 can be attempted without vastly more knowledge than we have today。 But perhaps； if our very existence is at stake； we will find ourselves Able to rise to this supreme challenge。
ALTHOUGH HE DID NOT quite use any of the arguments of the preceding chapter； it was Robert Goddard's intuition that 〃the navigation of interplanetary space must be effected to ensure the continuance of the race。〃 Konstantin Tsiolkovsky made a similar judgment：
There are countless planets； like many island Earths 。 。 。 Man occupies one of them。 But why could he not avail himself of others； and of the might of numberless suns？ 。 。 。 When the Sun has exhausted its energy； it would be logical to leave it and look for another； newly kindled； star still in its prime。
This might be done earlier； he suggested； long before the Sun dies； 〃by adventurous souls seeking fresh worlds to conquer。〃
But as I rethink this whole argument； I'm troubled。 Is it too much Buck Rogers？ Does it demand an absurd confidence in future technology？ Does it ignore my own admonitions about human fallibility？ Surely in the short term it's biased against technologically less…developed nations。 Are there no practical alternatives that avoid these pitfalls？
All our self…inflicted environmental problems； all our weapons of mass destruction are products of science and technology。 So； you might say； let's just back off from science and technology。 Let's admit that these tools are simply too hot to handle。 Let's create a simpler society； in which no matter how careless or short…sighted we are； we're incapable of altering the environment on a global or even on a regional sca