“For The United States, the leading space faring nation for nearly half a century, to be without carriage to low Earth orbit and with no human exploration capability to go beyond Earth orbit for an indeterminate time into the future, destines our nation to become one of second or even third rate stature. While the President’s plan envisages humans traveling away from Earth and perhaps toward Mars at some time in the future, the lack of developed rockets and spacecraft will assure that ability will not be available for many years.
Without the skill and experience that actual spacecraft operation provides, the USA is far too likely to be on a long downhill slide to mediocrity. America must decide if it wishes to remain a leader in space. If it does, we should institute a program which will give us the very best chance of achieving that goal.”

Source: Quoted in Woman power to the fore, by R.S. Binuraj, The Hindu (1 July 2017)

22 min 35 sec
Cosmos: A Personal Voyage (1990 Update), Who Speaks for Earth? [Episode 13]
Context: Our global civilisation is clearly on the edge of failure and the most important task it faces, preserving the lives and well-being of its citizens and the future habitability of the planet. But if we're willing to live with the growing likelihood of nuclear war shouldn't we also been willing to explore vigorously every possible means to prevent nuclear war. Shouldn't we consider in every nation major changes in the traditional ways of doing things, a fundamental restructuring of economic political social and religious institutions. We've reached a point where there can be no more special interests or special cases, nuclear arms threaten every person on the Earth. Fundamental changes in society are sometimes labelled impractical or contrary to human nature, as if nuclear war were practical or as if there's only one human nature. But fundamental changes can clearly be made, we're surrounded by them. In the last two centuries abject slavery which was with us for thousands of years has almost entirely been eliminated in a stirring worldwide revolution. Women, systematically mistreated for millennia are gradually gaining the political and economic power traditionally denied them and some wars of aggression have recently been stopped or curtailed because of a revulsion felt by the people in the aggressor nations. The old appeals to racial, sexual, and religious chauvinism and to rabid nationalist fervor are beginning not to work. A new consciousness is developing which sees the earth as a single organism and recognizes that an organism at war with itself is doomed. We are one planet. One of the great revelations of the age of space exploration is the image of the earth finite and lonely, somehow vulnerable, bearing the entire human species through the oceans of space and time.

Nobel Peace Prize Acceptance Speech (2012)
Context: The peace of our world is indivisible. As long as negative forces are getting the better of positive forces anywhere, we are all at risk. It may be questioned whether all negative forces could ever be removed. The simple answer is: “No!” It is in human nature to contain both the positive and the negative. However, it is also within human capability to work to reinforce the positive and to minimize or neutralize the negative. Absolute peace in our world is an unattainable goal. But it is one towards which we must continue to journey, our eyes fixed on it as a traveller in a desert fixes his eyes on the one guiding star that will lead him to salvation. Even if we do not achieve perfect peace on earth, because perfect peace is not of this earth, common endeavours to gain peace will unite individuals and nations in trust and friendship and help to make our human community safer and kinder.

1961, Speech to Special Joint Session of Congress
Context: Finally, if we are to win the battle that is now going on around the world between freedom and tyranny, the dramatic achievements in space which occurred in recent weeks should have made clear to us all, as did the Sputnik in 1957, the impact of this adventure on the minds of men everywhere, who are attempting to make a determination of which road they should take. […] Now it is time to take longer strides — time for a great new American enterprise — time for this nation to take a clearly leading role in space achievement, which in many ways may hold the key to our future on earth. I believe we possess all the resources and talents necessary. But the facts of the matter are that we have never made the national decisions or marshaled the national resources required for such leadership. We have never specified long-range goals on an urgent time schedule, or managed our resources and our time so as to insure theft fulfillment. Recognizing the head start obtained by the Soviets with their large rocket engines, which gives them many months of lead-time, and recognizing the likelihood that they will exploit this lead for some time to come in still more impressive successes, we nevertheless are required to make new efforts on our own. For while we cannot guarantee that we shall one day be first, we can guarantee that any failure to make this effort will make us last. We take an additional risk by making it in full view of the world, but as shown by feat of astronaut Shepard, this very risk enhances our stature when we are successful. But this is not merely a race. Space is open to us now; and our eagerness to share its meaning is not governed by the efforts of others. We go into space because whatever mankind must undertake, free men must fully share.

Kenneth Boulding (1965) Earth as a Spaceship http://earthmind.net/earthmind/docs/boulding-1965.pdf Lecture May 10, 1965, Washington State University, Committee on Spaces Sciences
1960s

Source: An Essay on The Principle of Population (First Edition 1798, unrevised), Chapter XIII, paragraph 2, lines 19-22

State of the Union address http://www.reagan.utexas.edu/archives/speeches/1986/20486a.htm, , quoted in [1986-03-05, Michael Kilian, Hypersonic flight just a hyperbolic Reagan rhapsody, The Evening Independent, http://news.google.com/newspapers?nid=950&dat=19860305&id=bmJQAAAAIBAJ&sjid=t1kDAAAAIBAJ&pg=4836,1112899]
1980s, Second term of office (1985–1989)

Source: Zero Gravity interview (2006), Ch. 5

The Notebooks of Leonardo da Vinci (1883), XV Astronomy
Context: The earth is not in the centre of the Sun's orbit nor at the centre of the universe, but in the centre of its companion elements, and united with them. And any one standing on the moon, when it and the sun are both beneath us, would see this our earth and the element of water upon it just as we see the moon, and the earth would light it as it lights us.