Between two worlds life hovers like a star,
’Twixt night and morn, upon the horizon’s verge:
How little do we know that which we are!
How less what we may be! The eternal surge
Of time and tide rolls on, and bears afar
Our bubbles; as the old burst, new emerge,
Lash’d from the foam of ages; while the graves
Of Empires heave but like some passing waves.

Between two worlds life hovers like a star, twixt night and morn, upon the horizon's verge.

Not one of those worlds will be identical to Earth. A few will be hospitable; most will appear hostile. Many will be achingly beautiful. In some worlds there will be many suns in the daytime sky, many moons in the heavens at night, or great particle ring systems soaring from horizon to horizon. Some moons will be so close that their planet will loom high in the heavens, covering half the sky. And some worlds will look out onto a vast gaseous nebula, the remains of an ordinary star that once was and is no longer. In all those skies, rich in distant and exotic constellations, there will be a faint yellow star — perhaps barely seen by the naked eye, perhaps visible only through the telescope — the home star of the fleet of interstellar transports exploring this tiny region of the great Milky Way Galaxy. The themes of space and time are, as we have seen, intertwined. Worlds and stars, like people, are born, live and die. The lifetime of a human being is measured in decades; the lifetime of the Sun is a hundred million times longer. Compared to a star, we are like mayflies, fleeting ephemeral creatures who live out their whole lives in the course of a single day. From the point of view of a mayfly, human beings are stolid, boring, almost entirely immovable, offering hardly a hint that they ever do anything. From the point of view of a star, a human being is a tiny flash, one of billions of brief lives flickering tenuously on the surface of a strangely cold, anomalously solid, exotically remote sphere of silicate and iron. In all those other worlds in space there are events in progress, occurrences that will determine their futures. And on our small planet, this moment in history is a historical branch point as profound as the confrontation of the Ionian scientists with the mystics 2,500 years ago. What we do with our world in this time will propagate down through the centuries and powerfully determine the destiny of our descendants and their fate, if any, among the stars

We have two lives about us,
Two worlds in which we dwell;
Within us, and without us, Alternate Heaven and Hell:
Without, the somber Real,
Within our hearts of hearts, the beautiful Ideal!

We live between two worlds; we soar in the atmosphere; we creep upon the soil; we have the aspirations of creators and the propensities of quadrupeds. There can be but one explanation of this fact. We are passing from the animal into a higher form, and the drama of this planet is in its second act.

Wandering between two worlds, one dead
The other powerless to be born,
With nowhere yet to rest my head
Like these, on earth I wait forlorn.

On this narrow planet, we have only the choice between two unknown worlds. One of them tempts us — ah! what a dream, to live in that! — the other stifles us at the first breath.

This narrow isthmus 'twixt two boundless seas,
The past, the future,—two eternities!

We stand on the threshold of a twilight-whether morning or evening we do not know. One is followed by the night, the other heralds the dawn.

The entire life of the human soul is mere motions in the shadows. We live in a twilight of consciousness, never in accord with whom we are or think we are. Everyone harbours some kind of vanity, and there's an error whose degree we can't determine. We're something that goes on during the show's intermission; sometimes, through certain doors, we catch a glimpse of what may be no more than scenery. The world is one big confusion, like voices in the night.

Compared to a star, we are like mayflies, fleeting ephemeral creatures who live out their whole lives in the course of a single day. From the point of view of a mayfly, human beings are stolid, boring, almost entirely immovable, offering hardly a hint that they ever do anything. From the point of view of a star, a human being is a tiny flash, one of billions of brief lives flickering tenuously on the surface of a strangely cold, anomalously solid, exotically remote sphere of silicate and iron.

And what is Life? — An hour-glass on the run,
A mist retreating from the morning sun,
A busy, bustling, still repeated dream;
Its length? — A minute’s pause, a moment’s thought;
And happiness? — A bubble on the stream,
That in the act of seizing shrinks to nought.

The realms of day and night. Two different worlds coming from two opposite poles mingled during this time.

So does a whole world, with all its greatnesses and littlenesses, lie in a twinkling star. And as mere human knowledge can split a ray of light and analyse the manner of its composition, so, sublimer intelligences may read in the feeble shining of this earth of ours, every thought and act, every vice and virtue, of every responsible creature on it.