Time Dilation

Time Dilation

Special relativity, fully worked out by Einstein in his middle twenties, is supported by every experiment preformed too check it. Perhaps tomorrow someone will invent a theory consistent with everything else we know that circumvents paradoxes on such matters as simultaneity, avoids privileged reference frames and still permits travel faster than light. But I doubt it very much. Einstein’s prohibition against traveling faster than light may clash with our common sense. But in this question, why should we trust common sense? Why should our experience at 10 kilometers an hour constrain the laws of nature at 300, 000 kilometers per second? Relativity does set limits on what humans can ultimately do. But the universe is not required to be in perfect harmony with human ambition. Special relativity removes from our grasp one way of reaching the stars, the ship that can go faster than light. Tantalizingly, it suggests another and quite unexpected method.

Following George Gamow, let us imagine a place where the speed of light is not its true value of 300,000 kilometers per second, but something very modest: 40 km per hour, say – and strictly enforced (there are no penalties for breaking laws of Nature, because there are no crimes: Nature is self-regulating and merely arranges things that you are approaching the speed of light on a motor scooter… Relativity is rich in sentences beginning “Imagine…” Einstein called such an exercise a Gedankenexperiment, a thought experiment).

Close to the speed of light, from your point of view, the world looks very old. Image by © Megan Jorgensen (Elena)

As your speed increases, you begin to see around the corners of passing objects. While you are rigidly facing forward, things that are behind you appear within your forward field of vision. Close to the speed of light, from your point of view, the world looks very old – ultimately everything is squeezed into a tiny circular window, which stays just ahead of you. From a standpoint of a stationary, light reflected off you is reddened as you depart and blued as you return. If you travel toward the observer at almost the speed of light, you will become enveloped in an eerie chromatic radiance: your usually invisible infrared emission will be shifted to the shorter visible wavelengths. You become compressed in the direction of motion, your mass increases, and time, as you experience it, slows down, a breathtaking consequence of traveling close to the speed of light called time dilation. But from the standpoint of an observer moving with you – perhaps the scooter has a second seat – none of these effects occur.

These peculiar and at first perplexing predictions of special relativity are true in the deepest senss that anything in science is true. They depend on your relative motion. But they are real, not optical illusions. The can be demonstrated by simple mathematics, mainly first-year algebra and therefore understandable to any educated person. They are also consistent with many experiments. Very accurate clocks carried in airplanes slow down a little compared to stationary clocks.

Very Long Period of Time

Very Long Period of Time

It is possible that at some later time with third and higher orders of colonies developing new worlds, another independent expanding civilization would be discovered. Very likely mutual contact would already have been made by radio or other remote means. The new arrivals might be a different sort of colonial society. Conceivable two expanding civilizations with different planetary requirements would ignore each other, their filigree patterns of expansion intertwining, but not conflicting. They might cooperate in the exploration of a province of the Galaxy. Even nearby civilizations could spend millions of years in such separate or joint colonial ventures without ever stumbling upon our obscure solar system.

No civilization can possibly survive to an interstellar spacefaring phase unless it limits its numbers. Any society with a marked population explosion will be forced to devote all its energies and technological skills to feeding and caring for the population on its home planet. This is a very powerful conclusion and is in no way based on the idiosyncrasies of a particular civilization. On any planet, no matter what its biology or social system, an exponential increase in population will swallow every resource. Conversely any civilization that engages in serious interstellar exploration and colonization must have exercised zero population growth or something very close to it for many generations. But a civilization with a low population growth are eased after reaching some lush Eden.

Million years is a very long period of time. Illustration by Elena

Carl Sagan’s colleague William Newman and he himself have calculated that if a million years ago a spacefaring civilization with a low population growth rate emerged two hundred light-years away and spread outward, colonizing suitable worlds along the way, their survey starships would be entering our solar system only about now. But a million years is a very long period of time. If the nearest civilization is younger than this, they would not have reached us yet. A sphere two hundred light-years in radius contains 200,000 suns and perhaps a comparable number of worlds suitable for colonization. It is only after 200,000 other worlds have been colonized that, in the usual course of things, our solar system would be accidentally discovered to harbor indigenous civilization.

Lex Galactica and Cosmic Violence

Lex Galactica and Cosmic Violence

If the nearest civilization is, say 200 light-years away, it takes only 200 years to get from there to here at close to the speed of light. Even at 1 percent of a tenth of a percent of the speed of light, beings from nearby civilizations could have come during the tenure of humanity on Earth. Why are they not here?

There are many possible answers. Although it runs contrary to the heritage of Aristarchus and Coepernicus, perhaps we are the first. Some technical civilizations must be the first to emerge in the history of the Galaxy. Perhaps we are mistaken in our belief that at least occasion civilizations avoid self-destruction. Perhaps there is some unforeseen problem to interstellar spaceflight – although, at speeds much less than the velocity of light it is difficult to see what such an impediment might be. Or perhaps they are here, but in hiding because of some Lex Galactica, some ethic of non-interference with emerging civilizations, We can imagine them, curious and dispassionate, observing us, as we would watch a bacterial culture in a dish of agar, to determine whether, this year again, we manage to avoid self-destruction.

But there is another explanation that is consistent with everything we know. If a great many years ago an advanced interstellar spacefaring civilization emerged 200 light-years away, it would have no reason to think there was something special about the Earth unless it had been here already. No artifact of human technology, not even our radio transmissions, has had time, even traveling at the speed of light, to go 200 light-years. From their point of view, all nearby star systems are more or less equally attractive for exploration or colonization.

Stop Cosmic Violence! Illustration: Elena

There may be many motivations to go to the stars. If our Sun or a nearby star were about to go supernova, a major program of interstellar spaceflight might suddenly become attractive. If we were very advanced, the discovery that the galactic core was imminently to explode might even generate serious interest in transgalactic or intergalactic spaceflight. Such cosmic violence occurs sufficiently often that nomadic spacefaring civilizations may not be uncommon. Even so, their arrival here remains unlikely.

An emerging technical civilization, after exploring its home planetary system and developing interstellar spaceflight, would slowly and tentatively begin exploring the nearby stars. Some stars would have no suitable planets – perhaps they would all be giant gas worlds, or tiny asteroids. Others would carry an entourage of suitable planets, but some would be already inhabited, or the atmosphere would be poisonous or the climate uncomfortable. In many cases the colonists might have to change –or as we would parochially say, terraform – a world to make it adequately clement. The re-engineering of a planet will take time. Occasionally, suitable world would be found and colonized. The utilization of planetary resources so that new interstellar spacecraft could be constructed locally would be a slow process. Eventually a second-generation mission of exploration and colonization would take off toward stars where no one had yet been. And in this way a civilization might slowly wend its way like a vine among the worlds.

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Lex Galactica and Cosmic Violence - Part II

If the nearest civilization is 200 light-years away, it’ll take it about 200 years to get from there to here at close to the speed of light.

Even at one percent of a tenth of a percent of the speed of light, beings from nearby civilizations could have come during the tenure of humanity on Earth. Why are they not here?

There are many possible answers. Perhaps we are really the first ever technical civilisation to emerge in the history of our Galaxy or even in the Universe (although it runs contrary to the heritage of Aristarchus and Copernicus).

Perhaps there is some unforeseen problem to interstellar spaceflight (although, at speeds much less than the velocity of light it is difficult to see what such an impediment might be).

Perhaps we are mistaken in our belief that at least some civilizations avoid self-destruction and manage to find a way to travel in deep space.

Perhaps their representatives are here, among us, but in hiding because of some Lex Galactica, some ethic of non-interference with emerging civilizations. In this case they might be here, curious and dispassionate, observing us, as we would watch a bacterial culture in a dish of agar, to determine whether, this year again, we manage to avoid self-destruction.

But there is another explanation that is consistent with everything we know. If an advanced interstellar spacefaring civilization emerged 200 light-years away, it would have no reason to think there was something special about the Earth unless it had been here already. No artifact of human technology, not even our radio transmissions, has had time, traveling at the speed of light, to reach their planet. From the point of view of such a civilisation, all systems may be equally attractive for exploration or even colonization.

A standard motif in science fiction UFO literature assumes extraterrestrials roughly as capable as we. Perhaps they have a different sort of spaceship or ray gun, but in battle – and science fiction loves to portray battles between civilizations – they and we are rather evenly matched.

But in fact, there is almost no chance that tow galactic civilizations will interact at the same level.

Indeed, in any confrontation, one civilisation will always utterly dominate the other.

A million years is a great many. If an advanced civilization were to arrive in our solar system, there would be nothing whatever we could do about it. Their science and technology would be far beyond ours.

It is pointless to worry about the possible malevolent intentions of an advanced civilization with whom we might make contact. The mere fact they have survived so long means they have learned to live with themselves and others. Our fears about extraterrestrial contact are merely a projection of our own backwardness, an expression of our guilty conscience about our past history: the ravages that have been visited on civilizations only slightly more backward than we. We remember Columbus and the Arawaks, Cortés and the Aztecs, even the fate of the Tlingit in the generations after La Pérouse. We remember and we worry.

But if an interstellar armada appears in our skies, we can predict we will be accommodating: A very different kind of contact is much more likely – the case in which we receive a rich, complex message from another civilization space, but do not make, at least for a while, physical contact with them. In this case there is no way for the transmitting civilization to know whether we have received the message. If we find the contents offensive or frightening, we are not obliged to reply. But if the message contains valuable information, the consequences for our own civilization will be stunning – insights on alien science and technology, art, music, politics, ethics, philosophy and religion, and most of all, a profound deprovincialization of the human condition.

When they show up high in our sky we’ll remember the fate of undeveloped peoples on our planet, that’s why we worry about our fate. Image: © Megan Jorgensen.

Moctezuma

Moctezuma

Moctezuma was told: “We are not as strong as they”, “we are nothing compared to them”. The Spaniards began to be called “the Gods come from the Heavens”. Nevertheless, the Aztecs had no illusions about the Spaniards, who they described in these words:

They seized upon the gold as if they were monkeys, their faces gleaming. For clearly their thirst for gold was insatiable; they starved for it; they lusted for it; they wanted to stuff themselves with it as if they were pigs. So they went about fingering, taking up the streamers of gold, moving them back and forth, grabbing them to themselves, babbling, talking gibberish among themselves.

But their insight into the Spanish character did not help them defend themselves. In 1517 a great comet had been seen in Mexico. Moctezuma, captured by the legend of the return of the Aztec god Quetzalcoatl as a white-skinned man arriving across the Eastern sea, promptly executed his astrologers. They had not predicted the comet, and they had not explained it. Certain of forthcoming disaster, Moctezuma became distant and gloomy. Aided by the superstition of the Aztecs and their own superior technology, an armed party of 400 Europeans and their native allies in the year 1521 entirely vanquished and utterly destroyed a high civilization of a million people.

Why are they not here, on Earth? Image: © Elena

The Aztecs had never seen a horse; there were none in the New World. They had not applied iron metallurgy to warfare. They had not invented firearms. Yet the technological gap between them and the Spaniards was not very great, perhaps a few centuries.

We must be the most backward technical society in the Galaxy. Any society still more backward would not have radio astronomy at all. If the doleful experiences of cultural conflict on Earth were the galactic standard, it seems we would already have been destroyed, perhaps with some passing admiration expressed for Sjakespeare, Bach and Vermeer. But this has not happened. Perhaps alien intentions are uncompromisingly benign, more like La Pérouse than Cortés. Or might it be, despite all the pretensions about UFOs and ancient astronauts, that our civilization has not yet been discovered?

On the other hand, we have argued that if even a small fraction of technical civilizations learn to live with themselves and with weapons of mass destruction, there should now be an enormous number of advanced civilizations in the Galaxy. We already have slow interstellar flight, and think fast interstellar flight a possible goal for the human species. On the other hand, we maintain that there is no credible evidence for the Earth being visited, now or ever, Is this not a contradiction?

The Tlingit and the Alien Culture

The Tlingit and the Alien Culture

The Tlingit had preserved in oral tradition an entirely recognizable and accurate account of their first, almost fully peaceable encounter with an alien culture. The account of Cowee, the Tlingit chief, shows that even is a preliterate culture a recognizable account of contact with an advanced civilization can be preserved for generations. If the Earth had been visited hundreds of thousands years ago by an advanced civilization, even if the contacted culture was preliterate, we might well expect to have some recognizable form of the encounter preserved. But there is not a single case in which a legend reliably dated from earlier pretechnological times can be understood only in terms of contacts with an extraterrestrial civilization.

If some day we make contact with a more advanced extraterrestrial civilization, will the encounter be largely peaceable, even if lacking a certain rapport, like that of the French among the Tlingit, or will it follow some more ghastly prototype, where the society that was a little more advanced utterly destroyed the society that was technically more backward?

In the early sixteen century a high civilization flourished in central Mexico. The Aztecs had monumental architecture, elaborate record-keeping, exquisite art and astronomical calendar superior to that of any in Europe. Upon viewing the Aztec artifacts returned by the first Mexican measure ships, the artist Albrecht Durer wrote in August 1520: “I have never seen anything therefore that has so rejoiced my heart. I have seen a sun entirely of gold a whole fathom broad fin fact, the Aztec astronomical calendar; likewise a moon entirely of silver, equally large, also two chambers full of all sorts of weapons, armor and other wonderous arms, all of which is fairer to see than marvels”.

A Gorgeous Elf. Image by Elena

Intellectuals were stunned at the Aztec books, “which, one of them said, almost resemble those of the Egyptians”. Henan Cortez described their capital Tenochtitlan as “one of the most beautiful cities in the world”. The people’s activities and behavior are on almost as high a level as in Spain, and as well-organized and orderly. Considering that these people are barbarous, lacking knowledge of God and communication with other civilized nations, it is remarkable to see all that they have”. Two years after writing these words, Cortes utterly destroyed Tenochtitlan along with the rest of the Aztec civilization.

Here is an Aztec account:

Moctezuma, the Aztec Emperor, was shocked, terrified by what he heard. He was much puzzled by their food, but what made him almost faint away was the telling of how the great Lombard gun, at the Spaniards’ command, expelled the shot which thundered as it went off. The noise weakened one, dizzied one. Something like a stone came out of it in a shower of fire and sparks. The smoke was foul; it had a sickening, fetid smell. As the shot, which stuck a mountain, knocked it to bits – dissolved it. It reduced a tree to sawdust. The tree disappeared as if they had blown it away. When Moctezuma was told all this, he was terror-struck. He felt faint. His heart failed him.