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J. Richard Gott III (1947—) is a professor of astrophysical sciences at Princeton University.
Our species, Homo sapiens, has been around for about 200,000 years. If there is nothing special about our time of observation now, we have a 95 percent chance of living sometime in the middle 95 percent of human history. Thus, we can set 95 percent confidence level limits on the future longevity of our species. It should be more than 5,100 years but less than 7.8 million years (5,100 years is 1/39th of 200,000 years and 7.8 million years is 39 times 200,000 years). Interestingly, this gives us a predicted total longevity (past plus future) of between 0.205 million and 8 million years, which is quite similar to that for other hominids (Homo erectus, our direct ancestor, lasted 1.6 million years, and Homo neanderthalensis lasted 0.3 million years) and mammal species generally (whose mean longevity is 2 million years). The average, or mean, duration of all species lies between 1 million and 11 million years.
J. Richard Gott, Time Travel in Einstein’s Universe: The Physical Possibilities of Travel Through Time (London: Phoenix, 2002), 210.
Some might claim that as an intelligent species—one able to reason abstractly, create art, ask questions such as “How long will our species last?” and so on—the normal rules of extinction do not apply to us. In theory, we could use our discoveries to better our position through genetic engineering (to alter ourselves as needed) or through space travel (to vastly expand our habitat). High technologies, however, also pose substantial risks, such as biological warfare or missile-borne nuclear weapons.
Ibid., 210–212.
If we remain on Earth, we will also be exposed to many of the same risks that other species face, including major epidemics, climatological and ecological disasters, asteroid strikes, and so on, and so one might argue that, therefore, our longevity will be similar.
Ibid., 212.
Given these implications of the Copernican principle, let’s consider what we could do to improve the survival prospects of our species. Self-sustaining colonies in space would provide us with a life insurance policy against any catastrophes that might occur on Earth, a planet covered with the fossils of extinct species. The goal of the human spaceflight program should be to increase our survival prospects by colonizing space.
Ibid., 229.
Chaos theory tells us that we may be unable to predict today the specific cause of our final demise as a species. By definition, whatever causes us to go extinct will be something the likes of which we have not experienced so far. We simply may not be smart enough to know how best to spend our money on Earth to ensure the greatest chance of survival.
Ibid., 229.
But spending money to plant colonies in space gives us more chances—like storing some of Sophocles’ plays away from the Alexandrian library.
Ibid., 229–230.
Since time is short, we should concentrate on establishing the first self-supporting colony in space as soon as possible. That it be self-supporting is important since this would allow it to continue even if funding for future launches from Earth were cut off. Existence of even one self-supporting colony in space might as much as double the long-term survival prospects of our species—by giving us two independent chances instead of one.
Ibid., 231.
We might want to follow the Mars Direct program advocated by American space expert Robert Zubrin. But rather than bring astronauts back from Mars, we might choose to leave them there to multiply, living off indigenous materials. We want them on Mars. That’s where they benefit human survivability.
Ibid., 231.
Colonies are an incredible bargain. One only has to send a few astronauts. They then multiply at no further cost to us: the colonists do all the work. Colonies can also establish other colonies.
Ibid., 232.
Establishing a Mars colony would probably require the human race to spend about as much money in real dollars on human spaceflight in the future as it has in the past, and over a similar time scale—not something unreasonable to ask for.
Ibid., 232.
The real space race is whether we will successfully colonize space before the money for space exploration runs out. If we lose that race, we will be stranded on Earth, where we will surely go extinct eventually, probably on a time scale of less than 8 million years.
Ibid., 232–233.
In the 1960s the argument was made that traveling to the Moon was too expensive in light of other demands on our resources, such as poverty, Vietnam, civil rights, and other problems, and that we should simply wait until the 1990s, when technology would make it much cheaper. But actually it became much more difficult at century’s end to raise money to go to the Moon. Fortunately, we went in the 1960s when we had the chance. If we had waited, we would have missed our chance and would not have visited the Moon yet.
Ibid., 234.
So this is a warning that our species should be getting off Earth and spreading out now, while we have the chance. We observe two frightening facts: our species has not been around very long (only 200,000 years out of a possible 13 billion years), and our species has just a tiny geographical range (one tiny planet out of a vast universe). These are two facts that one might expect to be correlated. Species with a limited geographical range don’t last as long as ones with a larger geographical range—simply because the latter are harder to wipe out. Species confined to single islands always face the greatest extinction danger. But in the universe, Earth is just a tiny island. We stay bound to Earth at our peril.
Ibid., 235.
And yet this warning is a double warning, for it cautions that the warning itself will likely not be heeded. Why not? Because you were born on Earth. Thus, of all human beings ever to be born—past, present, and future—a significant fraction must be born on Earth, or else you would be special. That means that it is not likely for the human race to heed this warning and escape Earth, moving out in a big way into the vast universe. And this may well be the reason for our likely early demise as a species. Abandoning the human spaceflight program would be a tragic mistake, yet it is a mistake we are likely to make.
Ibid., 235–236.
But it’s precisely in feats of understanding, rather than in longevity or power, that one might expect intelligent observers to excel. The ability to ask questions seems to give some ability to answer them, but it doesn’t give us a lot of time. That is the essence of the report from the future. One of the things we should understand about time is that we have just a little.
Don’t waste your time, humanity. You have just a little. It is the time traveler’s secret.
Ibid., 239.
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