He explains the Copernican Principle, derived from the discovery by Nicolaus Copernicus that our solar system is heliocentric rather than Earth-centered. The essential idea is that there is nothing special about this human time in history or this physical vantage point.
And as if what Copernicus discovered wasn't enough, the ordinariness of our place in the universe has been spectacularly confirmed by the discovery and distribution of the cosmic microwave background radiation, which has proved the Copernican principle on the largest of scales.
Berlin Wall falls
He recounts how, traveling to post-war Germany in the 1960's, he found himself wondering how long the Berlin wall might last. Turning to the Copernican Principle, he reasoned that his standing there at that point in time was not a special circumstance. Applying the math - sorry, I didn't get it! - he predicted the wall would last between 2 and 2/3 year and 20 years, a range that would turn out to be accurate.
He's made testable predictions - again, with great accuracy - on the longevity of Broadway plays and political figures.
Extending that line of reasoning to human longevity, he goes on to explain that "with 95 percent confidence," we have between 5,100 years and 7.8 million years left on Earth.
The key, as we will see, is "on Earth."
Describing the origin and extinction of many, many species, he suggests that if we're not special we'll face the same threat - perhaps from an asteroid or virus that isn't caught in time.
In fact, he points out, we know the majority of Earth species have had no successors.
Will We Quit the Space Program too Soon?
In 1993, he predicted that the space program would last between 10 months and 125 years - again this is with a 95 percent statistical confidence.
The danger is that we might quite the space program before successfully propagating humanity off-planet. To make the point, he quotes many early predictions of human spaceflight that haven't come true. Right now the Chinese, with a little additional effort, could break the distance record (from Earth) for manned flights by making a bigger orbit of the moon than the Apollo program craft.
The point is that we're farther away from going off-planet than we were in 1969, nearly forty years ago, with far more primitive technology. At risk: our survival.
Contrary to most science fiction, we're likely to be one of the bigger and more successful civilizations in the universe. But if we are not alone, he says that other intelligent species may still be on their home planets or have become extinct through a random event, because they quit the effort to colonize space.
If our survival is important - we after all spend billions on defense in the United States - then getting to space permanently should be considered a defense strategy.
We Need Lifeboats
Comparing the possibility of being hit by a comet, which is a big iceball, with the ice hit by the Titanic, he says "the Titanic had some lifeboats."
Showing a number of spacecraft proposed to get humans to Mars, he points out that they all involve a return. "I have a better idea," he says, "don't bring them back," which draws a laugh. He quotes Story Musgrave, an astronaut he knows, as saying he'd have volunteered at any time for a one-way ticket to the Moon or Mars. That draws a gasp.
If we send the same amount of human-sustaining material into low earth orbit in the next 40 years as we have in the past 40 years, we'd have enough material to have a potentially establish a self-sustaining colony on Mars. The danger, of course, is that we'll choose not to.
Gott emphatically says that we should not miss this opportunity in history. Modifying a famous Kennedy quote, he closes with this: "going to Mars is a challenge we should be willing to accept and unwilling to postpone."