In this book Asimov outlines the many ways which mankind might meet it’s final fate, from the least likely, to the most likely.
The most distant future in which the universe reaches maximum entropy wherein all the energies within the Universe are spread evenly brings an even coldness. If mankind survives this is what may spell the end, hundreds of billions of years in the future. At this time human technology may have advanced to the point where humans could extend their existence by locating and mining small pockets of low entropy. That is, if we are not destroyed by other forces first.
Other possible ends from Universe sources include the collapse of nearby stars, black holes, close proximity Quasars. Emission of deadly Gamma radiation in close proximity, from the closest stars, would be deadly. Gravity wells from black holes would stretch the Earth to bits.
Closer to home, the possible effects of catastrophes on the solar system only, leaving the rest of the Universe to go on it’s merry way, possible collisions of foreign bodies with the sun are considered.
Although only very remotely possible another star might collide with the sun. More likely, but still remote, in our solar systems travels through the Universe we might encounter a black hole, which if it a small one might collide with our sun will work from within and absorb it’s energies leaving us orbiting a black hole.
Free roving planetary bodies would most likely not affect the sun to a great degree, and unless the amount were excessive, pockets of antimatter would probably be endurable as well. Besides, such collisions are also only a remote possibility.
What about the Sun? What if it were to suffer death? It has been burning for 5 billion or so years scientists speculate, and will continue to burn for billions more. Humans will suffer the end this way, only if it survives other catastrophes. Even before the sun reaches it’s end, it will suffer expansion as it exhausts it’s fuel and becomes a red giant. The Earth might remain outside it’s sphere but still suffer vaporization from the heat generated by the bloated body. It just could be that we as a species if we survive would have technology sufficient to move outwards in the solar system and accommodate ourselves on a moon or build elaborate vessels in which we can extend our existence. Nevertheless, this would only be an extension, as eventually millions of years later, the sun would begin a collapse which will threaten us again.
Even before this scenario we could suffer destruction from the actions of the sun. Although our star is too small to suffer death as a supernova, something as seemingly benign as an excessive number of sunspots could do us in. Although Asimov fails to mention it, even a solar flare, properly aimed could wreak havoc with life on this tiny orb.
Events that might effect only the Earth and leave the rest of the solar system intact include collision with another planetary body, asteroids, comets, or even mini-black holes, should they exist. Then there is the possibility that some meteorite would bring a foreign life form which could infect life with terminal consequences.
Excluding sources of catastrophe from outside the Earth, there are still volcanoes and earthquakes. If that caldera in Yellowstone goes up it would not just be a catastrophe for the United States, but might be of such intensity that the earth’s climate would be changed, perhaps not permanently, but long enough for the human race to be eliminated through famine and an ice age.
Humans themselves, if they do not exercise care could destroy the planet, making it inhospitable to life, other than the smallest of creatures. In which case life might continue, just without us. Should we manage to keep our missiles in their silos, eventually we could use up our natural resources, as the mass of humanity ever increases. Our population will also cause great calamity. At the writing of his book, 1979, he mentions the Earth’s human population at 4 billion. Here in 2010 we have passed the 6 billion mark already. He, Asimov, hypothesizes, that the Earth’s capacity may be 12 billion humans. We could reach that in a hundred years or sooner at the rate we are multiplying.
I found the book an interesting read, and despite the fact it was written over 30 years ago, very appropriate. In his afterword he hopes humanity will spread itself through the Cosmos, making our demise less likely. In fact, it was his thought, that we should make that our goal. With all our eggs in one basket at present, humanity is too vulnerable to single hit or miss calamities. I think the culture and accomplishments of humanity are amazing and should be preserved by spreading out into the Universe. I agree, this should be our goal.