I want [upon death] to be buried, just like in the old days, where I decompose by the action of microorganisms, and I am dined upon by any form of creeping animal or root system that sees fit to do so.... I will have recycled back to the universe at least some of the energy that I have taken from it. And in so doing, at the conclusion of my scientific adventures, I will have come closer to the heavens than to Earth.
The Sky Is Not the Limit, p. 182
I remain fearless of airplanes [after 9/11]. But during a trip to Los Angeles on a Boeing 767, I couldn't keep my mind from drifting: What's the largest piece of this airplane that could crash into the World Trade Center, explode out the other side, and survive intact? The landing gear? My computer battery? My belt buckle? My wedding ring?
The Sky Is Not the Limit, p. 76
When you're a hammer (as the saying goes), all your problems look like nails. If you're a meteorite expert pondering the sudden extinction of boatloads of species, you'll want to say an impact did it. If you're an igneous petrologist, volcanoes did it. If you're into spaceborne bioclouds, an interstellar virus did it. If you're a hypernova expert, gamma rays did it.
Death By Black Hole, p. 281
The chunks of [comet] Shoemaker-Levy 9 were so large, and were moving so fast, that each hit Jupiter with at least the equivalent energy of the dinosaur-killing collision between Earth and an asteroid 65 million years ago. Whatever damage Jupiter sustained, one thing is for sure: it's got no dinosaurs left.
The Sky Is Not the Limit, p. 66
The number of people in the world engaged in this search [for catastrophic impactors] totals one or two dozen. How long into the future are you willing to protect Homo sapiens on Earth? Before you answer that question, take a detour to Arizona's Meteor Crater during your next vacation.
The Sky Is Not the Limit, p. 174
But to carve the Grand Canyon, Earth required millions of years. To excavate Meteor Crater, the universe, using a sixty-thousand-ton asteroid traveling upward of twenty miles per second, required a fraction of a second. No offense to Grand Canyon lovers, but for my money, Meteor Crater is the most amazing natural landmark in the world.
The Sky Is Not the Limit, pp. 168-9
Seventy percent of Earth's surface is water and over 99 percent is uninhabited, so you would expect nearly all impactors to hit either the ocean or desolate regions on Earth's surface. So why do movie meteors have such good aim?
The Sky Is Not the Limit, p. 171
If Earth ever suffers a runaway greenhouse effect (like what has happened on Venus), then our atmosphere would trap excess amounts of solar energy, the air temperature would rise, and the oceans would swiftly evaporate into the atmosphere as they sustained a rolling boil. This would be bad.
Death By Black Hole, p. 215
Something bad happened on both Mars [with its dried-up watercourses] and Venus [with its runaway greenhouse effect]. Could something bad happen on Earth too? Our species currently turns row upon row of environmental knobs, without much regard to long-term consequences.
Death By Black Hole, p. 81
The dominant species that replaces us in postapocalyptic Earth just might wonder, as they gaze upon our mounted skeletons in their natural history museums, why large-headed Homo sapiens fared no better than the proverbially pea-brained dinosaurs.
Death By Black Hole, p. 262
Eventually, the Sun will swell to occupy the entire sky as its expansion subsumes the orbit of earth. Earth's surface temperature will rise until it matches the 3,000-degree rarified outer layers of the expanded Sun.... But not to worry. We will surely go extinct for some other reason long before this scenario unfolds.
Death By Black Hole, p. 264
Trillions of years into the future, when all stars are gone...all parts of the cosmos will cool to the same temperature as the ever-cooling background. At that time, space travel will no longer provide refuge because even Hell will have frozen over. We may then declare that the universe has died—not with a bang, but with a whimper.
Death By Black Hole, p. 267