8. Cultures throughout history and around the world have engaged in ritual human sacrifice.

Say you’re about to die and are packing some supplies for the afterlife. What to take? A couple of coins for the ferryman? Some flowers, maybe, or mementos of your loved ones? If you were an ancient Egyptian pharaoh, you’d have your servants slaughtered and buried adjacent to your tomb. Concubines were sacrificed in China to be eternal companions; certain Indian sects required human sacrifices. The Aztecs slaughtered tens of thousands of people to inaugurate the Great Pyramid of Tenochtitlan; after sacred Mayan ballgames, the losing team was sometimes sacrificed.

It’s hard to tell fact from fiction when it comes to this particularly gruesome custom. Ritual sacrifice is described in the Bible, Greek mythology and the Norse sagas, and the Romans accused many of the people they conquered of engaging in ritual sacrifice, but the evidence was thin. A recent accumulation of archaeological findings from around the world shows that it was surprisingly common for people to ritually kill—and sometimes eat—other people.

9. We’ve already changed the climate for the rest of this century.

The mechanics of climate change aren’t that complex: we burn fossil fuels; a byproduct of that burning is carbon dioxide; it enters the atmosphere and traps heat, warming the surface of the planet. The consequences are already apparent: glaciers are melting faster than ever, flowers are blooming earlier (just ask Henry David Thoreau), and plants and animals are moving to more extreme latitudes and altitudes to keep cool.

Even more disturbing is the fact that carbon dioxide lingers in the atmosphere for hundreds of years. We have just begun to see the effects of human-induced climate change, and the predictions for what’s to come range from dire to catastrophic.

10. The universe is made of stuff we can barely begin to imagine.

Everything you probably think of when you think of the universe—planets, stars, galaxies, black holes, dust—makes up just 4 percent of whatever is out there. The rest comes in two flavors of “dark,” or unknown stuff: dark matter, at 23 percent of the universe, and dark energy, at a whopping 73 percent:

Scientists have some ideas about what dark matter might be—exotic and still hypothetical particles—but they have hardly a clue about dark energy. … University of Chicago cosmologist Michael S. Turner ranks dark energy as “the most profound mystery in all of science.”

The effort to solve it has mobilized a generation of astronomers in a rethinking of physics and cosmology to rival and perhaps surpass the revolution Galileo inaugurated on an autumn evening in Padua. … [Dark energy] has inspired us to ask, as if for the first time: What is this cosmos we call home?

But astronomers do know that, thanks to these dark parts, the universe is expanding. And not only expanding, but expanding faster and faster. Ultimately, everything in the universe will drift farther and farther apart until the universe is uniformly cold and desolate. The world will end in a whimper.