“Oh, the planets in the solar system haven’t formed yet right now. This disk of interstellar debris is the raw material they’re made up of.” Bai Bing pulled up a slider bar at the bottom of the window. “See, this lets you move through time.” He slowly dragged the slider forward. Two hundred million years passed before them; the disk of dust around the sun disappeared. “Now the nine planets have formed. The video window shows real distances and proportions, unlike your planetarium displays, so finding Earth is going to take more work. I’ll use the coordinates I saved earlier instead.” With that, the nascent planet Earth appeared on the screen as a hazy gray sphere.

Bai Bing scrolled the mouse wheel. “Let’s go down … good. We’re about ten kilometers above the surface now.” The land below was still shrouded in haze, but crisscrossing glowing red lines had appeared in it, a network like the blood vessels in an embryo.

“These are rivers of lava,” Bai Bing said, pointing. He kept scrolling down, past the thick acidic fog. The brown surface of the ocean appeared, and the point of view plunged lower, into the ocean. In the murky water were a few specks. Most were round, but a few were more complicated in shape, most obviously different from the other suspended particles in that they were moving on their own, not just floating with the current.

“Life, brand new,” Bai Bing said, pointing out the tiny things with the mouse.

He rapidly scrolled the mouse wheel in the other direction, raising their point of view back into space to once again show the young Earth in full. Then he moved the time slider. Countless years flew past; the thick haze covering Earth’s surface disappeared, the ocean began to turn blue, and the land began to turn green. Then the enormous supercontinent Pangaea split and broke apart like ice in spring. “If you want, we can watch the entire evolution of life, all the major extinctions and the explosions of life that followed them. But let’s skip them and save some time. We’re about to see what this all has to do with our lives.”

The fragmented ancient continents continued to drift until, at last, a familiar map of the world appeared. Bai Bing changed the slider-bar settings, advancing in smaller increments through time before coming to a stop. “Right, humans appear here.” He carefully shifted the slider a little further forward. “Now civilization appears.

“You can only see most of distant history on a macro scale. Finding specific events isn’t easy, and finding specific people is even harder. Searching history mainly relies on two parameters: location and time. It’s rare that historical records give them accurately this far back. But let’s try it out. We’re going down now!” Bai Bing double-clicked a location near the Mediterranean Sea as he spoke. The point of view hurtled downward with dizzying speed. At last, a deserted beach appeared. At the far side of the yellow sand was an unbroken grove of olive trees.