The last thing you’ll ever see?
Baseball is a leisurely game—some would say achingly boring—with no ticking clock forcing the players to hurry. But what if you could speed baseball up? Way, way up, up to a relativistic pace: What would happen if the pitcher wound up and released a baseball at 90 percent the speed of light?
Randall Munroe, the mind behind stick-figure comic XKCD, has a background in physics and computer programming, which heavily influences his work. Recently he launched a new weekly feature called “What If?“ in which he answers readers’ hypothetical questions. Like how to hit a baseball that is moving so fast, normal mechanics no longer apply and the rules of relativity come into play. The answer is that in relativistic baseball, you don’t hit the ball; the ball—or rather the plasma shockwave that the ball creates—hits you…and everyone else.
I feel younger already!
If all those vague exercise benefits like heart health and improved mood aren’t enough to get you moving, maybe this will be: By taking that morning stroll, you’re slowing down the rate at which you’re aging and netting yourself extra time—whole picoseconds of it. And you know it’s true, because Einstein said so.
By Valerie Ross
You’re squeezed into a middle seat, two rows from the back of the plane. It’s barely two hours into your cross-country flight, though you’d swear it’s been longer. Does it just seem like the minutes of your trip are crawling by — or does time actually pass more slowly for people who are mid-flight than for people on the ground?
Many of us have heard the idea that time doesn’t pass at the same rate for everyone. It’s a common narrative in science fiction, one that has its roots in Einstein’s theory of relativity. The story starts, let’s say, with two twins, one of whom stays on Earth while the other clambers aboard a rocket that’s making a round-trip journey, at a substantial fraction of the speed of light, to a planet in a not-too-distant solar system. When the traveling twin returns to earth, he’s aged more slowly, and now he’s younger than the twin who stayed behind.
This familiar — and paradoxical — plotline comes from a particular tenet of relativity theory known as time dilation. It predicts that a fast-moving clock will tick at a slower rate than a stationary one — or, a man on an interstellar voyage will age more slowly than his twin back on Earth. But time dilation also says that velocity isn’t the only thing that affects the rate at which clocks tick, or people age; gravity does, too. A clock in a stronger gravitational field (the Earth’s surface, let’s say) will have a slower tick rate than a clock subject to weaker gravity (such as a few miles up into the atmosphere).