Science has done it again everybody! Brace yourselves for this groundbreaking news, freshly determined by physicists: Time travel, if it exists, may have some weird consequences. Gosh, who’d have thunk it?
But no, seriously, a recent article suggests that a certain kind of theoretically possible time machine would wreak minor havoc with a firm principle of quantum mechanics, the often-weird science of the smallest bits of the universe. You know what this means: We get to explore the science of time travel!
Let’s get this out of the way first: Obviously time travel exists, because it’s already the third week of 2014. We’re all time travelers (chrononauts), technically, moving 1 second per second through time. Certain weird side effects of relativity theory also mean time can travel more quickly under certain conditions, so it’s even possible for you to travel into the future (someone else’s future, at least) faster than the usual rate.
The “useful” kind of time travel, though, for sci-fi authors and dreamers alike, is into the past, Back to the Future style. And, happily, relativity theoretically can make that possible, too, by warping the fabric of reality, space-time, so much that it loops back on itself. A so-called wormhole (again, officially deemed possible by science) could be the bridge that connects two different times.
Andrew Grant is an associate editor at DISCOVER. His latest feature, “William Borucki: Planet Hunter,” appears in the December issue of the magazine.
Last night Major League Baseball announced the winners of the Cy Young Award, given to the year’s best pitchers in the American and National leagues. The National League victor was New York Mets pitcher R.A. Dickey. That he won the award is remarkable, and not just because he is a relatively ancient 38 years old or because he plays for the perennial punch line Mets. Dickey is the first Cy Young winner whose repertoire consists primarily of the knuckleball, a baffling pitch whose intricacies scientists are only now beginning to understand.
Most pitchers, including the other Cy Young finalists, try to overwhelm hitters with a combination of speed and movement. They throw the ball hard—the average major league fastball zooms in at around 91 miles per hour—and generate spin (up to 50 rotations a second) that makes the ball break, or deviate from a straight-line trajectory. Dickey does neither of those things. Rather than cock his arm back and fire, he pushes the ball like a dart so that it floats toward the plate between 55 and 80 mph. The ball barely spins at all—perhaps a quarter- or half-turn before reaching the hitter.
In 1917, a year after his general theory of relativity was published, Einstein tried to extend his field equation of gravitation to the universe as a whole. The universe as known at the time was simply our galaxy—the neighboring Andromeda, visible to the naked eye from very dark locations, was thought to be a nebula within our own Milky Way home. Einstein’s equation told him that the universe was expanding, but astronomers assured him otherwise (even today, no expansion is evident within the 2-million-light-year range to Andromeda; in fact, that galaxy is moving toward us). So Einstein inserted into his equation a constant now known as “lambda,” for the Greek letter that denoted it. Lambda, also called “the cosmological constant,” supplied a kind of force to hold the universe from expanding and keep it stable within its range. Then in 1929, Hubble, Humason, and Slipher made their monumental discovery using the 100-inch Mount Wilson telescope in California of very distant galaxies and the fact that they were receding from us—implying that the universe was indeed expanding, just as Einstein’s original equation had indicated! When Einstein visited California some time later, Hubble showed him his findings and Einstein famously exclaimed “Then away with the cosmological constant!” and never mentioned it again, considering lambda his greatest “blunder”—it had, after all, prevented him from theoretically predicting the expansion of the universe.
Fast forward six decades to the 1990s. Saul Perlmutter, a young astrophysicist at the Lawrence Berkeley Laboratory in California had a brilliant idea. He knew that Hubble’s results were derived using the Doppler shift in light. Light from a galaxy that is receding from us is shifted to the red end of the visible spectrum, while a galaxy that is approaching us has its light shifted to the blue end of the spectrum, from our vantage point. The degree of the shift is measured by a quantity astronomers call Z, which is then used to determines a galaxy’s speed of recession away from us (when Z is positive and shift is to the red).