It’s a poignant intergalactic truth: “What people call the observable universe is what’s receding slower than the speed of light.” If inflation - the idea that the universe was very tiny before getting very big - is correct, he says, then there’s a lot of existence that we’ll never see again. “If something is receding from you faster than the speed of light, then the light emitted from it is being carried along by the same expansion, and it’s trying to get to you at the speed of light, but that whole piece of space is moving away faster than the speed of light,” he says. As Alan Chodos, the former associate executive officer of the American Physical Society, told New York, galaxies far, far away from us can be moving faster than the speed of light, not that we’d ever know. This is why “nothing moves faster than the speed of light” needs to be qualified: That idea works for objects within space, but not space itself. The universe is almost certainly expanding, perhaps infinitely - as Edwin Hubble observed back in 1925. Nothing in the universe can go faster than the speed of light, but the universe itself can. This is precisely what the Super-Kamiokande in Japan and other high-speed particle detectors use to study neutrinos: They look at the superluminal booms created by neutrinos, much like a detective figures out what happened in a gunfight by assessing bullets and ballistics. By looking at the size and shape of the superluminal boom that’s created, you can infer lots about the particles themselves. Physicists, clever as they are, have harnessed this as a sort of fingerprinting of superfast particles. The Idaho National Laboratory’s Advanced Test Reactor (ATR)
The same thing happens when cosmic rays collide with the Earth’s atmosphere: There’s a spray of particles, and some of them get superluminal. This creates a “superluminal boom,” similar to the supersonic boom that happens when a jet breaks the sound barrier. This is what gives the core of nuclear reactors their eerie blue glow: Water slows down light, so charged particles like electrons buzz around faster than light does. Thereafter, the effect was christened Cherenkov Radiation. “But nothing says that light can’t go slower than the speed limit,” Kessler says.Ĭonsider the Russian physicist Pavel Cherenkov, who first spotted superluminal stuff in 1934 when observing blue light emitted from a water bottle being bombarded with radiation, a discovery that won him the Nobel Prize in 1958. Unless you’re at the start of the universe, the speed of light - as the universal maximum - is constant. Slow light down, and particles will go faster than it. Indeed, given the right conditions - some well-proven, others highly speculative - it’s possible to go faster and slower than light. Magueijo’s theory advances a phenomenon that physicists have been tracking for the past couple decades: that light and its speed are more flexible than previously thought. It’s built into “the very geometry of space and time,” says Matt Strassler, a theoretical physicist and an associate of Harvard’s physics department. According to that century-old insight, the fastest anything can go is 671 million miles an hour, better known as the speed of light. The current understanding of the speed of light comes from Einstein and his special theory of relativity. That would mean that in the early universe, light traveled faster than gravity, which would overturn a fundamental principle of physics. The Imperial College London physicist who’s been developing the idea since the 1990s, João Magueijo, may soon be proven right if his prediction matches new satellite data coming in on cosmic-microwave background radiation. According to a theory advanced in a new paper, physicists are saying that at the birth of the universe, some 13.7 billion years ago, the cosmos was insanely hot, allowing light to travel at an “ infinite” speed. The speed of light is apparently less constant than Albert Einstein might have you assume. Photo: Chris Butler/Getty Images/Science Photo Library Active spiral galaxies emit huge amounts of energy at near–light speed.
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