Friday, November 23, 2012

From the Empirical Archives: Neutrinos Break Cosmic Speed Limit by Aliman Sears

Neutrinos Break Cosmic Speed Limit
Aliman Sears
Originally Published in Empirical magazine in May 2012

The bartender says, “We don’t serve your kind in here.” 
A neutrino walks into a bar.

What’s a neutrino? Look at one of your fingernails for exactly one second. During that second, about 65 billion subatomic particles called neutrinos passed undetected through the tip of your finger. Neutrinos are so small that they sail effortlessly through atoms, and the atoms don’t have a clue. Scientists thought they knew a lot about neutrinos, but in September 2011 these little buggers potentially turned the scientific world upside down. The European Center of Nuclear Research (CERN) in Switzerland announced that they had clocked a neutrino zipping along faster than the speed of light. This revelation shocked the physics world to its core. One ramification of this super-luminous travel is the mind-boggling idea of reversed causality.

Walking into a bar could still cause a bartender to insist that you’re an unsavory character, but in some circumstances the bartender insisting you leave the bar could cause you to walk into the bar. Sounds hinkey? That’s because it is. However, scientists are quick to tell us not to worry about trying to than light paradoxical ideas. First, it’s not clear that the CERN neutrinos actually broke the cosmic speed limit of 700 million miles per hour. Other teams of scientists are trying to replicate these results and hope to announce corroboration, or lack thereof, sometime in 2012. For reasons we’ll see in a moment, many scientists don’t believe the speedy neutrinos are actually that speedy. Second, scientists tell us not to worry about faster-than-light paradoxes because . . . wait for it . . . the causal structure of events isn’t really violated because there’s still a causal relationship—even if it’s a backwards relationship!

What are these scientists thinking?

The rest of us are still mystified about what a backwards causal relationship could possibly mean. One wonders what Immanuel Kant would think about backwards causation. Leaving these paradoxes aside, what exactly was the landmark discovery that shook the physics world in September? The OPERA team (Oscillation Project with Emulsion-tRacking Apparatus) shot neutrinos from an underground particle accelerator in Switzerland through 454 miles of rock into a neutrino detector in Gran Sasso, Italy. Using atomic clocks and GPS tracking systems, they determined that the neutrinos arrived in Italy 60 nanoseconds faster than they should have if they were traveling at the speed of light.

And why is this significant? Star Trek’s “warp speed” ships notwithstanding, anything traveling faster than light speed violates one of the main theories of modern physics, Einstein’s Special Theory of Relativity (STR) published in 1905. Part of SR is the well-known E=mc2. According to STR, if something has mass, even a tiny bit of mass like the neutrino, it should take an infinite amount of energy to surpass the speed of light. This is great news for the textbook publishing industry because if neutrinos did break the light barrier, then all of our physics texts are outdated and a massive re-writing and re-publishing is in order. A lot folks stand to make substantial amounts of money.

But it’s much more than just a boon for the publishing industry. It’s a colossal rethinking of nearly everything we know (or thought we knew) about physics. This is why many scientists don’t know whether to be shocked or skeptical. Many are saying OPERA overlooked a critical step in their months of painstakingly careful research, and simply published too soon. Others are ready to uncork their finest wine, set their scientific libraries ablaze, and revel in astonishment and awe in the face of a faster-than light universe.

Is this really that monumental? In a word, yes. Einstein’s SR, and by extension his General Theory of Relativity, published in 1916, have mountains of evidential support and are the blueprint for how we think the universe works. If those theories are wrong, then physicists are starting over from day one.

Let’s take three ideas that are well-known by college-level physics majors. Even though the following ideas sound strange, STR is accepted as solid today because scientists have experimentally confirmed that STR consistently makes reliable predictions across the board:

1. Lorentz Contraction : The faster you travel, the thinner you get. This effect is irrelevant at slow speeds, and has been measured in rockets and satellites, but at near light speeds you’d be squeezed into a small space from an outside observer’s point of view. For example, the USS Enterprise was about 950 feet long, but it’s apparent length traveling at 99.9% the speed of light would be just 14 feet long. Problem: the reason why Einstein concluded that the speed of light was the cosmic speed limit is because once you pass the light barrier, the Enterprise would have negative length. Go figure.

2. Time Dilation : According to STR the faster you go, the more time slows down for you. Experiments with 
supersonic aircraft show this. But let’s up the ante: if you embark on the Starship Enterprise to explore strange new worlds and seek out new life and new civilizations, and travel at the speed of light for about a year, then upon your arrival back at Starfleet Command your colleagues will have aged about ten years. So, time significantly slows down for you. Problem: If you’re traveling faster than light, time may slow down so much that it starts to go backwards. You may get back before you even left. Talk about back to the future.

3. Mass Gain: According to STR, you tend to get more massive (that is, put on more weight) as you move faster and approach the speed of light. This is because your energy equals your mass times the speed of light squared (E=mc2). In other words, because your energy is increasing with your speed, your mass necessarily increases. As you approach the speed of light, your weight becomes, well, huge. All those “yo’ mama” jokes suddenly become real: “Yo’ mama is so fat, small objects orbit her.” Her weight increases by 100, 1,000, 10,000 times. Problem: at greater-than-light speeds, she’d be infinitely heavy—heavier than the entire universe. No diet, however radical, can hope to save your mama at that point.

In short, all of physics is thrown into doubt if those neutrinos actually can achieve faster-than-light velocity. All is not lost yet, however. One issue is that the distance between the exact point that the neutrinos are shot out of the accelerator in Switzerland, and the exact point that they are detected in Italy, must be measured within inches. One thought is that maybe the GPS system isn’t accurate enough. There are several such speculations on what could have gone awry with the OPERA and its methodology, as well as workarounds that enable SR to retain its standing, such as quantum tunneling solutions, string theory solutions, and tachyon solutions. But scientists just don’t agree that there’s any solid ground to hold onto here. Time will tell. The universe is an amazing place. In lieu of a strange STR universe where time slows down and mamas gain thousands of pounds, we may have to get used to a bizarre faster-than-light universe where bartenders tell folks to take a hike—folks who haven’t yet walked into the bar.

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