Comet ISON is seen rounding the Sun in this animation of 96 images captured by the STEREO-B spacecraft between November 28 and 29. (Source: NASA / STEREO / Emily Lakdawalla) In a post yesterday, I declared Comet ISON dead after it appeared to have gone dark during its closest approach to the sun. And I had good reason. Scientists observing the event had proclaimed it so. But as the animation of images from the STEREO-B spacecraft above shows, something sure is glowing brightly as it speeds away from the sun now. Has it risen from the dead? If it has, is it now just a shadow of its former self — perhaps a clump of fragments traveling together but something we shouldn't call a bona fide "comet" anymore? Or as Karl Battams, an astrophysicist with the Comet ISON Observing Campaign put it in a headline on one of his fabulous blog posts, maybe it is "Schrödinger's Comet," meaning it is alive and dead at the same time, at least for now? For an explanation of exactly what this means, make sure to keep reading to the end... Whatever the answer may be, it will take more time to determine it. In the meantime, one thing is clear: After ISON failed to show up in images from the Solar Dynamics Observatory spacecraft, NASA itself was busy writing the comet's death certificate: "The comet is believed to have broken up and evaporated," the agency said. NASA was taking its cues, of course, from what scientists were saying. And during a NASA Google Hangout convened for the comet's closest approach to the sun, participating experts held out very little hope that it survived. For example, Alex Young, a solar scientist with the Goddard Space Flight Center, said that it seemed like "it just didn't have what it takes to stay together." Young pointed out that the intense gravitational forces of the sun would have put enormous stress on ISON's nucleus. "Gravity is so strong that it tears and rips and pulls at a comet," he said. "And in this case perhaps it just experienced so much stress that it broke apart, and once it broke into little pieces then they all melted much quicker, and perhaps we've just lost it." But notice that word "perhaps." For whatever reason, Young evidently felt that he needed to leave the door open just a crack. And then, wouldn't you know it, Comet ISON came roaring right through it. Or, more accurately, it came flying out from its close encounter with the sun, tail ablaze once again. ALIVE! Or maybe not? Or maybe both? This brings us back to Karl Battams and his"Schrödinger's Comet" blog post. This was, of course, a reference to the famous "Schrödinger's cat" thought experiment, proposed by Erwin Schrödinger back in 1935 to illustrate a paradox at the heart of quantum theory. According to quantum theory, a particle can exist in all of its theoretical states superimposed on each other at the same time. And it's not until an observation is made of the particle that this superposition collapses, and the particle appears in one particular state. Schrödinger's thought experiment scaled the whole thing up to, well, a cat — one that is sealed in a box with a vial of a radioactive substance. The idea is that there is a 50/50 chance that radioactivity will kill the cat. And we can't know whether it is dead or alive until we open the box. So far, so good. But Schrödinger's point was that if one particular interpretation of quantum theory was correct, then the only conclusion is that the cat is simultaneously alive and dead in the box until the observation is actually made. In other words, it is the act of observation that causes the superposition of dead cat/live cat states to "collapse," revealing a cat that is either one or the other. So what the heck does that have to do with Comet ISON? In an email this evening I asked Karl Battams what he had in mind with that "Schrödinger's Comet" headline, and here, in full, was his response:
First, everyone has been saying for months the now rather cliched line that "comets are like cats; they have tails, and do as they please". So Schroedinger's Cat/Comet is an obvious reference. But second, it is an apt title as we really do not know if comet ISON is dead or alive and - much like said theoretical cat - that answer will only come through observation! (And by "dead or alive" I mean, is there a nucleus or not -- we suspect so but we're only 60-40 in favor of that.)
And there you have it. Comet ISON: IT'S ALIVE! IT'S DEAD! For now, actually, both...
