Physics 1, ghosts 0

Last night I attended a fun event put together by the Illinois Science Council on the science of the spooky. My friend Dan Hooper, an astrophysicist at Fermilab, was presenting on “The physics of ghosts” (specifically: why they wouldn’t work), and it seemed like there might be some opportunity to heckle.

Before Dan, though, there was a talk was on the evidence for “psi” — which is just ESP, but called psi because the proponents know that people realize ESP research is bunk. It was, shall we say, typical of the form: Lots of plots showing effects that are just barely statistically significant, a discussion of how the methodology of previous studies was hopelessly flawed followed by a statement that this one was free of bias, and even a claim that Carl Sagan himself had agreed that psi was worth of study. (You’ll be shocked to learn that the last one was quote-mined.) Yawn.

Dan’s talk was much more entertaining. He took the question “is there a feature in the laws of physics that would allow ghosts to exists?” and turned it into an opportunity to take us on a tour of what’s known about the fundamental laws of physics. ZapperZ, who was also there and who told me about the event in the first place, wrote up a review of the arguments (and yes, he addressed the idea that ghosts could be dark matter). The central problem, Dan claimed, is that if they can interact with us at all then they have to have some kind of electromagnetic interaction; if you can be seen it’s because you’re emitting photons; if you can be heard, it’s because you’re pushing the atoms in the air around; if you can be felt it’s because you’re pushing on the atoms in the person who’s feeling you. However, it’s exactly this electromagnetic interaction that keeps things from moving through barriers like walls.

Actually, the issue that always bugs me was one that Dan didn’t get to: most rooms have 6 barriers, not 4. If ghosts can move through walls, then they can move through floors. To me, the ability to not be stopped by a floor does not sound like an advantage. Can you imagine waking up as a ghost, being shocked that you’re still conscious, and then going “uh-oh” as you realize that you’re falling through the Earth? And then you get to spend eternity in a giant ghost-ball at the center of the Earth with all the other poor souls who are stuck down there. Ouch.

Like ZapperZ, though, I was most interesting in the question session that followed. However, it was a different question that caught my attention. The question was: is there anything that scientists have evidence for and that they believe in, but to which there is no plausible explanation? Dan’s answer was quite good. We now have several, independent, lines of evidence that show that the expansion of the universe is accelerating. In standard cosmology with the types of matter that we’re familiar with that simply can’t happen. The evidence is so overwhelming, though, that almost everyone has become convinced that the effect is real. We’ve even made up a name describe the new kind of “stuff” that’s responsible: “Dark Energy”. We have no idea what this stuff is; we have no idea how to directly detect it; we have no idea where it comes from — but we are convinced that it’s there.

The question was obviously asked in the spirit of: “aren’t scientists so closed-minded that they won’t accept things that are out of the ordinary?” The answer is a resounding “no”. In 1998, when the cosmic acceleration was first discovered by systematic studies of supernovas, it was a complete shock to the community. No one had expected it. At the same time, the scientist involved couldn’t be more excited. Here is a major new find, a discovery that requires a huge shift in the way we conceive of the universe. We live for things like this. However, much of the next few years was spent trying to show how the result was wrong: maybe it was due to a new systematic effect; maybe there was some new aspect of how supernovas behaved that was skewing the result. And yet, not only did the observation survive each attack, every new observation provided even stronger support for the idea. This is the key difference between science and pseudo-science. The same people who were so excited about the discovery were the ones working tirelessly to disprove it. It is only after a barrage of such attacks that the community as a whole accepted the new idea.

I should note in closing that there was a third talk, by someone not listed on the program, on all the rather gristly things that had been done in the past as medicine. Unfortunately, I was distracted for most of it, and for a lot of the rest I wish I’d been distracted. Not because it was bad — the talk was fantastic — but let’s just say that it’s amazing what people will have surgically implanted to increase their virility.