The IceCube journal club talked about it this morning too, and the conclusion was the same.
The paper was billed as evidence for dark matter, as shown by odd features in the ratio of positrons to electrons hitting the AMS detector in orbit around the Earth. The notion is that the features are due to dark matter decaying into electron/positron pairs.
Unfortunately the structure shown doesn't really suggest much of anything, because nobody has a clear enough model of what to expect. Something is odd, but whether this is something like the knee in ordinary cosmic rays or something different is hard to tell yet. The most interesting information was left out (the highest energy region), probably because the uncertainties are much harder to determine.
The detector uses two methods of calculating energy: bending in a magnetic field and measuring how much light is produced when the particle smashes and "showers" in the "calorimeter". The problem is that at very high energies the track in the magnetic field is very nearly straight, and it gets harder to tell positive from negative then. And the shower of particles and light becomes large enough to leak out the back of the "calorimeter." So there are larger and more complicated uncertainties on the really high energy electrons.
The hoopla is fake and annoying. However, the work they did is quite good. They had to figure out which particles were electrons and which were the far more common protons, measure their energy two ways, and do all this in a satellite. It would be easy (relatively) to do this kind of thing with a ground-based machine where you don't have to worry about weight and can just plug into the wall for electricity. To do it in orbit is a tour-de-force.
But it says nada about dark matter. I can't blame the reporters for getting it wrong this time, the press release is full of enthusiastic hints.
BTW, if you look at the low end of the spectrum in their plot, you see a huge difference between the AMS and the Pamela data. That turns out to be easy to understand. What's plotted is a ratio between positrons and electrons hitting the detector, and the Sun has been acting up lately and slinging out a lot more electrons, so the ratio changed.
Many, including you, sponge, and bsking, have commented on journalists' willingness to overstate a finding. The usual argument is that they want to sell papers, or alternatively, show off that they can guess what the implications of all this are and thus, how clever they are. I don't quite approve of the former, but I understand it.
ReplyDeleteThe latter, which looks even more understandable to a conceited person such as myself, has a big missing piece that I have not seen comment on. Selling the story and making a living I can see. But I know people in the sciences, both online and in human space, and I would be humiliated to get it wrong in front of them. I exercise a proper caution because quite often, I know I don't know. I'm not going to blather about dark matter as if it's something I am familiar with if I am going to reveal in the second paragraph that I think it's sorta related to Darth Vader and Sith training.
So. Do these journalists 1) not know any scientists? 2) not care about humiliating themselves, or 3) not know they are humiliating themselves?
None of those would be an especially comforting possibility, yet one or more must be true.
What is most aggravating about this story is that press release. I can't blame the reporters for that.
ReplyDeleteIn general, I think reporters rely on people forgetting.