rounding errors, machine errors, so many possibilities for such a tiny discrepancy. Reminds me of the neutrino anomaly that supposedly disproved relativity, until it was later discovered faulty wiring was to blame.
This is a bit different. The neutrino error was when the only data-collection system was reporting surprising results, which can't really be invalidated without, well, getting another data-collection system and comparing.
These errors are surprises in the data itself: since the position of the object can be measured by multiple systems, it's considerably less likely that they would all make the same mistake. Of course it's possible that there's a 'single point of failure', like the data published back from the probe, that causes all the calculations to be off by the same amount.
On the other hand, the fact that these same probes/instruments can report everything else with extraordinary accuracy discounts that theory somewhat. It's still possible (perhaps the bug / cosmic-ray-induced bit flip only affects one particular data collection code path..) but it's less likely.
Altogether, my intuition for the neutrino result was "this is probably a broken experiment", but my intuition for this is "there's an effect that's not being accounted for". That effect could easily be forgetting to account for thermal radiation reflection or something else that's relatively uninteresting, but, I still think there's something going on.
It was in response to the parent wondering about overlooked phenomena. Perhaps sunlight or even earthlight heat the surface of the moon and cause thermal expansion. That could easily displace things by several millimeters.
The neutrino error was very much people saying, we don't think this is accurate, but we don't know why and we are not going to hide this data. I saw a video of the press release and the guy looked like he really did not want to be saying those words.
Now, after they said that plenty of people ran with it way to far. However, I feel the team did the right thing.
Nautilus has an interview with him (Antonio Ereditat) [ http://nautil.us/issue/24/error/the-data-that-threatened-to-... ]. From his point of view, he did the 'right thing' by announcing the apparent FTL result and inviting people to find out what was wrong.
He absolutely did the right thing. But in the end I think he resigned because the media circus that followed the announcement meant he could no longer contribute effectively to the project.
What happened before is described in the Nautilus article:
"In March of 2012, as the dust settled, the OPERA collaboration held another vote, this time to determine whether the collaborators had confidence in the leaders of the experiment. Each member institution got one vote. The tally ended at 16 to 13 favoring no confidence with several abstentions, well short of the two-thirds majority required to impeach the leadership, but enough to send a strong message. Both the OPERA leader, Ereditato, and the experimental coordinator, Dario Autiero, resigned."
He's, as far as I understand, now the director of the Laboratory for High Energy Physics at Bern University:
Because the sun attracts the probe (and vice versa). Or equivalently the probe is climbing out of the gravity well of the sun loosing kinetic energy in exchange for potential energy in the sun's gravitational field.
The same reason as when you throw a ball into the air, and it slows down despite moving away from the Earth (until it eventually stops and starts to fall again).
The Pioneer anomaly was solved IIRC. The likely culprit was identified as heat being emitted in a particular direction, accelerating the probe due to radiation pressure.
> The pioneer probes were nuclear powered through a radioisotope thermoelectric generator (RTG). These RTGs usually give off heat uniformly, but the design of Pioneer meant that some of the radiant heat was reflecting off the probe resulting in a thermal recoil.
ITM 0.1 km/h/year, and yes. The Pioneer Anomoly is a photon drive: the RTG gets hot, infrared photons get emitted preferentially in a particular direction (because the body of the spacecraft blocks them), and it's a simple reaction drive. Nothing fancy there.
You could make it loads more efficient by putting the RTG at the focus of a parabolic reflector. Now all the photons are being emitted in a single direction, which means you get much more thrust.
...a perfectly collimated photonic rocket runs at about 300MW/N. Assuming you're New Horizons, you have a mass of about 500kg and a 4kW RTG, so you'll get a thrust of 0.1mN, which means an acceleration of 5x10^-8 m/s^2. Assuming my arithmetic is correct (a totally unwarranted assumption!), then over a year this adds up to a velocity change of 1.5 m/s.
No, your maths is wrong.. in fact after 10 years the acceleration had provided a 1km/hr velocity, resulting in a 400km displacement from its projected position.
I know a lot of physics, and have strong opinions on physics writing, but I still think this was a pretty interesting and entertaining article. If we have problems with it can we say what they are instead of just assuming everyone agrees that it's bad?
I did read the article. It's not objectionable, although rambling is certainly a descriptive word. 'Starts With A Bang' articles often get posted to Slashdot, and I'm often careless enough to read them. Whenever I want a cursory yet breathless introduction to yesteryear's physics news, with a provocative title, SwaB delivers.
It's B-grade science writing, written to be interesting and informative to a mass audience. It probably does fairly well on its own terms. However, I'm not personally interested in a remedial physics education, I'm interested in physics news. For me, that's where SwaB consistently falls short. Or, to be more concise, the blog is generally lowest-common-denominator physics writing. I am unpleasantly surprised to be met with contradiction and derision based on your reading of one article.
It's a mediocre article. It glosses a bunch of history adequately and then points out a completely different anomaly. By "completely different" I mean "has all the signatures of an instrumental or analysis artefact." It's intermittent (huge red flag) and while the article doesn't say so (additional red flag) close to the threshold of observation.
There are completely mundane explanations (upper atmosphere models slightly wrong, unaccounted-for EM effects) so while there may be a fundamental cause (gravity is doing something exciting) the odds are that it's a boring effect, just like the superluminal neutrino observations.
I didn't find the writing misleading at all. It didn't overstate the likelihood that there is actually new physics to be found in these anomalies and gave a specific example where an anomaly was explained by known physics that was merely unaccounted for.
The article definitely did not state or suggest that it wasn't a boring effect. It was just enumerating surprises due to gravitational theories' mismatching reality.
Discovering that the Pioneer probes were off due to the moment of their thermal radiation was not 'new physics', but it was still interesting, in that it was missed in the initial attempt at modeling. And that's fine. It's still interesting and made for good reading.
Anyway, I liked it. I don't think it was mediocre at all.
