It was reported a few days ago that in order to resolve the so-called “Deflategate” controversy, the NFL’s investigators have been trying to enlist the support of physicists. The investigators apparently started asking the Columbia physics department for some help in figuring out whether or not the Patriots intentionally under-inflated some footballs at the AFC championship game.
While I applaud any news putting physics in a positive light (and it’s hard not to look good when compared to the NFL), I can’t help but be puzzled by this story. Surely it would be much easier just to buy a bunch of footballs and test them under similar conditions to the game. You don’t need to come up with a theoretical model of what happened when you can just replicate the conditions that you’re trying to investigate.
It’s been reported today that Rita Jeptoo, the winner of the women’s competition in both the Chicago and Boston marathons last year, has been banned from competing for two years after failing a drug test. Prior to this, she had been credited as the winner for three Boston Marathons and two Chicago Marathons.
It’s very disappointing that someone who had been doing so well at distance running for the past few years was actually cheating.
Another technical design report has appeared on the arXiv, this time for the proposed Muon (g-2) experiment at Fermilab.
The name refers to the anomalous magnetic moment (g-2)/2 of the muon. A naive application of quantum electrodynamics says that the gyromagnetic ratio of elementary spin-1/2 particles should be g=2. When higher order corrections are considered, the result is slightly different from 2. It also turns out that these corrections can be calculated to high levels of accuracy and also measured with astounding precision. This makes measuring (g-2) for different particles (like electrons and muons) an excellent test of the Standard Model.
The muon anomalous magnetic moment is measured by creating a muon beam in a ring. As the muons decay, the resulting electrons are emitted in directions that are correlated with the direction of the muon’s spin. The muon’s spin direction precesses in an electromagnetic field at a frequency that’s different from the frequency at which muons travel around the ring. The precession frequency is related to the anomalous magnetic moment, so (g-2)/2 can be measured very accurately.
In sad news, Charles Townes died on Tuesday. Townes is one of the people credited for helping invent the laser, without which many important pieces of technology could not exist. He helped build the first maser (the microwave equivalent of the laser) at Columbia in the 50s and was awarded the Nobel Prize along with two others in 1964. He also spent some time serving as provost of MIT.
Another thing about that NPR piece that I referred to previously:
In the piece, the author includes this quote by Sean Carroll:
“Whether or not we can observe [extra dimensions or other universes] directly, the entities involved in these theories are either real or they are not. Refusing to contemplate their possible existence on the grounds of some a priori principle, even though they might play a crucial role in how the world works, is as non-scientific as it gets.”
and sums it up as this:
Thus, for Carroll, even if a theory predicts entities that can’t be directly observed, if there are indirect consequences of their existence we can confirm, then those theories (and those entities) must be included in our considerations.
I have several problems with this:
- We can’t really “confirm” anything in the sense that we can show it to be true. We can show that our measurements are consistent with theoretical predictions.
- Referring to direct and indirect observations without defining them makes that a meaningless statement. To be fair, Sean Carroll mentions direct observations and the author uses similar language. What would it even mean to directly observe something? In HEP we identify particles by their effects on the materials in our detectors. We can’t just grab a particle and ask it what it is. For particles that decay quickly, such as the W and Z bosons, we can only infer their existence from a statistical analysis of data. We can’t look at an event and say that it includes a Z. We can only say that it is consistent with a Z. Furthermore, particles like gluons and quarks are even more complicated to find, but we still accept their existence.
- After reading the linked essay by Carroll, I don’t think that’s a great quote to use to talk about his position. In the case of string theory, he mentions that string theories (i.e. the specific theories allowed in the general string theory framework) can make very specific predictions, most of which are inaccessible due to technological limits. String theories are in principle falsifiable. The multiverse is not necessarily falsifiable, but according to Carroll does make real predictions that can inform our understanding of the universe (and our empirical data). I think the point on string theory is not very controversial, but the point on the multiverse (i.e. the multiverse doesn’t need to be falsifiable to be scientific because it can affect how we interpret our data) probably is.
Anyway, after writing this and rereading the previous post, I definitely get the feeling that the NPR blog post isn’t giving a great explanation of what this debate is actually about. It’s summarizing things too much and losing a lot of the nuance in everyone’s positions.
NPR’s 13.7 blog has a new post entitled “The Most Dangerous Ideas in Science.” In it, the author discusses two of the more controversial ideas in modern physics: string theory and the multiverse. The debate on whether or not these theories are useful endeavors is presented as a mostly philosophical disagreement between those who believe that theories that could be true even if we can’t get any evidence either way are interesting and those who believe that theory should be much more closely tied to experiment. The potential danger seems to be that theoretical physics could end up in a place where it is completely divorced from even any attempts at experimental verification/falsification.
The post is actually a little difficult to comment on because it contains so little information outside quotes and paraphrases from others. I think both sides – at least, as presented in the post – have some decent points. Requiring theory hew too strongly to experimental data might prevent a lot of possible advances in theory. Predicting new things with little to no evidence is one of the most important things for theorists to do. That helps experimentalists know what interesting things might lurk in their data. Additionally, even intentionally unrealistic theories could yield new insights into real world physics.
At the same, I do agree that it would be dangerous for theory to become wholly detached from empirical science. Ellis and Silk’s main point, which I don’t think is explained particularly well in the NPR post, appears to be that the idea that we should accept the truth of something like string theory without proper evidence is dangerous and not that string theory is itself dangerous. That is something that I don’t have a problem with. Accepting an idea due to ignorance of better alternatives or incredulity at the possibility of better alternatives is certainly logically unsound. However, I wonder if Ellis and Silk go too far in their criticisms. The things they criticize (string theory, the multiverse, and also many worlds) seem to me to really be frameworks within which potentially testable models can be built or (in the case of many worlds) are explicitly philosophical musings on how to interpret empirical theories. A framework could be difficult or even impossible to falsify, but any given model that fits within the framework likely can (at least in principle) be falsified. Ellis and Silk even admit that particular types of string theory yield empirical predictions and that some multiverse theories are also testable.
Even if we never find a viable way to experimentally test string theory, a string theory consistent with the Standard Model would still be a breakthrough because it would provide an alternative model to the quantum field theory framework in which the Standard Model was built. A viable string theory that describes real physics would be very elegant, but that wouldn’t make it true. It wouldn’t make it false either. As it is, we only know that the Standard Model largely accurately describes subatomic physics, but we have probably no idea how many alternative theories also accurately describe the same data. Choosing between effectively identical models isn’t scientific, but that doesn’t mean that theories that replicate our understanding of the universe but also include some unfalsifiable assumptions aren’t useful or interesting. Why not let theorists come up with as many ways to end up with something that looks like our universe as they can? If these ideas are fundamentally flawed, we should show that that is so. Otherwise, we should at least accept such theories as possibilities (not as the truth) and consider if and how they can affect our universe. Honestly, I’m not sure if many of the people involved would disagree with that.
Much of the northeastern US is preparing for a potentially record-breaking blizzard, expecting up to several feet of snow. The storm is expected to be strongest in coastal areas like New York, Boston, and much of Connecticut and Rhode Island.
Meanwhile, here in Colorado, we’ve been enjoying unseasonably nice weather, with temperatures possibly reaching over 70°F (~26°C) today.