How Likely is the Existence of the Bullet Cluster?

A new preprint asks, “How rare is the Bullet Cluster?”. In the paper, the authors use a numerical simulation of a universe with the current ΛCDM cosmology to see how many Bullet Cluster-like objects should exist in the universe. The simulation covers a volume of billions of cubic parsecs (a nontrivial fraction of the size of the visible universe) and contains dark matter “particles” with masses equivalent to tens of billions of suns. In this context, a “particle” is not a single dark matter particle but rather a clump of matter. Since matter is clumped together into these large “particles” in the simulation, the simulation will only be able to give information about what happens on scales much larger than a single “particle.”

The authors define a Bullet Cluster-like object via constraints, or cuts, on the properties of the sub-clusters. (Remember, the Bullet Cluster is the result of the collision of two large clusters and merger of some of the mass in the clusters.) These properties include the separation between sub-clusters, the sub-cluster masses, and the sub-cluster velocities. The search is restricted only to a limited range of redshifts. While the number of Bullet Cluster-like systems is quite dependent on the exact constraints, the authors find that it’s reasonable to expect around one such system given the constraints that they consider the most interesting. Thus, current knowledge of these systems in the real universe is consistent with the ΛCDM cosmology, but if too many more are discovered, their existence would potentially require cosmologists to reconsider their models.


Physics Makes Kids Stop Believing in Santa

Or so implies this Slate article. Apparently, some scientists have decided that it’s important to study how kids’ beliefs in things like Santa evolve. They suggest that many children are able to notice inconsistencies in the logic behind Santa Claus and are able to independently determine that Santa, or at least many of the legends involving Santa, must be false. In other words, kids are often smarter than people think and don’t necessarily blindly believe what their parents tell them.

io9 On Quarks

io9 has a nice short article on quarks and how they, despite being quite light (in the case of the up and down quarks) are able to give us so much mass. It also comes with a video showing some weird visualizations of matter at different scales – from strings/branes (totally hypothetical) to living cells. The video looks much more like an artistic rendering inspired by physics than an accurate representation of the subatomic universe.

Media Figures Supporting Science

Over at Slate, Phil Plait has an article on promoting media figures that support science. In particular, he discusses his decision to retweet a picture highlighting some famous Hollywood actresses who have shown some interest or aptitude in science. The controversy here is over the question of who should be applauded or treated as a role model for their interest or work in science and related fields.

The picture in question highlights five actresses with a variety of connections to science, from inventing new technologies to writing children’s books about math and science. Plait notes that the most controversial choice in the picture is the inclusion of Mayim Bialik, who earned a PhD in neuroscience. It’s not her actual work in earning the PhD that is controversial (as far as I know – I’ve never even taken a neuroscience class), but rather it is her apparent connections to various fringe groups pushing alternative medicine and anti-vaccination beliefs. Plait decided that Bialik’s work using her celebrity status to popularize science is more important the negative effects of her support for pseudoscience.

I would actually take the opposite position on this. The purpose of the image seems to be to highlight some celebrities who can also be seen as role models for children (and girls in particular) who might be interested in science. It shows that even cool people like science. However, in the case of Mayim Bialik, her support for pseudoscience and bad medical practices has far outweighed her scientific achievements in the eyes of the public (she has a PhD but doesn’t appear to have done any research since graduating). It’s difficult to hold her up as a role model when she’s setting back public support of science in other fields. While the idea of the image discussed in the article is fine, I think it would have been much better to showcase five people who have done real work (beyond student research/work) in science or popularizing science and who aren’t associated with anti-scientific groups. It really shouldn’t be that difficult to find five such people, although if it is difficult to do so then that might be a more interesting topic to talk about.

Study: Don’t Trust Medical Advice You Get From TV

A study published earlier this week on fact-checking medical claims made on TV has been popping up all over the internet for the past few days. The authors watched a number of episodes of two different medical talk shows, compiled a list of various recommendations and then tried to find evidence supporting these recommendations. This is a pretty qualitative way to study this, but sounds like a reasonable way to fact check these programs. A well-supported medical claim ought to be easy to find in the literature. Claims that can’t be found in a short search through the literature probably lack enough evidence to make a serious recommendation.

The article makes Dr. Oz’s show look particularly bad (and Dr. Oz’s credibility has already suffered a number of blows this year). Less than half of the 80 recommendations from his show included in the study were found to have any serious supporting evidence. Furthermore, it was rather shocking to see that Dr. Oz’s show mostly gives dietary advice (over 1/3 of recommendations) or recommends “alternative therapies.” This suggests that Dr. Oz is really just telling viewers what they want to hear and not what they need to hear. The other show, The Doctors, wasn’t great either but seemed to have a much more balanced mix of recommendations and also did a far better job at suggesting that people consult their actual doctors rather than just blindly following what they saw on TV.

Having prominent shows with millions of viewers peddling quack medicine is very bad for all science fields and not just medicine. Medicine is probably the closest most people get to actual science, so when unsupported recommendations don’t work they could lead to eroding the public’s trust in science. Furthermore, medical professionals have a duty not to mislead the public. This paper suggests that prominent public figures in medicine are failing at one of their most basic duties.

Stephen Colbert Shall Live Forever

Or, at least his character will. The Colbert Report ended last night in an episode with an absurd number of cameos from celebrities, media figures and politicians. Instead of killing off Stephen Colbert (with a silent t) as many expected, Colbert vanquished Death, attaining immortality in a scene that looked like an amalgam of the Seventh Seal, He-Man, and Highlander. Interestingly, the credits ran with Neutral Milk Hotel’s Holland, 1945 playing in the background instead of the usual music, a fact that many stories have discussed today. Colbert (now actually playing himself and not Stephen Colbert the character) will go on to take over the Late Show. We can only assume that he’ll do a much better job than Letterman.

US To Restart Relations with Cuba

In a huge and unexpected story today, it was announced that the US and Cuba will resume diplomatic relations for the first time in over 50 years. This is quite possibly the biggest story in the Caribbean region since I was born. While easing restrictions on Cuba is not really that unexpected, the timing is. The negotiations were held in secret, so people are only finding out about everything today. This also comes along with the US and Cuba swapping some prisoners and Cuba releasing some political prisoners. The embargo is still in place, but many travel restrictions are being eased and embassies will reopen in the next few months. Congress has to end the embargo since that’s controlled by legislation, but the embargo doesn’t seem to be very popular in the US anyway. It’s failed to do any good for decades so ending the embargo can’t really be any less effective than keeping it. With this, the US now has diplomatic relations with all but four countries (according to Wikipedia).