It’s a 24-hour dance…er, science party!

Please join us tomorrow to raise money so that CosmoQuest can continue to do its good work on science outreach!

Tomorrow, I’ll be spending an hour talking about my work with CosmoAcademy: the online classes offered through CosmoQuest. However, my colleagues Pamela Gay (AKA StarStryder) and Nicole Gugliucchi (AKA the Noisy Astronomer) will be hosting an entire 24 hour fundraising hangout! Please check in tomorrow, watch the conversations, and please please donate if you can. In this era of budget cuts and sequestration, public science education is suffering and you can help. Other guests will include Phil Plait (the Bad Astronomer), the Death by Puppets crew, and a variety of scientists!

The priors don’t lie: all the ladies love Bayesian statistics

Statistics is rarely sexy, sometimes satisfying, occasionally misused, but useful enough that more people should know how to use it than do. (Insert obvious condom joke here.) However, a particular method in statistics got additional attention last fall during the United States national elections: Bayesian inference. I wrote two pieces last week, drawing from a recent Science article, that highlighted Bayesian methods. The first (written for Ars Technica, now picked up at WiredUK!) was about Bayes’ theorem and why its use is still controversial for some people.

Bayes’ theorem in essence states that the probability of a given hypothesis depends both on the current data and prior knowledge. In the case of the 2012 United States election, Silver used successive polls from various sources as priors to refine his probability estimates. (In other words, saying he “predicted” the outcome of the election is slightly misleading: he calculated which candidate was most likely to win in each state based on the polling data.) In other cases, priors could be the outcome of earlier experiments or even educated assumptions drawn from experience. The wise statistician or scientist constructs priors that are informative, but that isn’t always easy to do. [Read more…]

My second, follow-up piece was for my own blog, and included a tutorial introduction to Bayes’ theorem. Admittedly, this example is very simple and doesn’t do justice to the power of Bayesian methods, but a better example would be pretty involved, so I decided to hold off for now. (I may revisit the topic later, though, depending on time and inspiration.)

So, Bayes’ theorem reads: the probability of a hypothesis being true (based on the data and prior information) depends on the probability of the hypothesis from prior knowledge, multiplied by the likelihood of that particular data showing up, divided by the chance of the data showing up based on the priors alone. Using Bradley Efron’s example from his Science article, consider the case of a couple whose sonogram showed they were due to give birth to male twins. Given that data, they wanted to know what the chances were that the twins would be identical as opposed to fraternal — a genetic question undecidable by sonogram. [Read more…]

I am a RealScientist!

OK, it’s not quite like Pinocchio‘s “I’m a real boy” transformation, but I will be handling the RealScientists Twitter feed this week, talking about what I do as a professional science writer and (of course) physics, astronomy, cosmology, music, comics, or whatever I usually talk about. If you’re on Twitter, follow along, and make sure you stick around: that feed hosts many excellent people from all over the world in a variety of disciplines. (The official introduction is at the RealScientists site.)

Thanks to Upulie DeNovo who invited me to participate in this project, and to the other RealScientists administrators.

Danish physicist Niels Bohr, whose model of atoms helped explain the spectrum of light emitted and absorbed by different elements, as illustrated by the spectrum emitted by the Sun. [Credits: AB Lagrelius & Westphal, via Wikipedia (Niels Bohr photo); N.A.Sharp, NOAO/NSO/Kitt Peak FTS/AURA/NSF (solar spectrum); moi (composite)]

Danish physicist Niels Bohr, whose model of atoms helped explain the spectrum of light emitted and absorbed by different elements, as illustrated by the spectrum emitted by the Sun. [Credits: AB Lagrelius & Westphal, via Wikipedia (Niels Bohr photo); N.A.Sharp, NOAO/NSO/Kitt Peak FTS/AURA/NSF (solar spectrum); moi (composite)]

Many of us are familiar with the Bohr atom: a simple model with a nucleus and planet-like electrons orbiting in circular paths. It’s a useful picture, even though it’s not complete. Bohr proposed it in 1913, but it took about ten more years for physicists to work out why it worked — and to refine it into the quantum-mechanical picture of atoms we have today. However, we’re still probing the structure of atoms, especially the really bizarre behaviors under extreme conditions. Bohr’s contributions are still relevant today.

Despite a century of work, atomic physics is not a quiet field. Researchers continue to probe the structure of atoms, especially in their more extreme and exotic forms, to help understand the nature of electron interactions. They’ve created anti-atoms of antiprotons and positrons to see if they have the same spectra as their matter counterparts or even to see if they fall up instead of down in a gravitational field. Others have made huge atoms by exciting electrons nearly to the point where they break free, and some have made even more exotic “hollow atoms,” where the inner electrons of atoms are stripped out while the outer electrons are left in place. [Read more…]

A century of the Bohr atom

I don’t spent a lot of time thinking about the multiverse: the possible existence of regions of the cosmos that have never been connected to ours at any time, and may never be in the future. That’s because those parallel pocket universes aren’t directly detectable, and may never be even indirectly detectable, putting them into a category that’s hard for a scientist to deal with. However, inflation — the extremely rapid expansion of the Universe in its earliest instants — almost certainly would produce those pocket universes, so I’ve reluctantly come to terms with the existence of the multiverse, on the principle that the alternative ideas are largely problematic.

Some physicists have gone a bit farther with the multiverse idea. Since our Universe has the correct physical/chemical properties to harbor life (self-evidently, since we’re here to talk about it), and those properties depend on a delicate balance of physical parameters, then maybe the multiverse can help explain what makes our pocket universe habitable. If those other pocket universes have different physical parameters, maybe the set ours has came about by a random process: no need for “fine-tuning”. However, as I argue in a new piece for the Nautilus blog, the fine-tuning problem is separate from the question of the multiverse, and philosophy won’t provide the solution to either.

We know that the universe is capable of supporting life, and that any physical parameters must be consistent with that obvious fact. Beyond that, we can’t go yet: We have no more evidence for multiverses than we have evidence for life beyond Earth—though it’s reasonable to think both exist. The uncomfortable possibility is that there are other pocket universes, but we’ll only ever know about them indirectly. That doesn’t make them any less real, just discomforting. [Read more…]

On the multiverse, metaphysics, and meaning