Predictions of physics theories

Over at Cosmic Variance, Sean Carroll posted yesterday about a straw poll taken at a small gathering of physicists who focus on the cosmological theory of inflation, asking them what they thought the likelihood of the general principle of the theory being true was. He noted that his estimate of of 75% chance was on the low side compared to the majority of the people attending the conference who put the likelihood of inflation being a fact at around 90%. After the conference, he asked several of his colleagues at Caltech, and found that many of them, none of whom were directly working on inflation, put the likelihood at only 25%.

He then asked his readers to present their own estimate for the probability that inflation was true. And he added a few other major theoretical concepts in physics: supersymmetry, string theory, the Higgs boson, large extra dimensions, WIMP dark matter, and “any non-cosmological-constant explanation for cosmic acceleration.” He left the categories quite vague (for example, does “large” mean, “micro/macroscopic” or just “larger than Planck length”) because there are often multiple theories within each category, but for the most part there is a single unifying concept for each theory.

60+ people with a wide range of backgrounds have responded with their estimates now. And the results are interesting in a couple of ways. The two charts below show the how many people proposed specific percentages of the likelihood of each theoretical concept. The interactive versions are available on GoogleDocs.

Compiled likelihoods of several physics theories, based on predictions given by commenters at Cosmic Variance

Compiled likelihoods of several physics theories, based on predictions given by commenters who indicated an educational/professional background in physics at Cosmic Variance

The first things that jump out at me are that pretty much no one believes that large extra dimensions have any chance of existing (average likelihood being 9.08% with a standard deviation of 15.47), while the Higgs particle is considered quite likely to exist (average = 79.52%, std dev = 26.77), with inflation also having a better than 2/3 chance (average = 67.02%, std dev = 28.81). Amongst those who claimed an educational and/or professional background in physics (and astronomy), large extra dimensions are considered similarly unlikely, but the Higgs boson, inflation, and WIMPs are both considered ~10% more likely than by the commenters as a whole.

On the other hand, the chances given to supersymmetry, string theory, and non-cosmological-constant cosmic expansion are all stable in being considered relatively unlikely by both laymen and scientists alike.

It’s an interesting little bit of meta-analysis, really, which raises some questions about why certain major theories are accepted both in and outside of those educated in physics, why some of those are more accepted within the subset, and why other theories are considered equally less likely, regardless of education. It is likely that “insiders”, as it were, have a firmer basis in the fundamentals of physics and so they are better able to evaluate the theories themselves, which would explain the variation between the insiders and outsiders on certain topics. But I don’t think there is anything about the Higgs boson, or inflation, or WIMPs which differentiates them from the other theories that makes them less comprehensible to those with a physics background.

And since this is a non-rigorous, loosely defined survey, I wouldn’t really want to try to draw any significant conclusions from it. But it is interesting to get a general picture of how various theories are viewed and accepted within the physics community as a whole, and amongst the larger population of laypeople who are interested in modern advancements in the science.

Update 2/11/2011: Over 100 people have commented now.

Inflation SuSy Strings Higgs
Avg Std Dev Avg Std Dev Avg Std Dev Avg Std Dev
Everyone 66.79 28.63 44.07 30.24 30.52 30.47 76.96 27.41
Physics Background 71.43 22.13 45.56 27.99 25.37 26.83 85.32 20.61
Difference 4.64 -6.5 1.49 -2.25 -5.15 -3.64 8.36 -6.8
large xtra D WIMPs non-CC exp
Avg Std Dev Avg Std Dev Avg Std Dev
Everyone 11.76 20.01 58.41 29.36 27.74 28.38
Physics Background 8.54 14.67 60.84 25.48 25.07 25.01
Difference -3.22 -5.34 2.43 -3.88 -2.67 -3.37

Compiled likelihoods of several physics theories, based on predictions given by commenters at Cosmic Variance

Compiled likelihoods of several physics theories, based on predictions given by commenters who indicated an educational/professional background in physics at Cosmic Variance

A bird’s eye (ok, back) view of flight

Ride onboard a peregrine falcon and a goshawk. One is the fastest animal on the planet, the other is one of the most maneuverable. I’m not sure you can watch this and not say, “Man I wish I could do that.” Unless you have vertigo or get motion sick, that is.

One of the questions that people always seem to ask during group building activities is always, “What’s your favorite animal?” or “What animal do you wish you could be?” My answer has been the peregrine falcon more often than not. Now I had a chance to ride along with one, which is quite awesome.

Darwin’s other “secret”: terraforming Terra

Imagine you’re exploring the remote islands documenting aspects of the various ecologies you encounter. One of these islands is used as a waystation by the British Navy, but due to its volcanic history and remoteness is woefully lacking in significant vegetation and wildlife. What do you do?

If you are Charles Darwin, you encourage a friend of yours, who you know will be visiting the same island, to establish a series of shipments of trees, grasses and bushes and other forms of flora from botanical gardens from all across Europe to be planted on the island to flesh out the ecosystem on the island.

Why would you do that? To increase local water supplies. The trees and other plants capture rain and reduce evaporation, even with the dry prevailing winds in that area of the ocean. Over time, the plants turn the volcanic rocks into extremely rich soils. Now, the island is a cloud trap and home to a full-fledged forest, albeit one unlike any other on the planet — playing home to eucalyptus, pine, bamboo and banana trees and many others.

And why is this significant? One of the biggest problems with human exploration of the other planets in the solar system is that they aren’t “habitable” — they lack liquid water and breathable atmospheres. The science fiction and science of changing those worlds is “terraforming”: “making like Terra”. But it is rare for scientists to have real world examples of how terraforming can work. The island of Ascension is one of those examples. While it isn’t a completely isolated system the way that Mars is, there are significant ideas that can be applied to the concept of terraforming Mars.

The more we learn about Mars, the more we learn that it is potentially terraformable. But it will likely take more than the few generations. We can’t start with trees, ecologies are much too complex and trees have too many large requirements. We’d have to start with extremophile bacteria and other simple life forms such as lichen to begin creating usable soils and adjusting the atmosphere and then working our way up. One of the better looks at the process in science fiction is Kim Stanley Robinson’s trilogy Red Mars, Green Mars and Blue Mars.

Until we get to Mars though, we can continue to be amazed at the wonders of nature of planet Earth.

This was done with a slide rule

This. So hard, this.

Though I have to admit I was quite bad about doing my homework. But I learned HOW to do the math anyway. If and when I have kids, I’m going to be teaching them basic math outside of school, because I don’t want them to be stuck using crutches to solve simple problems.