Monthly Archives: February 2011

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

The ebb and flow of battle

For as long as humans have been describing warfare and battles we have described the ebb and flow as first one side and then the other gains the upper hand, pushing their opponent back across the battlefield (or, in the larger picture, across the map.) However, I don’t think any accounts of such events have ever really lent themselves to a true understanding of just how battle lines can shift within the duration of a fight.

Prior to the development of the modern firearm and the introduction of armored vehicles, a battle line was very much a line. A mass of men armed with melee weapons and short range projectiles, occasionally aided by archers and/or cavalry. The two sides faced up against each other and bashed each other in the face. Depending on the situation, it might have been tightly formed lines such as the Roman legions or Greek phalanx, where only the first few lines were actively fighting at any one moment, or it might have been more loosely formed, where the two masses became wholly interspersed amongst one another (as seen in Braveheart).

Early modern firearms still relied on massed lines of men, but that was because of the inaccuracy of the weapons and because battles usually still resorted to hand-to-hand combat.

Both of these periods saw tactics in which reserve units were sent to reinforce ones’ own weak lines, or to overload weak spots in the opponents. The attacks and counters in this manner are what led to the forward and backwards movement of the fighting across unprepared (lacking significant constructed defenses) battlefields.

Even into the 1900s, hand-to-hand combat was quite common, despite the increase in accuracy of firearms. Bayonet charges were quite common in both WW1 and WW2. However, in WW1, battles were often dependent upon the ability of one side to gain control of prepared defensive positions, making it a much more static environment in terms of what could be gained and lost. Attacks were often made with multiple waves of infantry charges. If an attack failed, the defender had not lost any ground and the attacker had not gained any.

By WW2, the days of inaccurate, low rate of fire weapons were gone. And as a result, so too was the day in which two groups massed on a field and fought face to face (if they could help it). The nature of the war had one side utilizing infantry distributed amongst prepared, static, defensive positions and artillery with mechanized reinforcements, while the other used a combination smaller individual units of infantry supported by armored vehicles, aircraft, and much more accurate artillery and naval fire to help overcome heavily prepared defensive positions. Because of the less solid nature of the lines of combat, the ebb and flow of the battles were much less obvious (to anyone who wasn’t actually in the middle of it all).

The modern development of video has given us the ability to record and see just how lines of combat ebb and flow. But because of the shift away from massed front lines, there isn’t much chance for us to actually view the ebb and flow of a battle. And most cameras brought to the front lines of a combat zone are usually in the thick of things, not getting a bird’s eye view of the larger situation. But the last few days have presented us with something we’ve never had before. A top-down look at fighting between two large crowds primarily armed with melee weapons and simple projectiles — rocks and molotov cocktails. The clashes between the anti-government protesters and what seem to be government controlled thugs have been recorded and broadcast by several news agencies who have set up their cameras on balconies, high up in nearby hotels.

In the clip below, the government thugs have maneuvered some trucks across the road to provide themselves with some cover, and to force the protesters back into Tahrir Square. However, the protesters attack and push the thugs back. There are numerous similar videos available if you can find them, where you can see first one crowd flowing forward and the other backward, and then the process reverses. At one point the group attacking the protesters sends people up into a nearby building to throw rocks and brickwork down on the protesters. At various points, the attackers pushed the protesters all the way back into the square, but by nightfall the protesters had pushed out to the end of the road and set up makeshift barricades (which I have been calling Mubarricades in my head), to defend themselves from the rocks and molotov cocktails which were being hurled at them. I asked a couple of folks on Twitter who are in the military and/or study military history and didn’t get any affirmative responses that there is any video from earlier conflicts which show this back and forth. It’s definitely something that might be of interest to the military, riot police and security forces. And anyone who might be contemplating any popular insurrections as well.