What’s the matter?
A few years ago there was much excitement regarding the possible discovery of pentaquarks. In 2002/2003 there were six papers published with data suggesting that the pentaquark existed. Some of the papers calculated a 95% confidence limit.
Just in case you’ve forgotten, atoms are made of protons and neutrons which are in turn made of quarks. Previous to these experiments, we had only ever seen particles containing 2 or 3 quarks. For example, protons and neutrons are made of 3 quarks. The discovery of a particle that contained 5 quarks (a pentaquark) would open a door to new physics.
I remember much excitement in my research group about these discoveries, especially from one academic. He concluded that the evidence was fairly conclusive. Being the doubting Thomas that I am, I decided to read one of the papers. After reading this paper, I came to the conclusion that they just did not have the data to justify their claim. In particle physics, I have seen claims made by researchers based on a very low number of data points. I was always questioning how they could possibly justify their claim and whether a same number of randomly generated points could show the same thing. That is, the data could just be a statistical fluctuation.
Anyway, I was due to give a talk to the Physics community and I decide to be mischievous. It was presented as a talk about how physicists use detectors to discover new particles. But the subtext was the use and misuse of statistics, focusing on the paper I had read.
I came to the point in my presentation where I talked about the confidence levels of an experiment. A 95% confidence level can be described as such:
If you think you have a set of data that is evidence, for example, of a new particle, generate 99 graphs using random data points. Mix in the graph of the real data and show the 100 graphs to your friend. Tell them to pick 5 graphs that show evidence of a new particle and if the real data is in that 5, then you have a 95% confidence level that the data does in fact show the existence of a new particle.
This is what I did in my talk with the data from the paper, except that I told the audience that that data was of a fictitious particle. They didn’t know it had come from that paper. Anyway, no one was able pick the graph which had the real data in it. The randomly generated graphs also showed signs of a “new particle”. I then showed them the graph from the paper (they still didn’t know that the data was from a research paper). I asked them if they would conclude that the graph showed evidence for a new particle. Nearly all the audience said no. That’s when I confessed about the origin of the data and the claims made in that paper. After my talk, I remember having a few conversations with those that still thought that the data was conclusive, taking into account the other published papers. I was of the opinion that more data needs to be gathered before making such a claim.
Three years later and after more data gathering it seems as if the pentaquark has bitten the dust. Sure, they may be still a slim chance that it exists, but it seems that the earlier experiments were in fact statistical glitches. And here is the great thing about science, even the original author of the paper now concedes this point. However he still thinks that later experiments may show a pentaquark.
Here’s one for the kitchen
In a two layered steamer, does the food cook faster in the bottom layer or the top layer?
This question was put to me and I gave them my reasoned answer. I then had an interesting discussion with someone who argued the opposite. What do you think and why? (In this discussion, I finally said let’s do the experiment to see who is right. It was interesting to hear them give excuses as to why they wouldn’t do the experiment then and there. Isn’t experiment the way to find out who is right?)
High Voltage Rock and Roll
There was a hard rubbish collection in my folk’s area a couple of weeks ago and I scavenged the electronics from a few old computer screens and video recorders. From the bits and pieces I made a Jacobs Ladder. This is the contraption seen in the labs of mad scientists in old sci-fi films that has two long metal wires sticking up with an electric arc that travels up between them.
Here are photos of it. Excuse the quality. The pictures were taken by a phone.
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