Category: Observation

Something learned about the natural world, as from personal experience or from someone else’s insight.

Posted on

Freedom and the Nature of Science

Freedom and Science are inseparable. Photo by programwitch.

Freedom plays a central role in the practice of science. There is no one meaning to the word, “freedom,” that alone summarizes its role in science. We will begin with some basic definitions and then explore each meaning. Through such exploration will we arrive at a fuller understanding of how the freedom and science are interlocked.

Let us begin with a basic definition of science. There is much thought about the nature and practice of science, but in the modern understanding of what we call “the scientific method”  there are three basic ingredients: “the recognition and formulation of a problem, the collection of data through observation and experiment, and the formulation and testing of hypotheses [1].” The scientific method is not a recipe; it’s a set of guidelines that allow for observers to develop a consistent approach to understanding the natural world. The method is predicated on the tenet that observation of the natural world, and formulation of theories that explain existing observations and predict new ones to be tested, is a consistent means to arrive at truth about the natural world. A “hypothesis” is a proposed explanation of a series of observations. A “theory” is a set of principles that result from hypothesis-testing, which itself creates new knowledge in that it explains observations rather than just reporting on them. After enough time has passed, and no violations of a theory have been observed, it is often raised to the level of a “law”.

While this sounds like an orderly progression, science is rarely orderly. The scientific method is not the pursuit of the lone investigator; rather, it is a social process with redundant self-correcting mechanisms. Individuals practicing the method may seek to advance their own views or biases; an essential component of science is the “review process,” where data, hypotheses, and theories are submitting to a community of peer experts for scrutiny. This happens in many layers: amongst one’s own local group of collaborators, with peer-reviewed journal editors and referees, and eventually with the whole communities of readers of the published work. Scientific practice by a lone investigator, or even a community of investigators, must still stand the long test of peer review. Even then, even decades or centuries later, old ideas may be found to be narrower than originally believed and absorbed into a larger theory which explains more observations and is based on a wider set of hypothesis testing. Science is a frontier ever in motion.

Within this framework, there are many freedoms which are central to the process. The ones which I will discuss here are: the freedom of the investigator to pursue their work, wherever it may lead; the freedom of others to criticize that work and demand more evidence; and the freedom to challenge authority in all of its forms, including the many tyrannies of popular belief, established scientific theory, and experts. This last one is a freedom often on display in the public square, especially surrounding issues that are uncomfortable to the general public: climate disruption, human sexuality and reproduction, and the evolution of biological life, to name a few. I’ll address this one last.

Let us begin with the freedom of the individual to pursue their own work. Central to the scientific process is the liberty of an investigator to apply the scientific method to a question of interest. There are many vague terms here, which I would like to define more clearly. By “liberty,” I mean the absence of restraint on the investigator to address their central question through the scientific method. By “interest,” I mean a question that bears on a subject of curiosity for the investigator, a subject of importance within a field of scientific inquiry, or a question that has obvious alignment with societal values.

Within this freedom, there is an interesting nexus that often leads to controversy: what happens when the freedom of the investigator meets the values of a society? There are two outcomes in that case: either the question under investigation is aligned with social values, and thus is accepted as a good; or, the question challenges existing social values, and is seen as controversial. There are many gradations in this scale. For example, the freedom to investigate a chemical means to disarm the “Lethal Factor” of Anthracis Bacillus would be seen as a social good. Anthrax is a potentially deadly biological weapon, and the lethal factor is the chemical secreted by the bacterium which ultimately leads to the fatal symptoms in humans. This is clearly aligned with a current societal good in the United States – the pursuit of countermeasures to biological terrorism. However, the development of a vaccine for the most prevalent forms of the Human Papilloma Virus (HPV), which causes the majority of cervical cancers in women, is also a social good (prevention of cancers) which has aspects that clash with other social values (HPV is sexually transmitted, and sex is a taboo in the U.S.). Human cloning, which may lead to the ability to regenerate fragile organ tissue, is widely viewed as primarily aligned against societal values in the U.S. There are societal concerns over questions of individuality and the ability to replace individuals by whole copy, and what that would mean for society, which have not been clearly addressed.

However, the freedom of the scientists to pursue the question to its conclusion is central to the kinds of innovation that have given the U.S. its current prosperity. Technological invention (computing, information, efficient manufacturing), biological invention (food science, for instance), and medical invention (new chemical and biological agents to treat disease), are all central in our economy. Not all questions have immediate application, but all questions are interesting to someone. The freedom to pursue those questions, however important or uncomfortable, is what enables discovery. It is discovery that is the driver of invention, and invention becomes the engine of economic growth and prosperity. If you do not have the freedom to question, if you are prevented from investigation, then there can be no discovery.

The second freedom is that of the scientific community to criticize or scrutinize the work of another scientist. Science requires both the freedom to inquire, and to be questioned by others. This is the “peer review” process mentioned above, and it is ultimately the most important self-correcting aspect of the scientific process. No claim can stand unchallenged, and scientists must be free to question all claims of discovery. There have been many false discoveries in the history of science: “the weight of the soul” claim by Dr. Duncan McDougal [2] and “cold nuclear fusion” [3] are a few well-known ones. It is the weight of peer review – both criticism of the original work and later efforts to independently reproduce the work – which leads to validation or invalidation of the original claim.

The reason this freedom is so important bears directly on the idea that the practice of science eventually leads to an understanding of “truth.” Truth is a prize held in the highest regard; it is the ultimate goal of science, of philosophy and religion, and of the legal system. Truth means something different to each of these endeavors; within science, a complete understanding of the natural world is the greatest outcome of investigation. If a discovery is claimed, then it must be questioned; for, if that is a false claim, then it does not help us to obtain the truth.

From a societal perspective, false claims and misdirection waste resources and lead scientists down a road that bends away from truth. Such information cannot lead to practical applications (because it is based on falsehoods) and thus stalls the engine of economic growth. Peer-review can’t prevent a bad idea from being aired, but it can prevent a bad idea from spawning worse ideas, or more importantly from leading investigators down alleys that will only ever be blind.

The freedom of one scientist to challenge the claims of another has served as the most important self-correcting mechanism of the scientific process; it doesn’t always work quickly, but it works. If we are not free to question each other’s evidence, hypotheses, and theories, then we cannot filter the truth from the mis-information.

The final freedom I wish to discuss here is the freedom to challenge authority. This is very much related to both of the previous freedoms discussed, but has some extreme and unique characteristics that make it important to discuss. Authority cannot be held in high-regard in the scientific community. Why? Because a pronouncement from authority does not, in and of itself, require the necessary ingredient of science: evidence. When a person, or even an idea, rises to the level of “authoritative,” then we risk assuming it will always be correct.

This assumption has proven wrong so many times, it’s impossible to conceive of a scientific process that has to respect authority. Witness the deference with which Newton’s Laws and the study of Mechanics (the orderly working of matter in a fixed framework of space and time) led most 19th-century physicists to assume that Maxwell’s Equations, which explained light, could not be complete. Maxwell’s Equations described a wave that traveled with the help of no medium; the laws of mechanics said all wave phenomena required a medium. It was physicists like Einstein who challenged the original assumption of the authority of Newton’s Laws that led to a better understanding of space and time, one which encompassed Newton’s Laws but defined a broader theory of nature.

This freedom is often mistaken in the public square are the freedom to arbitrarily challenge a scientist or scientific idea simply because we don’t agree with them. For instance, the theory of evolution – one of the strongest scientific theories in existence today – constantly is challenged in the public square even though within the scientific community there are no serious fundamental issues that have ever been identified with it. Certainly, there are many scientists who are actively testing the limits of the theory; but they do this by gathering data, forming hypotheses to explain the data, and seeing whether those hypotheses confirm the theory or challenge the theory. They are not challenging the theory simply because it challenges traditional societal values about the place of humans in the universe.

It is one thing to challenge scientific authority with evidence; it is quite another to challenge it with values or opinions. Values are sometimes built from evidence, but not always. Opinions, too, are sometimes evidence-based, but not always. The freedom to challenge authority is central to science – how else can we hope to come to a better understanding of the natural world if we are not free to challenge old ideas and assumptions? However, that freedom comes interlocked with a responsibility to do so only by the same means the authority was originally established: the scientific method.

There are many freedoms. The three I have described here are central to the scientific process. Scientists must be free to inquire, even if that inquiry challenges societal values. Scientists must be free to challenge each others’ claims. Without this, there can be no ascension of correct ideas and pruning of false ideas. Finally, there must be the freedom to challenge scientific authority, be it a scientist held in high regard or a scientific theory held in high regard. The responsibility that is locked to this freedom is that the challenge must apply the same tool: the scientific method. It is sweet poetry, that this central framework for developing new knowledge – the scientific method – both leads to the development of theories and laws and provides the means to challenge them in order to come to a better understanding of the truth. Freedom to inquire, to criticize, and to challenge is the glue that binds these things together.

[1] http://www.merriam-webster.com/dictionary/scientific%20method

[2] http://www.scribd.com/doc/20281719/21-Grams-Hypothesis-Concerning-Soul-Substance-Together-with-Experimental-Evidence-of-The-Existence-of-Such-Substance 

[3] http://en.wikipedia.org/wiki/Cold_fusion

[4] Photo from http://www.flickr.com/photos/programwitch/2505184887/sizes/m/in/photostream/

 

 

Posted on

Head Start

[This post was inspired by a comment in an article on PhysOrg, http://www.physorg.com/news/2011-09-cern-faster-than-light-particle.html. Thanks to Randy Scalise for bringing it to my attention.]

Supernova 1987a seen in visible and x-ray light
The expanding supernova remnant around Supernova 1987A and its interaction with its surroundings, seen in X-ray and visible light.

In 1987, a distant star exploded. Here on Earth, it was named “SN1987a” – Supernova 1987a. Here are some basic facts about SN1987a: it occurred (51.4 +/- 1.2) kiloparsecs from Earth, corresponding to a distance in meters of (1.586 +/- 0.037)x1021 m, and we saw the  visible light from the event beginning on Feb. 23, 1987.[1] [2]

Light travels at a finite speed. In the vacuum – completely empty space – that speed is 299,792,458 m/s (meters per second). The uncertainty on that speed is in the last digit, which represents a precision far greater than our knowledge of the distance to SN1987a. Therefore, in all future calculations the uncertainty on this speed will be ignored and numbers will be assumed to have uncertainties dominated by the distance measurement.

Once the light from the supernova collapse and subsequent explosion escapes the star, the time required to travel from SN1987a to Earth is (5.290 +/- 0.0736)x1012s. There are about 3.153×107 seconds per year (fast fact: you can very closely approximate the number of seconds in a year by multiplying the number π, 3.14159…, times 107s. That gives you 3.14×107s, which we see is extremely close to the correct number). If we convert to years, the light from SN1987a required (167,800 +/- 3900) years to travel to Earth.

A recent preliminary, un-reviewed, unpublished, and unconfirmed result from the OPERA Collaboration suggests that neutrinos travel faster than light [3]. Specifically, within the framework of their measurement they find that the speed that muon neutrinos travel through the Earth from CERN to their experiment is (299,799,893 +/- 1,230) m/s.

Supernova collapse is known to lead to the production of neutrinos; in fact, neutrinos from SN1987a were detected by multiple neutrino experiments that were operating in the late 1980s. Based on the difference in speed between light and muon neutrinos, where muon neutrinos are measured by OPERA to travel at a speed EXCEEDING that of light in vacuum, let’s see when we would have expected the supernova-produced neutrinos to arrive at Earth.

Before we proceed, let’s note that we have a potential problem with this calculation – the uncertainty on the distance to SN1987a is HUGE. Our uncertainty on how long light took to travel from SN1987a to Earth has an uncertainty of 3900 years – that covers the entire period of human development back to ancient civilizations such as China and Egypt. Instead, let’s calculate the RATIO of travel times of light and neutrinos. We can then apply this ratio to any time period and evaluate the relative arrival times of neutrinos and light.

The OPERA paper actually provides this number. The ratio of travel times between neutrinos and light is:

(v-c)/v = (2.48 +/- 0.41)x10-5

which means that the neutrinos arrive 0.00248% faster than light. What does that mean for SN1987a?

If we take the light travel time to be 167,800 years (exactly), then in that same time neutrinos take 167,796 years to reach Earth. That’s 4 years earlier than the light. What if, instead, the travel time was 3900 years less (one standard deviation DOWN). Then the travel time of light is 163,900 years and for neutrinos it is 163,896 years – again, 4 years earlier.

So the time difference, regardless of the ACTUAL time it took light to travel, is about 4 years. One would not expect neutrinos to accompany the light when the light reached Earth in 1987.

What was observed?

Here is the summary from the Wikipedia article on SN1987a:

Approximately three hours before the visible light from SN 1987A reached the Earth, a burst of neutrinos was observed at three separate neutrino observatories. This is likely due to neutrino emission (which occurs simultaneously with core collapse) preceding the emission of visible light (which occurs only after the shock wave reaches the stellar surface). At 7:35 a.m. Universal time, Kamiokande II detected 11 antineutrinos, IMB 8 antineutrinos and Baksan 5 antineutrinos, in a burst lasting less than 13 seconds. Approximately three hours earlier, the Mont Blanc liquid scintillator detected a five-neutrino burst, but this is generally not believed to be associated with SN 1987A. [4]

Neutrino interactions in the detectors were observed to increase in rate just before the light reached the Earth. This was consistent with the physics noted above; neutrinos are essentially free to leave the star once it collapses since the material density in the star is not sufficient to completely prevent neutrinos from leaving. Light, however, is trapped in the collapse until the blast wave reaches the surface of the star; this is at a later time than the nuclear reactions that produced neutrinos. So even though light travels slightly faster than neutrinos (due to the neutrinos’ small but non-zero masses), the light didn’t catch up before reaching Earth and the neutrinos arrived about 3 hours before the light.

So the time difference was just 3 hours, not 4 years. Of course, nobody was looking for neutrinos from SN1987a 4 years before it happened, but the fact that a burst of neutrinos was observed just hours before the light is evidence that the neutrinos were not too far ahead of the light. Calculations of the neutrino and light arrival times within the framework of core-collapse supernova modeling suggest that this time difference (neutrinos leading light) is not a surprise, given that neutrinos escape before light escapes the supernova.

Some criticisms of this calculation

  1. This calculation assumed that the neutrinos produced by supernova are the same as those studied by OPERA. OPERA studies muon neutrinos. The neutrino experiments which detected neutrinos from SN1987a were sensitive to electron neutrinos. So all we can really say is that electron neutrinos arrived just hours before light. Muon neutrinos may have also been produced directly by SN1987a, or produced by neutrino mixing between the explosion and the time the neutrinos reached Earth. One could argue, therefore, that perhaps the undetected muon neutrinos arrived much earlier.
  2. Nobody was looking for muon neutrinos from space/supernovas in 1983. That’s a hole in the argument, given that the calculation suggests the muon neutrinos would arrive 4 years before the light.

A comment on item #1: there is no evidence that electron neutrinos are so different from muon neutrinos. One would have to gather such evidence. In the meantime, one would have to postulate a mysterious and VAST difference in the speeds of electron and muon neutrinos.

Another comment: neutrino mixing is easily explained if neutrinos have mass. Mass prevents a particle from traveling at the speed of light in vacuum. If the OPERA result is correct, very little makes sense anymore regarding the Theory of Relativity, which has withstood precision tests for about a half-century. Certainly, it only takes one confirmed and reproducible measurement to bring a scientific theory into question. The OPERA result is neither confirmed nor even reproduced at this point. It’s not even published.

Conclusions

The neutrino is a mysterious particle. But so far, it hasn’t been so mysterious as OPERA would suggest. Data from SN1987a suggests that electron-type neutrinos arrived just hours before light, consistent with the different interactions neutrinos and light would suffer in the environment of a core-collapse supernova. This contradicts the expectation from OPERA, albeit that measurement applies to muon-type neutrinos.

Personally, I’m not holding my breath for this result. I’ll bet anybody $10 it’s wrong. And if instead I am wrong, I will pay up with a smile on my face and joy in my heart.

[1] http://heritage.stsci.edu/1999/04/fast_facts.html

[2] Panangia, N. “Distance to SN 1987 A and the LMC.” New Views of the Magellanic Clouds, IAU Symposium #190, Edited by Y.-H. Chu, N. Suntzeff, J. Hesser, & D. Bohlender. http://adsabs.harvard.edu/full/1999IAUS..190..549P

[3] http://arxiv.org/abs/1109.4897

[4] http://en.wikipedia.org/wiki/SN_1987A

Posted on

Dig Deep

This is shaping up to be a tremendously exciting year. The Large Hadron Collider is poised to return to normal data-taking operations in just over a month, and the expectations are that the dataset is going to grow extremely quickly. With about 40/pb (“forty inverse picobarns” [1]) of data currently being scrutinized, ATLAS is digging deep into what we have so that we are ready to tunnel to the bottom of the coming 2011 data sample. There is exhaustion and excitement; exhaustion, because the demands of physics analysis and review are large, but excitement because of the discoveries that may lie in wait.

For the first time since I joined ATLAS over a year ago, I’m finally feeling connected to the experiment and caught up in some of the excitement. It was VERY hard to plug into the collaboration, and even at this point it’s not entirely clear to me how I would advise another person to do it (especially a new faculty member). I think for post-docs and students who devote all of their time to being involved, it’s a lot easier than for a distracted faculty member who is trying to lead, teach, and serve all the same time.

I’m still learning. But I feel some of that child-like thrill of finally understanding something enough to tear it apart. Or, at least, feeling comfortable enough with the shovel to begin digging deep.

[1] http://en.wikipedia.org/wiki/Barn_%28unit%29#Inverse_femtobarn