Here’s a talk I gave to my descriptive astronomy students on the nature and limits of science. Suggestions on how to improve it for my next batch of students are welcome.
And now, a word of self-justification. I know many of you are annoyed with me for making this introductory course harder than you expected. We haven’t just been looking at pretty pictures this semester. You’ve been forced to acquire a real understanding of things like blackbody radiation and Newtonian gravity. You’ve had to reproduce the analyses of some of the pivotal orbital and spectroscopic measurements that establish the key results of this field. Why did I do this to you?
First of all, because college is not meant for everyone; it’s meant for the intellectual elite, so you should expect that all of your professors will expect a lot more of you than your high school teachers did. More importantly, this course satisfies your science graduation requirement–I realize that’s the reason a lot of you took it–and the purpose of this requirement is to expose you to the scientific enterprise and the sort of reasoning that’s proved effective for quantitative, empirical fields. As you’ve seen, the scientific method is an incredibly powerful tool, one which you may find useful in your own fields. Regardless, you will be forced to deal with scientists and scientific claims later in life, whether as a consumer, a patient, or a citizen. You need a clear idea of how this “voice of science” is to be treated, and for that, I thought you needed a peek “under the hood” to see what sort of reasoning and testing underlie one real scientific discipline.
Some of the points for you to take away are
- Scientific results have varying degrees of certainty. Some things are extremely well tested. At this point, we can be extremely confident about Kirchhoff’s laws, the H-R diagram, or the existence of atoms (although there no doubt ar details about atoms, stars, and radiation that we don’t yet know). On the other hand, some of the stuff we discussed later in class–for example the details about neutron star and black hole interiors and formation mechanisms and the stuff about dark matter distributions–has much less conclusive evidence behind it and cannot be regarded as being nearly so certain. In fact, I strongly suspect that some of what I told you on those subjects will be revised in the next few years. This means first that it’s neither crazy nor antiscientific to be skeptical about novel claims scientists make to the press, although it may be foolish to dismiss them out of hand. Scientific knowledge at the frontier is often revised as better data and theories come along. It also means that it would be wrong for you to take this process of revision to mean that everything science has discovered is equally up for grabs. There are many things that we’re very sure of.
- The scientific method is extremely powerful when applied to certain types of problems: problems that involve the quantitative properties of observable phenomena. Having gone through every step in the chain of observation and reasoning that grounds our understanding of main sequence stars, you can see that this understanding is well-motivated by the facts. It is not something that scientists just made up and then imposed by social pressure. Good science, where the scientific method is properly applied to a scientific problem, must be taken seriously. It’s not simply one narrative among others that you can take or leave at will.
- On the other hand, I think today the greater danger is the opposite, that people tend to treat the pronouncements of scientists as if they were oracles of Apollo or something, that what scientists say on any topic must be accepted without question. There are a number of questions–questions about ethics, religion, metaphysics, history, and aesthetics–which are not amenable to the empirical scientific method. This doesn’t mean that these aren’t good and meaningful questions; it doesn’t mean that we can’t find objective answers to them or that there aren’t rigorous intellectual disciplines for doing so; it just means that those disciplines are not those of the empirical sciences. However, scientists have been given great prestige by society at large, and there is always the temptation for us to abuse that trust to promote our own opinions on issues where our expertise do not apply. In this class, I’ve been very careful never to give away my opinions on anything outside my discipline, and that’s why. So, how can you tell when a scientist is stepping over the line? Most of all, by understanding how real science is done, you can have a good idea what sorts of problems it can properly be applied to. Another rule of thumb is the following: when somebody says “Science proves such-and-such” be on your guard. Scientists presenting legitimate results are always more likely to say “such-and-such experiment proves…” or “such-and-such calculation leads us to expect…” There’s no unitary “Science” that can bring the entirety of its authority to bear on any one question.
To close off, I’d like to say something about the past. People sometimes act like the progress of science gives us reason to look down on our ancestors, who believed many things we now know to be false. “How stupid they must have been to think the sun went around the Earth!” For me, the lesson is the opposite: the history of astronomy should fill us with humility and gratitude. The ancients weren’t dumb–the sun really does look like it’s going around the Earth, and you’ve seen in our celestial sphere section how complicated that model ends up being and how well it captures what we see. And yet it was wrong, as even greater geniuses were able to show. How much of the stuff in this course could you have come up with on your own? I know I’m not smart enough to have come up with any of it, or at best a very little. Let us then be grateful that so much has been bequeathed to us, and that we now know so many marvelous things about the universe.