“…I barely know her, but if I were you, I would not mention cosmology.”
Jon’s advice was not surprising. Danielle did not mention what she was studying when the likely responses were astonished stares, ill-fitted jokes, and awkward silences before someone said that she must be very smart. Cosmology, experience had taught her and Jonathan, was not a profession one flaunts in a social gathering. It drew embarrassingly little interest, unless someone confused it with cosmetology.”
From Initial Conditions

A man I had briefly met once or twice before approached me at a party. He had heard that I published a book about physicists and wanted to know what qualifications I had to write about the subject. Apparently satisfied with my academic credentials, he shifted the conversation to cosmology. Going over all his remarks is way too long for the blog, but I think that the following three misconceptions are worth repeating and rebutting.

1. While the “technical stuff” (interpreting data from experiments and observations and solving nasty equations) is hard to perform and requires expertise, the underlying “physical” ideas are quite simple to grasp.

I can see where this belief comes from. When writing for popular media, physicists and science writers make complex concepts sound simple. Just recently, we saw Canadian prime minister nonchalantly explain how a quantum computer works. Randal Munroe (a.k.a xkcd) provides an explanation on how Einstein’s special and general theories of relativity work, “using only the ten hundred words people use the most often.”

On one hand I am all for science popularization. On the other hand I’m wary when it promotes an impression that the ideas at the core of theoretical physics are easily comprehensible. It is hard to dissuade someone that reading a few popular physics books and being familiar with terms like “spacetime” and “curvature” does not mean he understands what he is talking about. Popularization and visualization of fundamental ideas leads to a misconception that they are pretty simple. They are not. Here is what Kevin Drum wrote about the subject:

“Relativity and quantum mechanics are both famously hard to grasp once you go beyond what they say and demand to know what they mean. In truth, they don’t “mean” anything. They do gangbusters at describing what happens when certain actions are taken, and we can thank them for transistors, GPS satellites, atom bombs, PET scans, hard drives, solar cells, and plenty of other things. The mathematics is difficult, but often it looks kinda sorta like the math for easier concepts. So quantum mechanics has waves and probability amplitudes because some of the math looks pretty similar to the math we use to describe ocean swells and flipping coins. Likewise, general relativity has curved spacetime because Einstein’s math looks a lot like the math we use to describe ordinary curved objects…
…Objects with mass attract each other, and if you know the math you can figure out exactly how much they attract each other. Calling the path of the objects a geodesic on a 4-dimensional curved spacetime manifold doesn’t really make things any clearer. In all likelihood, a picture of a bowling ball on a trampoline doesn’t either.
But we keep trying. We just can’t help thinking that everything has to be understandable to the h. sapiens brain. This makes interpreting difficult math an excellent way to pass the time for a certain kind of person.”

2. Cosmology is based on assumptions that no one can check.
More specifically, the partygoer noted that since our spaceships have never explored the space beyond the Solar System, physicists’ assumptions about the Nature at a distance of billions light years from us are merely “speculations” that cannot be justified scientifically.
He had a point. If scientists had the nature’s ‘operating manual’, they would not have to make assumptions to construct the perfect theory. Since they have to do without it, cosmologists base their models on the available data (that is also why theoretical physicists ask for accelerators, observatories and other super expensive machines). Measurements performed on Earth and within the solar system are the basis to our knowledge. To make use of the information gleaned from distant sources, physicists extrapolate what they know to interpret data reaching us from events that had happened a long time ago in faraway galaxies. An example of one of the most fundamental assumptions in physics is Einstein’s postulate that the speed of light is constant (a finite number, independent of the motion of its source). Can physicists prove that this postulate is also correct a billion light years away from us? Not directly. But nothing in the data gleaned from a mind-boggling amount of independent sources suggests that this assumption is not valid. It has passed every test physicists could think of.

More generally, to be considered as a viable model, a) none of the model’s assumptions may contradict observations, b) it has to be mathematically self-consistent and c) it should account for all the available data. So, while it is true that cosmologists cannot prove the veracity of their theory, they can easily refute any model whose predictions do not fit observations.

3. There is a spiritual element in cosmology.
The Greek words kosmos and logia mean, respectively, “world” and “study of”. Long before the dawn of modern science, ancient civilizations pondered and tried to explain the origin, evolution, and eventual fate of the universe. According to Wikipedia , mythological and metaphysical cosmology concern themselves, among other things, with consciousness and spirituality. However, cosmology studied in various physics departments does not concern itself with our world, its people and their place in the celestial order. Actually, it had nothing to do with constellations and whatever one can see in the starry sky. Unlike astronomy, which deals with stars and planets, cosmology is a branch of physics that studies the evolution of the (observable) universe on very large length scales (broadly speaking, swaths of space that stretch over distances larger than individual galaxies).

An afterthought: I think it’s important to demystify misconceptions about cosmology, even if it causes someone interested in the field to think “Why bother, if cosmology is complex and demanding and irrelevant to humankind.” In the last chapter of Surely You’re Joking Mr. Feynman!, Richard Feynman wrote:

“I would like to add something that’s not essential to the science, but something I kind of believe, which is that you should not fool the layman when you’re talking as a scientist. I am not trying to tell you what to do about cheating on your wife, or fooling your girlfriend, or something like that, when you’re not trying to be a scientist, but just trying to be an ordinary human being. We’ll leave those problems up to you and your rabbi. I’m talking about a specific, extra type of integrity that is not lying, but bending over backwards to show how you’re maybe wrong, that you ought to have when acting as a scientist. And this is our responsibility as scientists, certainly to other scientists, and I think to laymen.

For example, I was little surprised when I was talking to a friend who was going to go on the radio. He does work on cosmology and astronomy, and he wondered how he would explain what the applications of this work were. ‘Well,’ I said, ‘there aren’t any.’ He said, ‘Yes, but then we won’t get support for more research of this kind.’ I think that’s kind of dishonest…”

Image from xkcd