The ability to make observations is a core skill of scientists, yet not far removed from the skills we all use to get through life. Sherlock Holmes, the first forensic geologist, used to say, "You see, Watson, but you do not observe." But we make observations, say, in selecting a ripe melon at the market. Let's take that common-sense notion a bit further.
There are two special things about making observations, as opposed to just noticing things: observations are systematic, and they are recorded in some way.
Observation Is Systematic Perception
Observing is a disciplined form of attention; I think of it as a dialogue between the mind and the eyes (or ears, fingers and so on). Observing is treating something as a clue, not just a perception.
Any of us, for instance, can hear a bird sing. Some of us may be able to name the bird's species, at least if it's a familiar one. But when a birdwatcher hears the song, she quickly notes all the important attributes of the bird call—its pitch and pattern, the number of times it was repeated, the kind of habitat the bird was in, the season and time of day, and so on. She may name the bird's species right away, but unlike the rest of us she can also address each of the reasons behind her identification. If it's a bird she doesn't know, she uses her observations to consult her books. The birdwatcher has learned to ask, and answer, a systematic list of questions about what she perceives.
Geology, even at the amateur level, is a bit more complicated than bird identification. Observing minerals, observing rocks and their arrangements, observing landforms, observing fossils—in the field, the geologist does all of this simultaneously. And then she goes back to the lab and makes more observations. Those results might call for another visit to the field. So the observing process can extend for years, not just a moment.
Observation Is Taking Note
Observing also involves making records of what we observe. We all make mental notes, and so do scientists, but those are fragile. Memories are fallible. Worse, they are not reproducible. Records last longer than memories, and they allow other observers to consult them. Even better, they allow others to assess the person who made them.
Photographs and notebook entries are typical things we might consider notes. But rock samples and drill cores, given identifying numbers and annotated, are notes too. The long set of atmospheric carbon dioxide data from Hawaii's Mauna Kea peak, kept up since 1959, are recorded not just as notebook entries but also as air samples.
Another important skill is separating evidence from interpretation. We are all familiar with this in courts of justice, where a piece of evidence may point in more than one direction depending on its interpretation. In science, too, an observation may be true but its interpretation may be in error. Good notes keep the two separated.
Observation Takes Training and Practice
Like any other working skill, observing must be learned and practiced. The geology student is trained to look for a wide range of things when examining a rock or mineral or fossil. An important part of that is learning diagnostic properties, the decisive features that make observing easier. Examples include the red-brown streak that distinguishes hematite from other metallic minerals, the nine-sided prism shape of tourmaline, or the extreme hardness of diamond.
A related skill is economy: learning what to rule out. Discussing mineral identification, geology professor Steven Dutch quotes the medical adage, "when you see hoofprints, think horses, not zebras." Learning what's likely and what's not is a large part of the rockhound's craft.
A college education is how geologists get this training. A career, whether in industry or in academia, is how they keep up their practice. The amount of knowledge needed to do science professionally is far above what any amateur can acquire alone. This inevitable gap in knowledge between professionals and the public leaves room for popular delusions, like those held by creationists or expanding-Earth believers. Thus a final important skill is the ability to explain observations in words as plain as possible.
Observation Takes Organized Communities
There is a third, less appreciated attribute of observations: they involve communicating with people in other places and times. Observations are a language that requires a community of fluent speakers.
The scientific community maintains standards. The simple Mohs scale of mineral hardness is one example that has been the same for almost 200 years. A standard may be a code of practice like the type specimen system that has served paleontogists as a simple way to define fossil species. It may also be a chemical standard like Vienna Standard Mean Ocean Water (VSMOW), a carefully prepared mixture of distilled waters from the world's oceans that laboratories use to calibrate instruments and report the isotopic chemistry of water samples.
The scientific community has a lot invested in keeping quality of observations high. Laboratories commonly compare results with each other. Researchers may confirm the results of others independently. And at every meeting of geologists, specially organized field trips enable colleagues from around the world to stand in front of the same outcrops, survey the same landscapes, and compare their observations face to face.