Many years ago I read a news item in which a scientist said that a sodium cloud issuing from a volcano on Jupiter’s moon Io was “the largest permanently visible feature in the solar system” (Science News 137 359).

That remark stopped me cold. What does it mean to “see” a sodium cloud? More generally, what do scientists mean when saying they see dark matter or black holes? Are they speaking precisely or metaphorically? What is perception? Questions like these were a big factor in attracting me to the philosophy of science. Perception, I decided, isn’t as easy as it looks. To be a scientist is to develop an extended ability to perceive – and the science of the planets in our solar system is replete with examples.

Seeing like a rover

When scientists say they see things like sodium clouds, they speak rigorously. To perceive is not just to grasp something somewhere from a single perspective. It is also to have a sense, however rudimentary, of how that thing looks from other perspectives. Whenever I see a cup, I see only one profile of it. But thanks to our earlier experiences with cups, to see something as a real cup – rather than as a cutout or hallucination – means to anticipate other profiles; how it’ll appear if I walk around it, pick it up and so on. Sometimes these profiles surprise us, or we turn out to be deceived or wrong, but to perceive is always to grasp a profile of something and have a set of expectations about other anticipated profiles. Perception, in short, has a deep structure.

The same is true for a space scientist’s perception, except that it is technologically mediated. In philosophical language, scientists sometimes “embody” their instruments, seeing the world through them relatively directly, just as a blind person sees the world through a cane. When we perceive a planet or comet through an optical telescope, for instance, our previous experiences make us expect the object to be visible at other times in other locations – and that when observed through stronger telescopes it will have profiles that we might not know but that we can guess. At other times, scientists don’t embody but “interpret” their instruments. Just as we say “it’s cold outside” by looking at a thermometer, so a space scientist “sees” a sodium cloud with filters and spectrometers if these belong to expected profiles.

Astronomical perception involves a complex combination of these two concepts of embodiment and interpretation. An interesting case study is found in the 2013 article “Mediating Mars: perceptual experience and scientific imaging technologies” (Foundations Sci. 18 75) by the philosopher Robert Rosenberger from the Georgia Institute of Technology, US. In it, he describes a debate about a rock formation imaged by NASA’s Mars Global Surveyor in a Martian crater known as Eberswalde. Some scientists argued they were looking at the remains of a river delta, others an alluvial fan, still others that they were seeing the product of mudslide-like events.

Rosenberger shows that the scientists went about resolving the controversy, not by evaluating competing theories or explanations about the rock formation itself, but by appraising the different strategies that they were using to produce the images. They asked themselves, Rosenberger writes, “How does the process of transforming this object of study (i.e. a rock formation on Mars) into a specific form we are able to perceive here on Earth (i.e. images) leave these images open to interpretation in particular ways?” Without being able to move freely around the formation as they would on Earth, the scientists had to sharpen their perception of the rock formation by understanding the profiles better, and by analysing other profiles provided by shadows, laser altimeter data and so on.

Another analysis of scientific perception is found in Seeing Like a Rover: How Robots, Teams, and Images Craft Knowledge of Mars (2014 Princeton University Press) by the Princeton University sociologist Janet Vertesi. She based her book on two years spent as an ethnographer studying scientists in NASA’s Mars Exploration Rover mission. Vertesi found the researchers’ workspaces, computer screens and Powerpoints were saturated with images: filtered, false-colour, 3D, fish-eye, panoramic and more.

Taken by the two rovers Spirit and Opportunity, these images let the researchers “see” on Mars, but not with a human eye. One researcher told Vertesi that the two rovers’ view of the world was like “trying to make your way through a dark cluttered room with nothing but a flashbulb”. Yet the researchers became skilled at it, seeing and manipulating phenomena on the Martian surface. “When you work with the team for a while,” another researcher told her, “you kind of learn to see like a rover.”

Vertesi’s book shows that seeing like a rover is not just a matter of grasping profiles and horizons, but also involves ways of speaking and gesturing, emotional connections, habits and even the research group’s social and organizational structure. Seeing like a rover, she writes, “is…a question of seeing from somewhere, not adopting a view from nowhere” – with the “somewhere” referring not just to the rover’s cameras but to the entire research team and its activity.

The critical point

The curse of current-day philosophy of science is the lingering but fraudulent idea among philosophers that science involves the quest to see phenomena from nowhere. Instead, it’s done by people with inherited concepts using particular equipment to study topics that seem important. To perceive a scientific phenomenon involves grasping how all of the profiles you can see of it – and how others that you don’t yet or never will see – hang together. Not only that, but mediated scientific perception deepens and extends our notion of what it is to perceive at all.