There’s something deflating about the first time you spot a nebula through a telescope. You’re standing outside in the dark and the cold, squinting and fiddling with knobs, trying to chase down some tiny patch of sky through a tiny circle of glass – until suddenly an unthinkably vast cosmic structure comes into view from across the interstellar void. It’s stunning, even humbling. Yet you can’t help thinking: “Where are all the colours?”
For decades now we’ve been treated to photographs of space presented in rich, vibrant hues. The famous photograph taken by the Hubble Space Telescope in 1995 of the ‘Pillars of Creation’ – towering columns of dust and gas in the Eagle Nebula some 7,000 light years away – is a lush mix of turquoise and mustard cut through by the occasional pink star. More recent, even more detailed photos of the same structures taken from the James Webb Space Telescope show deep, luxuriant blues.
But these images, taken from space, involve long exposures and even go beyond the visible light spectrum into infrared. When you’re looking at deep-sky objects through a telescope on earth, however, the light is too faint to trigger the colour-sensing cones in your retinas. Near-ish planets aside, most things will look pretty washed out.
So, which is correct: what we observe through the telescope, or those photos pumped out by NASA? Is space really colourful, or really monochrome? The answer to that will depend in part on what we think counts as observing an object, regardless of whether that object is a galaxy or an atom.
If we think that only seeing things with the naked eye counts as ‘real’ observation, then space is mostly pretty drab. Some philosophers do, in fact, think that. Bas van Fraassen has argued that only things we can see unaided are truly observable. But when you’re outside with that telescope and you find Saturn and its famous rings, surely that’s observing? Yes it is, according to van Fraassen, because if you were floating around near Saturn instead of standing on Earth you’d be able to see the rings with your own eyes. These rings were thus observable for millions of years, even if in practice nobody had a way to observe them before Galileo spotted them through a telescope in 1610.
But what about, say, bacteria? We will always need a microscope to see those. Other kinds of scientific imaging complicate the idea of ‘observing’ even further. Functional Magnetic Resonance Imaging (fMRI) has been a game changer both for medicine and for understanding how the brain functions. It allows researchers to see a visual depiction of brain activity as it is happening, and enhance our understanding of how brain anatomy relates to experience and behaviour. These findings are often presented to us lay people by saying that a part of the brain ‘lights up’ when a certain experience happens. But brains don’t actually glow. When an area of the brain ‘lights up’ on an fMRI machine, this bears no real relation to anything we could see if we were somehow looking directly into a person’s skull. What appears on the fMRI screen is a visual representation of something that is not itself visual.
So why limit the observable to what we can see with our unaided eyes? At the heart of van Fraassen’s argument is the claim that whenever we make an observation using an instrument, even something relatively simple like a basic telescope or an x-ray machine, our observation always passes through a theory. Standing between us and the lit-up brain that appears on the fMRI machine are more things than just expensive electronics and powerful magnets. There’s also untold numbers of theoretical posits too: models taken from physics, biology, chemistry, without which we can’t ‘see’ anything on the screen at all.
New kinds of technology can sometimes invite competing theories to explain what we are seeing. In 1939, the Soviet inventor Semyon Kirlian discovered that running an electrical current through his hand while holding it against a photographic plate produced an image of light streaming from his fingers (he also got quite badly burnt in the process). Like the ‘Pillars of Creation’ picture, Kirlian photography is undeniably beautiful – but what does it actually show?
Kirlian himself suggested he had found a way to visualise the ‘aura’ of living things, allowing us to detect changes in their health and wellbeing. Others took up this suggestion with gusto. Here, it was claimed, was a technique to make a completely new kind of energy field visible for the first time. Sadly, Kirlian photography in fact captures nothing more mysterious than a momentary coronal discharge. But what you ‘see’ here depends on which theory – standard physics or a theory of ‘auras’ – you subscribe to.
You might well reply that of course a Kirlian photograph only shows an electric discharge, because, after all, auras don’t exist. And this is where things get awkward.
There are any number of things in this universe – black holes, viruses, Higgs bosons – that we can only observe indirectly, through scientific instruments such as radio telescopes, scanning electron microscopes and particle accelerators. In some cases, such as the Higgs boson, the entity was predicted by a theory well before it was found. That doesn’t mean the existence of the Higgs boson is doubtful, any more than the existence of the rings of Saturn are doubtful. But it is a case where what we take to exist, and what we see when we go looking for it, is entirely mediated by theory, just as someone who sees an ‘aura’ in a Kirlian photograph is seeing an entity mediated by theory. Some theories are just (considerably!) better than others.
So while the scientific revolution has opened up new possibilities for knowledge, one of the trade-offs might include changing what we mean by ‘observe’ – and even what we mean by ‘exist’. The microscope revealed that we share our world with uncountable trillions of tiny creatures we had never noticed before. The Large Hadron Collider made the Higgs boson leap out of arcane mathematics and onto coffee mugs at the CERN gift shop. And the Hubble telescope makes a riot of cosmic colour manifest to us that would never be visible to our own fleshy eyes. Squinting into a viewfinder in your backyard, it’s all still going to look grey.
Even then, what you’re observing through your telescope is not just mediated through theory, but through time and space. When you observe the rings of Saturn, you’re seeing how those rings looked more than an hour ago, for that is how long light from Saturn takes to reach earth. Looking at a nebula? You might in fact be seeing how things looked millions of years in the past. There is a theory that the ‘Pillars of Creation’ may have been obliterated by a supernova some six thousand years ago. It’s possible that those columns only survive in those photos, but we won’t know for sure until the light from their destruction reaches our telescopes, millennia from now.
Still, even if they are gone, we know that they existed. But what of things that are simply unobservable? Not in the way the rings of Saturn were unobservable before the telescope, but unobservable as such, completely and permanently. Could such things be?
Logically, we have no way of ruling them out. Yet by definition, such entities could never form part of the scientific worldview. If something cannot be observed – even indirectly – then it cannot interact with anything else. It literally makes no difference. We can’t count them in our inventory of the universe, but we can’t rule them out either. Perhaps Kirlian was right, and we do have auras – it’s just that we can never see them. The night sky is alive with colours we cannot see directly. Maybe there are yet other things we can never know, and cannot even conceive.
From the Observation edition of New Philosopher, available from our online store
