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Imagine spending decades studying the Universe, building elaborate theories about how it works, and finally announcing that you have a pretty good idea of what is going on. Then someone asks an awkward question: what if you have got it wrong?
That is the uncomfortable possibility facing cosmologists following a recent article in BBC Science Focus questioning whether dark energy actually exists.
According to our current understanding, ordinary matter – stars, planets, people and the occasional disappointing politician – accounts for only about five per cent of the Universe. The rest is attributed to dark matter and dark energy. We cannot see either directly, and scientists still do not know precisely what they are.
Dark matter is invoked to explain gravitational effects that visible matter alone cannot adequately account for. Dark energy is the name given to whatever might be responsible for the accelerating expansion of the Universe.
Rather conveniently, we have names for two things we do not understand. Science has always been rather good at that.
Now some physicists are asking whether dark energy is really necessary. Perhaps our understanding of gravity is incomplete. Perhaps assumptions made when modelling the Universe are misleading us. Perhaps the explanation is something entirely different.
To be clear, nobody has suddenly proved that dark energy is imaginary, and the case for dark matter remains supported by substantial evidence. But questioning accepted explanations is precisely what science is supposed to do.
So what happens if the doubters turn out to be right?
For a start, cosmology textbooks would need rewriting. Our understanding of the Universe’s past, present and future could change dramatically. Theories about how galaxies formed, how cosmic expansion behaves and what ultimately happens to the Universe might need substantial revision.
Researchers who have spent their careers investigating these mysterious ingredients might find themselves investigating something else entirely. Scientific reputations could be made, Nobel Prizes might follow, and a few distinguished professors might quietly remove certain confident predictions from their websites.
But there is a more important consequence.
Science is not a collection of eternal truths handed down by people in white coats. It is a process of observation, experimentation, argument and correction. Even our most successful theories are descriptions of reality, not necessarily reality itself.
Consider Newton. His laws of motion transformed our understanding of the physical world, yet Einstein showed that Newton’s picture was incomplete. Newton was not utterly wrong; his theories remain remarkably effective within their proper limits.
The same could happen to modern cosmology. Its current model might prove incomplete without everything it explains suddenly becoming nonsense.
And there is a final lesson for the rest of us. We should be wary both of scientists who claim to have solved every mystery and of headlines announcing that an entire scientific discipline has been demolished.
A challenge to a theory is not the same as its destruction. Extraordinary claims require extraordinary evidence, whether they come from established authorities or enthusiastic challengers.
Meanwhile, the Universe continues expanding, galaxies continue forming, and nobody has yet produced a satisfactory instruction manual.
Perhaps dark matter and dark energy really are out there. Perhaps they are clues that we have misunderstood something fundamental.
Either way, there is something rather reassuring about living in a Universe where even the experts can admit they do not know everything.
Although I would prefer them to work out where the missing 95 per cent has gone. It is considerably more than I lose down the back of the sofa.
Jackie@JBeedie.com