The Unknown Unknowns
During the production of this edition of Australian Science Illustrated, I got into a debate on Quora (the website where you ask questions and then get answered hopefully by people with some actual knowledge of the subject) with a man who insisted that humans would never never EVER never achieve interstellar spaceflight.
Interplanetary is no problem - he seemed happy to accept that we would ultimately colonise the entire solar system. But go on from there to Alpha Centauri? No chance.
His argument, broadly, is that no objects in nature routinely travel interstellar distances. This is di erent to our other achievements. Flight, you see, was obviously possible because birds fly. Very fast land speeds using some kind of machine was obviously possible, because stronger, more-specialised animals run faster. In more recent times, our observations of various atmospheric e ects show that supersonic velocities are physically achievable, and naturally-occurring isotopes of Uranium reveal the secrets of nuclear power.
In other words, this man claimed, everything humans have actually achieved was done first, in some way, by nature. And there’s nothing in nature that flies from star to star. Of course, he means there’s nothing we
know of, nothing we’ve yet observed doing this. That doesn’t mean nothing does. In fact some things definitely do, such as so-called rogue planets that have been gravitationally ejected from their original systems.
(As for this whole idea of us only copying nature, I personally cannot name the species of bird that flies to the moon, or the natural occurrence of a nuclear fusion reaction maintained by a ”magnetic bottle” rather than the intense gravitational pressures at the heart of a star. Or an organism that communicates across the entire planet at near-light-speed by manipulating streams of electrons and photons.) The other big problem with my Quora friend’s argument was that he assumes that physics is already completely understood, in a fundamental way. He assumes we will never experience another revolution of thought similar to Relativity. We will never learn to look at the building blocks of the universe in a di erent way to quantum theory. Presumably, he believes quantum theory and the standard model will never be united. Gravity, which we currently do not understand very fundamentally at all, will never be fully described.
This seems like a fairly dangerous prediction to make. After all, previous civilisations from the Ancient Greeks and Egyptians, to the great Islamic scientists and astronomers of the middle ages, to Europe’s own Enlightenment thinkers and even the scientists of the 19th and early 20th, all had models of the way the universe works, and these models allowed them to make predictions about things (which is the only way you can really say whether a model is ”good” or not). But they weren’t perfect. They had holes.
At the absolute cutting edge of particle physics and cosmology and quantum mechanics, all the scientists working in those fields know it’s a ”work in progress”. Their models can help your car use less fuel, can light up a room on less electricity, can treat your cancer and accurately predict if it will rain tomorrow (next Wednesday, not so much). But they’d don’t predict everything. Yet.
There’s still more to be discovered. Lots more. And maybe an equation will pop out of some mathematics graduate’ head, one that will, just like E=MC2 did for nuclear power, make a trip to Alpha Centauri just another thing that humans do.