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When I look up at the stars, I like to imagine the thousands of alien worlds in orbit around them.

Most are likely barren deserts, like Mars or Venus. Some may have simple life in ponds and oceans, like alien algae. But maybe a special few have life with knowledge. Through countless generations, like us, perhaps they have learned what the stars are and their potential for creating life.

I imagine there’s a creature on one of these alien worlds, looking up at its own constellations at the same time as I am.

Artist’s impression of the night sky from an alien planet, by Gate to Nowhere

I’d imaging that both of us look at the Milky Way galaxy stretching across the sky, and consider every star it contains as another possibility for a creature like ourselves.

But we know that despite the enormous number of stars, they are just one ‘layer’ of the universe. The entirety of the Milky Way, with its 300 billion stars, is just one galaxy in an ocean of others, whose every crashing wave is older than both our species.

Beyond the galaxies is the next layer, the superclusters of galaxies, that are like the tides and currents of an impossibly enormous cosmic web of over 100 billion galaxies.

I imagine that we both know we’re neighbours on a microscopic raft. Sharing a fate for where the slow tides take us, yet unaware of each other’s existence except for a spark of imagined connection.

That is what I like to think the word ‘universe’ means.

But I have to remind myself that it is only half the picture.

We’ve been looking up, but to see the universe in its entirety we also have to also look down. Not into the ground under our feet, but into the building blocks of our reality. Into atoms and the worlds they contain, each one as different from each other as the Earth is to the Milky Way.

Looking Down

The first layer is the world of the molecules, where chemicals and materials can react in trillions of different ways to form an array of endless combinations. The study of this world is chemistry.

Then comes the world of the atoms, a place dominated by charge and valence, where electron clouds swarm above a tiny nucleus and are almost entirely empty of anything physical. The study of this world is atomic physics.

Next, even smaller than the atom, comes the world of quantum mechanics. At this level of reality, everything is made from ripples in great fields of energy that extend throughout the entire universe, a finding that is both startling and incredibly philosophical.

This kind of thought experiment places the world that we are used to, made of houses, trees, and buildings, as a middle-sized world. It’s wedged between the extremes of enormous galaxies one one hand, and miniscule atoms and strange quantum worlds on the other. And each end grows increasingly mysterious and incomprehensible the further you travel into it.

Quantum mechanics is as far as our instruments have been able to see, but we know it’s not the end of the line.

The leading theory of what comes next is called string theory. It predicts that the ripples of the quantum world are ultimately caused by vibrations of strings and that all of reality arises from different combinations of these vibrations, like music turned solid.

There may be no limit to how strange the things can go. Centuries from now, we may discover that reality is endless, and our Earth is just one frame in an infinite vista of strange realms of size and magnitude, like we’re the citizens of a M.C. Escher style universe.

M.C. Escher was a Dutch artist who specialised in depicting strange worlds using complex and bewildering mathematical art. Image credit: The M.C. Escher Company.

If the Milky Way is our imaginary raft, then these tiny worlds of chemistry, atoms, quantum mechanics, and string theory are the ropes and sinews that hold it together. They are the the fabric of our reality, and they are what this section of the Big Ideas Network is about.

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Ben McCarthy

Ben McCarthy
