When I look up at the stars, I like to imagine the alien worlds that are in orbit around them.
Most of them are probably likely deserts, like Mars or Venus. Some have life on their surface and in their oceans, with flourishing ecosystems full of strange creatures. But a special few planets have intelligent life, with creatures that have knowledge.
Through countless generations, like us, perhaps they have learned what the stars are and their potential for fuelling life.
I imagine there’s a creature on one of these alien worlds, looking up at the stars above its head at the same time as I am.
I’d imagine 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 different version of a creature like ourselves.
But we know that despite the enormous number of stars, they are just one small part 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 are the superclusters of galaxies, and they flow with the currents of an impossibly enormous cosmic web of over 100 billion galaxies.
I imagine that we both know we’re sharing the same cosmic raft. We share a fate for where the immense tides take us, but are unaware of each other’s existence except for a spark of imagined connection.
This 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 layers of reality they house, each one as different from each other as the Earth is to the Milky Way.
If the Milky Way and the Earth are our imaginary raft, then by turning our attention in the other direction we can examine the ropes and sinews that hold it together.
The first thing we would notice is that everything in the universe is constructed from a loose mesh of molecules.
It is a place where chemicals and materials react in trillions of different ways to form endless combinations. The study of this world is chemistry.
Within the molecule is the atom, a place dominated by strange laws of 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.
Even smaller than the atom is 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.
Quantum mechanics is as far as our instruments have been able to pierce, but we know it’s not the end of the line.
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.
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 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.
These tiny worlds of chemistry, atoms, quantum mechanics, and string theory are the the fabric of our reality, and they are what this section of The Big Ideas Network is about.