As each new generation of scientists pushes against the limits of what we know about the universe, the smaller our world seems to get.
Early humans once no doubt thought that their vast river valleys were all that there was in the universe.
Sometime later, we believed that the Earth lay at the center of the universe, until we discovered that it was one planet among many around our Sun.
Sometime later, we found that our Sun was one among billions in the Milky Way galaxy.
Then we discovered that the Milky Way was one among billions of galaxies, which outnumber every human being who has ever lived.
From a certain perspective, history could be organised into a series of thresholds where we discover that our ‘everything‘ is just a tiny part of a much grander whole.
But it has become somewhat frighteningly apparent that the very materials that we are made of are just another threshold.
We are all made of something that scientists call ‘matter’. It means that everything from moon rocks to London busses are made up of molecules, which are made up of atoms. Atoms are then made from quantum mechanical particles like quarks and gluons.
But in the late 20th Century, cosmologists discovered that there was more to the universe than just matter. There were new, strange forms of energy that exist around us at all times, though they are invisible and travel straight through us like ghosts.
What’s more, when they estimated how much of the universe was ordinary matter and how much was these strange new forms, it became apparent that most of the energy in the universe belonged to what they now call dark matter and dark energy.
Dark matter and dark energy still remain mysterious. We haven’t yet found a way to study them, and the only thing we really know about them apart from their approximate energy is their effect on gravity.
Meanwhile, ordinary matter has its own thresholds. It’s the result of numerous layers of complex structures that are stacked on top of each other, from still theoretical strings up until you arrive at moon rocks and London buses. The deeper we look, the more layers we uncover.
For instance, it’s theorised that quarks and other quantum mechanical particles are actually made up of tiny, one-dimensional things called strings
The fact that these tiny layers of exist in the ordinary world around us, but beneath our perception is hugely unintuitive for us, as our sensory perception of the universe is fundamentally limited by our biology.
We can imagine our senses as a lantern illuminating of a tiny part of an immense, pitch black cavern. Our progress has come from building ever more elaborate instruments like the telescope, microscope, space telescopes, and hadron colliders. Almost always, what they reveal we find mysterious, counterintuitive, and unusual.