When ancient civilizations looked up at the stars and began questioning the nature of the universe and our place in it, it was logical for them to conclude from their observations that the earth was relatively flat. The ancients also believed that the earth was located at the centre of the universe, and that it was the focal point around which all other matter in the universe revolved. This view of the universe was known as the Geocentric Model, and was how Aristotle in ancient Greece and Ptolemy in Roman Egypt understood the universe.
Around the third century BC, observations of the earth’s shadow on the moon and constellations appearing at different elevations at different latitudes led to the conclusion that the earth was a sphere. Like Torontonians today, the ancients’ belief that they were at the centre of the universe persisted. It wasn’t until the 17th century that the earth-centred Geocentric Model was supplanted by Copernicus’s heliocentric model of the earth revolving around a stationary sun.
After that, the universe was fine until Galileo pointed his telescope at Jupiter in 1610 and observed that there were moons orbiting the planet. Galileo confirmed the heliocentric model of smaller bodies revolving around larger ones, but if that was possible for small moons to revolve around distant planets, then perhaps the sun was not at the centre of the universe after all.
Passing over the monumental contributions of Newton’s creation of calculus as a new form of mathematics in the late 17th century to explain his laws of gravity and inertia (which founded classical physics and the laws of motion) Newton recognized that the sun was not the centre of the universe, and that wherever the centre was it was in a fixed position around which all other bodies were in motion. From the late 18th century onwards, consensus began to build around the model of a galactic centred universe, where stars and solar systems revolved around some central point of our Milky Way galaxy. This was a fine and dandy explanation… until other galaxies were first observed in the early 20th century.
The pace of our evolving understanding of the nature of matter and the universe quickened in the early 20th century with Edwin Hubble’s discovery that the universe was expanding. Moreover, distant galaxies were moving away from earth faster than closer galaxies, which couldn’t be the case if our Milky Way was at the centre of the universe. The explanation isn’t that the galaxies are moving through space away from earth - the space between galaxies is itself expanding.
Discoveries in the 1990’s led to the understanding that this expansion was accelerating due to unknown forces, referred to as dark energy. By calculating how much dark energy is needed to overcome the gravity of the observable universe, it is believed that dark energy comprises 68% of the universe, dark matter, 27%. The remaining 5% is ordinary matter, the things we can touch and feel and the known particles like light photons, and force carrier boson particles (electromagnetism, strong and weak nuclear forces, etc.). So, essentially, most of our universe is missing, In the 1950’s scientists noticed that distant stars were rotating around the centres of galaxies at the same rate as those near the centre. This could only happen if there was some extra mass to galaxies that they could not observe – which they eventually called dark matter.
Einstein developed a mathematical ‘cosmological constant’ to explain why the universe wasn’t
expanding, as theory of relativity predated Hubble’s discovery of the expanding universe, and Einstein referred to this as his ‘greatest blunder’. But Einstein’s theories did permit for the creation of new space, and now this constant seems to explain dark energy. Predicting that empty space can have its own energy, the constant indicates that as more space emerges, more energy would be added to the universe, increasing its expansion.
As usual, the universe is unfolding as it should, and we are continuously grasping in the dark to understand it. We have come a long way, but add to the mix concepts like quantum mechanics, the existence of hidden dimensions, the multiverse, and recently, the idea of the bubble verse, our understanding of the universe continues to evolve.