It looks like planets go around stars and stars go around galaxies. And in three dimensional Newtonian space so they do. This is not the whole story, though. The universe moves in four dimensions, because Time is a constant too. Einstein’s eureka moment was understanding Newtonian mechanics in the universe of Spacetime. Circular orbits are made by gravity as gradually decreasing circles in a three dimensional sense but this is not the reality of gravity in the universe.
Objects move in straight lines through Spacetime. Circle plus time equals straight line from A to B, gravity is not a electromagnetic or nuclear force but a displacement in Space – the footprint of matter – creating a curve in Spacetime towards the centre (i.e. deepest) point. All matter is affected once it encounters the edge of the curved space, captured if no other forces propel it beyond the curved space and once captured matter moves in a straight time through Spacetime to the centre.
This movement plays out on Earth as things falling to the ground if dropped from a height.
But gravity plays out across Spacetime everywhere in the universe. It is the tie that binds. It is the motor driving detectable matter throughout interstellar and intergalactic Space.
The Milky Way is falling towards Andromeda.
The Sun is falling towards the centre of our galaxy.
The Earth is falling towards the centre of the Sun.
Everything on our planet is falling towards the centre of the Earth.
People have mass too. People curve space. The curve is usually so small it’s irrelevant versus the curve made by Earth.
We talk about falling in love and being bound by promises or in matrimony. Maybe this is describing a reality more accurately than mere metaphor.
Gravity is a fact, a reality nothing can ignore, escape becomes impossible once close enough to the singularity.
At the singularity, the curve in Space becomes infinite, it is the end of the straight line through Spacetime. Nothing escapes. Physics breaks down. Does everything become one again, is the infinite curve at last a hole in Spacetime? It could lead to nowhere or the beginning of time, it could be the echo of dark energy or the converging fuel of inflation and the big bang..!
Everything falls in a straight line through Spacetime. Observing the falling is limited by relativity. It’s only on Earth we see things falling in straight lines because we are falling along the same line in Spacetime. Elsewhere we see gravity’s effect relative to our subjective observation point, different line, Space and Time separate, we see three dimensional reality: straight lines in Spacetime become circles and orbits in Space.
Oh and let’s not forget the probably spurious but nicely poetic quantum entanglement. Imagine the entangled starting in the supernova that made the elements in our bodies, the very neurofabric of who we are. But since the supernova chaos, worlds had to form, chemistry needed the eons to do what was very unlikely, tangled atoms would be separated far and wide. Gravity brings some together. In rocks. In oceans. In swirling gas giants. Billions years further down the line, atoms into molecules into cells into neurons and synapses. Consciousness. People. And yet one person can be drawn to another, just one, in an inexplicable way. Maybe it’s the supernova elements finally coming close enough, in the strange bodies of two, to become entangled active again. Gravity is gravity but here’s the greater force, once it’s in play, drawing together with an intensity that’s the manifestation of love and passion such as poets and songs try to embody.