People used to think Earth was flat. Since flat things have edges, Earth had edges, which meant Earth was likely finite. If someone walked in one direction far enuf, they would fall off an edge or hit a wall, one or the other.
People now know Earth is a ball moving thru space. Walk far enough on a ball, get back where you started, right? Does this simple fact imply Earth is infinite? Of course not. We know it isn’t. Earth has finite area, which can be roughly calculated.
Today, no one understands enough about space to know how much of it there might be. Some think space goes on forever. Regardless of direction, spacecraft can never reach the end because space is all there is and must therefore be infinite.
The problem with this view comes from what folks think they know about gravity. Massive objects seem to bend and twist space in ways that make time slow down and light bend. It’s mysterious, because if you think about it, why should they?
Isn’t it crazy that massive objects have profound effects on things they don’t touch? They change path and timelines of whatever travels nearby. Something unseeable transforms invisible oceans of spacetime putty, which pushes about whatever lies buried inside.
Einstein showed how to calculate power of massive objects like stars and (then unknown) black holes to warp space in ways that forced changes to direction and speed of anything at all that moved by, but he didn’t explain why or how. It seems puzzle pieces are missing which found would at long last reveal what this malleable stuff might be.
It’s nothing we measure. Many have tried but space seems to be entirely empty. Virtual particles pop in & out of existence, yes, but taken together their measurable qualities add to zero.
What answer makes sense? —infinite space or not?
Einstein’s answer was that spacetime makes no sense apart from existence of mass & energy, which are two sides of a coin, like light, which measured becomes point-like momentum or spreading energy undulation. Apart from mass & energy, space & time cannot, do not exist.
Isn’t non-existence the meaning of the word “space”? Under any scenario that can be imagined, space & time have no meaning except to help thinking people describe peculiar relationships between objects we observe & measure. In this sense, every massive thing is connected to every other.
Energy saturates the universe. It’s everywhere we look. It fills gaps between objects with 3 dimensional ripples of undulating something or other. It means that we—tiny neural networks that we are—live trapped in cosmic amber, like prehistoric insects.
At the scale of stars and galaxies we are truly constrained; frozen in time; unable to move in any way that can be noticed—were anyone out there at scales able to observe & take notes. It is impossible for any living thing to secure vantage points in spacetime where it might observe the entire universe.
In this sense, the Universe is a single, solid object, which is imagined by something conscious trapped inside. Perhaps, somewhere far away beyond our vision an event horizon emerges beyond which mass & energy have no place.
The universe ends not with a wall or wail but instead a whisper, a whimper, a last desperate gasp. Light fades to embers, then into dark night where imagination does not go and black birds no longer sing.
Billy Lee
Note: a version of this essay was first published by Billy Lee on Quora in January 2025