There is a new(ish) article in Aeon that may be of interest to folks interested in the historical sciences. It concerns the question of whether time had a beginning— or, to be more precise, it concerns whether physical science is capable of showing that time had a beginning. Everyone knows about the “Big Bang”: the (originally satirical) name given to the idea that the universe expanded from an almost unfathomably hot and dense state. Less people know about Kant’s first antinomy, by which he meant a contradiction between two apparently reasonable beliefs. According to Kant, pure reason is incapable of deciding between the idea that the world is finite in space and time, and the idea that it’s infinite in space and time. But these cannot both be true. So here pure reason runs headfirst into a limit.
For a time, physics rushed in where pure reason feared to tread. After Einstein (or perhaps after Hawking and Penrose), the thesis that time is finite seemed to have the support of mathematical physics. But perhaps Kant will have the last laugh. As Daniel Linford, author of the Aeon piece, writes: “The beginning of time, once imagined as igniting in a sudden burst of fireworks, is no longer an indisputable scientific fact.”
You have my attention.
Now, I’m not at all qualified to judge this statement. But I can say that the essay is a little triumph of lucid exposition. Linford has a knack for explaining complex ideas in just a few sentences (and as someone who has consumed plenty of popular books on physics, this is a rare skill). Again, I’m not qualified to say whether these simplifications are over-simplifications: probably some are, and perhaps this is unavoidable in a piece like this. But I will say that I find the whole thing impressive, and entertaining.
I’m not going to attempt a summary of Linford’s account. Just go read it! Still, I’ve extracted a few passages that give some indication of the overall drift and urgency of the argument:
As the 20th century progressed, questions began to emerge about the Big Bang. Was it truly the Universe’s origin? The observable Universe may once have expanded from a hot, dense state, but that doesn’t necessarily mean the entire Universe did so, or that there was nothing before the hot, dense state.
And:
In recent decades, more physicists have started to think that the ‘cataclysm’ will be replaced with something else in a future theory. And even more radical arguments are now emerging that question our established ideas about the Big Bang— ideas that have been missed in popular accounts of the Universe. These arguments address spacetime’s global structure, and they strongly suggest that no theorem and no amount of data will ever allow us to know whether spacetime originated in some past cataclysm.
Finally:
The Malament-Manchak theorem presents us with a sobering limit: our observations, no matter how extensive, may never be sufficient to determine spacetime’s global structure. Mathematically, the possible shapes and properties of the Universe remain too numerous— many versions fit equally well with the data available from our past light cones. Though the Big Bang has been popularly hailed as the origin of our Universe, many physicists and philosophers remain unconvinced.
Heady stuff!