Do We Live in a Block Universe?
Exploring Time, Causality, and Free Will in Einstein's Spacetime
The Question
Einstein’s theory of relativity transformed our view of the universe, challenging our most basic intuitions about time and space. These changes took a more radical turn when Hermann Minkowski showed that space and time can be woven together into a single fabric, spacetime: a four-dimensional structure in which space and time play seemingly identical roles. Einstein himself initially resisted this development before later embracing it.
But some thinkers have taken Minkowski’s insight further, suggesting this picture compels us to view spacetime as a fixed ‘block’ where past, present, and future all coexist, and the flow of time is an illusion. If true, the future would be as settled as the past, and our experience of choice and genuine change merely illusory. This idea, the block universe, is often presented as scientific proof of predetermination: that everything that will ever happen has, in some sense, already happened.
Does spacetime physics really force this view upon us? This series argues that it does not. The step from physical theory to metaphysical conclusion rests on misunderstandings, especially about the relativity of simultaneity: the result from relativity theory that forms the crux of the block universe argument.
Why This Series?
The block universe idea persists largely through lack of clarity about the key concepts and the mechanics of using different reference frames. Yet discussions of the subject tend to be either superficial - inadequate for something so easily misinterpreted - or more involved, but confused.
This subject demands precision. Relativity is notorious for its ‘paradoxes’: aspects that appear self-contradictory even to physicists on first encounter. Students must grapple with these paradoxes as part of learning the theory. Physicists debated the ‘Twin Paradox’ for decades before atomic clocks settled the matter in the 1960s–70s, despite the physics pointing clearly to the resolution all along. The concepts aren’t mathematically complex, but they’re profoundly counter-intuitive, requiring us to rethink fundamental assumptions about reality. Mastering them takes time and repeated engagement. A shaky grasp invites serious error.
Unlike the twin paradox, the block universe debate appears immune to experimental testing. This makes careful reasoning essential. My aim in these essays is to provide that clarity. Proponents of the block universe correctly recognise that relativity demands we rethink time and existence. But I contend they misidentify what that rethinking requires. The third essay in this series illuminates what the relativity of simultaneity actually reveals: insights that are real, but not those claimed by the block universe argument.
The Essays: A Guide
I’ve written three main essays addressing different aspects and audiences, plus two companion explainers that fill in the physics.
Rethinking the Andromeda Paradox examines a simple, popular thought experiment known as the Andromeda Paradox. This serves as a useful introduction for readers new to the block universe idea. The reasoning is easy to follow, and the flaw relatively easy to spot. Yet the error here is essentially the same as in academic arguments, making this a good entry point for the key issues.
This essay can be read with only a brief glossary for orientation. By using Minkowski’s spacetime diagrams I am able to avoid the need for formal mathematics. These deceptively simple yet powerful visual tools allow rigorous analysis whilst remaining accessible. For readers who still find the ideas difficult to grasp or accept, there are links from the glossary to the explainer essays.
Rethinking the Andromeda Paradox addresses more technical versions of the argument, including the forms independently developed by Rietdijk and Putnam in the 1960s. The explainer essays will be particularly helpful here, though not essential.
Time, Causation, and the Meaning of “Now” presents a framework for thinking about time and space in relativity that respects the mathematical structure of spacetime whilst accommodating the conceptual shifts relativity demands. I contend that thinkers have failed to make these adjustments, leading to confusions like the block universe.
Explainer 1 is an extended glossary explaining the key ideas and demystifying peculiar concepts, with detail that would be distracting in the main essays.
Explainer 2 goes deeper, explaining how the relativity of simultaneity and related concepts arise from the theory. This will help readers who want more than assertions about relativity’s strange claims, those who rightly feel that deeper knowledge of the physics will aid philosophical understanding, and those simply curious to understand this fascinating subject more fully. The spacetime diagrams really come into their own here, allowing us to see how the structure of the theory leads to its counter-intuitive results.