Humanity’s search for a theory of everything is one of the motivating forces behind the whole scientific endeavour. But is it possible for an observer within the universe to know everything about the universe? Philosopher of science JB Manchak here argues that we cannot know the structure of all of spacetime from any specific point within it – and this is the case even if we somehow collected all the possible perspectives, from every point in the universe. Due to arguments made available by Einstein’s general relativity, we cannot know the universe from within it.
It is well known that the region beyond the 'observable universe' is unknowable. What is less well known is this: even if one were somehow able to observe this unobservable region, the universe would remain unknowable. Indeed, the puzzling state of affairs would persist even if one were given an all-access pass to every possible observation at every possible place and time -- here, there, past, present, and future.
In what follows, I will argue that there is a sense in which the universe is fundamentally unknowable via any number of observations made from within it. This claim amounts to a theorem of Einstein's general theory of relativity and the argument amounts to a simple proof sketch of this theorem. Only a few key definitions will be needed to state the theorem and sketch the proof.
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