Things become weird and wonderful when physicists or cosmologists or astronomers talk about the “edge of the universe” or the “finitely bounded but infinite universe” or the “expanding universe” which does not expand into anything but creates space as it expands (the balloon analogy). I read that the Big Bang occurred 13.8 billion years ago but the size of the universe is said to be a diameter of (around) 93 billion light-years. Some photons, they say, have traveled 46-47 billion light-years since the Big Bang. Now how did they do that in just 13.8 billion years? The answer, say the physicist-philosophers, is that things aren’t moving away from each other so much as that the space between them is expanding. Really!
How can the universe be 93 billion light-years across if it is only 13.8 billion years old? Light hasn’t had enough time to travel that far…? Ultimately, understanding this facet of physics is the key to understanding what lies beyond the edge of the observable universe and whether we could ever get there.
To break this down, according to special relativity, objects that are close together cannot move faster than the speed of light with respect to one another; however, there is no such law for objects that are extremely distant from one another when the space between them is, itself, expanding. In short, it’s not that objects are traveling faster than the speed of light, but that the space between objects is expanding, causing them to fly away from each other at amazing speeds.
Ultimately, this means that we could only reach the edge of the observable universe if we develop a method of transport that allows us to either 1) Travel faster than the speed of light (something which most physicists think is impossible) 2) Transcend spacetime (by using wormholes or warp drive, which most physicists also think is impossible).
The reality, I think, is that human cognition is limited. I reject the converse, that human cognition is unlimited, because, if it was, we would not have imponderable questions. Stephen Hawking has often said that “outside the universe” makes no sense, because if the universe came from nothing and brought everything into existence, then asking what lies beyond the universe is an invalid question. When physicists invoke dark energy and dark matter and, in the same breath, point out that they are unknown and undetectable, then it follows that human understanding is incomplete because of the limits to human cognition.
If human cognition is limited, whether at the level we have reached or ten times that level, our understanding of the universe around us is, and will be – and must be – also limited. We will always have a “conceptual edge” to the universe around us corresponding to our cognitive limits. Beyod this edge lies what is “unknowable”. The edge of the real universe lies at at the furthest reaches of our cognitive abilities.
As most fish (with exceptions for flying fish and lung fish) cannot conceive of the world beyond the surface of the water, so can humans not conceive a universe beyond the “conceptual edge” defined by their cognitive ability.
We can never observe what is beyond the “observable universe” because light will never get there. But it isn’t just light that doesn’t get there. Our minds don’t reach there either. There may be a multiverse out there – or maybe not. There may be just the ultimate void being converted into space-time as our universe eats into it. Or maybe there is The Restaurant at the End of the Universe awaiting the intrepid few who get there. Or maybe there is a Thing with a long white beard observing us to see if any human-fish manage to leap through the “edge of the universe”.
Tags: edge of the Universe
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