The Hartle-Hawking no-boundary proposal is fascinating, but it isn’t quite ready for grade school science classes yet. Why? Well, we still lack a complete theory of quantum gravity. If we had that, we wouldn’t need to debate how the universe began; the answer would be clear.
Hawking’s theories rely on numerous assumptions and approximations, which may not reflect reality. For instance, even if we accept his framework, the universe he describes is actually smaller and less inflated than ours. This leads to a conundrum: the most probable universe isn’t quite like the one we inhabit. It’s like being told that the best possible version of you is someone else entirely. This is known as the Boltzmann Babies problem, where the likely universe resembles a smaller, younger “cosmological baby.” It’s a quirky name, sure, but it highlights a real dilemma.
Hawking also performed some mathematical tricks, such as switching from real to imaginary time, to arrive at his conclusions. However, alternative approaches suggest that instead of a neat universe, what we actually have is chaotic and unpredictable. This complexity isn’t great if you’re trying to make accurate predictions about our universe.
Then we hit the issue of probabilities. In standard quantum mechanics, we have the Born rule to convert wave functions into observable probabilities. But applying this to the universe as a whole raises questions. How can we treat the universe like we do electrons? This leap seems shaky and could be why Hawking’s answers sometimes fall short.
Moreover, how do we measure the universe when we’re already part of it? It’s like trying to read a book while being inside the story. This complicates our understanding of observation in quantum mechanics, and the same challenges carry over to cosmology.
Hawking assumed that the initial universe would be smooth, making it easier to predict how it developed. Roger Penrose pointed out that this assumption makes it tricky to claim any kind of victory in the predictions made about the arrow of time. Smoothness was baked into Hawking’s model from the start.
When it comes to time, Hawking’s proposal suggests that time itself emerges from the universe’s geometry. This raises questions: if time didn’t exist, how could the universe “begin” in the first place? It feels like a puzzle with pieces that don’t quite fit together.
In conclusion, while the no-boundary proposal is intriguing, it has fundamental flaws. Without a robust quantum theory of gravity, we can’t determine whether we’re on the right track or wandering down a false path. Even if we accept Hawking’s ideas, it leaves us wondering: why do the laws of physics exist in the first place?
As of now, that question remains unanswered.
