Imagine opening the weekend paper and looking through the puzzle pages for the Sudoku.
I must have made a mistake, you think.
So you retry, this time starting from the corner you couldnt finish and working back the other way.
But the same thing happens again.
Youre down to the last few squares and find there is no consistent solution.
Working out the basic nature of reality according to quantum mechanics is a little bit like an impossible Sudoku.
(This is what makes quantum mechanics so much fun.)
Back in the 1940s, Einstein called this spooky action-at-a-distance.
We know today it is very unlikely there is any such better theory.
Loosening our grip on reality
What if the world isnt made of well-defined, independent pieces of stuff?
I hear you say.
Then can we avoid this spooky action?
Yes, we can.
And many in the quantum physics community think this way, too.
But this would be no consolation to Einstein.
Einstein had a long-running debate with his friend Niels Bohr, a Danish physicist, about this very question.
In Bohrs view, the world doesnt have definite properties unless were looking at it.
When were not looking, Bohr thought, the world as we know it isnt really there.
Credit: Paul Ehrenfest.
But Einstein couldnt have both a well-defined, independent world and no spooky action-at-a-distance … or could he?
The Bohr-Einstein debate is reasonably familiar fare in the history of quantum mechanics.
But we will need to get weird in other ways.
This hypothesis is called retrocausality, because the effects of doing the experiment would have to travelbackwards in time.
If you think this is strange, youre not alone.
This is not a very common view in the quantum physics community, but it has its supporters.
No view from Olympus
Imagine Zeus perched atop Mount Olympus, surveying the world.
Imagine he was able to see everything that has happened and will happen, everywhere and for all time.
Call this the Gods eye view of the world.
Recent researchin quantum mechanics suggests a Gods eye view of the world is impossible, even in principle.
And there might well be no absolute fact of the matter about whos correct not even Zeus could know!
So next time you encounter an impossible Sudoku, rest assured youre in good company.
The entire quantum physics community, and perhaps even Zeus himself, knows exactly how you feel.
