Don’t ask how I came to look into this, but when you find yourself walking into a wall you might as well make the most of it. So while studying the wall I found this:
One of the most central ideas of quantum physics is the theme of uncertainty. Quantum mechanics says that the location of anything is always uncertain. If you are looking at a book on a bookshelf, you can't say with 100% certainty that the book is on the bookshelf. Nor can you say that the book is still on the bookshelf when you leave the room.
Now this I believe. We have a bookshelf like that in The House. My brother and I have both noticed it. It’s in the room that used to be Mum’s sewing room. Every time one takes a good look at that bookshelf, there seems to be books in it that one has never seen before, or the books are in a different order than the last time. While Mum was still an avid reader, there was nothing really strange about this. It was after she claimed to have given up reading in the later years of her life that it became odd. Odder still over the year that has passed since her death, with dad hardly having been able to walk the stairs at all (and definitely not reading fiction). It still seems to me the books keep changing! I have been sort of wondering (jokingly) whether perhaps we have a library ghost. But now I find that it is all explained by quantum physics... ;)
To return to the Wall:
Quantum tunneling is when particles will jump from point A to point B without passing though the space in between. This is an actual observed effect that has some applications in technology today. --- singular atoms may do this, but humans are made up of a lot more atoms. This means if quantum tunneling were to take effect, all the atoms in your body would move from one side of the wall to the other without passing through the wall itself.
If you would like to try this, go ahead, just walk into any wall....... about a couple of trillion times. One of those trillion times, your atoms are likely to tunnel right through the wall. Unfortunately, the time it would take you to run into a wall that many times would take you billions of years. Anyway, you would be dead after a certain number of intentful hits to the head. Or you could save yourself the time and just use the door!
J.K. Rowling plays with the idea of walking through a solid brick wall in the Harry Potter books.
Hagrid, meanwhile, was counting the bricks in the wall above the dustbin.
’Three up… two across…’ he muttered. ‘Right, stand back, Harry.’
He tapped the wall three times with the point of his umbrella.
The brick he had touched quivered – it wriggled – in the middle, a small hole appeared – it grew wider and wider – a second later they were facing an archway large enough even for Hagrid, an archway on to a cobbled street which twisted and turned out of sight.
’Welcome,’ said Hagrid, ‘to Diagon Alley.’
And at Platform 9 3/4 at King’s Cross Station:
‘How to get on to the platform?’ she [Mrs Weasley] said kindly, and Harry nodded.
‘Not to worry,’ she said. ‘All you have to do is walk straight at the barrier between platforms nine and ten. Don’t stop and don’t be scared you’ll crash into it, that’s very important. Best do it at a bit of a run if you’re nervous. Go on, go now…’
The idea is older than the Harry Potter books, though:
On the evening of that first day of the week, when the disciples were together, with the doors locked for fear of the Jews, Jesus came and stood among them and said, ‘Peace be with you!’ (John 20:19)
They were startled and frightened, thinking they saw a ghost. He said to them, “Why are you troubled, and why do doubts rise in your minds? Look and my hands and my feet. It is I myself! Touch me and see; a ghost does not have flesh and bones, as you see I have.” (Luke 24:37-39)