vibrations in the air—sound—that cause your common wall to vibrate and push on the air in your room to transmit the same sound waves to your ear. But if you could behave like an atomic nucleus then you would sometimes be able to pass, ghost-like, straight through a solid wall.*2 A hydrogen nucleus in the interior of the sun manages to do precisely this: it can spread itself out and “leak” through the energy barrier like a phantom, to get close enough to its partner on the other side of the wall to fuse.
