8 February

If you’ve never seen a camera obscura, the effect is striking. A small hole in a wall or blind won’t just let light in, it projects an entire image of the outside inside the room. Most cameras use this principle, they just add lenses. But if you look closely around you, the same effect happens all over the place. Look at this picture of the shadow cast by a tree during an eclipse. You’ll notice that a ‘picture’ of the eclipse has been captured by many of the tiny gaps between the leaves, causing them to project multiple images of the eclipse onto the side of a house. Traditional theories of light and vision and images can make no real sense of how this all works. It would say a small hole would let light through, but has no convincing explanation for why an entire ‘image’ of the scene seems to come through that hole.