This is likely to blow your mind – but colour doesn’t really exist.

Glenn Barden, one of the “brains”, excuse the pun, behind the PBS/BBC series The Brain with David Eagleman, explains.

We all think we know what reality is – it’s the rich textured world that’s all around us. But what if I told you that the real world is very different – it’s a place with no sound, no smell, no taste, and no colour. Sounds crazy right? You won’t be the first person to disbelieve me, I almost came to blows in a pub when I tried to explain this to someone. But however strange it sounds it is true – our reality is constructed by our brain and the world outside our head is very different.

The more we learn about the brain the more we are beginning to learn about the true nature of reality. What neuroscience is telling us is that the brain takes in information from the world outside our heads, turns it into electrochemical data and presents reality to us.

There’s a separation between us and the world outside.

The brain is in fact the universe’s ultimate storyteller because we believe whatever our brain serves up to us. But the reality we experience is a construction – a show put on inside our heads….

So what is the outside world really like?

Well, the answers that physics give us can seem shocking.

First…sound.

In the world outside our heads, there’s no such thing.

Simply the compression and expansion of air molecules. Our ears pick up on those changes, and turn them into electrical signals. But It’s the brain that creates from these, the sensation of hearing.

The world is also odourless.

Different molecules floating through the air are picked up by receptors in the nose.

The brain attaches labels and sensations to them, and we experience smell.

But the most striking trick that the brain performs, is with something that feels like a fundamental part of the physical world. That trick is convincing us that we live in a world of color.

Colour doesn’t actually exist in the outside world – all we have is electromagnetic radiation that bounces off of objects. And our brains interpret that as colour. Most human brains can distinguish between around 10 million different combinations of wavelengths of radiation. But they only become colours once those signals have been processed.

I know it’s hard to believe but all of the colour of the world we perceive is actually painted on by our brain. So, even though colour is a construction of the brain, it becomes part of our reality.

Our brain presents to us a very particular perception of the “real” world, and this perception is different to that experienced by other animals of this planet.

“Each creature perceives only what it has evolved to perceive,” says neuroscientist Professor David Eagleman. “So for a dog he’s tuned into a whole world of scent molecules that I’m not. His experience of smell is as rich as my experience of vision. In the blind and deaf world of the tick, the important signals are temperature and the smell of body odour.For bats, it’s the echo location of air compression waves.

But no one is having an experience of objective reality of the world that really truly exists.”

Our brain sculpts our reality using the narrow trickle of data that it can gather through the senses, and from that trickle it tells a story about our world. It’s possible that every brain tells a different narrative and with 7 billion human brains wandering the planet and trillions of animal brains, no one is tapped into the full picture.

Each brain carries it’s own version of what’s outside us. But whatever the picture, all realities are equally valid.

So what is reality? It‘s whatever your brain tells you it is.