EYE-OPENING BOOK, "AN IMMENSE WORLD," BY ED YONG, WHICH IS ALL ABOUT HOW VARIOUS CREATURES PERCEIVE THE WORLD AROUND US.

TAKE JUST ONE SENSE, SIGHT, WHICH IS PRIMARILY BASED ON PERCEIVING LIGHT.

LIGHT IS BOTH A WAVE AND A PARTICLE, FOR REASONS I CAN'’T GET INTO IN THE 90 SECONDS THEY GIVE ME HERE.

DIFFERENT ANIMALS HAVE DEVELOPED DIFFERENT SENSITIVITIES TO THE DIFFERENT WAVELENGTHS OF LIGHT AND FOR HUMANS THAT MEANS COLOR.

HUMANS SEE SOMETHING AT 700 NANOMETERS AND PERCEIVE IT AS RED AND SOMETHING AT 500 NANOMETERS AND SEE IT AS BLUE.

BUT, THERE IS NOTHING FUNDAMENTALLY BLUE ABOUT 500 NANOMETERS OR RED ABOUT 700.

THOSE WAVES ARE SIMPLY STIMULATING ONE OF THE THREE SETS OF CONE CELLS IN OUR EYES AND THEN OUR BRAINS MAKE SENSE OF IT.

IT'’S DIFFERENT FOR DIFFERENT ANIMALS.

READY TO HAVE YOUR MIND BLOWN?

PURPLE DOES NOT EXIST IN THE RAINBOW AND CANNOT BE EXPRESSED WITH A SINGLE WAVELENGTH OF LIGHT.

INSTEAD, OUR RED AND BLUE CONES ARE STIMULATED TOGETHER, AND OUR BRAIN REGISTERS PURPLE.

HUMANS SEE COLOR IN THREE DIMENSIONS.

BUT BIRDS, REPTILES, INSECTS AND EVEN THE HUMBLE GOLD FISH CAN SEE FOUR DIMENSIONS OF COLOR.

THEY CAN PERCEIVE ULTRAVIOLET COLORS IMPERCEPTIBLE TO MOST HUMANS.

IT'’S LITERALLY IMPOSSIBLE TO SHOW YOU HOW A HUMMINGBIRD MIGHT SEE THE WORLD.

YOU MAY THINK CREATURES EVOLVED TO SEE COLOR TO BETTER DISTINGUISH BETWEEN DIFFERENT TYPES OF FOOD.

AMAZINGLY, IT IS THE OPPOSITE.

THE ABILITY TO SEE COLOR CAME FIRST, AND THEN THINGS LIKE PLANTS AND FRUIT DEVELOPED COLORS TO ENTICE OR REPEL CREATURES.

SO, IN A SENSE, THE ANIMAL WORLD WAS READY TO SEE COLOR, AND NATURE ROSE UP TO MEET THE CHALLENGE.

IT GIVES YOU A LOT TO THINK ABOUT THE NEXT TIME YOU SEE A RAINBOW.

THE EVOLUTIONARY MIRACLE THAT'’S GOING ON IN YOUR EYES AND BRAIN TO SEE IT.

THE FACT THAT IT'’S IMPOSSIBLE TO KNOW EXACTLY HOW ANOTHER BEING PERCEIVES IT.

AND A REMINDER THAT WE HAVE POTENTIAL IN US TO SENSE AND UNDERSTAND THINGS WE DON'’T ALREADY, BECAUSE WE AND THE WORLD ARE STILL EVOLVING TOGETHER.