This may surprise you but colours don’t exist.

British spelling.

The combination of our eyes and brain presents us with spectacular colours but surprisingly everything in the Universe is colourless.

Colour only exists in regard to living things that have evolved sensory light-collecting cells. Other species will see colours differently from us.

Depending on how their eyes have evolved other animals will see the light spectrum in a different way from us.

Objects don't have colours, we perceive colours, by how light bounces off an object and enters our eyes, from our eyes signals go to our brain which gives a certain object a familiar colour.

Other species of animals will have better or poorer vision than humans depending on how their light-sensing eyes have evolved.

The amazing range of complex eyes.

Light is something we take for granted, we give it little thought as we go through our daily lives.

Photo by Harry Quan on Unsplash.

Within the broad spectrum of light, gamma rays are at one end with short wavelengths, and radio waves with longer wavelengths at the other end. Within that broad spectrum of light, the wavelengths visible to the human eye occupy a very narrow band.

The colours we see are governed by the wavelengths being reflected from the surface of objects. An object appears black when all the wavelengths are being absorbed and white when all the wavelengths are reflected. We can also see the different colours when light travels through a prism and of course, we see them in a rainbow.

Photo by Yulia Gadalina on Unsplash.

The first primitive eyes found on a fossil animal can be traced back to about 540 million years ago, which is not very long when you consider that life has been on our planet for nearly 4 billion years.

Animals with no eyes had to manage as best they could due to their lack of vision.

Primitive light censors evolved so that animals were finally aware of their surroundings, which may have been the catalyst for a time of rapid expansion of different forms of life on our planet, we call that time the Cambrian explosion. Since then eyes have evolved into the thousands of different and complex types that exist today.

Scientists analyse the light coming from stars and other objects in space to gain more information. Within the spectrum of light, there are dark or bright spectral lines that can be observed as emission or absorption lines, they correspond to certain atoms and molecules contained within an object that is being viewed.

Spectral lines can also give information about the temperature, density and magnetic field of a star.

When a star or object is moving away from us it is known as red-shifted because the light waves are being stretched, and when an object is coming toward us the light waves are being compressed and that is known as blue-shifted. This is called the Relativistic Doppler Effect. Now you can see why light is so important for astronomers.

When we look at an object, say, a red rose, green grass, or blue sky, most of us would think that other animals would see the same colours, but no, other animals will see less or they will see more of the light spectrum.

When we look at an object, say a cucumber, the reflected light determines what colour we see. The light waves reflect off the cucumber and hit the light-sensitive retina at the back of our eye, in the retina humans have three cone types, tiny cells which respond to red, green and blue colours, from there the cones send signals to the brain, which provides us with the familiar colours.

Photo by Jakob Kac on Unsplash.

My dog Kobi will not see a red apple the way I see it, dogs, cats, and most mammals have only 2 cones, the missing one being red. Other animals including insects can have poorer or much better sight than what we have, some can see parts of the light spectrum that we cannot see.

Some animals have no eyes, like the star-nosed mole, Texas blind salamander or the Mexican tetra to mention a few. They have evolved this way because they live out their lives in pitch-black surroundings, like in caves or beneath the ground or in the depths of the ocean.

Human eyes are known as "camera-type eyes" as they cannot function without some light.

For about 2 to 3 billion years primitive life forms on Earth had no way of detecting light, they had to live out their lives in a pitch-black world.

Photo by David Clode on Unsplash.

We know that Trilobites had evolved compound eyes by studying their 550 million-year-old fossils. We still see compound eyes in some animals today.

From that first simple eyespots, we now witness a wide diversity of complex eyes throughout the animal kingdom.

Surprisingly, there is a species that has only one eye, they are from a genus called copepods. they are small creatures measuring just a few millimetres in length.

A weathervane scallop has around one hundred simple eyes.

The prize for the largest eyes in the animal kingdom goes to the colossal squid. Their eyes can measure as much as 27 centimetres across, over 10 inches, the size of a soccer ball. Maybe the largest eyes of any creature that has ever existed.

Over many thousands of generations, little evolutionary improvements were made to eyes before some animals finally evolved complex camera-style eyes like the ones that are seeing this article.

Image by Sofie Zbořilová from Pixabay.

Regards.