Redshift is one example of how reality can depend on our interpretation. While an observer standing still might be able to see an object change colour, an observer moving at the same speed as the object would not. Can you think of some other situations where different people might interpret reality differently?
Transcript
Redshift is an effect created by light waves. It causes the colour of an object to become redder as it moves away from an observer. This is because red light has the longest wavelength of all the colours on the visible spectrum. Redshift is not something that humans often see, because an object must be travelling very fast to visibly change colour. However, we can observe a similar effect with sound waves, when the pitch of a car horn changes as the car drives away. Redshift is important because it has helped astronomers make observations about the universe. In 1929, the redshift of galaxies caused astronomer Edwin Hubble to discover that the universe is expanding. Today, astronomers also use redshift to find the locations of planets outside of our solar system.
The human perception of colour is caused by the way our eyes to light. While humans can see many different colours, light that is visible to humans only makes up a small amount of the light in the . This is because of the limits of the photoreceptors in our eyes. Human eyes contain types of photoreceptors known as cones, which are responsible for detecting coloured light. Because light is made up of , each type of light has a different wavelength. Cones can pick up on these wavelengths, which is how we differentiate between colours. Humans have three types of cones in our eyes – known as red, green, and blue cones. We can see any colour of light with a wavelength within the range of those cones. However, light outside of the visible range – such as infrared and ultraviolet light – can’t be seen by the human eye. Though this light is invisible to us, it isn’t invisible to every . Different animals have different amounts of cones in their eyes. Dogs, for example, only have two types of cones, and therefore can’t see as many colours as we can. An animal known as the mantis shrimp, however, has sixteen types of cones. That means that its range of visible light is much wider than ours, and it can see colours we can’t even .
Comprehension questions
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Discussion/essay questions
Many scientists have wondered if we all see the same colours, or if we have learned to call different colours the same names. One person could possibly call a colour “red” that another person sees as blue. We have no way of proving or disproving this, because it is difficult to describe what a colour looks like. Do you think it is possible that we all have a different perception of colours?
Transcript
The human perception of colour is caused by the way our eyes respond to light. While humans can see many different colours, light that is visible to humans only makes up a small amount of the light in the universe. This is because of the limits of the photoreceptors in our eyes. Human eyes contain types of photoreceptors known as cones, which are responsible for detecting coloured light. Because light is made up of waves, each type of light has a different wavelength. Cones can pick up on these wavelengths, which is how we differentiate between colours. Humans have three types of cones in our eyes – known as red, green, and blue cones. We can see any colour of light with a wavelength within the range of those cones. However, light outside of the visible range – such as infrared and ultraviolet light – can’t be seen by the human eye. Though this light is invisible to us, it isn’t invisible to every species. Different animals have different amounts of cones in their eyes. Dogs, for example, only have two types of cones, and therefore can’t see as many colours as we can. An animal known as the mantis shrimp, however, has sixteen types of cones. That means that its range of visible light is much wider than ours, and it can see colours we can’t even imagine.
