What on Earth? Is the grass really greener?

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Why does the grass look a lighter green at a distance? When you paint a landscape, you are told to paint the background lighter than the foreground because this is the way it looks in real life. Why?

Why does the grass look a lighter green at a distance? When you paint a landscape, you are told to paint the background lighter than the foreground because this is the way it looks in real life. Why?

There are lots of atmospheric effects near ground level that affect how we perceive things at a distance. The amount of dust in the air between you and the object increases with distance, and heat rising from the ground can change the refractive index of the air. These factors will tend to scatter and smear out the light you receive from an object. The further away the object is, the more the smudging will be evident.

Light from the sun is made up of all colours. Grass close to you will reflect green light, absorbing the red and blue light. You see the grass as green. More distant grass will also reflect the same amount of green light, but dust in the atmosphere above it will reflect white light (all colours) towards you, too. This scattering of light dilutes the green you see from distant grass. The light you receive will be a faded (but still bright) version of the closer grass.

This is most obvious in cities. If you look out of a tall building, distant buildings seem paler than closer ones. They will not, however, seem darker because lots of light is being reflected towards you, it's just that it is not all of a specific colour.

Do any animals have eyeballs that retract when they close their eyes?

As they lack well-developed eyelids, frogs do withdraw their eyes into their sockets while they are in resting mode. They are also able to use their eyeballs during swallowing, in order to help push food down their throat. They retract one eye at a time, which presumably creates some kind of peristaltic motion.

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