Day length, or length of day, or length of daytime, is the time each day from the moment the upper limb of the sun's disk appears above the horizon during sunrise to the moment when the upper limb disappears below the horizon during sunset. Due to the diffusion and refraction of sunlight by the atmosphere, there is actually daylight even when the sun is slightly below the horizon. The period when it is still somewhat light even though the sun is below the horizon is called twilight.
Read more about Day Length: Description, Alternate Definition, Historical Variation of Day Length Because of Tidal Acceleration
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“For after all man knows mighty little, and may some day learn enough of his own ignorance to fall down again and pray. Not that I care. Only, if such is God’s will, and Fate and Evolution—let there be God!”
—Henry Brooks Adams (1838–1918)
“No doubt, the short distance to which you can see in the woods, and the general twilight, would at length react on the inhabitants, and make them savages. The lakes also reveal the mountains, and give ample scope and range to our thought.”
—Henry David Thoreau (1817–1862)