This is what a crescent moon actually looks like. But we never see it this way because our eyes can’t simulataneously discern between such light and dark regions. To wit:

Called earthshine or the ‘da Vinci glow’, the unlit part of a crescent Moon is visible but usually hard to see because it is much dimmer than the sunlit arc. In our digital age, however, the differences in brightness can be artificially reduced. The featured image is actually a digital composite of 15 short exposures of the bright crescent, and 14 longer exposures of the dim remainder. The origin of the da Vinci glow, as explained by Leonardo da Vinci about 510 years ago, is sunlight reflected first by the Earth to the Moon, and then back from the Moon to the Earth.

Now for yeh.

(Image: Miguel Claro (TWAN, Dark Sky Alqueva))

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Behold: the sunlit crescent of da Vinci glow caused by earthshine (light reflected from a bright planet Earth) on the moon. To wit:

..a description of earthshine in terms of sunlight reflected by Earth’s oceans illuminating the Moon’s dark surface was written over 500 years ago by Leonardo da Vinci. One lunar month ago [this] da Vinci glow was captured in stacked exposures from the Badain Jilin Desert of Inner Mongolia, China. This year marks the 500th anniversary of Leonardo da Vinci’s death.

(Image: Likai Lin)

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