We have often heard about the moon's dark side, but a latest animation by planetary scientist James O'Donoghue has shown that sunlight actually falls across the moon while it orbits the Earth. This constant rotation leaves a moving shadow on the moon which the scientist referred to as the "Night Side".

Thus, it can be said that there is a side of the moon which we don't see from the Earth, but it's not dark all the time.

James O'Donoghue, a former NASA scientist who now works at the Japanese space agency (JAXA), wrote on Twitter: "Remember not to say 'dark side of the moon' when referring to the 'far side of the moon." Sharing his animation on the social media, he said: "This graphic shows the dark side is always in motion."

The animated video explains how the sunlight falls across the Earth's satellite as it orbits Earth. Reports state that in an orbit of about 29.5 days, all sides of the moon get sunlight at some point of time.

We see the same side of the moon

It is said that the moon is tidally locked with our planet. This means that people from the Earth are always looking at the same side of the moon, while the other side, which can be referred to as the far side, is not visible to us. But that side is not in permanent darkness.

The animation shows the view from the Earth as the moon passes through its month-by-month phases from full moon to new moon. At the bottom right corner of the video, one can also see the boundary of sunlight that falls across the moon as it rotates.

Thus, at any given point of time, half of the moon appears to be in darkness, but that darkness is constantly moving as there is no permanent dark side of the moon.

The moon is seen during a lunar eclipse over Cairo, Egypt July 27, 2018.
The moon REUTERS/Amr Abdallah Dalsh

Can we still say the dark side?

"You can still say dark side of the moon, it's still a real thing," O'Donoghue posted on Twitter. "A better phrase and one we use in astronomy is the Night Side: It's unambiguous and informative of the situation being discussed."

Last year, O'Donoghue created these a series of scientific animations and his first animations were for a NASA news release about Saturn's vanishing rings. Following that, the scientist moved on to animating other difficult space concepts, like 'the torturously slow speed of light'.

"My animations were made to show as instantly as possible the whole context of what I'm trying to convey," O'Donoghue previously told Business Insider, referring to those earlier videos. "When I revised for my exams, I used to draw complex concepts out by hand just to truly understand, so that's what I'm doing here."