The new moon is not visible to observers on Earth because the sun and moon are aligned, with the moon positioned between the Earth and the sun. This means that the side of the moon illuminated by the sun is facing away from Earth, leaving the dark side facing us.

Here's a simple analogy: imagine you're holding a flashlight and shining it on a ball. If you're looking at the ball directly in front of the flashlight, you won't see any light reflecting off of it. This is similar to the new moon, where the sun's light is shining on the moon's far side, invisible to us.