What primarily causes the visual phenomenon of a string of moving lights across the night sky?

Answer

Visible result of modern large-scale satellite deployment efforts

These linear patterns are the visible result of newly deployed satellites separating sequentially after being delivered into a specific initial orbit by a rocket's upper stage.

What primarily causes the visual phenomenon of a string of moving lights across the night sky?

#Videos

Starlink satellites, the string of lights in the night sky. - YouTube

What Happens If SpaceX Starlink Satellites Start Colliding - YouTube

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