
kreisen
to orbit
To move in a circular or elliptical path around a central point.
Die Planeten unseres Sonnensystems kreisen um die Sonne.
The planets of our solar system orbit the sun.
to orbit / circle
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to orbit
To move in a circular or elliptical path around a central point.
Die Planeten unseres Sonnensystems kreisen um die Sonne.
The planets of our solar system orbit the sun.

to revolve around
To keep coming back mentally or in a conversation to a particular topic or person.
Seine Gedanken kreisten ständig um die bevorstehende Prüfung.
His thoughts constantly revolved around the upcoming exam.

to circle
To move slowly, often in the air, in circles.
Ein Geier kreiste hoch über der Wüste auf der Suche nach Beute.
A vulture circled high above the desert in search of prey.
The verb 'kreisen' is derived directly from the noun 'der Kreis' (circle). So the basic meaning is always to be in, or move in, a circular motion.
Die Kinder fassten sich an den Händen und tanzten im Kreis.
The children held hands and danced in a circle.
The perfect tense of 'kreisen' is usually formed with 'haben'. The auxiliary verb 'sein' can be used when movement along a path is emphasized, but this is rarer.
Der Hubschrauber hat lange über der Unfallstelle gekreist.
The helicopter circled over the accident site for a long time.
In the figurative meaning for thoughts or conversations, 'kreisen' is almost always used with the preposition 'um' and the accusative. The topic in question follows after 'um'.
Das ganze Gespräch kreiste nur um das Thema Geld.
The whole conversation revolved only around the topic of money.
In the meaning 'sich um einen Punkt bewegen' (to move around a point), 'kreisen' is very often used in astronomical contexts for planets, moons, or satellites. Here, the preposition 'um' is also typical.
Der Mond kreist in etwa 28 Tagen um die Erde.
The moon orbits the Earth in about 28 days.
to turn / film
Sich um ein Thema drehen usually only means that the topic is the main focus. Um ein Thema kreisen, by contrast, emphasizes that thoughts or conversations keep returning to it. Drehen is appropriate for the mere content, while kreisen is used for repeatedly coming back to the topic.

Das heutige Gespräch kreist immer wieder um die geplante Reise.
Today's conversation keeps coming back to the planned trip.
Das heutige Gespräch dreht sich um die geplante Reise.
Today's conversation is about the planned trip.