A 20-foot-radius invisible sphere spreads out from a point you choose within range. The sphere may cause a slight visual distortion in the area.
If you chose a point on an object you are holding or one that is being worn or carried, the field emanates from the object and moves with it. Completely covering the affected object will reduce the area of effect. If the object is moved, creatures affected by the spell do not automatically move with it and risk falling out of the sphere. 
Objects and creatures within the sphere are not affected by gravity and can move freely in any direction. However, creatures that begin their movement in the sphere or change their direction while in the sphere have their speed halved. If a creature starts its turn in the area, have it make a Dexterity check against the caster's spell save DC. On a failure, the creature's movement becomes zero for that turn and moves 10 feet in a random direction or remains still, decided by the DM. Movement in the sphere may be affected by other things, such as the force of a spell, pushing and pulling from other creatures, and using objects as anchors. All Dexterity saving throws made within the area are at disadvantage. 
The caster may also choose to center the sphere on themselves. This is not considered flight. Starting or stopping movement may be difficult, as well as changing direction, as determined by the DM.

At Higher Levels. When you cast this spell using a spell slot of 6th level or higher, the area of effect increases by 10 feet per additional spell level.