Não, você não pode.
O feitiço afirma especificamente que:
A 5-foot-diameter sphere of fire appears in an unoccupied space of your choice within range and lasts for the duration. Any creature that ends its turn within 5 feet of the sphere must make a Dexterity saving throw. The creature takes 2d6 fire damage on a failed save, or half as much damage on a successful one.
If you ram the sphere into a creature, that creature must make the saving throw against the sphere’s damage, and the sphere stops moving this turn.
When you move the sphere, you can direct it over barriers up to 5 feet tall and jump it across pits up to 10 feet wide. The sphere ignites flammable objects not being worn or carried, and it sheds bright light in a 20-foot radius and dim light for an additional 20 feet.
Isso claramente fala com a solidez da esfera. É um objeto que tem que se mover em torno de obstáculos, e pula sobre os poços (note que diz pula, não paira). Além disso, ele distintamente afirma que as criaturas dentro de um raio de 1,5m, mas não declara nada sobre o término da curva no quadrado das esferas.