# Physical simulation- how to create anti-gravity in objects like hot-air balloons

How do you create objects that "defy" gravity like an hot-air balloon?

Then halfway into animation, how do you make the hot-air balloon drop anti-gravity, as it loses heat?

What kind of object?

### Rigid body

An individual rigid body cannot be made anti-gravity, however you can make the entire scene gravity point upwards by changing Z=-9.8 to a positive number in the Scene Gravity settings:

"Gravity" is a property that can be keyframed, i.e. you can make it change at a given frame.

### Cloth or soft body

For cloths and soft bodies you can choose what Gravity each object is feeling. There is a "Field Weight" panel in the Physics settings. There you can change Gravity to a negative number (assuming that you don't change the Gravity scene settings!). The slider won't allow you to do that, but you can just type something like -0.5.

Again, this can be keyframed.

Here is a scene with a Soft Body hot air balloon, with its Gravity Field Weight set to -0.3 (Scene Gravity is untouched), and with a Wind Force Field at a given altitude (also a Turbolence Force Field for more wiggling):