Zero gravity
Zero gravity or null gravity, also abbreviated zero grav or zero g, was the natural free fall environment of space, where there was the illusion of weightlessness despite the surrounding objects still exerting a gravitational force.

The command module of the Ares IV, an Earth spaceship, had a zero gravity environment. ()

By 2151, artificial gravity had been invented to counter zero gravity. However, every ship still had an area where zero gravity was maintained. Travis Mayweather called the area the "sweet spot" during his youth aboard the . ()

Cargo module 4 aboard the  was intentionally kept in a zero, or low, gravity environment. There, members of the crew could throw a football through the low gravity area while standing in an artificial gravity zone at the catwalks. ()

In 2371, Commander Benjamin Sisko installed a gravity net in the floor of his lightship because weightlessness made him queasy. ()

Kathryn Janeway conducted her zero gravity training in the Coral Sea. ()

Although artificial gravity was usually maintained in most sections of a starship, a vessel's environment can revert to its natural zero gravity state when its artificial gravity systems fail. (; ; )

See also 
 Null-gravity combat exercises and Zero-gravity combat training
 Null grav suite
 Zero Gravity Therapy Ward
 Zero-grav tumbling

Background information 
A jar which appeared in the  sickbay in  and which was sold off on the It's A Wrap! sale and auction on eBay has the label Do not store under null gravity condition.

External link 
 
Physics