In 1992, Nasa put live frogs and their eggs aboard the Space Shuttle; the eggs were fertilised and developed in microgravity

• For a developing frog embryo, gravity is more than the force that keeps it on the ground.
• It can provide a reference for how the egg is oriented as development begins, helping establish the direction in which the embryo will form.
• Nasa wanted to find out what would happen if that reference disappeared.