Scientists have now levitated mice using magnetic fields.
Other researchers have made live frogs and grasshoppers float in mid-air before, but such research with mice, being closer biologically to humans, could help in studies to counteract bone loss due to reduced gravity over long spans of time, as might be expected in deep space missions or on the surfaces of other planets.
Scientists working on behalf of NASA built a device to simulate variable levels of gravity. It consists of a superconducting magnet that generates a field powerful enough to levitate the water inside living animals, with a space inside warm enough at room temperature and large enough at 2.6 inches wide (6.6 cm) for tiny creatures to float comfortably in during experiments.
The researchers first levitated a young mouse, just three-week-old and weighing 10 grams. It appeared agitated and disoriented, seemingly trying to hold on to something.
"It actually kicked around and started to spin, and without friction, it could spin faster and faster, and we think that made it even more disoriented," said researcher Yuanming Liu, a physicist at the Jet Propulsion Laboratory in Pasadena, Calif. They decided to mildly sedate the next mouse they levitated, which seemed content with floating.
A plastic cage was also designed by physicist Da-Ming Zhu at the University of Missouri, Kansas City, to keep the mice in during levitation. Its top remained open to let in air, food, water and video surveillance, and its bottom was filled with small holes to allow waste removal.
From time to time, mice would kick the walls of the cage, causing it to briefly drop off from the levitation zone before re-entering it and floating again.