Travel beyond the earth's atmosphere.

Condition in which no acceleration, whether due to gravity or any other force, can be detected by an observer within a system. It also means the absence of weight or the absence of the force of gravity acting on a body. Microgravity, gravitational force between 0 and 10 -6 g, is included here. (From NASA Thesaurus, 1988)

The use of wings or wing-like appendages to remain aloft and move through the air.

That branch of medicine dealing with the studies and effects of flight through the atmosphere or in space upon the human body and with the prevention or cure of physiological or psychological malfunctions arising from these effects. (from NASA Thesaurus)

A weight-carrying structure for navigation of the air that is supported either by its own buoyancy or by the dynamic action of the air against its surfaces. (Webster, 1973)

Members of spacecraft crew including those who travel in space, and those in training for space flight. (From Webster, 10th ed; Jane's Aerospace Dictionary, 3d ed)

Design, development, manufacture, and operation of heavier-than-air AIRCRAFT.

The motion of air relative to the earth's surface.

A family of the order Rodentia which contains 49 genera. Some of the more common genera are MARMOTA, which includes the marmot and woodchuck; Sciurus, the gray squirrel, S. carolinensis, and the fox squirrel, S. niger; Tamias, the eastern and western chipmunk; and Tamiasciurus, the red squirrel. The flying squirrels, except the scaly-tailed Anomaluridae, also belong to this family.

A genus comprised of spinner, spotted, and striped DOLPHINS, in the family Delphinidae. Schools of Stenella, that may number in the thousands, often associate with schools of TUNA, and are thus vulnerable to accidental harvesting.

Actions which have a high risk of being harmful or injurious to oneself or others.

That phase of clinical dentistry concerned with the restoration of parts of existing teeth that are defective through disease, trauma, or abnormal development, to the state of normal function, health, and esthetics, including preventive, diagnostic, biological, mechanical, and therapeutic techniques, as well as material and instrument science and application. (Jablonski's Dictionary of Dentistry, 2d ed, p237)