What does it mean to experience complete weightlessness and how is it possible?

A spell of remarkably likeable characters involved in space travel – notably Major Tim Peake (Britain’s first official astronaut) and Commander Chris Hadfield (the first Canadian astronaut to walk in space), has fed a growing appetite for all things space, including zero gravity aircraft.

What is zero gravity?

Zero gravity is a condition of weightlessness referring to the absence of a gravitational force (g-force or Gs) – a measurement of the acceleration due to gravity that causes weight. A body in a “zero gravity” (or “microgravity” – a state of near weightlessness) environment is acted upon only by gravity, with no reactionary forces exerted by its surrounding matter, the person therefore enters a state of freefall where all objects in that given space are falling at the same rate.

Passengers on a zero gravity flight (and astronauts on a spacecraft) appear to be floating around inside the plane but they are in fact falling at the same rate as the aircraft.

A zero gravity flight follows a parabolic flight path, which involves three stages. The first part of the trajectory sees the plane – which is specially customised, and boasts a padded interior to avoid injury – reach an altitude of 24,000 feet (7315 metres), at which point the nose of the plane is lifted upward to an angle of about 45 degrees until the plane reaches around 32,000 feet (9754 metres).

At this point, the nose of the plane is lowered to a level position during which passengers experience a sense of weightlessness for the next 20-30 seconds. After these few seconds, the nose of the plane is tilted back downward 45 degrees to complete the third and final stage, before it levels off to a normal altitude.