What is microgravity?

On Earth we are continually subject to the force of gravity. Objects in orbit around the earth are still subject to almost exactly the same gravitational force as objects on earth, but since they are in ‘free fall’ they appear to be weightless. The weightlessness in orbit is similar to what would happen if you were in a lift and the cable was cut, in effect you would float in relation to the lift, as long as you were both falling at the same speed. This environment is sometimes refered to as ‘Zero-G’, which is a simplified and perhaps misleading way of thinking of the environment of objects orbiting the earth.

In a similar way the term microgravity refers to an environment characterised by the weightlessness of free fall. Unfortunately, all spacecraft need to adjust their positions (for example to point their solar panels towards the sun or to correct their orbits) and this causes tiny accelerations to all objects on board. Small effects can also be caused by drag and by astronauts moving around. These accelerations have the same effect as a minute and varying gravitational force, hence the term ‘microgravity’. In addition over time the term 'a microgravity environment' has started to encompass not only the weightlessness of space but also the phenomena that weightlessness causes such as the absence of convection currents; in addition unrelated features of the space environment such as the high levels of radiation have been grouped under the heading 'a microgravity environment'.

Many physical processes are strongly affected by the pull of gravity. In most cases it makes the process more complex and therefore harder to understand. By removing this effect, some processes change in ways that makes them easier to predict or easier to study.

There are many types of experiment that can be done in these microgravity conditions - experiments that would be affected by convection currents or sedimentation if carried out on Earth. These include important areas such as fluid flow, protein crystallisation, plasma physics and cell behaviour. There are also many applications in the field of human health, such as the study of osteoporosis and development of drugs.

Further details of research areas and applications

Links

• 'Understanding Microgravity' useful information about research in microgravity from NASA
• Basic introduction to Microgravity from the Canadian Space Agency (CSA)

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