Thus, in a state of free fall, the weight would be zero.

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Metrology define calibration dating video

In the teaching community, a considerable debate has existed for over half a century on how to define weight for their students.

The current situation is that a multiple set of concepts co-exist and find use in their various contexts.

Discussion of the concepts of heaviness (weight) and lightness (levity) date back to the ancient Greek philosophers.

The unit of measurement for weight is that of force, which in the International System of Units (SI) is the newton.

For example, an object with a mass of one kilogram has a weight of about 9.8 newtons on the surface of the Earth, and about one-sixth as much on the Moon.

In this sense of weight, a body can be weightless only if it is far away (in principle infinitely far away) from any other mass.

Although weight and mass are scientifically distinct quantities, the terms are often confused with each other in everyday use (i.e.

comparing and converting force weight in pounds to mass in kilograms and vice-versa).

There is also a rival tradition within Newtonian physics and engineering which sees weight as that which is measured when one uses scales.