In space, nothing has any weight.
Astronauts have major problems weighing anything in space because the term "weight" actually means the force that an object is attracted to the earth by gravity. There is no gravity in space, which means that objects don't actually weigh anything at all. What they do have, however, is mass. How much an object would weigh on earth can be calculated once its mass is known.
Weight vs Mass
The weight of an object varies hugely depending on which celestial body the object is on. Objects weigh six times less on the moon than on the Earth because the moon has a much lower gravitational pull. Mass is the amount of material that an object contains. No matter what planet an object is on, or even if it is floating in space, its mass will be exactly the same. Because these two terms are often confused, this concept can be tricky to grasp. In everyday usage, "mass" and "weight" are interchangeable and both are measured in kilograms. In science, they are two very different things and weight is in fact measured in Newtons, which takes into account the downward pull of gravity.
Calculating Mass on Earth
The weight of an object on earth in Newtons is found by the equation w = m x g, where w is weight, m is mass and g is the acceleration of gravity. The acceleration of gravity on Earth is always 9.8 metres per second per second, denoted as 9.8 m/s2. This means that every second an object is falling it will increase in speed by 9.8 m/s. This downward force applies even when an object is on the ground, but the rigidity of the floor prevents it falling further. Therefore, the weight of a 1 kg mass on earth is 1 kg times 9.8 m/s2, which equals 9.8 Newtons. If you were to calculate the mass of something which weighed 9.8 Newtons, you would use the equation m = w divided by g, so the mass equals 1 kg.
Calculating Mass in Space
An inertial balance scale is used to weigh small objects which can be measured in a space shuttle. It is a spring to which objects can be attached. The spring is then vibrated. The frequency of the vibrations indicates the mass of that object. Multiplying that by Earth's gravitational pull, which is 9.8m/s2, will give the weight of the object on Earth.
Large Masses
Scientists can determine the mass of large objects in space, like stars or galaxies. This is calculated by studying the object's gravitational interactions. For example, the mass of a star could be calculated by observing its gravitational pull on a planet orbiting it. The mass of both can be determined if scientists know how long it takes for the planet to orbit the star, and how far apart they are.
Tags: gravitational pull, that object, weight object, acceleration gravity, Calculating Mass
