n work out how big the mass of the earth is, not by trying to weigh it because that is merely impossible. Instead they used the gravity on the earth to help them. We know the velocity at which objects fall to the earth, so from this scientists were able to work out the mass of the earth. So they found the total mass of the earth, and compared that to a mass made up of just the crust and the mantle. They could get this mass reading because they know the density of the crust and the mantle. However even after working this mass out the total amount was well short, compared with the mass they found from using the velocity at which objects fall to the earth. So they were convinced by these results that the mantle was not the only thing down there, they put the lack of mass to believing that something heavier and denser was in the middle.When the earth formed it originally condensed, by gravitational attraction of cosmic dust and gas. The continuing contraction of these materials caused them to heat, as did some of the radioactivity of some of the heavier elements. As this progressed the earth became very hot and it began to melt. This caused the different layers to form in the earth, because all the lighter materials moved up to the surface to produce the crust. So the heavier materials like the metals iron and nickel sank to form the core, the materials in the mantle were made form the silicates that didn't sink or float.When meteorites reach the surface of our planet before they are entirely consumed, they provide us with valuable information. Meteorites are believed to be fragments from other planets, formed some 4.6 billion years ago. Around the same time as the earth was been formed. These meteorites are mostly made up of iron; this is what excites scientists. As they believe that this is proof that the middle core of our earth is made from solid iron. Thinking that meteorites are part of planets that have broken up and sent fragments f...
