Each layer is layed down during a certain time period, so sedimentary rocks can be used to tell the geological record of an area. Scientists can tell when an organism lived through which layers its fossils are in. It's almost like looking back in time, pretty neat. Sedimentary rocks can also be quite beautiful. Take a look at this picture .
All planets have gravity.
Some planets have more than others. Right now, we know that only Earth has life , although we are always look ing for others. Can you please tell me some information on Rutherford or John Dalton who were scientists who discovered the atomic structure. Here is our page on Ernest Rutherford, and here are several other pages with information on Rutherford and Dalton . Did Albert Einstien have anything to do with the building of the atomic bomb.