What is a light year? explain why light-years are used to measure distances and sizes in the universe

In attempt to solve the working problems created by the industrial revolution, the united states and many countries in europe considered and/or adopted

25) a student takes four samples of a white crystalline solid and places each in a well plate. on top of each sample, she carefully places 20 drops of clear mystery liquids a, b, c and d. her results for each well are: liquid a: the solid dissolves quickly. liquid b: the solid appears unchanged. liquid c: a brownish colored liquid is produced. liquid d: fizzing occurs and the well becomes warmer. in which well does a physical change occur?

What is the difference between an igneous, sedimentary and metamorphic rock