It is useful to know the approximate sizes of things. Is something bigger than a shoebox? Will it fit through a doorway? These are all questions that we may find ourselves asking about objects on a regular basis. When it comes to things that are bigger or smaller than we can see with our eyes, it is important to understand that there can be a large difference between things that are too small or too large to see. For example, the E. coli bacteria which can make people ill and the DNA that provides the blueprint for what we look like are both too small to see. However, E. coli is about a 1000x larger than DNA. When scientists measure size and scale, they use the metric system.
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