What is the Relationship Between Size and Scale?
Very small objects need to be measured on a scale that is appropriate for their size. For instance, as seen in some of the examples above, it would not make sense to measure a school bus at the nanoscale because the numbers would just be too big and cumbersome to manage and would lose their meaning for the individual(s) interested in the measurements. Based on this concept, it is helpful to understand how the various ranges in size are classified into different scales.
Humans live in the macroscale. This is the world that we experience directly. We can see macroscale objects with our naked eye, without the help of special tools or instruments (excluding any form of eyeglasses or contacts). Within the macroworld, the behavior of matter is predictable using classical mechanics. Objects in the macroworld fall within the approximate range of greater than10 -4m (or 100m).
Objects too small to see with the naked eye vary in size within the world of invisibility. Individual cells are typically the representative benchmark objects for the microscale. Microscale objects can only be seen with the aid of a magnifying device such as an optical microscope. Matter in the microworld falls within the range of 10 -7 to 10 -4m (or .1 to 100m, 10 2 to 10 5 nm). Classical mechanics is generally an adequate method for explaining the behavior of objects within the microworld. The nanoworld is the next smaller scale after the microworld. Objects within this scale are defined within the range from 10-9 to 10-7 m, (or 1 to 100nm). Representative benchmark objects for the nanoscale include the diameter of the DNA helix and the diameter of a buckyball. Optical microscopes cannot be used to observe matter at the nanoscale. If at least one dimension of an object falls within this range it is considered to be nanoscale matter. At this scale, classical mechanics is not a reliable method for predicting the behavior of matter; it becomes necessary to apply quantum mechanics. Objects smaller than one nanometer are classified in the atomic scale. The atomic scale includes individual molecules, atoms, and subatomic particles that include protons, neutrons, and electrons. The representative benchmark object for the atomic scale is the hydrogen atom. The behavior of atomic scale matter is explained by quantum mechanics. 3
The scale of the smallest dimension of an object determines how it is classified. The divisions between the macro, micro, nano, and atomic worlds are not absolute but are helpful because they group matter by the methods or models useful for explain their phenomena and the tools used for observation.
A suggested activity for this concept is for students to match objects to their particular measurement scale.
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