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About these units
Millimeter (mm)
A millimeter is one-thousandth of a meter and is used extensively in fields that require fine control and precision. Engineers and machinists frequently rely on millimeters in technical drawings and machining specifications, since the unit supports very precise tolerances without resorting to decimals. In construction, millimeters provide clarity for component dimensions, door and window fittings, and joinery work. Millimeters are also critical in medical imaging (such as CT or MRI slice thickness), entomology, electronics, and automotive design. Many mechanical failures or malfunctions arise from deviations of only a few millimeters—highlighting the importance of precision. On a more everyday level, rainfall measurements and snow depth reports often use millimeters for accuracy.
Gigameter (Gm)
A gigameter, one billion meters (10⁹ m), moves firmly into interplanetary territory. Astronomers use gigameters to express distances within the solar system, such as the average separation between planets or the orbital paths of spacecraft. For example, the Earth–Moon distance (~384,000 km) can be expressed as 0.384 Gm, and distances to nearby planets often fall in the range of tens or hundreds of gigameters depending on orbital positions. The gigameter is particularly useful in scientific models where distances are massive but still fall short of interstellar scales. It reduces the need for unwieldy scientific notation and gives researchers a manageable unit for calculations involving gravitational fields, orbital dynamics, and space mission planning.