The scale of measurement from atoms to macromolecules to cells.

Scientific understanding becomes more concrete when you can relate the scale of phenomena from the different sciences, for example, to be able to relate the distance of chemical bonds to the scale of a virus.

Divide a meter by 1000 and you have the millimeter. Perform the operation again, dividing the millimeter by 1000 and you have a micrometer, µm (10-6 m). Divide this distance by another 1000 and you have the nanometer (10-9 m), and then by another 10 and you have reached the exceedingly small scale of the angstrom, (10-10 m) The spacial dimensions of atoms and the molecules they comprise are measured in angstroms, (10-10 m) to the degree such phenomena may be measured. Atomic radii and the covalent bonds between atoms are typically 1 to 2 angstroms.

Smaller biological molecules such as mono or disaccharides or amino acids are several to ten angstroms long, ranging upwards of a nanometer in length (10-9).

Ten times larger still are the more massive biological molecules such as the protein hemoglobin approaching 100Å. Viruses range from several hundred angstroms in size (polio at 28nm or 280Å) to several thousand angstroms (smallpox at about 2000Å), which is also the scale of smaller organelles such as ribosomes (so viruses and small organelles range from hundreds to several thousand chemical bonds in diameter. Try to picture it!) If a virus were laid out on your desk, scaled up to the size of your desk, you would just be able to make out the individual atoms like grains of sand.

Bacteria range in size from 1000Å (100nm or 0.1µm) to more than 50,000Å (5000 nm or 5µm), which is also the scale of mitochondria. The scale of bacteria and mitochondria are among the smallest objects which can be viewed by the light microscope (the visible light range is approximately 10-7m or 0.1µm). Small eukaryotic cells, such as red blood cells or human liver cells, are approximately 10µm in diameter.

Larger cells such as an amoeba are 100µm in diameter (0.1 mm). At 1 mm in diameter, fish eggs can be seen by the naked eye. Now we have reached the spacial scale encompassing the phenomena of 'every day life'. We can continue panning back to see the room, measured in meters, the town, measured in kilometers, and the solar system, measured in millions of kilometers. In the vacuum of space, the distance travelled in one second by light is 3 x 108 m, or three hundred million meters (three hundred thousand kilometers).