Bacteria
Year of Discovery: 1680
What Is It? Microscopic organisms exist that cannot be seen by the human
eye.
Who Discovered It? Anton van Leeuwenhoek
Why Is This One of the 100 Greatest?
Just as Galileo used his telescope to open the human horizon to the planets and stars of
space, so van Leeuwenhoek used his microscope to open human awareness to the microscopic world that was invisibly small and that no one had even dreamed existed. He discovered protozoa, bacteria, blood cells, sperm, and capillaries. His work founded the science of
microbiology and opened tissue studies and plant studies to the microscopic world. He
completed human understanding of the circulatory system.
How Was It Discovered?
Anton van Leeuwenhoek was born in 1632 in Delft, Holland. With no advanced
schooling, he was apprenticed as a cloth merchant and assumed that buying and selling
cloth would be his career.
But van Leeuwenhoek was curious about the world and interested in mathematics.
Completely self-taught, he learned enough math to moonlight as a surveyor and read what
he could about the natural world around him. He never learned any language other than
Dutch, so he was never able to read any of the scientific papers and research (all written in
Latin or French).
Microscopes existed in Holland by 1620. Christian Huygens and Robert Hooke were
the first two scientists to make scientific use of microscopes. Both designed and built
two-lens microscopes (two ground glass lenses inside a thin metal barrel).
In 1657 van Leeuwenhoek looked through his first microscope and was fascinated. He
tried a two-lens microscope, but was disappointed by its distortion and low resolution.
When he built his first microscope, he used a highly curved single lens to gain greater
magnification.
By 1673 van Leeuwenhoek had built a 270-power microscope that was able to see objects only one-one-millionth of a meter in length. Van Leeuwenhoek remained very secretive about his work and never allowed others to see his microscopes or setup.
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