Where the facts come from
Every factual claim on this site links to its source. This is the full list.
How we checked
Each fact was written in our own words alongside its source. Our build script stores the text of every source and, for each fact, checks that the key words and figures really appear in it. 113 of 113 checks passed when this site was last built (13 November 2026). Where we couldn’t find a named source saying something, we left it out. Where good sources disagree, we say so and give both.
Where sources differ
- How many simple machines. Six: inclined plane, lever, wedge, wheel and axle, pulley and screw (Britannica’s simple machine article; Science Trek). Five, without the inclined plane (Britannica’s pulley and wedge articles). A different six, with the block and the gear (US Navy manual), which also says physicists recognise only two principles.
- Hero’s five. Lever, pulley, wheel, wedge and screw (University of Oklahoma) or winch, lever, pulley, wedge and screw (Acta Baltica).
- Who made it six. Galileo, who added the inclined plane in Le Mecaniche (Acta Baltica); Simon Stevin worked out its mechanical advantage in 1586 (Ohio University).
- “Give me a place to stand”. Apocryphal (Britannica). Plutarch’s version: another earth to stand on. The famous lever wording: John Tzetzes, 12th century AD (Rorres, NYU).
- Door handles. A wheel and axle (US Navy manual, for a doorknob) or a lever (Science Trek).
- Who invented the screw. Archytas, the “alleged inventor”, and the water screw “usually ascribed to Archimedes” with an earlier Egyptian device (Britannica), or Mesopotamia in the first millennium BCE (Ohio University).
All sources (27)
- Science Trek (Idaho Public Television): Simple machines (19 facts)
- OpenStax College Physics 2e (Rice University), 9.5 Simple machines (14 facts)
- Encyclopaedia Britannica: Simple machine (13 facts)
- Ohio University, R. L. Williams: History of mechanisms (PDF) (10 facts)
- US Navy, Basic Machines and How They Work, ch. 1: Levers (5 facts)
- BBC Bitesize: What are levers? (4 facts)
- Encyclopaedia Britannica: Archimedes (4 facts)
- Encyclopaedia Britannica: Inclined plane (4 facts)
- Encyclopaedia Britannica: Pulley (4 facts)
- Encyclopaedia Britannica: Screw (3 facts)
- Encyclopaedia Britannica: Work (physics) (3 facts)
- Illinois State University Physics: Simple machines (3 facts)
- Pisano and Bussotti, Acta Baltica Historiae et Philosophiae Scientiarum (PDF) (3 facts)
- US Navy, Basic Machines and How They Work, ch. 3: The wheel and axle (3 facts)
- US Navy, Basic Machines and How They Work, ch. 5: The screw (3 facts)
- Chris Rorres, Archimedes: quotations about the lever (NYU) (2 facts)
- Encyclopaedia Britannica: Wedge (2 facts)
- Encyclopaedia Britannica: Wheel and axle (2 facts)
- MacTutor History of Mathematics (University of St Andrews): Archimedes (2 facts)
- US Navy, Basic Machines and How They Work, ch. 4: The inclined plane and wedge (2 facts)
- University of Oklahoma Libraries, Galileo’s World: Mechanics (2 facts)
- Encyclopaedia Britannica: Galileo (1 fact)
- Encyclopaedia Britannica: Lever (1 fact)
- Encyclopaedia Britannica: Mechanical advantage (1 fact)
- Encyclopaedia Britannica: Simon Stevin (1 fact)
- Indiana Public Media, A Moment of Science: Ode to the zipper (1 fact)
- US Navy, Basic Machines and How They Work, ch. 7: Work (1 fact)