Forces
Measured fact
A force is a push or a pull.
How we know
A spring scale stretches when you pull, and the stretch measures the force.
Photo credits
Pictures were resized to fit. Nothing else was changed.
- Charles Darwin. Julia Margaret Cameron. Public domain.
- Jane Goodall. U.S. Department of State. Public domain.
- George Washington Carver. Public domain. Restored by Adam Cuerden.
- Barbara McClintock in her laboratory. Smithsonian Institution. Public domain.
- Ernest Everett Just. Public domain.
- Wangari Maathai. Kingkongphoto. CC BY-SA 2.0.
- Marie Curie. Henri Manuel. Public domain.
- Rosalind Franklin at a microscope. MRC Laboratory of Molecular Biology. CC BY-SA 4.0.
- Percy Julian. Public domain.
- Tu Youyou. Bengt Nyman. CC BY-SA 4.0.
- Dmitri Mendeleev. Public domain.
- Alice Ball. Public domain.
- Isaac Newton. Godfrey Kneller. Public domain.
- Michael Faraday. Public domain.
- Chien-Shiung Wu. Smithsonian Institution. Public domain.
- Ada Lovelace. Alfred Edward Chalon. Public domain.
- Shirley Ann Jackson. World Economic Forum / Qilai Shen. CC BY-SA 2.0.
- A later drawing of Hasan Ibn al-Haytham. Public domain.
- Mary Anning. Painting credited to Mr. Grey. Public domain.
- Katherine Johnson. NASA. Public domain. Restored by Adam Cuerden.
- Mae Jemison. NASA. Public domain.
- Nicolaus Copernicus. Public domain.
- Galileo Galilei. Justus Sustermans. Public domain.
- A wood frog. The Cosmonaut. CC BY-SA 2.5.
- A honey bee on a flower. Tanner Smida. CC BY 4.0.
- A button mushroom. chris_73. CC BY-SA 3.0.
- A chimpanzee in a forest. Giles Laurent. CC BY-SA 4.0.
- Rainforest canopy in the Amazon. CIAT. CC BY-SA 2.0.
- Sweet wormwood, the plant artemisinin comes from. Kristian Peters. CC BY-SA 3.0.
- A university science building. Mike Peel. CC BY-SA 4.0.
- A magnet pulling a piece of magnetite. GOKLuLe. CC BY-SA 3.0.
- Earth, photographed from Apollo 17. NASA. Public domain.
- Jupiter's clouds, from NASA's Juno spacecraft. NASA / JPL-Caltech / SwRI / MSSS. Public domain.
- The Hubble Space Telescope above Earth. NASA. Public domain.
- Telescope domes on Mauna Kea. T. Wynne / NASA JPL. Public domain.
- Hands being washed with soap. Lars Klintwall Malmqvist. Public domain.
- A common octopus. Albert Kok. CC BY-SA 3.0.
- Stonehenge, an old stone circle used to track the sky. garethwiscombe. CC BY 2.0.
- A microscope on a bright table. Ann 2000. CC BY-SA 4.0.
- A lab dish with spots of germs. SS. Antonio e Biagio e Cesare Arrigo. CC BY-SA 4.0.
- The Wright Flyer on its first flight in 1903. John T. Daniels. Public domain.
- Part of Babbage's Difference Engine. geni. CC BY-SA 4.0.
- Lyme Regis, England, beside the sea cliffs. Eugene Birchall. CC BY-SA 2.0.
- St Mary's Hospital in London. Enric. CC BY-SA 2.0.