Forces
Measured fact
Light can travel through empty space.
How we know
Sunlight reaches Earth across space, where there is almost no air.
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.