Galileo’s career was marked by many discoveries; while the discoveries remain in the mind, there were considerable flops as well. And some facts people think they know about his work are pure fiction.
Galileo Galilei made several inventions; he also developed existing inventions; some of these contributed considerably to his income (the list is probably not complete):
1. Slide rule. His first full publication in 1606 Il compasso militare e geometrico was written to defend his invention against a similar device invented in Milan by Baldassare Capra. Printed advertising is not an invention of our time.
2. Reinforced magnet. In the Dialogue of 1632 (third day), he described how in his opinion the reinforcement should augment the magnetic force. If you haven’t heard of it, don’t worry, it doesn’t work.
3. Microscope. Galileo called it Occhialino (little glasses), but Giovanni Faber of the Academia dei Lincei coined the name microscope for it. The principle of how a microscope works were worked on since about 1600 and several other people had constructed one prior to Galileo. The invention of the first microscope, though, is attributed to Hans and Sacharias Janssen in Middelburg in 1590.
4. Jovilabium. The device would have allowed seamen to compute their longitudinal position with the help of Jupiter’s moons. The Dutch government had set out a prize of 30,000 guilders to the inventor of a precise method to do just that, but Galileo never managed to claim the sum despite several tries.
5. Thermometer. His thermometer worked but was not too precise. Daniel Gabriel Fahrenheit would perfect it to fully working instrument in 1710.
6. Hydrostatic balance. This device allowed measuring the specific weight of objects.
7. Pendulum clock. He brought the theory to paper, but never built it. His son Vincenzo started building it, but didn’t finish it before he died. The invention is therefore attributed to Dutch scientist Christiaan Huygens as the first patent holder.
8. Swiss Army Knife. Only in drawing, Galileo combined a hair comb with spoon and knife. Maybe some basic idea about hygiene made him desist from building and using it.
9. Tube telescope. The lens based tube telescope was not an invention by Galileo, and he never claimed it as his invention. The myth of him being its inventor was propagated by various literary inventions; the most influential of these was probably Bertolt Brecht’s drama which was used to produce several films. Tube telescopes appeared from three different lens making shops in the Netherlands all at about the same time; Hans Lipperhey from Middelburg and Jacob Metius from Alkmaar applied for a patent, while Sacharias Janssen was already selling it at the Frankfurt Fair.
10. Horse drawn pump. Galileo was granted a patent on his horse drawn water pump.