According to a different source, these are the options that come with this question:
Estimate the speed of light.
Propose the heliocentric theory.
Discover radioactivity.
Define and measure speed.
Invent the reflecting telescope.
Galileo Galilei was the first person to attempt to measure speed, specifically the speed of light. He attempted to do this in the 1600s, with the help of an assistant. Galileo tried to measure how quickly light would travel from one hilltop to another one. However, light was so fast that it was impossible to measure it in this way.
