In 1821 Francois and Biot extended their results to the north measuring the force of gravity using a pendulum at Leith near Edinburgh and in the Shetland Islands. His experiments with electricity and magnetism were major contributions that led Faraday to explain them subsequently as induction. He discovered rotary magnetism and the fact that most bodies could be magnetised. Working with Fresnelon, he discovered the principles governing the polarization of light and established the theory of light as a wave. In optics an Arago or Poisson spot is a bright point that appears at the centre of the shadow of a circular object lit by light from a point source.

He also studied the velocity of sound, leading to the later invention of the polariscope. He is also believed to be the first person to construct an electromagnet. He became a member of the French Academy of Science at the young age of twenty-three and the French emperor appointed him as an astronomer at the Royal Observatory. Craters on the moon and on Mars and a ring of Neptune bear his name.

His political career began in 1830 as a liberal republican, serving as minister of war in the provisional government of 1848, one of his important reforms being the abolition of slavery in France and its colonies. In addition, he improved rations and abolished flogging in the navy. He was also influential in obtaining funding for and advancing scientific endeavours, publishing works by Fermat, for example, and developing railways and the telegraph. President of the Executive Power Commission he served in this capacity as provisional head of state from 9 May to 24 June 1848