Copernicus was a Renaissance-era mathematician and astronomer who formulated a model of the universe with the Sun in the middle, rather than the Earth. This is, of course, not correct, but in coming to this conclusion he demonstrated his ability to reason and think critically and to use the evidence both around him and experimentally to influence his thinking. His work and accompanying diagrams were published in 1543, the same year of his death.
Initially there wasn’t much push back, except for the “Chief Censor of the Catholic Church” wanting to “stamp out” the new theory (nobody seemed to mind and then he died). Years later the criticism ramped up, with other astronomers coming at it from a scientific angle and the Church trying to quash the publication of the work on theological grounds.
There is far too much to write here in three paragraphs about his work and the criticism surrounding it, plus all of the other characters involved. Indeed, there are whole books on the subject. Copernicus didn’t suffer for his science as much as Galileo (dying the same year it was published helped), but it’s a fascinating story nonetheless and one well worth looking at in more detail.