Writing in Novum Organum (published in 1620), Bacon claims the following:
“For out of twenty-five centuries, with which the memory and learning of man are conversant, scarcely six can be set apart and selected as fertile in science and favorable to its progress. For there are deserts and wastes in times as in countries, and we can only reckon up three revolutions and epochs of philosophy. 1. The Greek. 2. The Roman. 3. Our own, that is the philosophy of the western nations of Europe: and scarcely two centuries can with justice be assigned to each”
Is it true that at the time of writing there were only 3 periods of advancement in science? Over those 25 centuries were there really only 6 which provided any further understanding?
This is just the usual "Renaissance myth", basically "The ancient Greeks and Romans were really great, and their greatness is reborn in us, so we're much better than those primitive Medieval people." It's a common myth even in modern science teaching (but not in the teaching of the history of science). Depending on the subject, history as included in science teaching will often also dismiss Greek and Roman science. For example, some physics teaching makes it look like everything about mechanics before Galileo was wrong.
In many fields of science, there was much progress in the 1000 years between the fall of (Western) Rome and the Renaissance. Medieval scientific progress is better characterised as continuous progress linking Greek and Roman science to Early Modern science - a graph showing progress would look more like a continuous exponential curve than a gap.
For example, the European study of mechanics began with the Greeks, but a key problem remained mysterious: projectile motion, and specifically how and why the projectile continues moving after it is thrown, with no further propelling force applied. The post-Aristotlean progress began is in the early Medieval period, with the 6th century Byzantine philosopher John Philoponus. Progress continued, including the recognition of projectile motion as uniformly accelerated by gravity, throughout the Medieval period (including progress in Western Europe and in the Islamic sphere), with Galileo essentially adding a few more pieces to the puzzle. For more on this, see, e.g.,
In optics, we have ancient recognition that light travels in straight lines, and that vision can be described in terms of rays (but emitted by the eye, or coming into the eye from outside sources?). Medieval progress clearly related vision to rays of light (from external light sources), and there was much progress in other parts of optics. Al-Haytham's turn-of-the-millennium work on optics was a significant milestone marking that progress, and was a scientific best-seller for the time. Al-Haytham's explanation of the rainbow was incorrect, and inspired some readers to find the correct explanation (Theodoric of Freiberg and Kamal al-Farisi (both 12th century IIRC) were notable for independently providing the same correct explanation. Remarkably, both used water-filled glass spheres as analogs of raindrops to study the paths of light in water drops.)
Even ignoring East Asian and Indian scientific progress, Bacon's "Medieval people did nothing scientific" is simply wrong. We can note that there was also much Medieval progress in technology, with many improvements over the best of ancient Roman technology, but since Bacon wrote about philosophy rather than technology, he didn't explicitly dismiss Medieval technological progress.
(How seriously should we take the scientific writings of a lawyer who couldn't keep himself out of jail, and killed himself with a chicken when he tried doing experimental science?)