We can't avoid the problem that people look at religions and think that they can't be true because they don't have modern knowledge. However, in that area, people are misperceiving.
There are reasons the Buddha could not include modern knowledge in his teachings about 2500 years ago. First, it doesn't work to tell people something they don't have the knowledge to understand. If the Buddha had told people that electrons and protons have opposite charges, people 2500 years ago wouldn't have understood that at all. A second reason is that if the Buddha had neglected the religious instruction to spend vast amounts of time teaching modern knowledge from the beginning, it is almost certain that people would have misused the knowledge. They would, for example, have used the knowledge to make nuclear weapons to try to conquer other nations, which would also have been making nuclear weapons. And many other things.
There are some hints however. For example, one teaching has been that there are a vast number of planets, and the Buddhas and Bodhisattvas teach beings on those planets. Chinese call these the three thousand great thousand world systems, with "thousand" being a Chinese word for a very large number, larger than a literal thousand.
A good reference which is available to look at is Herbert Guenther, translator, sGom.po.pa, THE JEWEL ORNAMENT OF LIBERATION, 1971, Berkeley:Shambala Publications.
Chapter 19, "The Spiritual Levels" discusses 10 levels of Bodhisattvas, also called bhumis.
The lowest level Bodhisattva can simultaneously teach beings on 100 planets. Then, as the Bodhisattva progresses from level to level, the number of worlds increases greatly, to an enormous number in keeping with the number of galaxies and suns we now know exist. 2500 years ago, thinkers and the public in the West did not think that there were a vast number of other worlds, so this is a rather impressive hint.
Note that now that nuclear weapons are out of the bag, so keeping modern knowledge secret is no longer relevant, His Holiness the Dalai Lama has been working with scientists on the effects of meditation on activity of the brain. This has become reputable enough that the work of His Holiness was featured in an article in the July/August 2013 edition of SCIENTIFIC AMERICAN MIND.