In the Anubhashya, Shree Mahaprabhuji defines Shastram while giving commentary on the First Chapter, First Section, Second Sutra "Janmadyasya yatah shastrayonitvat" as :
Shaastiti (Shaasti iti) shastram vedah |
That which governs is the Shastram as per the Vedas.
Shree Navneetpriya Shastriji in his book Pushti-Pulin, also quotes similar definition "shansati it shastram".
As per this defintion, the modern civilization is governed by both ancient scriptures as well as recent scientific theories. Thus, modern science is just the natural expansion of Shastram. Understanding it in a harmonious manner is a prerequisite to the ultimate goal of serving the Supreme Lord Shree Krushna.