Physics studies the physical, material creation by defining it with logical and rational construct. It uses sensory perception and observance. It is, simply put, the raw documentation and information of the subject of study - Creation.
The Signs of Allah, however, cannot just be 'studied' rationally nor through sensory observance, because they are beyond physicality. They must be interpreted with depth and a heightened sense of spiritual emotion. As such, one could be looking at a Sign of Allah, but that is all he is doing - 'looking'. He cannot see it.
By extension, all of Allah's Creation is a Sign of Allah, because the impetus of a Sign is not in the Sign, but in that which it signifies. Mankind, for example, is a Creation that is also a Sign by its descriptive of a Vicegerent (Baqarah 2:30), a representative of Allah's Sovereignty.
It can be argued that Allah’s Creation can be studied scientifically, but the Creation is also a Sign of Allah, ergo the Sign can be studied 'scientifically'. The Logic is sound, but not necessarily true. Because the term "science" is defined as "knowledge of", and one can have "knowledge of" something, but not "knowledge itself". Thus the "knowing of something" is defined as the "Science of" something.
Science of the Universe - Cosmology. Science of Living Organisms - Biology. Science of Religion - Theology. And so on…
"Knowing something" and having "knowledge of something" are two different things, in the same way as having Knowledge and having Information. You can have "knowledge of" Allah's Creation, but to truly "Know" Him, you must have a deeper understanding of His Signs, which are themselves beyond rationality and sensory perception. One needs insight, spiritual emotion, and faith, and ultimately this is sufficient enough without the science of it.